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Biology: Parasite,Plants nutrition, Osmosis,Pollination and others


 An organism that lives permanently or temporarily on or inside the body of another organism and depends fully or partly on the host organism for
its nutrition is called a parasite

Characteristics of Parasites :

1. Their Physiological systems are of simple type.
2. The external body covering of the endoparasites is firm but semipermeable.
3. The parasites have higher reproductive capacity.
On the basis of the location of parasites on the host body, the parasites are of
two types, Ectoparasite and Endoparasite.
1. Ectoparasite : They live on the outer side of the host body, e.g. Leech.
2. Endoparasite : They live inside the host body, e.g. malarial parasite.
Parasite and parasitism : We have learnt earlier that the round worm lives as
a parasite inside the host body and gets nourishment by taking digested food
materials from he intestine of its host. So it is called an endoparasite. Round
worm gets shelter and nutrition from the host body, as a result of which the host
suffers from anemia and malnutrition. The relationship that is formed between
the host and the parasite is known as parasitism.
Excretory System : Excretion is the process of discharging unwanted
nitrogenous waste materials from the body. The structure of the excretory
system of round worm is very simple. The system consists of two-long tubes at
the two sides of the body against the lateral lines. Meeting together at the other
end, the two tubes open outside through the excretory pore or cloacal aperture.
Reproductive System : The round worm is a unisexual animal. Generally the
male worm is smaller in size than the female and the posterior part of its body
is bent.
Male Reproductive System : The male
reproductive system consists of a testis,
sperm duct, seminal vesicle and an
ejaculatory duct. The testis is formed like
a coil and occupies a greater portion of
the body. The sperm duct is located
behind and the bulky posterior part is the
seminal vesicle. It later opens into
cloacal aperture. They have a pair of
penialsetae. Male round worm discharges
sperms through the cloacal aperture.
Female Reproductive System : The
Female round worm is larger in size than
the male. The female reproductive
system consists of two ovaries, two uteri
and one vagina. These organs, are
situated in the posterior half of the body
of the worm. The ovaries are coiled and
narrow. Eggs are produced at the.
posterior part of the ovary. The oviducts
are connected with the ovary. The eggs
produced in the ovaries pass to these
ducts. A part of the oviduct enlarges to
form a seminal receptacle. Here the
sperms are stored. The oviduct meets the
uterus. The two uteri uniting together
form the tubular vagina. The vagina
opens outside. through the female genital
Life cycle : The ovum and sperms of the round worm meet together at the
upper side of the uterus. After fertilization the zygote or fertilized egg is
covered by a wall made of chitin. The eggs of roundworm are very small and
elongated. Along with the faeces of the host these eggs come outside of the
host body. Embryo formation begins inside the fertilized egg when it remains
within the shell. The primary larval stage of the roundworm is called Rhabditiform larva.
Infection : No intermediate host is required for the infection of round worm.
Eggs enter directly into the body of the new host along with contaminated air,
food and drinks.
Hatching of embryo : Hatching of embryo usually occurs within two hours
after the egg reaches the intestine through stomach of the host body.
Transformation to adulthood : After the entry of the egg in the intestine of
the host, the shell is dissolved by the intestinal juice of the host and the larva is
freed from the shell. They pierce the intestinal epithelium and enter into the
lymphatic vessels or the blood capillaries. They travel to various organs along
with the blood circulation: At this condition, for sometime, the larvae are entrapped in the lungs. Ascending the respiratory tube the larvae reach to the pharynx. Due to their presence the throat of the host irritates and this may cause coughing. Along with cough the larvae comes up to the throat. They again reach the intestine if one swallows the cough. The larvae once again change their shell in the intestine. Here ends their migratory life. When inside the intestine, they are nutrited by taking digested food juice from the host. Within a
few days the larva changes into a full worm. In Bangladesh the incidence of
infection of this worm is very high. Most of the children of our country suffer
from this infection. A single host may contain 100 to 400 worms. They produce
Ascariasis disease in children. When intensity of infection is high, the illness
may take a serious turn. An affected person shows the following symptoms:
1. The belly of the children becomes swelled up.
2. When the number of worms increases in the intestine, vomiting tendency and
loss of appetite are observed. In the final stage worms may come out with
3. Indigestion and physical weakness are seen.
4. Balance between acid and alkali is lost in the intestine.
5. Due to infection with round worm the patient feels pain in the belly and
anemia is developed.
Prevention: In the mean time, we have known that most of the children of our
country get infected with round worms. As a result, these children suffer from
anemia and malnutrition. Following measures should be taken if one wants to
get-rid of the round worms:
1. Stop the habit of discharging faecal matters at open places and use sanitary
2. Take green fruits after thorough washing with pure water.
3. Keep your hands clean and clip your nails.
4. Before taking food and after using latrine wash your hands well.
5. Abstain from taking cold and rotten food.
6. Get rid of the worms by taking medicine after consulting a physician.

Physiological Activities in Plants Nutrition

Plant Nutrition And Nutrient Elements :
Green plants manufacture carbohydrate foods by the process of Photosynthesis. 
These foods again break down to water, CO2 and energy. That energy is used in 
plants growth and other process. But only Carbohydrate is not sufficient for 
healthy growth, physical development and regenerations of the plant body. 
Beside these, for normal completion of other physiological functions plant 
absorb different kinds of inorganic minerals from nature. The process of 
absorption of necessary minerals for healthy growth of the body; physical 
development and regeneration is called Nutrition or mineral nutrition of plant.
Nutrition and its Components:
Several nutritionists proved that, there are 16 inorganic elements necessary for 
normal growth and development of the plant. They are so important that they 
are called essential elements. Their characteristics are as follows: -
* They are essential for normal development and reproduction or the plant.
* For shortage of any one of them, deficiency symptoms shows in the plant 
* Function of one element cannot be done by another one.
Mineral nutrients are divided into two groups, depending on how much of it is 
required for normal growth and physical development.
1. Macronutrients: Comparatively they are needed in large quantities. 10 
minerals are macro nutrients, they are: - Nitrogen (N), Potassium (K), Calcium 
(Ca), Iron (Fe), Magnesium (Mg), Carbon (C), Hydrogen (H), Oxygen (O), 
Phosphorus (P), and Sulphur (S).
These 10 macronutrients can easily be remembered by the following 
sentence -Mg.K. CaFe for Nice CHOPS = Mg.K Cafe for good chops. Here Mg for Magnesium, K for Potassium, CaFe for Calcium and Iron, CHOPS for 
Carbon, Hydrogen, Oxygen, Phosphorus and Sulphur.
2. Micronutrients: They are needed in minute amount. Following six elements 
are micronutrients: Zinc (Zn), Manganese (Mn), Molybdenum (Mo), Boron 
(Bo), Copper (Cu), and Chlorine (Cl). Beside these Sodium (Na), Aluminum 
(Al). Silicon (Si). and Cobalt Co) are also needed.
Source of Nutrients :
 Among all the nutrients the plants from atmosphere absorb only Carbon and 
Oxygen. Other elements are absorbed from soil by root. These elements are 
present in the soil as different salts, but plant cannot intake them directly They 
absorb as different ions.
Action of different mineral nutrients in plant nutrition:
Actions of different elements are very acute in plant nutrition. For these 
elements are termed as essential elements. Formation of chlorophyll is 
hampered for the deficiency of Nitrogen. If chlorophyll is not formed 
manufacturing of food is hampered. If manufacture of food is seized it 
hampered the process of respiration and causes less production of energy. 
Magnesium is one of the elements of chlorophyll. As a result for deficiency of 
it will seize the formation of chlorophyll and manufacture of food by 
photosynthesis. Potassium acts as a catalyst in many biochemical reactions in 
plants, for this it is necessary in plant nutrition. The development of plant by 
cell division is also control by potassium. So without it plant nutrition is not at 
all possible. We use Nitrogen (Urea), Potash (Murrate of Potash), Phosphorus
(Triple supper Phosphate) ect. for crops as it play valuable role in nutrition.
Deficiency Symptoms of Nutrients :
Plants show special symptoms in case of deficiency of any element. These 
symptoms are called Deficiency Symptoms or deficiency disease. We can 
ascertain the deficiency of any element by observing these symptoms. 

Imbibition, Osmosis, Ascent of Sap

 If one side of a piece of blotting paper is touched water surface, the blotting
paper will gradually absorb water and becomes wet. We can do this experiment
with a piece of newspaper too. Imbibition is also a process of water absorption.
Absorption of water by dry, semi-dry colloidal substances called Imbibition.
More easily it can be said that the process of absorption of water by plant cell
wall, protoplasm etc. is called imbibition. The amount of water absorbed by dry
seeds during germination is done by imbibition.
The substances, which absorb water, are called Hydrophilic (water loving)
substances. Hydrophilic substances contracted for shortages of water, again
when it gets water become swollen by absorbing it.
It is seen that in winter the wooden doors and windows make gaps for
contraction and in the rainy season they swells up by absorbing water and it
become harder to open the doors and windows. It is a result of imbibition.
 If a spoon of sugar dissolves in a glass of water, the sugar molecules spread
throughout the whole glass of water; as a result the whole water becomes
equally a sweet. If a spoon of salt is dissolved in a glass of water, it is seen that
whole water becomes equally salted. Let us see what happens if some crystals
of Potassium permanganate (KMn04) is dropped into a glass of water. After
some times it will be seen that the whole water in the glass becomes violet.
Dropping a drop of ink in the glass may do this experiment.
Actually in a crystal of sugar, salt or potassium permanganate there are any
molecules compactly combined together. When the crystal is dropped in water
the water molecules attract its molecules very strongly. As a result the crystal is
completely dissolved in water and its molecules are spread throughout the
water evenly. The molecules of sugar, salt or potassium permanganate
distributed throughout the water by the process diffusion.
At a constant temperature and atmospheric pressure movements of the molecule of a substance from a region of high concentration to a region of low
conecentration is known as diffusion. The term diffusion means to distribute
Diffusion Pressure :
The potential ability of a substance to move from a region of high concentration
to a region of low concentration at a constant, temperature end atmospheric
pressure is called diffusion pressure. The diffusion pressure of gas is a gas
balloon is higher than the diffusion pressure of its surrounding air. So when the
balloon bursts, the gas inside the balloon spread throughout the surrounding air
due to its higher diffusion pressure.
Factors Affecting Diffusion:
Diffusion of a substance depends on temperature, atmospheric pressure.
Concentration of molecules of that substance and concentration of the medium.
Temperature: with the increase of temperature diffusion usually increases.
Concentration of the substrate: The rate of diffusion will be higher if the
concentration of molecules of the substrate is higher; if the concentration is
less, rate of diffusion will be less.
Concentration of the medium: If the concentration of the medium, like water
or air, is more, the rate of diffusion will be less; and if the concentration is less
the rate of diffusion will be high.
Atmospheric pressure: Increase of atmospheric pressure will reduce the rate
of diffusion and decrease of atmospheric pressure will increase the rate. Usually
temperature and pressure at a certain place remain same at a certain time, in
that case the concentration of the substance and the concentration of the
medium become the factors to control diffusion. If the medium and the
diffusion substance are same (as in the balloon and the surrounding air) then
diffusion will continue till the concentration of the two become same.
Diffusion through membrane :
If two solutions (mixture) of different concentrations is separated by a
membrane then the rate of diffusion between two solutions will depend on the
nature of the membrane. Usually we find three types of membrane in plants: -
* Permeable Membrane: Molecules of both solute and solvent can be
 diffused through this membrane. Cell wall, made of cellulose, is of this type.
* Selectively permeable (Semi permeable) membrane: Only the solvent
 molecules can diffuse through this membrane, not the solute molecules. Cell
 membrane is a semi permeable membrane.
* Impermeable membrane: molecules of both solute and solvent are
 impermeable (can not pass through= can not diffuse) through this membrane.
 Cell wall coated with cutine or suberine is impermeable membrane.
Importance of diffusion :
Diffusion plays a great role in plant life. CO2 - necessary compound for
photosynthesis is absorbed from air (atmosphere) by diffusion process. The
process happens in the spongy parenchyma of leaves. Oxygen - necessary for
respiration, is also intakes from air by diffusion. Movement of water and
mineral salts in the plant body takes place by diffusion. Diffusion also
responsible for loss of water from the aerial shoot of the plant.
If a raisin is kept in a cup of water for some times it will be shown that the
raisin will absorb water and become full and flashed. The outer covering of the
raisin is a semi permeable membrane. Out side this membrane there is water in
the cup, and inside the membrane there is sweet juice of raisin. The amount of
water in the cup is more (actually whole amount is water) but that inside the
raisin is very little. In this condition water from the cup enter into the
concentrated region inside through the semi permeable membrane of raisin. As
a result the raisin swollen and filled with juice. It is happened by a special
process known as Osmosis. Osimosis may be defined as -a process by which
solvent (water) diffuse from an area of high concentration through a semi
permeable membrane to a area of low concentration solution is termed as
Osmosis. The process continues till the concentration of two solutions become
same. Osmosis is a special type of diffusion.
We know solution is a mixture of solute and solvent, for example mixture of sugar and
water is a solution. Here water is the solvent and sugar is the solute and the mixture is the solution. In osmosis diffusion of solute never takes place, only solvent diffuses that is in case of plants only water diffuses.
Two types of Osmosis:
* Endosmosis: osmosis in which solvent (water) from outside enter inside the
cell, is called endosmosis. Concentration of cell sap is more than the concentration of the outer solution. Put some raisins in water Water will enter inside the fruits (raisin) and the raisin will swell up like a grape being filled with juice.
* Exosmosis: Osmosis in which water (solvent) comes out from inside the cell
is called exosmosis. Exosmosis takes place when the concentration of external
solution is more than the concentration of cell sap.
Put some grape in salt solution and observe it. Water will come out from the
grape and it will contract.
Condition of Osmosis: The process of smosis may occur under the following
* There should have two solutions. One concentrated and other dilute.
0. A semi permeable membrane should separate the two solutions of different
* The two solutions must be of same solvent.
* Temperature and atmospheric pressure should be same.
Osmotic Pressure: = OP:
In the process of osmosis pressure required from higher concentration area to
stop the movement of solvent from lower concentrated solution to
higher concentrated solution when a semi permeable membrane separates the
two solutiions, is called Osmotic Pressure (OP). More the difference of
concentration of two solutions more the OP, and less the difference of
concentration, less will be the OP. if the concentration of two solutions is same
there will have no OP and osmosis will not run.
Turgor Pressure
 Due to endosmosis water enter into the cell and the cell become swollen.
This swollen condition of the cell is called turgidity. Due to turgidity the
protoplasm exert a pressure on the cell wall; this pressure is called Turgor
An Experiment of Osmosis:
 Osmosis can be observed by putting a Potato Osmoscope.
Requirements: A large Potato, A Bowl, Water and Sugar solution.
Procedure: Take half bowl of water. Cut two ends of the potato and make a
hole at one end. Now fill up half of the hole of the potato by sugar solution and
keep the potato (Potato Osmoscope) in the bowl's water. Care should be taken
so that water level should be below the top of the potato cup.
Observation: After some times it will be seen that the level of the solution in
the potato cup is increased.
Conclusion: Outside surrounding the potato there is water and inside the hole
there was sugar solution. Cell walls of potato is permeable and the cell
membrane is semi permeable (selectively permeable). So the water from the
bowl enters through the cell wall and cell membrane to the solution in the hole
of the potato. As water enters to high concentration solution through
semipermeable membrane so other process is osmosis.

Necessity of Osmosis in Plant Life:

Necessity of osmosis in plant life is unlimited. A short description about this is
given bellow:
* Absorption of water: Plant absorbs water by root hairs in the process of
* Movement of water: Water moves inside the, plant body by cell-to-cell of
* Opening and closing of stomata: Opening and closing of stomata is
controlled by osmosis. So osmosis also controls the rate of transpiration.
* Swelling and growth of cell: For normal growth and expansion of the cell it
needs to swell. Cells become expanded by absorbing water through osmosis.
This osmosis plays an important role for the growth of the cell and maintains its
normal shape and size.
* Equal distribution of water: Water is essential for almost all the organic
activities. These activities are going on in the living cells. Osmosis is very
active to reach water to every living cell from root to leaf.
* Turgidity of the cell: Soft cells become turgid by absorbing water. Cell
absorbs water by osmosis.
* Germination of seeds: The success of germination depends on the process of
Absorption of water & minerals by the plant:
 Both water and minerals are essential for plants. Plants absorb water and
minerals from soil. The process of absorption of water and minerals is
described very briefly :
Absorption of water:
 The higher plants absorb water from soil by their root hairs. Root hair
region is termed as absorption region. Unicellular root hairs are specially
modified epidermal cell for absorption of water. Cell walls of root hairs are
made of cellulose and thus it is permeable. Beneath the cell wall, there is the
cell membrane, which is selectively permeable. Inside the root hair the cell sap
is concentrated and in the outside there is water in between soil particles. So
water from soil enter into the cell through permeable cell wall and selectively permeable cell membrane by osmosis. Afterwards this water from root hair
reaches the vessels of xylem tissue by cell-to-cell osmosis From vessels the water moves to leaves.

Absorption of minerals :
Cell division region at the top of the root is known as mineral absorbing area,
some salts also absorb by root hair. Plant cannot take solid salts. The salts
(minerals) dissolve in soil-water and converted to Cation (+) and Anion (-), root
absorb them as ions. Na+ is a Cation Cl_
 is an Anion. K+, Ca++ are Cations;
NO3, PO4, SO4 are Anions.
Difference between Absorption of Water and Minerals:
Water absorbed directly and minerals are taken as ions. Water absorbed by root
hairs and minerals are taken by cell division region at the top of the root. Water
is absorbed by osmosis and some portion of minerals is taken by diffusion.
Water with dissolved mineral salts inside a cell is called Cell Sap or Sap. The
apical region of root (Meristamatic region and root hair region) absorbs water
and mineral salts from soil. The process by which the cell sap raises from
absorption region to the leaf and other parts is called ascent of sap. This raising
of sap takes place through Vessels and Tracheids of Xylem tissue. The
root hairs are spread in the spaces between soil particles. In the spaces
there are capillary water. The concentration of cell sap in the root hairs is more than the water and dissolved mineral salts in the soil. Thus water enters
into the root hairs by osmosis. When water enters into the root hairs the concentration of its sap become less than the concentration of the sap of the adjacent cell. As a result water from root hair moves to adjacent cell by osmosis. In this way water moves from one cell to another and
ultimately reaches the vessels of xylem tissue crossing the endodermis placed at the central region of the root. The vessel cells are tubular and are placed end to end forming a continuous tube from root to leaf. Water molecules are attached one another in such a way that is called Cohesion. Water molecules are also attached with the vessel walls this attachment is
called Adhesion. Due to cohesion and adhesive force of vessels, and the pulling force (drawing force) of transpiration, the stream of water remain continuous. In this way water and dissolved mineral salts from root reach up to different organs like branches, leaves and flowers etc.
We can observe ascent of sap by a nice
experiment in the laboratory. It will require a fresh Peperomia plant. The stem of Peperomia Plant is transparent.
Partly fill up a beaker with water and make it red by mixing a small amount of
safranin. Put the plant in the coloured water in such a way so that its roots
remain submerged in coloured water. After few hours it will be seen that the
stem of Peperomia plant become red because of gradual up rise of red water
through the xylem tissue of the stem.
Transpiration is a physiological process. In this process plant loose water in the
form of water vapour through their aerial parts mainly through the leaves. So it
may be defined as "Loss of water in the form of water vapor from leaves and
other aerial parts of a plant is called ''transpiration.'' Plant absorbs water by their roots. This water conducted to all aerial parts like stem branches and leaves. So the water vapour that comes out from the plant is of water.

Types of Transpiration:

Internal water of plants usually comes out by three ways. Depending on these
ways transpiration is of three types :
1. Stomatal transpiration: There are pores with two guard cells in leaves,
young stems, in calyx and corolla of flower. These pores are called stomata
(sing: stoma). Number of stomata is found more in leaves than other parts. For
this reason in Bengali stomata are called pores of leaf. About 90% to 95 % of
transpiration of plant takes place through stomata. Transpiration that takes
place through stomata is called stomatal transpiration.
2. Cuticular Transpiration: There are Cutine coatings in young stems and
leaves. This cutine coating is called Cuticle. Usually vapour does not come out
through cuticle. But if the cuticle is thin and if the stomata are closed then a
small part of transpiration takes place through cuticle. As transpiration take
place through cuticle, it is called Cuticular transpiration.
3. Lenticular Transpiration: Due to secondary growth in stem, there develops
small pore by rupturing the epidermal layer at places. These pores are called
Lenticels. Some portion of transpiration takes place through these lenticels. As
transpiration takes place through lenticels, it is called Lenticular
 Stomata are present in leaves, young
stems, calyx and corolla of flower etc. a
small pore encircled by two guard cells is
called a Stoma. Cell walls of guard cells
adjacent to stomata are thick but the walls
on opposite side are thin. There present a
large nucleus and many chloroplasts. The
swelling and looseness of the guard cells
regulate the opening and closing of stomata.
When the guard cells swell up the stomata
opens and when it looses the stomata closes.
The ventral surface of dorsiventral leave
bears more stomata.

Process of Stomatal Tranpiration :

 Stomata are present on the leaf, usually on the ventral surface. At the upper
epidermis of dorsiventral leaves there are palisade parenchyma and at the lower
epidermis there are spongy parenchyma. In spongy parenchyma there are many
air spaces. Stomata are present near the air space and placed on the lower
epidermis. Usually vascular tissues i.e. xylem and phloem are present at the
connecting zones of Palisade and Spongy parenchyma. Root hairs absorb water
from soil and reach to the leaf through stem by vessels and Tracheids of xylem
tissue. On reaching leaf the water come out of the xylem tissue and spread
throughout all the cells of the leaf. The outer walls of the spongy parenchyma
always remain wet to absorb carbon dioxide (CO2), necessary for
photosynthesis. The air inside the air space of spongy parenchyma come in
contact with water of spongy parenchyma and absorb water vapour and store in
the air spaces behind the stomata. Later on the vapour come out to the
atmosphere through the open stomata. Air, O2 and CO2 also moves through
open stomata. In most plants stomata remain open during daytime and closed in
night. In succulent plants stomata remain open at night and closed in daytime.
As a result of photosynthesis the carbohydrates inside the guard cells converted to soluble glucose and the guard cells absorb water from adjacent cells and
become turgid and the stomata opens. During night. the soluble glucose
converted to insoluble carbohydrate, the guard cell loose water to the adjacent
cells by exosmosis and become flaccid. As a result the stomata closes. For this reason transpiration takes place in daytime.

Factors affecting Transpiration :

 Affecting factors of transpiration are of two types; External and Internal.
External Factors:
Light: Photosynthesis takes place in presence of light and as a result stomata
opens. So light is the main factor, which influence transpiration
Temperature: With the increase of temperature water vapourises rapidly and
increased the humidity in the atmosphere. So temperature controls the rate of
Relative Humidity: If relative humidity is less the water vapour holding
capacity of the air decreases, therefore rate or transpiration decreases.
* Air Current: The air current disposes the saturated air (as a result of
transpiration), away from the plant and thus increases the rate of
* Atmospheric pressure: Under low pressure water vapourise at low
temperature. So if pressure decreases the rate of transpiration increases and if
pressure increases the rate of transpiration will decrease.
* Soil water: If availability of soil water is less the rate of transpiration will
Internal Factors:
* Root-Leaf Ratio: If the number and total surface area of leaves become
much less in comparison with root region (absorption region) the rate of
transpiration will reduce.
* Leaf area: The greater the leaf area, greater will be the rate of transpiration,
and lesser the leaf area the lesser the rate of transpiration.
* Internal surface of leaf: Thin cuticle, thin cell walls, exposed stomata, and
well-developed spongy parenchyma favour transpiration. On the other hand leaves
those possesses thick cuticle, thick cell walls, well-developed palisade parenchyma, Sunken stomata etc. will reducd the rate of transpirations.

Importance of Transpiration :

Transpiration is important to plants. The importance of transpiration is
discussed briefly: -
* Ascent of water and cell sap: Transpiration creates a pull on the water
column in the xylem vessel (which is called transpiration pull); as a result the
water absorbed by the root and cell sap goes upwards.
* Conduction of water and minerals to leaves: water and minerals conducted
to the leaves by transpiration pull. So water, necessary for photosynthesis and
Mg, necessary for production of chlorophyll, conducted to leaves by
transpiration. So it can be said that transpiration plays an indirect role on
manufacturing food by photosynthesis.
* Maintaining proper temperature and release of energy in leaf: Leaves are
taking energy from the sun every moment. Only 1 % of this energy is utilized
in different reactions. The rest heat energy released by transpiration. If the
temperature in leaf does not remain in optimum condition, all the organic
activities would have been seized. So this is also a good aspect of
* Cell division and physical growth: Transpiration indirectly maintains
osmosis and thus keeps all the cells rigid. As a result it enhance cell division
and development of the organ.
* Resistance to Fungal infection: Due to transpiration there deposits certain
hygroscopic salts on the leaf surface, which resists fungal infection.
* Absorption of C02 for photosynthesis: Spongy mesophyll cells of leaves
receive C02 from air present in the air spaces, by diffusion. For this the outer
layer of the spongy mesophyll should always be wet. The air inside the air
spaces absorbs water from here and transpires through stomata.
Excess of transpiration may cause shortage of water in plant. So excess of
transpiration is harmful to plants.

Photosynthesis and Respiration

Photosynthesis is a biochemical process. In this process green parts (specially 
leaves) of plants manufacture carbohydrate food by CO2 and water with the 
help of energy obtained from sunlight. Here light energy is converted to 
chemical energy. Plants absorb CO2 and release O2 as bi-product in the process 
of photosynthesis. The components required for this process are: - (i) Light, (ii) 
Chlorophyll, (iii) Water and, (iv) Carbon dioxide (CO2).
Chlorophyll pigments are present in the chloroplasts of plant cells. Water 
absorbed by roots reaches to the mesophyll cells in the leaves. The process of 
photosynthesis is shown by the following reaction:
6CO2 + + 6H >12H2O C6H12O6 6O2 + 2O

''Photosynthesis is such a biochemical reaction by which chloroplast, in the
plant cell, uses the energy, received from the photon of sunlight, manufactures
carbohydrate food by CO2 of the atmosphere and water and other organic
substances in the CO2 cell.
Process of Photosynthesis:
Photosynthesis is a complex and lengthy process. In 1905 A.D. Blackman
divides the process into two phases namely: 1. Light Phase and 2. Dark Phase.
Both the phases are described here: -
1. Light Phage: Light is essential for this phage. In this process water breaks
down to O2, e- (electron) and Hydrgen (proton = H+) by the help of energy
obtained from sunlight. Such break down is called as Photolysis or Photolysis
of water. Large amount of light energy is assimilated in chemical compound
named ATP (Adenocine Tri Phosphate) and NADPH2 (Nicotinamide Adenocine Dinucleotide Hydrogen Phosphate) as chemical energy. ATP and NADPH2 are called assimilatory Power. This process of formation of ATP by using light energy is called Photophosphorilation.
Photophosphorilation may be of two types - Cyclic and Non-cyclic. Two pigment systems (Pigment system-1 and Pigment system-2) control the light phase of photosynthesis.
2. Dark Phase: Light is not required in this process. ATP a NADPH2,
produced in light phase, are utilised in this process to manufacture
carbohydrates. The process of manufacture of carbohydrate is as follows: -
CO2, from atmosphere enters inside the leaf thus in the cell, through stomata.
CO2 combined with Ribulose 1,5 Diphosphate, present in the ccll produces an
unstable compound named Keto acid. This Keto acid later on break down into
two molecules named a 3 -Carbon compound named 3-Phosphoglyceric acid
(first stable compound). This Phosphoglyceric acid then converted to 3-
Phosphoglyceraldehyde and Dihydroxy Acetone Phosphate utilising ATP and
NADPH2, produced earlier in light phase. By several successive reactions these
3-Phosphoglyceric acid and Dihydroxi Aceton Phosphate ultimately produce
Carbohydrate (Sucrose-Sugar) in one side and Ribulose 1,5, Diphosphate on the
other side.
Prof. Calvin and Bassham of California University discovered this cylce of
producing carbohydrate by utilising CO2 of the atmosphere. Thus this cycle is
named as Calvin and Bassham cycle. First stable compound of this cycle 3-
Carbon compound thus these types of plants are called C3 plants.

Another cycle of producing carbohydrate has discovered. It is called Hatch and
Slack Pathway. In this process the first stable compound is a 4- Carbon
compound, named oxalo-acetic acid. These types of plants are called C4 plants.
Sugarcane, Maize, Cyprus grass etc. are examples of C4 plants. You will know
more detailed in higher classes.
Organ of Photosynthesis:
Photosynthesis occurs in green parts in leaves. Various types of tissues are
present in the leaf, such as upper epidermis, lower epidermis, vascular tissues and mesophyll tissue. Mesophyll tissue again are of two types-compactly,
arranged elongated cells at the upper epidermis are the palisade parenchyma
tissue and loosely arranged cells at the lower epidermis is the spongy par￾enchyma tissue.
Usually photosynthesis occurs in palisade parenchyma cells of the leaf.
Palisade parenchyma contains innumerous chloroplasts. The process of
photosynthesis completed in these chloroplasts.

Factors Affecting Photosynthesis:
Factors involved in photosynthesis are of two types - External and Internal

External Factors :
0. Sunlight: Sunlight is essential for photosynthesis. The high-energy
compound - ATP and NADPH2 are formed utilising the Sunlight which help
carbon reduction in dark phage. High intensity of light reduces the rate of
0. Carbon dioxide: Manufacture of carbohydrate is not possible without
carbon dioxide. Thus if the amount of CO2 reduces in air (in air there is 0.03%
of CO) the rate of photosynthesis reduces.
0. Water: Water makes the guard cells turgid and the stomata opens. on the
other hand water is utilised as a raw material in dark phase of the process.
0. Temperature: Photosynthesis seized near 0¡C and above 45¡ of temperature.
Optimum temperature for photosynthesis is 22¡C- 35¡C. Below 22¡C and above
35¡C rate of photosynthesis decreases.
@.Oxygen: If density of oxygen increases in atmosphere the rat of
photosynthesis will decrease.
Importance of Photosynthesis:
The importance of photosynthesis is unlimited. A short description is given
regarding this: -
@. Manufacture of plant food: To live food is essential. Green plants
manufacture food by the process of photosynthesis. If the green plant would not be able to manufacture food, then no plant could live in this world.
@.Supply of food for Animal Kingdom: Only green plants manufactures food
by the process of photosynthesis. No animal, even man can manufacture their
food. Rice, Bread, Fruits Fish Meat, Milk etc. whichever we eat all we get
directly or indirectly from plants. So the Animal Kingdom is completely
dependent on green plants, and the green plant manufacture these food by the
process photosynthesis. So it can be said, the process of photosynthesis
prepares of all the foods for both plants and animals.
@.Source of Energy: Much energy is exhausted in our works and movements.
Source of this energy is food. Green plants manufacture food by the process of
photosynthesis. Energy comes to food from the Sun light energy trapped as
chemical energy in foods manufacture by photosynthesis. Food breaks down in
every living cell producing energy. Source of our all energy is food and source
of energy of food is the sun. So Sun is the source of all energy. Energy that
needs in metabolic activities in plants and animals come from food too.
@. Ecological Balance: In maintaining Ecological Balance particularly
balancing the ratio of O2 and CO2, photosynthesis plays a special role. The
amount of oxygen gas in the airs 20.946% and that of carbon dioxide is
0.033%. This is the normal amount of oxygen and carbon dioxide gas in the
atmosphere. For normal growth and living of plants and animals in this world,
amount of these gases should be within normal range. On variation of the
normal ratio the atmosphere will be imbalanced. We know respiration goes on
in every living being (plants and animals). In respiration O2 gas is taken in and
CO2 gas is driven out. Plants and animals both are taking O2 and releasing CO2
during respiration. If this system goes on successively there would have
shortage of O2 and excess of CO2. But as green plants absorb CO2 and release
O2 during Photosynthesis, so the ratio of O2 and CO2 in the atmosphere is still
all right. Due to excessive deforestation the ratio of these two gases in the
atmosphere is being destroyed. Therefore, we should have to plant trees
more and more.
@. Contribution of Photosynthesis in Human Civilization: Men survive only
because photosynthesis is present in green plants. But apart from the survival,
the contribution of photosynthesis is unlimited in the arena of human
civilisation. Coal, Petrol, Rayon, Cellophane, Paper, Rubber and Medicines etc.
all are the gift of plant's.

Evolution of O2 during photosynthesis :
In non-cyclic stage of photosynthesis in the light phage, O2 evolved from splitted water. If O2 was not relesed in the atmospher in the photosynthesis process, then there would be a great scarcity of O2 in the atmosphere. As a result the entire living creature would have perished because
our respiratory system stops functioning for want of O2.
Production of Carbohydrate during Photosynthesis:
 Carbohydrate is produced during photosynthesis. Plant reserved the excess
carbohydrate after their requirements. For example: Paddy, Wheat, Maize,
Barley, Potato, Sweet Potato, Sugarcane etc. We took these as food. If green
plants do not manufacture carbohydrate in photosynthesis, then for want of
food all of the members of Animal Kingdom including human beings would
have been destroyed.
What would happen if there were no Sunlight
If there were no Sunlight on the Earth there will have no Photosynthesis.
Without photosynthesis there would be no movement of energy. The earth
would become motionless. Without Sunlight no living being could exist.
Every living being (Plants and Animals) have organic activities. Any
work/function outside or inside the body there need energy. The main source of
this energy is the Sun. Green plants trapped light energy in carbohydrates (and
others) food. This food successively being oxidised release energy. Using these
energy living world performed all functions and reactions. O2 is needed to
oxidize these organic compounds. As a result of oxidation CO2 is formed inside
the living body. Therefore it is revealed that organic compounds oxidize by the
reaction with O2, which is absorbed from the atmosphere. As a result of
oxidation energy and CO2 are releases. Living bodies utilize the energy but
release CO2 to the atmosphere. The process ran in both plant and animal cells.
The process, by which energy and CO2 are produce by oxidation of food
materials combining with O2, is called Respiration.
 In respiration carbohydrate, protein, fat, organic acid etc. are oxidize and
produce energy. The substances which take part in respiration are known as
Respiratory substrate.
Respiration occurs in cytoplasm and mitochondria of a living cell. There is
no definite time for respiration. This process runs 24 hours throughout the day
and night. Though respiration occur in all the cells yet the rate of respiration is
more in developing region like flower and leaf buds, germinating seeds, apical
region of root and stem. The process of respiration is explained by the
following reaction.
C6H12O6  + 6O2 >6CO2 +6H2O +38ATP

Types of respiration

Respiration is of two types . (1) Aerobic Respiration and (2) Anaerobic
Respiration. The respiration where O2 is essential called aerobic respiration The
respiration that does not require O2 is called anaerobic respiration. Aerobic
respiration occurs in all higher plants. Only few lower plants (some Bacterial
and Fungi) have anaerobic respiration. The processes are discussed below:-
1. Aerobic Respiration: Aerobic Respiration is the normal respiration in plant
and animals. In this process Carbohydrates break down and produce CO2 water
and energy. Usually aerobic respiration is completed in four steps. the steps are
as follows: -
Step - 1: Glycolysis: In this step one molecule of glucose, a 6-Carbon
compound, after 9 successive reactions produces two molecules of Pyruvic,
Acid, a 3- Carbon compound. In this step 4 molecules of ATP (2 molecules
utilised) and 2 molecules of NADPH2 are produced.
Step - 2: Formation of Acetyle CO-A: Each molecule of Pyruvic Acid
produce during glycolysis after four successive reactions produces, one
molecule of Acetyle Co-A, a 2-Carbon compound, one molecule of CO2 and
one molecule of NADH2. [From 2 molecules of pyruvic acid there produces 2
molecules of Acetyle CO-A, 2 molecules of CO2 and 2 molecules of NADH2]
Step - 3: Krebs Cycle: Every molecule of Acetyle Co-A enter Krebs Cycle and
after 10 successive reactions produces 2 molecules of CO2, 3 molecules of
FADH2, and I molecule of GTP (=ATP). From two molecules of Acetyle CO-A
there produces 4 molecules of CO2, 6 molecules of NADH2, 2 molecules of
FADH2, and 2 molecules of GTP (=ATP).
Step - 4: Electron Transport System: NADH2 and FADH2 produced in the
first step, being oxidized produce ATP and water.
 In aerobic respiration the complete oxidation of one molecule glucose totally
produces 6 molecules of water and 38 ATP (686 K. Cal. Energy). First two
steps occur in cytoplasm and next two steps occur in mitochondria. Every
reaction of respiration is completed with the help of special types of Enzymes.
2. Anaerobic Respiration: Anaerobic Respiration does not require any O2. It
occurs in two steps, they are: -
Step - 1: Glycolysis: In this step from one molecule of glucose there produces
2 molecules of Pyruvic Acid, 4 molecules of ATP (2 molecules utilised) and 2
molecules of NADH2.
 Step - 2: In this step from each molecule of Pyruvic Acid there produces one
molecule of Ethanol (Alcohol) and one molecule of CO2. Or from each
molecule of Pyruvic Acid there produces only one molecule of Lactic Acid.

Importance of Aerobic Respiration:

1. Energy produced in this process is utilised by living beings to perform all
sorts of reaction and other functions.
2. CO2, released in this process is utilised directly or indirectly in
photosynthesis and produces carbohydrate food.
3. This process helps plants in absorption of water, which indirectly keeps
running growth and other organic processes.
4. Organic acid that produces in respiration is necessary for other organic
activities, Respiratory energy also heps cell divinion.
Importance of Anaerobic respiration :
1. Some Bacteria cannot live in presence of oxygen. Among them the only
process of producing energy is anaerobic respiration.
2. In this process Ethyl alcohol is produced, industries, which is used in
different industries.
3. The process is utilised in Lactic Acid fermentation.
Factors Affecting Respiration:
Affecting Factors may either be external or internal: -
(a) External Factors:
 1. Temperature: Below 20¡C and above 45¡C the rate of respiration
reduces. The optimum temperature for respiration is 20¡C - 45¡C.
2. Oxygen: If the amount of oxygen is reduced the rate of respiration will
3. Water: Optimum supply of water maintains the rate of respiration normal.
Rate of respiration reduces for scarcity of water.
4. Light: The stomata opens in light, so rate of respiration comparatively high
in day time.
5. Carbon dioxide: With the increase of CO2 in air, rate of respiration
decreases slightly.
(b) Internal Factors:
1. Food materials: During respiration food materials break to release water and
CO2. So the quality and quantity of food materials in the cell regulates the rate
of respiration.
2. Age of cell: Rate of respiration is maximum in young cells especially in
meristamatic cells (as there is much protoplasm).
3. Enzymes: Different reactions of respiration need different kinds of enzymes.
The process completely depends on their presence.
4. Inorganic salts: Rate of respiration increases if there is more inorganic salts in the cell.

Growth and Development of Plant

 We know seeds give rise to seedlings, from seedlings there develops a large 
plant. Plant produces flowers and fruits. These are all the results of growth and 
development of the plant. Embryo is present in the seed. Growth of embryo is 
the germination. So without the growth of embryo germination of seed will not 
take place. Without germination seedlings will not produce. Without growth of 
seedlings a large plant will not develop. Without development of a large tree we 
shall not get flowers, fruits, seeds, wood, crops, or the forest and nothing of this 
sorts. So growth and development of plant is essential for them so that they can 
again produce seed to maintain their growing by reproduction. Again the 
growth and development of plant is essential for all animals including human 
beings, because with growth and development of plant we will not get anything 
like - food, medicine, cloths, house building materials and a habitable 
environment. Growth is a fundamental characteristic of all living organisms. 
Growth means a permanent increase in shape, size weight and in bulk of a plant 
or its organ.
Region of Growth: The ideal growing region of plants are its root and shoot 
apex. In root or shoot apex there are apical meristems. This region is also 
known as primary meristamatic region or primary growth region.
Growth in length: The apical Meristamatic tissue by successive cell division 
creates new cells. The new cells later on increase in size. In this way by the 
formation of new cells and their increase in size, the apical parts successively 
increase in length. Formation of young leaf and bud is also the function of these 
 At the top of the root there present a cover like structure, which is called 
root cap. The cell division region is behind the root cap region. The cell of this 
region divide rapidly and forms many new cells. Behind the cell division region 
of elongation. Cells of this region increase in size and volume especially in 
length, as a result length of root increase. Behind the region of elongation lies 
the permanent region. Cells of this region are mature and are different is shape and size.
At the top of stem there is a bud called apical bud or shoot apex. Cells of
apical bud are meristamatic cells. Therefore this is the cell division region,
because cells of this region divide rapidly and increase in number. Behind this
region is the region of elongation, as cells of this region rapidly increase in
length. Behind this region is the permanent region, cells of this region is mature
and are different in shape and size.
Growth in breath:
The breath of a one-year-old mango tree increases after one year. In this way
with the increase in age its breath also increase. Breath of a mature root and
stem is increased by secondary growth (lateral growth). Usually secondary
growth occurs in gymnosperms and dicot plants. So all the broader plants of the
world either gymnosperm or dicot plant. Examples of gymnosperms are Cycas
and Pinus. Mangos, Jamboline, Litchi, Shaal, Garjan, Sundary, Teak, Gamari,
Karai etc. are examples of dicot plants.
How increase in breath take place?
Increase in breath takes place in root and stem by their secondary growth in
intrastellar or extrastelar region. First in the intrastelar region of vascular
bundles there develops a cambium ring. This cambium ring produces secondary
xylem tissue towards the center and secondary phloem tissue towards the
periphery. As many secondary xylem and secondary phloem is formed from the
cambium ring so much increase the breath. Secondary growth also takes place
in extrastelar region (out side the pericycle).
Apical Dominance:
We came to know that apical region of stem is the ideal region of growth.
During apical growth there develops young leaves and sometimes axillary bud.
Always the rate of development of axillary bud is lesser than that of apical bud.
It is observed that if the apical bud is removed the growth of axialiary bud
expedite. For production and better growth of buds at the lower region in many
cases the apical bud is removed. In Tea plant if apical bud is removed many
axillary buds produces. In this way the tree characterstics of tea plants changes
to shrubby nature, and production of bud therefore, the production of tea
increases. By the influence of apical bud usually the production of axillary bud
seized, or if produce always the growth of axillary bud is dominated by the growth of apical bud. The dominating tendency of
apical region of stem is called apical dominance.
 The growth regulatory substance named Auxin mostly present at the shoot
apex, for which growth rate is higher at this region. When apical bud is
removed Auxin flows downwardly, thus produces axillary bud or accelerate
their growth.
 You can demonstrate the apical dominance very easily. Cut the apical bud of
a potted chili or ornamental plant. Then it will be observed that the axillary
buds developed to branches. Without cutting the apical bud not much branching
will occur.
Growth regulatory Substances: Growth Regulators
 There are some biochemical substances, small amount of which regulate the
growth of plants. These substances are produced in the plant bodies. As they
regulate the plant growth so they are called growth regulators. Earlier they were
called Hormone. As they are produced in plants they are now named
phytohormone. Phyto- means plant.
Growth regulators are divided mainly into two types: -
(1) Growth promoter and (2) Growth inhibitor.
Growth promoters are Auxin, Gibberellin, Cytokinin and Flowering hormone.
And Growth inhibitors are Dormin or absecic Acid.
Influence of Auxin :
 (i) Auxin increases the length of the cell, (ii) Produce apical dormancy (iii)
Initiates the formation of root, (iv) Help to produce seedless fruits.
Uses of Auxin: (1) Used for germination of seeds (2) As Auxin Initiate root
formation so it is used in grafting of mango, litchi, Psidium etc. plants. (3) It
used in case of early fruit fall. (4) Auxin also used in production of seedless
fruits, in floriculture, tissue culture and in management of weeds.
Influence of Gibberellin: (1) Gibberellin increases the length of stem. Breaks
the dormancy of seeds and buds (3) Help to bloom the flower.
Influence of Cytokinin: Cytokinin accelerates cell division.
Uses of Cytokinin: (1) Used for production of seedless fruits (2) In tissue
Abscisic Acid: Leaves and buds droped by its influence. inhibit growth of bud.


 When one look at the Banyan tree it will be seen that the branches and
sub-branches are growing towards the light, but the Prop roots originated from
the branches growing towards the earth. If a gram seed is kept on wet soil it
will germinate within a few days. It will be seen that its radicle gradually
develop and goes into the soil and plumule goes upwards against the soil. The
movements of plant organ towards certain direction like light; earth or water is
called tropism. The tropism maybe towards stimulant like light, earth or water
or may against to those. Movement of plant organ towards the stimulant is
called positive tropism. On the other hand movement against the stimulant is
called negative tropism. Tropic movement towards light, earth, water and any
chemical is described briefly:
(a) Phototropism : The stem and branches of plants always expanded towards light but root and its branches expands against the light. Movement of stem towards light is called positive phototropism and movement of root against light is called negative phototropism.
A seedling of gram or chili may demonstrate phototropism. Take a glass
bottle with cork. Fill up the bottle with water. Insert the plant into the bottle
through the cork so that the stem remains outside the cork and the roots remain
inside being immersed in water. Place the bottle at a place where it gets light
from one side. After one day it will be seen that the stem bends towards light
but the tip of the root bends against light. Phototropism may also be
demonstrated by putting a potted plant on a perforated wooden box. Leaves of
plant manufacture food by using energy from sunlight and both plants and
animals world depends on this food.
(b) Geotropism : Movement of root is towards the earth and movement of stem is against the earth. A movement towards the earth is negative geotropism.
Put a germinating gram seed on soil in a pot and keep the pot in such a closed room so that light cannot come from any direction. After one day it will be seen that the root of germinating gram seed bended and enter into the soil and the stem bended
against the soil.
Majority of food for plants remain in earth. Root absorbs these foods. So the
movement of root towards earth is quite significant.
(c) Hydrotropism: The movement of root is towards water and expansion of
stem is against water. The movement of root towards water is positive
hydrotropism and expansion of stem against water is negative hydrotropism.
(d) Chemotropism: Earth contains more organic manure thus the root and its
branches expanded towards that direction. Movement towards chemical
substances is Chemotropism.


 We know all the fruit yielding plants like Aam, Jaam, and Boroi etc. plants
are planted at almost every home in Bangladesh. It will be seen if you observe
carefully that all the plants does not flowers in the same time. Mango tree
flowers in winter and its fruits ripe in summer. But Boroi flowers in autumn
and fruit ripe in winter. Let we have another example. Bean is a winter
vegetable. Cultivated almost at every home in Bangladesh. Its seeds are sown in
rainy season and the plant flowers in winter. At the end of winter it's flowering
stops and in the next winter after the year it flowers again.
We know the length of daytime is short (long night period) is winter in
Bangladesh and in summer and rainy season length of day is longer (Night time
shorter) A short day time is required to product flower in bean plants. So it
flowers in winter. As the daytime is longer in summer so bean plants does not
bloom in summer. Therefore it is observed that in Bean plants vegetative
growth takes place in longer day period and in shorter day period it flowers i.e
starts yielding. Thus it is understand that in growth and development of plant
(Bean is only one example), there is influence of light.
 The influence of length of daytime on flowering of plants is called
Photoperiodism. In 1920 Garner and Allard observed the affect of
photoperiods in Maryland Mammoth a variety of tobacco plant. According to
effect of length of day and night (photoperiods) upon the flowering time Garner
and Allard classified the flowering plants into three classes:
1. Short day Plant: These plants flowers when day length is short. Dahlia,
Tobacco, Chrysanthemum are short day plants. They may also call long-night
plants. Two species of jute are short - day plants. In 10 - 12 hours photoperiods
plants flower in 30 days. More than 12 hours of photoperiods delayed
2. Long day Plant: These plants give flower, when day-length is longer.
Sponge guard (Luffa) Lettuce and Beta palonga (Palong) is long day plants.
They may also call short night plants.
3. Day-Neutral Plants: Flowering time of these plants does not depend on the
duration of daylight. They flower when necessary vegetative growth is
completed. Day-neutral plant can be grown in both winter and summer. They
flower in both the seasons. Sunflower is a plant of this type. Aus paddy usually
a day-neutral plant.
Leaves receive the stimulation of photoperiods.

Importance of photoperiodism:

If all the plants were short-day plant or all long - day plant, then we would get
only one crop in a year. There would be problem in preservation of crops, again
in a certain time in the year there will be scarcity of various fruits. As there are
short day plants, long-day plants and day-neutral plants in nature, thus we get
some one or other crops, vegetables or fruits throughout the year.
Like light, temperature and cold also have effects on plant growth and
flowering. It was seen, that in many germinating seeds when treated with cold
cause early flowering. Application of cold treatment to germinating seeds to
effect early flowering is called vernalization.
 In 1920 AD Russian scientist T. D Lysenko invented this method of
acceleration the ability to flower by cold treatment and named as Jarovization.
Later the term Jarovization was renamed in Latin as vernalization.
 Vernalization is induced on germinating seeds or young seedlings. They are
kept in low temperature (usually 13¡ - 15¡C) for some days thus cold treatment
completed. The apical meristamatic cells of the plumule or seedling receive
stimulation of vernalization.
Importance of Vernalization: In Russia Biannic wheat is converted to annual
one by vernalization treatment. In our country large amount of paddy is being
destroyed by flood. If the flowering time of paddy be accelerated by 5 - 10
minutes then it will be possible to protect paddy of Crores of Taka.


Flowers are the most beautiful and charming creation of thenature. we all love
flowers; trees full of red Shimul, Palash, Madar, or Krishnachura, field full of
yellow mustard, beels and Jheels full of violet Kalmilata, hedges full of blue
Aparajita, gardens full of roses, China-Roses, Gandhoraj, Kamini, Shephali,
Bokul etc. are all dear to us.
Are all these flowers around us are alike? No, if you observe carefully, it will
be seen that among them some are red, some are yellow, some are blue or some
are white. Again some one of them has strong smell (Hasnahena), some one has
sweet smell (Rajanigandha, Chapa, Gandharaj). Again some has no smell at all
(Jaba). As There are diversity in colour and smell among them they also differ
in structure.

Different Parts Of A Flower:

 A flower has several parts. Different parts have several functions. Taking a
flower in hand we can observe its different parts. Let us see what parts are there
in a'datura [Dhutura] flower. Different parts of Datura flower from out side are:
1. There is a green slender stalk (Pedicel) at the base of the flower the pedicel is
swollen. On this swollen part other whorls of the flower are arranged. This part
is called thalamus. Thalamus is present in all flowers but all flower not have
pedicel. Flower with pedicel is called pedicelate (e.g. Datura, China-rose) and
flower without pedicel is called sessile [e.g. Colocasia (Kachu), Polianthus
Function: To hold other parts of the flower and to attach a sessile flower with
2. Out side the flower there is a green tubelike structure at the base. Top of this
tube is splitted into five,segments. From this it is understood that these five
segments are combined together to form the tube. This outer green whorl of the
flower is called the Calyx. Each of the five parts that comprises the calyx is
called a sepal. Sepals may be united together (as in Datura) or may be separated
(as in Brassica). In China-rose (Jaba) outside the calyx there is another whorl
like the calyx called Epicalyx.
Function: To protect other internal parts in the bud from adverse external
3. Next to, petals combined together, to make the corolla. Usually corolla is the
show part of the flower. Petals may be united (as in Datura). or may separate
from each other [as in Brassica (Sharisha)].
Function: To attract insects and to protect internal parts of the flower.
4. Inside the corolla there is five rod like organ attached at the base. Each of
these organs is called Stamen. Each stamen is divided into two parts the slender
part is the filament and swollen part at the top is the anther. Inside anther there
lies pollen grains. The total stamens of a flower collectively form a whorl,
which is called the Androecium.
Function: Main function of the Androecium is to produce pollen grains.
5. The central part of the flower is the Carpel. Swollen part at the base of
carpel is the Ovary, long slender part at the middle is the Style and lobbed
part at the top is the Stigma. Inside the ovary there are small round parts
call Ovules. Ovules later develop to seeds. In Datura flower there are two
carpels united together. The whorl of a flower that is formed by one or
more carpel called the Gynoecium. The ovary of a flower develops
to a fruit. In china-rose five carpels are united to forms the gynoecium.
Function: Functions of the gynoecium is to produce fruits and seeds.
From the above discussion it is understood that a Datura flower has five parts
namely: l.thalamus, 2. calyx, 3. corolla,4. androecium or male whorl and (5.
gynoecium or female whorl. Among these thalamus is an axis on which other
four whorls are arranged.
Datura flower has five parts. But some flowers may have thee or four parts. The
flower, which has five parts, is called an ideal flower.

Function of flower: 

The main function of a flower is to produce fruits and
seeds for reproduction of the plant. Androecium and gynoecium are directly
involved in seed production, thus they are called essential whorls. Calyx and
corolla are called accessory whorls.
Different kinds of Flower:
If we examine various flowers surrounding us it will be seen that all the flowers
are not alike. Like colour and smell they have many variations in their structure
too. A description about this is given below:
(A) According to completeness:
1. Complete Flower: A flower that possesses all the five whorls is said to be a
complete flower. Datura, China-rose etc. are complete flowers.
2. Incomplete flowre : A flower is said to be an incomplete flower that does
not have all the five whorls. Lau, Kumra, shasha, jhinga etc. are incomplete
flowers. In these flowers either male or female whorl is absent.
(B) According to sex argan :
1. Bisexual flower: Flowers, which bear both male and female whorl
(Androecium and Gynoecium), are called Bisexual flowers. Datura China-rose,
Brassica (Sharisha) etc. are bisexual flowers.
2. Unisexual flower: Flowers, which have either male or female whorl, are
called unisexual flowers. Flower that bear only female whorl is called female
flower and flower that bears only male whorl is called male flower. In plants
like lau (Bottle Gourd), Kumra (Gourd), Jhinga (Luffa) etc. male and female
flowers are grown separately in the same plant.
(C) According to Regularity of Organ:
1. Regular Flower: Flowers in which the members of each whorl are similar in
shape and size called regular flower. e.g. Datura, Brassica, Hibiscus (China￾rose) etc.
3. Irregular flower: A flower having member of each whorl (especially calyx
and corolla) dissimilar in size and shape is called irregular flower. pisum
(Motor), Clitoria (Aparajita), Beans (Shim), etc. are irregular flowers.
(D) According to Symmetry:
1. Symmetric Flower: A flower, which may be cut into two equal halves by
one or more vertical plane passing through the center of the flower is called a
smymetric flower. Symmetrical flowers are of two types: -
(i) Zygomorphic: Flowers, which may be cut into two equal halves by only
one vertical plane passing through the center of the flower is called
Zygomorphic flower e.g. pisum, Beans, Clitoria etc.

(ii) Actinomorphic : Flowers, whcih may be cut into two equal halves by more
than one vertical plane passing through the center of the flower, is called
actinomophic flower. e.g Datura, Hibiscus, Brassica etc.
2. Asymmetric Flower: Flowers, which cannot be cut into two equal halves by
any vertical planes is called asymmetric `flower. Canna (Kalabati) flower is an
asymmetric flower.
(E) According to Presence of Bracts:
1. Bracteate Flower: Flowers, which have bract or bracts at its base is called
bracteate flower, e.g. Crotalaria (Atoshi).
2. Ebracteate Flower: Flowers, which have no bract at the base is called
ebracteate flower. In Brassica flower there is no bract.
A bract is a small leaf or leaf like organ in the axils of which arise flowers.
(F) According to the position of Ovary:
1. Hypogynous flower: A flower in which Calyx, Corolla and Androecium lies
beneath the ovary is called hypogynous flower. Flowers of Datura, Hibiscus,
Brassica, Solanum, and Chili etc. are hypogynous flowers.
2. Epigynous flower: A flower in which Calyx, Corolla, and Androecium are
placed above the ovary is called epigynous flower. Flowers of lau (Lagenaria),
Kumra (Cucurbita), Jhinga (Luffa) etc are examples of epigynous flowers.
3. Perigynous flower: A flower in which Calyx, Corolla and Androecium are
placed around the ovary is called perigynous flower. The thalamus of perigynous flower is cup shaped and the ovary is placed in the concave center of the thalamus, e.g. Rose. ovary is placed in the concave center of the thalamus, e.g. Rose.

Pollination, Fertilization,
Dispersal of Fruits and seeds

Every fertile stamen contains an anther. Inside the anther develops the pollen
grains. At one time the anther bursts and pollen grains are carried and attached
to the stigma (of same flower, or flower of the same plant or flower of the same
species of a different plant), by insect, air or any other agent. Process by which
pollen grains are transferred from anther to the stigma is called pollination.
Pollination of two types: 1. self-pollination and 2. cross-pollination.
1. Self-pollination: When pollen grains from the anther are transferred to the
stigma of the same flower or a flower of the same plant is called self￾pollination. In self-pollination the genotype (factors those control the characteristics of living beings) of two flowers remains alike. Self-pollination occurs in a small numbers of plants in nature. Self-pollination takes place in flower like Bean, Tomato, Commelina etc
2. Cross - Pollination: When pollen grains are transferred from the anther to
the stigma of flowers of same species of a separate plant is called cross￾pollination. In cross-pollination the genotypes of two plants have some
variation, in nature, cross-pollination occurs in most of the plants. Examples of
cross - pollinated plants are Paddy, Wheat, Maize, Mustard, Silk Cotton
(Shimul), Madar, Mango etc.
Significance of self-pollination: As this type of pollination takes place
between two flowers having similar genotype, the genotype of the produced
seeds remains unchanged. So the plants that produce from these seeds have got
the character just like the mother plant. In this way the hereditary character
remains similar i.e. it maintains the purity of species. This is most significant in
Merits of Self -pollination:
1. Pollination is ascertained. 2. Very few pollen grains are lost.
3. Maintains the purity of species. 4. Less dependent on external agent.
Demerits of self-pollination:
1. No new variety is produced as there is no combinations of new characters.
2. Produce weaker progeny with less vitality.
3. New progeny are borne with less adaptability.
4. The species may extinct in future.
Significance of Cross -pollination :
Pollination occurs between two flowers having difference in genotype. Thus the
seed that is produced from this have variation in genotype. Therefore the new
plant grown from this seed is not identical with the mother plant. New variation
may produce even a new species. Due to combinations of the most plants their
adaptability increase so natural calamity (disaster) cannt extinct them easily
Merits of cross pollination:
1. Combination of new character occurs.
2. New varieties may be originated
3. Seeds become more viable and more tolerant.
4. Adaptability of new plants increases.
Demerits of Cross - Pollination:
l. Depends on external agent.
2. Pollination is uncertain.
3. There is loss of a large amount of pollen
4. Purity of species is lost/destroyed

Pollinating Agents

Pollination, especially cross - pollination takes place by four different agents
like insects, wind, animal and water. A short description about this stated
1. Pollination through insects: In most.cases at the time of collection of
Vnectar pollen grains from one flower is transferred to another flower by insects.
Flowers in which pollination occur through insects are known as entomophilous
flowers. Mustard, Basils, Orchids, Roses, Cucurbita, etc. are entomophilous flowers.
Characteristics of entomophilous flowers:
a) Flowers are bright coloured.
b) Most of the flowers are sweet scented.
c) Flowers contain nectar at the base.
d) Pollen grains are sticky.
e) Stigmas are sticky.
2. Pollination through wind: In many plants Pollination occurs through wind.
Flowers in which pollination occur, through wind are known as Anemophilous
flowers. Paddy, Wheat, Maize. Sugarcane, Palm etc, are Anemophilous or
wind pollinated flower.
Characteristic of Anemophilous flowers:
a). Flowers are usually unattractive and have inconspicuous colour
b). Flowers usually are without sweet scent and nectar.
c). Pollen grains are very light and are produced in large numbers.
d). Stigmas are large, feathery and sticky, so that pollen grains carried by wind
may attach very easily
3. Pollination through Animals: In many flowers pollination occurs through
Birds, Bat or Snails etc. Flowers which are pollinated by animals, are called
zoophilous flowers. Madar, Shimul, Kadam etc. are zoophilous flowers.
Characteristics of zoophilous flowers
(a) Flowers are usually large.
(b) Flowers have bright colour,
4. Pollination through Water: Many aquatic plants are pollinated by water.
When pollination is accomplished by water the flowers is said to be
hydrophilous flowers. Vallisneria, Urticularia etc. are Hydrophilous flowers.
Characteristics of hydrophilous flowers:
a) Flowers are usually unscented.
b) They grow under water.
c) Female flowers are solitary and with long stalk.
d) Male flowers are light, transferred by water through floating.


We know there are small organs named ovules in the ovary of a flower. These
ovules later on develop to seeds. The seeds we see in the fruits like Mango,
Jambolina (Jaam), Lichi, Jackfruit etc. all are the developed ovule. When the
ovule gradually develops to seeds at the same time the ovary of the flower
gradually develops to a fruit. Ovules are developed to seed as a result of
fertilization. Usually without fertilization ovules cannot be developed to seeds
Again fertilization also causes the ovary to form a fruit. For fertilization it is
necessary to originate male and female gametes. In flowering plants union of
male and female gametes is called fertilization.
Formation of male gamete: Inside the anther there are pollen mother cells. By
meiosis four pollen grains are produced from each pollen mother cell. Each
pollen grain contains two coverings, the outer coating is called exine and the
inner one is called intine. In the exine there is a pore named germ pore Nucleus
of the pollen grain undergoes mitotic division and forms tube nucleus and
generative nucleus. Usually pollination occurs at this bi-nucleated condition.
As a result of pollination, the pollen grains become attached to the stigma and a
pollen tube is developed from the pollen grain. The tube gradually makes its
way down into the ovary through the style. The tube nucleus enters the pollen
tube followed by the generative nucleus. The generative nucleus undergoes
mitotic division and form two male reproductive cells or male gametes or
sperms. The male gametes are haploid.
Formation of female gamete:
Inside the ovary of a flower there lies the ovules. In each of these ovules one
megaspore mother cell (female reproductive mother cell or egg mother cell) is
produced. This cell undergoes meiotic division to give rise to four haploid
megaspores. In most of the cases three out of four degenerate and only one cell
survives. The nucleus of the survived large cell divides mitotically to give rise
to two at first, next from these two forms four and then from four to eight
nucleus. These eight nucleus remains at two poles of a sac like structure. The
sac like structure is called embryo sac. One nucleus from each pole moves to
the centre of the embryo sac and fuse together to form a secondary nucleus. The
three nuclei remaining at the micropyler end of the embryo sac are called egg
apparatus. The central one of these three is larger one and it forms the egg or
ovum, and the other two besides the ovum are synergides. Ovum is the female
reproductive cell or female gamete. The rest nuclei of the embryo sac are called
antipodal cells. The ovum is haploid.
Union of female and male reproductive cell: The pollen tube gradually proceeds and moves downwards and ultimately reaches the embryo sac. When the pollen tube reaches the embryo sac the tip of the pollen tube bursts and the two male gametes are released. One of the male gametes. (sperm cells) unites with the egg and complete the process of fertilization. The other male gamtees unite with the secondary nucleus. This union is called triple fusion. This
process is known as double fertilization.

Stages of Fertilization: From the above discussion it is understood that there
are three stages in the process of fertilization, namely - 1. Development of male
gametes, 2. Development of female gametes and 3. Union of male and female
Development of Embryo: Embryo develops after fertilization. A diploid
zygote is developed as a result of the union of male and female gametes. It is
also called a fertilized egg. The zygote remains in resting stage for sometimes
(may be few hours, days or even months). After the resting period the zygote
cell undergoes a transverse division to form a bi-celled pro-embryo. The pro￾embryo then undergoes successive cell division at different plains to form an
embryo. An embryo consists of cotyledon and an axis. The upper portion of the,
axis is the plumule and the lower portion is the radicle. In a monocot seed there
is only one cotyledon (e.g. coconut, paddy etc) and in a dicot seed there are two
cotyledons (e.g. mango, bean, gram, pea etc.).
Development of Endosperm:
 Endosperm is an essential constituent part of the seed. The food for
developing embryo is preserved in it and the embryo absorbs food from the
endosperm. The triploid cell originated from the union of secondary nucleus of
the embryo sac and a male gametes, is the first cell of the endosperm. The
triploid cell undergoes mitotic division repeatedly to give rise to a mature
endosperm. The endosperm is triploid i.e. three nuclei fused together to form it.
 In many plants endosperm is present in a mature seed. During germination,
the embryo absorbs food from the endosperm. These types of seeds are called
endospermic seed - e.g. Paddy, Wheat, Ricinus etc. In many other plants
endosperm being absorbed and stored in cotyledon and is utilised during
germination. This type of seeds are called non-endosperm seed e.g. Gram seed,
Pea, Mango etc.
 After fertilization the ovary is developed to fruit and the ovule developed to

Significance of fertilization:

As a result of fertilization the ovary of a flower develops to a fruit and ovules to
seeds. Seeds maintain and increase the generation by reproduction. If there
were no seed probably the plant would have perished. This may be said in other
words as, if there was no fertilization the plants would have perished. Again
animal world especially human being live on fruits and seeds of plants. If there
was no fertilization seeds and fruits would not have grown. No animal life
could exist without the food produced by plants. So the significance of ferti￾lization is unlimited
Dispersal of Fruits and Seeds:
Usually a plant produces a large number of fruits and seeds. Some fruits are
carried from one place to another by human beings for their own interest e.g.
Litchi, Mango, Jackfruit etc. In some plants fruits and seeds remains just under
the tree. Again in some plants fruits and seeds are taken away from the mother
plant by various agents and are distributed to distant areas. This process of
distribution of fruits and seeds to a distant area from its mother plant by several
means is called dispersal of fruits and seeds. Usually dispersal of fruits and
seeds take place by the following means. Here is a brief discussion.
1. Dispersal by wind: Seeds of many plants are carried away by wind and are
distributed at distant places. These types of fruits and seeds are very light, small
and provided with wings. So the wind may carry these seeds easily to different
places. Fruits of sunflower have pappus, in Chhagalbati the style is persistent and feathery, in Mehogany and Shajina there is flat appendage in the
seeds. The seeds of Akonda and Chhatim are provided with hairs. Thus fruits
and seeds of these plants can easily travel by wind and can be scattered to
distant places. Occasionally we find seeds of Chhatim and Akonda are flying in
the wind.
2. Dispersal by water: Shapla, Padma or even coconut float on water and
moves to distant places. Fibrous or spongy tissues cover their fruits and seeds,
thus they float on water very easily.
3. Dispersal by explosion of fruits: There are some fruits, which produce a
vibration when it burst. By vibrating force the seeds are scattered to a good
distance. Castor, pea, Dopati etc. are fruits of these types.
4. Dispersal by Animals: Fruits of some plants adhere to the body of animals
and are carried away from one place to another. Fruits of Prem Kata
(chrysopogon Aciculatus), Have Sticky Glands On Their Bodies, Khagra
(Xantiuun indicum) has hooks on its body, etc. are dispersed by adhering to
animal body even to clothing of human beings.
5. Dispersal by Birds: Some fruits are carried away by birds on their beaks to a
great distance. Litchi is one of these types of fruits. Birds eat some fruits but its
seeds cannot be digested and come out with stools and from that seedlings
grow, e.g. Date-palm, Pisum, Tamarind, Ficas etc.
Besides these, man willingly carried many fruits and seeds from one place to
another, even from one country to another.
Importance of Dispersal of Fruits and Seeds:
Without favourable conditions seed do not germinate. Again without favourable
environment no seedling can grow big. If all the fruits or seeds of a plant fall
directly under the mother tree, then many of them will fail to germinate, for
want of space, water, light and air, many of the germinated ones may die
because of the shade of the plants. The rest survivors will gradually perish. So
for maintaining the existence and increasing of generation of plants in
favourable environment dispersal of fruits and seeds is essential.


If we want to plant a Jackfruit (Artocarpus heterophyllus) tree we sow a seed of 
a Jackfruit, because Jackfruit tree originates from Jackfruit seed. in this way we 
get Jaam (black berry) tree from a Jaam seed, Coconut tree from Coconut, Jute 
plants from Jute seeds, paddy plant from paddy seed. Again some time we can 
get new plants from stem cutting also. The process by which a plant gives rise 
to grow a similar new plant is known as reproduction. Reproduction is one of 
the most important features of living beings.
Types of Reproduction:
 We can grow a new plant from seeds, or some other organ of the plant may 
give rise to grow a new plant. So the process of reproduction is not of only one 
type. Different types of reproduction is described below:
1. Sexual Reproduction: We have learnt from the chapter fertilization that the 
union of male and female gametes develop seeds. seeds are the product of 
sexual union. So the reproduction that takes place by Seeds is sexual 
reproduction. We get plants like Paddy (Oryza sativa), Wheat (Triticum),
Maize, Jaam, Jackfruit etc. from their seeds.
2. Asexual Reproduction: Reproduction by any organ other than seed is called 
asexual reproduction. Asexual reproduction may be of two types: (a) by 
asexual spore and (b) by vegetative organ. Plants like Algae, Fungi, Moss, Fern 
etc. reproduce by asexual spores.
3. Vegetative Reproduction: Reproduction that takes place by vegetative 
organ is called vegetative reproduction. Vegetative reproduction usually takes 
place by organs like root, stem or leaf etc. Vegetative reproduction again are of 
two types: (1) Normal and (2) Artificial.
Normal Vegetative reproduction: If we sow a potato or sweet potato, a root 
of Kakrol or a branch of Madar it will naturally gives rise to grow a new plant. 
But if we plant a branch of Mango tree it will not give rise to grow a new 
planty rather it dies. When any part or organs of a plant naturally give rise to grow new plant is called natural vegetative reproduction. natural vegetative 
reproduction may occur by following means:
By Roots: Plants like sweet potato (a modified root), Dahlia, Kakrol, and Patol 
etc. reproduce by roots.
By Stem: Plants like Zinger, Turmeric, Shati, potato, Olkachu, Onion (these are 
modified stems) etc. reproduce by stems. Banana, Pudina, Pineapple, 
Chrysanthemum etc. reproduce by sucker (a modified stem). Shajina, Madar, 
Chhatim, and Jiga etc. give rise to grow new plants by planting their branches. 
New plant also originates from young Bamboo shoots.
By leaf: Reproduction of Pathharkuchi (Bryophyllum) takes place by its leaf. 
When a leaf is left on the earth new buds originates from every notch of its 
margin and gives rise to a new plant.
Artificial Vegetative Reproduction: Branches of mango tree do not give rise 
to grow a new plant rather the branch become sapless. But if a bandage layering 
is made by the branch and plants it, it gives rise to a new plant. Artificial 
vegetative reproduction is being done in various methods by human beings. 
Various methods of vegetative reproduction are: Cutting, Layering, Budding, 
and Grafting etc. artificial vegetative reproduction may be done in plants like 
Mango. Lichi, Boroi etc.
Merits of Vegetative Reproduction:
1. The flowers and fruits of new plants bear the similar characteristics as those 
of its mother plant.
2. The new plants give early flowers and fruits.


Everything surrounding us forms our environment. There are two types of
environment which are recognized, the non-living environment and the living
environment. The relation between these two environments is very intimate.
The main factors of non-living environment are soil, water and air which
provide food and shelter to the living organisms.
The environment influences our life deeply. We get all kinds of things from the
environment that helps us to stay alive. Different types of animals grow in
different environments, e.g. rivers, canals, lakes, ponds etc., which are able to
meet the requirements of different aquatic animals but the terrestrial animals
cannot live in this type of environment. There is scarcity of water in the desert,
so the number of plants growing in the desert is very limited. In this type of
environment, plants are rarely seen. Aquatic animals and plants are almost rare.
If we observe, we will notice that both plants and animals living in the saline
soil of the Sundarbans are not found in the forests of Sylhet and Chittagong Hill
tracts. From this, it is understood that the organisms, which grow and live in
some particular natural environment have their own individuality. In this way,
different organisms (plants or animals) together form a biotic community. Each
community consists of plants, animals and micro-organisms. They live together
in co-operation with one another. The climatic condition of a particular
geographical region depends upon the topography and configuration of that
region. The animals and plants of a particular region are influenced by the
climate of their habitat.
Besides, the animals of that region also have influence upon the plants. In this
way the inseparable relation between the environment and the biotic
community of a particular region is formed. The biotic community and its non￾living environment are dependable on each other.
You have learnt before that the size and nature of the plants and animals
depend on their environment. All the regions of the world are not similar.
Sundari, garan and gewa plants are found in the Sundarbans. The rivers of
this forest have crocodiles, Royal Bengal Tiger and spotted deer are found on
this land. These animals and plants are not found in the forests of Sylhet and Madhupur. Why is this so? It is very natural to ask such a question. All these
happen due to the diversity of a particular environment.
The organisms return all the elements that they have taken from the
environment. It becomes difficult to survive for the plants and animals if the
environment lacks any biological or physical factors. The plants absorb
nutrition from the fertile soil. The animals in turn get their food from the plants.
Through this mutual co-operation the plants and animals grow.
Due to overpopulation, human habitation and number of industries have
increased. For this reason the areas of traditional cultivable land and natural
forests have decreased. Sound, smoke, industrial waste, garbage and bad smell
of the factories etc. are polluting the environment. As a result the balance of
environment is being disrupted.
The different animals of the world are not only dependable on one another, they
are also dependable upon the physical factors of the environment e.g. soil,
water, air and plants. For this reason, living beings cannot be separated from the
nonliving. There is an intimate relationship between the living community and
the non living environment for survival. The inter relationship between
organisms and their environment is ecology.
Components of Ecology
We understand from the discussion above that ecosystem has two components.
One is biotic community and the other is non living environment. It is the non￾living environment, which holds the biotic community. In any particular
environment of a geographical region, the relation and interactions between
living and nonliving objects are collectively known as Eco-system.
Non living components
We have learnt before that the non living elements influence the living
elements. Inorganic, organic and physical components are included in non￾living components.
1. Inorganic components: Water and mineral salts are inorganic components
of eco-system. In addition to these there are other gaseous elements like O2
(oxygen), N2 (nitrogen), CO2 (carbon dioxide) etc., which are necessary for the
nutrition of the plants and respiration of organisms.

2. Organic components: It is the rotten parts of the dead body of plants and
animals. The dead body of plants and animals after being decomposed forms
urea and humus. These constitute the organic elements of the soil. Saprophytic
fungus and bacteria acting on dead plants and animals form the organic
components. Some of its parts are converted into inorganic salts. These
inorganic salts are taken as nutrients by the green plants. Now you have
understood, how the organic components maintain link between the biotic and
abiotic parts of the environment.
3. Physical components: The environment is largely dependent on certain
physical factors. They are:
i. Climate: The climate of a particular environment depends on rainfall, air
movement, temperature, humidity, amount of sunlight, snow fall etc.
ii. Soil factor: Condition of soil in any place influences the animals and plants
living there.
a) Soil composition: The relative amount of sand, clay and silt etc, determines
the quality of the soil. The quality of the soil has a special influence over the
animals and plants of that particular area.
b) Humus and Mineral salt: The rotten manure, produced from the dead
plants and animals is the humus. In humus there is a large amount of mineral
salt. Plants absorb this mineral salt with the help of their root hair.
c) Soil water condition: The life of animals and plants also depend on the
quantity of the water, the level of underground water, drainage of excess water
and also on the porosity of soil.
1) Topographic factor: The topographic factor of a particular region
influences the animals and plants living there. Weather, soil factor and
topographic factor are the inorganic components of eco-system. The main
source of energy is the sun. The green plants with the help of chloroplast,
inverts the solar energy into organic component and stores it in the body.
indirectly this solar energy is flowing within the living community. Thus the
life process and energy flow on this earth is maintained.
B. Living components: Every organism is a part of the eco-system. In eco￾stem the non-living and living components are interdependent. Absence of one
affects the other in maintaining their natural activities. The habits of plants
influence the animals characters of eco-system. Every living being takes food
for its physical growth, reproduction and existence. Every organisms gets
energy from food. We have learnt before that the source of energy flowing in
biotic community is the sun.

Food chain: We know that it is the green plants which manufacture their own
food by using the solar energy. As the green plants can prepare their own food,
they are autotrophic. Green plants in the presence of sun light react with the
inorganic substances (CO2 and water) and make their own food. The plant's
body preserves the solar energy in the form of potential energy. Of the food
manufactured by the plants, only small portion is used for its own requirement
while the major portion is stored in its body. The herbivorous animals eat this
stored food and the carnivorous animals eat these herbivorous animals. They
are consumers. The decomposers (bacteria, fungus) use plants, herbivorous,
carnivorous animals etc. as food and transforms those into humus. From
inorganic components of soil the green plants again produce their food with the
help of solar energy. It is now clearly understood that starting with plants,
through various types of animals and decomposers, step by step, the food
substances are transferred from one to another and finally return to the green
plants. This cyclic transfer of food and the relation of food and its consumer are
known as the food chain.
Generally the final consumer is not eaten by any other animal. His death occurs
due to disease, normal or abnormal causes.
In an eco-system there maybe different types of food chains. Usually two types
of food chain are found in nature.
1. Grazing food chain or Predator food chain.
2. Saprophytic food chain or Detritus food chain.
1. Grazing or Predator food chain: The food chain starts from the green
plants, goes to grazing herbivores and gradually moves from the smaller
carnivores to the bigger. It is known as predator grazing food chain. e.g. deer
eats grass, tiger eats the deer (this is a predator grazing food chain).
2. Saprophytic or Detritus food chain: Different micro-organisms or fungus
splits up dead body of plants and animals into organic components. The
splitting organisms are decomposers. The splited organic compounds are taken
as food by some animals and then the decomposers are converted into foods of
other animals. Such as, Dead organism-Decomposer-Amoeba -Hydra
Food web: Previously we came to know that any food chain cannot remain
scattered in nature. One food chain is linked with the other. When in a given
eco-system, more than one food chain exists, the food chain becomes very
complex and in this case the members of different types of food chain become
interrelated. The well organized interrelated arrangement of more than one food chains formed by various species together is known as the food web.
Producer: Solar energy is the main source of energy in the ecosystem. the
green plants, in presence of sunlight react with carbon dioxide and water and
produce carbohydrate and oxygen as excess. In this way, the solar energy stored
in chemical compounds or food. Those who accomplish this significant
function are known as producers. Green plants are the main producers in eco￾system. Producers are autotrophic. The producers do not depend upon other
organisms for nutrition.
Consumers: The living organisms which cannot manufacture their own food
using the solar energy like the green plants and get their nutrition by eating
other organisms are known as consumers. Most of the consumers of the living
world are animals, e.g. mynas eat the insects, lion eats the deer, tiger eats men
etc. So Myna, lion and tiger are consumers. As the consumer depends upon
other living organisms for food or nutrition they are called heterotrophic. There
are three levels of consumer's namely Primary consumer, Secondary consumer_
and Tertiary consumer.
(i) Primary consumer: Herbivores or Green plant eating animals are known as
Primary consumers. Zooplankton. various types of insects, goats, cows etc
dircetly denends on plants.
(ii) The secondary consumer : The animals which live on primary consumers
are known as secondary consumers, e.g. frogs eat insects and tiger, jackal etc.
eat herbivores animals.

(iii) Tertiary or highest consumer: Those who live on secondary consumer,
are tertiary or highest consumers. e.g. vulture, falcon, crocodiles. sharks etc are,
tertiary consumers because they live on secondary consumers.
There are many animals which live on food of more than one level e.g. when
the peacocks live on plants, they are primary consumers and when they eat
small insects, they are tertiary consumers. These sorts of animals are known as
omnivorous animals. Man also consumes foods of different levels of the food
chain to stay alive.
Decomposer: In an eco-system there is another type of heterotrophic organism
which is collectively known as decomposers. This includes mainly the bacteria and fungi. From the body of the decomposers enzymes are secreted and that decomposes the dead body of the plants and animals to form simple chemical compounds. These chemical compounds are absorbed by the bacteria and fungi
as nutrients. Besides this, the decomposers perform an important function which is to transform organic substances into inorganic ones. These inorganic
substances are used by green plants for food preparation.
Nutrient flow in Eco-system: It is observed that plants accept inorganic
substances and manufactures
food by respiration the process
of photosynthesis. A small
portion of the food produced by
the plants is used by them and the
rest is reserved in the body. The
herbivorous animals eat this and
gradually herbivores are eaten by the carnivorous animals. The decomposers transform the plants, herbivorous and carnivorous animals into inorganic substances.
Using the inorganic, substance the green plants can again manufacture food
with the help of solar energy.
In an eco-system the transfer or flow of energy and nutrient from one trophic
level to other is in succession. In each trophic level of food chain energy available decreases step by step, decomposers rot the dead body of the organisms and inorganic nutrients are stored in nutrient storage of environment.
The green plants again find inorganic nutrients from the storage environment.
The cyclic flow of nutrients is known as nutrient flow. Food chain and nutrient
flow are the important characters of ecosystem.
Energy flow in Ecosystem: Green plants. are the primary producers, which
produce energy by using solar energy. Green plants hold solar energy as
chemical energy from where it flows as energy or chemical compounds to the
herbivorous animals and from the herbivorous animals to carnivorous animal
Energy is spent in every step on the way to flow from the producer to the
carnivorous animals. Almost all the energy is spent at the time of transfer of
energy to the decomposers- from producers, herbivorous and carnivorous
animals. This causes no energy to be transferred at the time of nutrient flow to
inorganic nutrient storage. Inorganic nutrient materials are again transferred to
producers from the nutrient storage. From this, it is understood that in eco￾system the nutrient flows in a cyclic order with the eco-system. The energy
flow is however, one way and not cyclic.
 Decomposition and Transformation of Energy: We know that among the
physiological processes of organisms, excretion is one of them. The animal
excrete the nitrogenous waste products from the body through excretion. In this
process some energy is spent. Besides this, the living organisms lose energy
due to other physiological process. Living organisms come to an end through
death and lose energy. This energy is called lost energy. The decomposers get
necessary energy from the dead bodies and excretory products of different
trophic level. In this way energy is transferred and the food chain remains
Some examples of food chains are given below with which a human being is
related in some way and they are the last level of the chain. It is seen that some
of these food chains are very small and others are very large.

Living organisms spend a lot of energy in respiration and other biological
functions. If the food chain is short, less energy is spent and if it is long then
more energy is spent. From this rule it is understood that more the energy is
transferred from producers to higher levels less the energy remains.
Major Eco-systems
According to the environment the ecosystem is divided into two parts, one
Terrestrial Eco-system and the other one is Aquatic Eco-systems.
The Environment of a place depends on the topography, weather and climate of
that place. The animals or plants of a particular region are dependant on some
natural characteristics such as nature of soil, rivers, deserts, hills, mountains,
climate etc.
1. Terrestrial Ecosystem: There are different types of terrestrial eco-system in
different parts of the earth surface due to difference of rainfall, temperature,
wind flow etc. There are many differences in ecology of agricultural land,
grassland, desert and forest. Instead there are differences in ecology of
mountain, hill, plain land, cold area, temperate area and tropical area. It is not
possible to describe all types of eco-system in this chapter, so two of our known
eco-systems are described here briefly.
A. Eco-system of paddy field: Due to cultivation, manure and irrigation the
fertility of the land is increased. Paddy is the main plant of paddy field. Besides
this there grow grass and many other weeds. They are the producers of the eco￾system. Different types of insects infect the paddy. They are the primary
consumers. Toad and different birds lives on the insect, snake lives on toad, the
predator birds lives on small birds. When they die the saprophytic insect (ant,
larvae of flies) and bird (crow, vulture) eat them. Besides these different types
of bacteria and virus decomposes the dead bodies of plants and animals into
organic compounds. In this way the eco-system of paddy field is formed.
Their analysis is found in the following list.
Producer: Paddy, grass and weeds.
Primary consumer: Insect and worm, cow, goat

(2) Aquatic Ecosystem: Aquatic eco-system is divided into three categories.
(1) Pond ecosystem (2) River ecosystem and (3) Marine ecosystem.
A. Pond ecosystem: The mutual relation between the living organisms and
non- living things of a particular area is known as ecosystem. In every
ecosystem, every organism has a definite habitat and a definite life pattern. It is
the main characteristics of an ecosystem.
A pond is a self-sufficient and an ideal example of ecosystem. In a pond, the
intimate relation between the inhabiting living and non-living components is
well understood. The non-living objects are various types of organic and
inorganic substances such as water, sun rays, CO2, oxygen, calcium,
phosphorus, humic acid etc. The living components are producers, primary
consumers, secondary consumers, tertiary consumers and various types of
Producers: Various types of photosynthetic algae and shallow water plants
living in the pond are the producers. The floating organisms are called
plankton. The minute plants of plankton type are known as phytoplankton.
Green aquatic algae and other aquatic plants can live by producing food by the
process of the photosynthesis, so they are called producers.
Primary consumers: These are various types of floating minute insects, larvae
of mosquito and other microscopic animals like zooplankton etc. Floating
minute animals are called zooplankton. These consumers cannot manufacture
their own food and they live on by eating the producers directly.
Secondary consumers: Small fishes, some aquatic insects, prawns, frog etc.
are secondary consumers. They can neither manufacture their own food nor
accept the producers as food. They live on by eating the primary consumers:
Tertiary consumers: Small fishes, prawn and all other animal that feeds, upon
the secondary consumers are known as tertiary consumers. Large fishes like
shoal, boal, vetki, stork and heron are the tertiary or highest consumers.
Decomposer: In pond water, various types of fungi and bacteria live as,
saprophytes which are- known as decomposer. These decomposers can live by floating on water or live at the bottom clay. They attack living or dead consumers and help to rot. As a result, organic and inorganic chemical substances usable by the producers are fornmed again. The producer community of the pond use these decomposed elements. The flow chart gives
an idea about the components of pond ecosystem.
B. River Ecosystem: water body often the rivers may have strong currents. For
this reason, there is a noticeable difference between the environment and the
living communities of rivers with those of the ponds. In river there are different
types of algae fishes like Hilsha, Pungas, Chital, Boal etc. live in the rivers. The
bodies of. these fishes are laterally compressed. For this feature of their body
shape they are capable of moving easily in strong current. Near the bank of the
river where the current is less, living communities like those of the ponds grow
there. In the ecosystem of rivers the food chain is short e.g. Algae, Hilsa, Boal.
(iii) Marine Ecosystem: The water of the sea is saline. In the saline water the
sea there lives numerous phytoplanktons and zooplanktons. Coral, Prawn
Starfish, Snail, various types of small and large fishes, tortoise, dolphin, shark.
whale etc. live in the sea. Phytoplankton and sea algae are the only producer in
marine environment. Prawn, bivalve, zooplankton, minute pelagic animals and
small fishes are the primary consumers. Large fishes, tortoises, whales etc. are
the secondary ones. The sharks and various predatory fishes the tertiary ones.
Generally the small fishes are herbivorous. The starfish, prawns, snails are
detritus eating animals. The food chain of whale is also short like that of hilsa
such as plankton, whale, plankton, small bivalve's and whale.
Ecosystem is a self-sufficient unit: Every ecosystem is more or less a self￾controlled unit. In nature the number of a particular living being cannot
increase too much. All organisms are interrelated with each other in the form of
food and consumers chain. Any one of these systems cannot be completely
eliminated easily. The proportionate number of different level of biotic
communities always remains more or less unchanged.
In spite of various changes in the environments, the natural balance is
maintained for a long time. By some reason, if the number of a particular
animal of a place increases, the number of other living beings of that ecosystem
will change in such a manner that the balance of the number of other living
beings is maintained. If it is discussed with example, it will be easy to
understand. Suppose in a forest, tiger, deer, cows, pigs etc. live. Deer and pig
are the foods of tigers. If the number of deer and pigs increase, the tiger will
have enormous quantity of food and consequently the tiger Production will
increase and if the number of tiger's increases, large number of deer and pigs
will be killed, as a result, the number of deer and pigs will be decreased. This
will cause a dirth of food for tigers and the number of tigers will be decreased.
On the other hand, if the number of tiger decreases the number of deer and pigs
will increase. In this way, through decrease and increase of different animal
population of the ecosystem of an area is automatically controlled.
The responsibility of man in maintaining balance of an environment:
Starting from the producer up to the highest consumer there is a proportion of
number of different tropical level in the ecosystem. Here the different processes
of ecosystem are maintained nicely. It is called environmental balance. The
relation between the inorganic and organic elements is very intimate in an
ecosystem and the elements of an ecosystem maintain balance with each other.
But different types of natural disasters, e.g. earthquake, tidal bore, draught etc.
may destroy the balance. Besides these, man misuse natural resources for their
own comforts. This affects the natural balance. For this reason there is a gulf of
difference between the environment of ancient time and the present time.
Human beings are now facing two problems. The first one is the excessive
population increase and food crisis. The second problem is the conservation of
natural environment. Conservation of nature is one of the main steps to
maintain the balance of the environment. In this way the components of
environment can be saved. Climate, Solar energy, minerals, soil, plants, wildlife
etc. are natural resources. Naturally very little of these resources decrease or
being misused and nature herself always balance these. But soil, fresh water,
forest, wildlife etc. are nature's perishable resources. Due to continuous use the
quantity of these resources are becoming less. The goal of conservation is not to
stop the use of these perishable resources and that is quite impossible. On the
basis of knowledge from ecology, fresh water, soil, forest and wildlife can be
conserved by definite plans. The main object of conservation is to use the
natural resources by well planning to stop all types of misuse and dispotic use
and in probable case revive the past condition.


Now a days environment is taken into consideration extensively more than it 
was before. Conservation and long time management of the components of 
environment like soil, water, air, plants and animals etc. has now become the 
most important matter to us. Now a days man has come to realise that it is 
better to try to adjust with nature than to conquer it.
Soil pollution:
Soil is the upper layer of the earth crust which is soft and consisting of a 
mixture of various organic and inorganic substances. We live on the surface of 
the soil. We take different necessary elements from the soil. The remains of 
plants and animals return to the soil. Thus we can utilise repeatedly the 
different ingredients of the soil by rotation. So it can be said that our relation 
with the soil is very close. If soil is polluted it will have deadly effect on our 

Soil is polluted by several means. Soil is eroded by different natural factors like 
flood, volcanic eruption, rainfall, and wind flow etc. Due to flood soil is eroded 
and become unproductive. Plant cannot grow on that soil. Rainfall and wind in 
the same way erode the upper layer of the earth and make the soil. barren.
 Several activities of human beings,cause the soil to be polluted. Destruction 
of forests and plants, excessive cultivation and irrigation cause soil pollution. If 
there is no plant and cultivation is done in excess, it will erode the fertile layer 
of the soil surface and thus soil will become non-fertile. Excess irrigation 
causes waterlogging and makes the soil saline. Underground salt being 
dissolved in water come to the surface and make the soil non-fertile. Various 
types of waste materials are one of the causes of soil pollution. Harmful 
chemical substances and substances that is not absorbed by nature (e.g. 
polythene, plastic etc.) cause soil pollution. When soil is polluted no plants, 
insects or microorganisms can grow on it. As a result the soil becomes 
unproductive and unfit for human habitation. To keep the natural environment 
balanced a fertile and productive soil is necessary. Therefore, we all should take 
care so that the soil does not get unfertile and polluted. One of the ways to 
protect soil pollution is to plant more and more plants. There should have 
necessary laws so that industries do not leave their wastes here and there. If we 
all are careful against soil pollution it is possible to prevent the pollution.
The gaseous layer that surrounds the earth from above the soil and water layer 
is the atmosphere. It is differentiated into three layers:
 (i) Troposphere (adjacent to earth's crust): Above the Earth's crust this 
layer is extended from 10 K M. (at polar region; 
to 16 K.M. (at equator).
(ii) Stratosphere: Above the troposphere this layer is extended up to 80 
K.M. from the Earth's crust. 
(iii) Ionoshpere : Above the stratosphere and extended up to 3500 K.M

Fog mist, dust particles, clouds, and wind etc. are limited only in the Troposphere. In this layer the average ratio (depending on density) of different components are as follows: Nitrogen - 78%, Oxygen - 21%, Argon - 0.93%, 
Carbon dioxide - 0.03%, and a trace of water vapour, Methane, Helium and 
Krypton etc.
Beneath the Stratosphere (25 to 30 K.M. from Earth's crust) there is a dense 
layer of Ozone. It is called Ozone barrier. This layer protects the life from the 
harmful effects of the radioactive waves particularly the Ultraviolet Rays of the 
Sun. The density of air in the ionosphere is very light. Due to the effect of the 
radioactive rays of the Sun the components of the air remain in ionic forms.

Air Pollution:
 Like soil air is also polluted by
natural or human activities. Air is
polluted by natural causes like
sandstorm, forest fire, volcanic
eruption etc. Dusts, smoke and
poisonous gases mix with air and
make the air polluted.
 Air is being polluted by smoke
from mills and factories, automobiles
and from bad smell of waste
materials. In the smoke of industries
and automobiles there are CO2, CO,
SO2 and various other harmful gases.
What will happen if the concentration
of CO2 increases in the air? The effect resulting the increase of CO2 in the
atmosphere is known as Green House Effect. This topic has been elaborately
discussed in the next chapter. As a result of green house effect the temperature of the
atmosphere increases. For this, there is a possibility of dissolving the ice of polar
region and that may cause great flood. Many seaside and low-lying countries will be submerged. When carbon monoxide mixes with blood, it totally destroys the
Oxygen transport capacity of blood. Without Oxygen people will die. Sulphur
dioxide and Nitric oxide, produced by Nitrogenous fertilizers, when mixed with
rainwater causes acid rain, which is very much harmful for plants, animals,
buildings, and instruments. CFC (Chloro-Fluoro Carbon) gas evolves from
various materials used by human beings gets in the atmosphere. CFC gas is
responsible for damages in the Ozone layer. Detailed discussion in this respect
will come later.
The most effective way to stop air pollution is to increase the number of plants.
This will maintain the balance of the amount of O2 and CO2. On the other hand
it is necessary to take care so that no harmful gas can be mixed with the air.
Condition will improve if filter is used in mills and automobiles.
Water Pollution:
 We have so much water in our country that mostly we do not feel the
effect of water pollution. Water is polluted by natural means like flood and
rainfall. As a result of flood many impurities are mixed with water. Water is
mostly polluted by man-made causes. Industrial wastes, household garbage,
rainwater containing chemical fertilizer and insecticide, all these mixed with
water make it polluted. Due to water pollution extreme harm is caused to
aquatic plants and animals. The oxygen content of water becomes reduced and
thus many fishes and aquatic animals die and float on the water surface. There
are strict regulations against water pollution in European countries. All water
transport vessels are to take necessary measures so that their oil and waste
materials do not pollute water. There are provisions of severe punishment or
heavy penalties if such measures are not taken. To prevent water pollution in
our country primarily people should be motivated through different medias.
Later regulations should be implemented very strictly and impartially.
Sound Pollution :
 Sound is a constant companion of the city dwellers. Sounds of vehicles and
vendors wake us up in the morning. All through the day sound pollution occurs
with mixed sound of different machineries, telephones and loud voices of
human beings in the offices and these have become very normal sound pollution. When a man comes back home and listens to Radio, T.V. or Tape recorder then there is also sound pollution.
If sound exceeds a certain limit (80 decibel). it reaches the stage of pollution.
The effect of sound pollution is quite harmful to animals. It causes high blood
pressure, insomnia (sleeplessness), loss of hearing capacity and extreme case of
mental disorder.Ozone layer :
Ozone is one kind of gas. Three oxygen
atoms together constitute one molecule
of ozone. The chemical formula is O3,
Certainly you know about the three
layers of atmosphere Troposphere, and
Stratosphere Ionosphere. A dense ozone
layer exists in the stratosphere zone
about 25 to 30 K.M. above the Earth
surface. Ozone is also present in the
troposphere zone. This layer of ozone
surrounds the Earth from all sides. You
have learnt that from time immemorial
this ozone layer has been protecting the
living beings of the earth from deadly
ultraviolet rays radiated from the Sun.
Ultraviolet rays are of three types: UV-A rays consist ofvlong wavelength.Ultraviolet-B consist of medium wave length. And UV -C consist of short wave length. The ozone layer in the stratosphere zone prevents the total amount of the most dangerous UV -C and most part of less harmful UV -B. The rest amount UV -B is prevented from coming to the earth, by the troposphere zone and clouds.
Two American Scientists Maria Molina and Sherwood Ronald in 1974 AD first gave the idea that the chemical compound Chloro Fluoro Carbon (CFC) that is used in our daily life is responsible for the damage of ozone layer. CFC compound is used in the cans of Aerosol and in making of various foams.
Getting release in to the atmosphere it moves to the higher atmospheric zone.
The CFC compound does not break easily in the lower zone of the atmosphere.
Reaching stratosphere CFC comes in contact with ultraviolet rays and releases
chlorine after breaking itself. The free chlorine then acts as a catalyst and break
the ozone molecule to an oxygen molecule and one oxygen atom. This process
goes for years after years. Some other chemical compounds like Carbon
Tetrachloride Trichloromethane and Helone also adversely affect the ozone
Ultraviolet rays are harmful to living bodies. It is proved that an increased
exposure to UV -A and UV -B resulting an enhanced possibility of skin cancer.
Besides, various eye diseases like formation of cataract, distortion of eye￾lenses, and lose of eye-sight found in aged people, are due to the effect of UV -B. Due to the reduction of the power of disease resistance, contaminations of various infectious diseases increased.

Green House Effect

You know what is green house. cold countries plants are grown in a green
house to protect them from external cold. Usually this house is made of glasses.
As a result sunlight can enter inside. Inside the room plants live on
carbohydrates manufacture through photosynthesis by the help of sunlight.
With the help of sunlight the internal environment of the house remain warm.
As glass is bad conductor of heat so external cold cannot reach inside nor
internal heat can go out.
 Carbon dioxide in the atmosphere acts almost like the glass of the green
house. The earth is heated by sunlight. Much of this heat is lost to the space-by
radiation through the atmosphere. As a result the temperature of the atmosphere
remains more or less same. But if the amount of CO2 is increased in the
atmosphere, the condition becomes different. Some of the radiated heat is
absorbed and retained by carbon dioxide; this results in the increase of atmospheric temperature. Scientists have calculated and found that the amount of CO2 in the atmosphere has been increasing day by day. You must know why the amount of carbon dioxide is increasing. Large-scale deforestation is one of the main reasons. Another reason is the use of fossil fuel. Petrol, diesel, kerosene, coal etc. are mineral fuel. Its uses are increasing in factories, vehicles, and household purposes. As a result the amount of carbon dioxide in the atmosphere is increasing day by day.
Can you realise the effect of increased atmospheric temperature on the
environment due to green house effect? You know that huge amount of ice is
deposited in the two polar regions of the earth. With the increase of the
atmospheric temperature this ice will start melting. As a result the water level
of seas will increase. Many islands, seaside cities and countries will gradually
go under water. Many areas of Bangladesh may submerge under the water of
the Bay of Bengal.

Role of Human beings in conservation of Environment:

From above discussion you must have learnt that various activities of human
beings are responsible for pollution of the environment. Men knowingly or
unknowingly are polluting the environment. So attaining the knowledge about
environment pollution and developing consciousness should be the primary
responsibility for preventing environment pollution. If we are aware of
pollution of the environment, have willingness and desire to prevent it then we
will be able to do it.
Effect of Urbanization and Industrialisation on Environment:
For fair livelihood in a comfortable environment we need many things like
houses, roads, schools and colleges, shops and markets, hospitals and post
offices etc. A town or city develops with all these facilities. The system by
which a town or city develops is called urbanization. To develop an ideal town
some important aspects should be taken into consideration. Towns and cities of
our country have not been developed in well-planned way as those of the
developed countries of the world. Except the new part of Dhaka and some areas
of Chittagong, our towns are developed absolutely without any planning. While
establishing an ideal town some important aspects should be taken into
consideration with great importance.
 1. To establish a town primarily it is necessary to select a suitable site.
 2. To live in comfort it is necessary to construct neat, clean and comfortable
 houses. In these houses there should have clean and pure water supply,
 electricity, gas supply and proper sanitary system.
 3. For proper supply of daily necessities and fresh vegetables, fish and meat,
 there should have shops and markets
4. For maintaining cleanness and healthy condition in these shops and
markets, Public health department should supervise them regularly.
5. For treatment of diseases there should have dispensaries and hospitals,
population control and family planning centers, maternities etc.
6. Along with schools and colleges for children's education there should
have arrangement to establish libraries, recreation and health-care
centers, including playgrounds, clubs, parks etc.
7. There should have suitable recreation center for aged people so that they
can pass a life of ease.
8. There should have arrangements for prevention and treatments of
various contagious diseases so that these may not turn into epidemics.
9. There should have necessary job provision for the town dwellers.

Due to gradual increase of population there develops undesired formation of
slums in vacant places inside and around the towns. In these slums uproote
people live in extremely miserable condition. This situation is gradually turning
to be more acute. As a result various social and hygienic problems are being
created. Unplanned urbanization results extreme deterioration of the
 The environment of the slums, developed for the new comers from the
villages, is dirty and unhealthy. Because in these slums there is no water supply
or drainage and sewerage system. There is no facility of collecting water from
rivers, canals, ponds or pools like villages. As a result the slum dwellers often
suffer from various water borne diseases. From these slums diseases spread to
other areas of the town also. But in towns purified and chlorinated water is
stored in big tanks at a high level. Water is then supplied to different areas of
the town through pipelines. But for excess population the stored water is not
sufficient. Consequently the inhabitants of the town suffer from water shortage.
 The supply of fuel is a significant problem of unplanned urbanization
Previously in town also, wood and dry cowdung were used for cooking. But at
present natural gas is being used. Now a day, in many countries, Bio-gas is
being used for cooking. Smoke originates from both wood and dried cow dung
and pollutes the air. For unplanned urbanization supply of natural gas cannot be ensured to every corner and for all the time.

Because of rapid increase of population people from villages are rushing
to towns in search of livelihood. The urbanization process must be planned for
them. Otherwise there will be no comfort in life of the town dwellers and the
environment will be polluted day by day.
 Commercial establishment of mills, factories and machineries for the
production of various necessary materials for the people is known as
industrialisation. With the objective of industrialisation various types of
industries have been established in the world.
 Previously men were dependent more on articles available in the nature.
But with the advancement of human civilization; industrialisation is also
improving rapidly. In the recent past there was a balance between birth rate and
death rate in the world, particularly in Bangladesh. At present number of death
caused by natural calamities like cyclone, famine, different fatal diseases,
aggression and bite of harmful animals, is much less than as prevaile in the
past. Now a day there are preventive measures for protections against the
disastrous effect of every natural calamity. For example the forecast of cyclone
is available before hand and taking shelter in safe places people can save their
lives. With the improvement of communications system famine do not occur as
frequently as before, even if it occurs food can be supplied easily. Prevention of
hunting wild animal and adopting defensive measures against their attack has made human life safer than before. Taking effective and preventive measures
against severe diseases man has become able to recover from his illness and
avoid inevitable death. Thus the average longevity of human being has
increased. As a result with increased longevity people can give birth to children
in greater number. Above all the general people of Bangladesh are reluctant to
adopt family planning for which the population of this country is increasing
rapidly. For this increase in population the cultivable land and forest areas are
gradually decreasing. Thus the demands of agriculture as the main livelihood of
our country can no longer be met from agriculture alone. For this reason it is
necessary to establish industries in a well planned way. But our conventional
industries are dependent on our natural resources. As the raw materials
produced in our country are not sufficient for the need, thus necessary raw
materials are to be imported from foreign countries.

Industrialisation is mainly of two types :
A. Such materials should be produced which are at present imported from
abroad e.g. production of superior quality of cloth.
B. Such materials should be manufactured for which raw materials may be
imported from abroad, and utilising cheap labour of this country, those items
may be produced and exported abroad, e.g. garments and ceramic industries.
Cloths being imported from outside and by utilising cheaper local labour
garments are produce and exported. It is a profitable business.
Unplanned growth of industries deteriorates the environments in many
ways. Mills and factories should not be established in human habitation.
1. Industrial smoke pollutes the air of the locality.
2. If unused and excess raw materials and by-products are, not removed
properly, these may often decompose and pollute both soil and air.
3. Often in the name of by-products the industrial wastes are thrown to the river
or other water reservoirs. As a result the water of the reservoir become polluted
and may cause harm to fishes and other aquatic animals living there. Use of this
polluted water may also do harm to human beings. So industries should not be
established here and there in unplanned way.
4. If industries, producing high sounds are established in human localities,
people of those areas will become victim of soun pollution. In this way
unplanned industrialisation directly or indirectly may affects the environment.
Unplanned industrialisation deteriorates the public hygiene of environment. so
before establishing any industry in an area the above factors should carefully be
taken into consideration.

Natural Diversity of Bangladesh - Distribution
 of Plants and Animals

Bangladesh is a small country of an area of about 1,47,570 square kilometers. 
It'is situated in between 20û34¡ and 26û38¡ northern latitude and 88û01¡ and 
92û41 eastern longitude. Though the country is small yet the plant and animal 
resources is not so little. River washed Bangladesh is the largest delta in the 
world, having characteristics of natural diversities. Growth rate of population in 
this country is very high. The density of population is increasing day by day. To 
meet the needs of this additional population, homesteads and furniture are being 
made, and cultivable lands are being procured by destroying valuable forests. 
As a result forestland is terribly destroyed. Many species of plants and animals 
are becoming extinct. Thus plant and animal resources are being lost. As a 
result the topography (land forms) of this country is being changed very 
The nature of any region is the combination of various inorganic components 
like topography, climate, rivers and canals, mountains and hills etc. The nature 
and natural flora and fauna of a particular region together form the natural 
environment of that region. The characteristics, which prevail in a particular 
natural environment, are known as natural characteristics of that region. The 
natural environment of a particular region is dependent on the topography and 
climate of that region.
Bangladesh may be divided into several regions on the basis of topography or 
landform. The environmental components, flora and fauna of this region are 
full of special characteristics.
Some of these are discussed below: Recent flood plain 2. Haor and marshy 
lands 3. Pleistocene uplands, 4. Tertiary hilly region 5. Coastal mangrove forest 
and 6. Saint Martin's Island.
1. Recent flood plain:
This region comprises of the vast plain land of Bangladesh. The land is formed 
by the alluvium carried by different rivers, particularly the Ganges, the 
Brahmmaputra and the Padma.
Environmental characteristics: The soil of this region is made of alluvium 
and is very fertile. In the rainy season many aquatic plants, by death and 
decomposition, converted to organic manure and thus make the soil more 
Plants: Among the aquatic plants Nymphaea noucheli (Shapla) [our national 
flower], Lotus, Ipomea, Halencha, Shola, Vallisnaria (Pat Shaola) Urticularia, 
Azolla, Lamna, Wolfia (smallest flowering plant) Eichornea (Kachuripana), 
Pistea (Topapana), Trapa (Paniphal), Polygonum (Panimarich), and various 
types of grasses are the major plants. In this region there grows plenty of fresh 
water algae among which phytoplankton, a primary producer, serve as the food 
of fish and other aquatic animals.
In uncultivated lands, Kalkesunda (Cassia), Shetodron (Leucas) Raktodron, 
Dhutura (Datura), Hatishur (Heliotropium), Mikania, Bhat (Clerodendron),
Muktajhuri (Acalypha), Kachu (Colocasia), Khagra (Xanthiun) etc. are the 
major plants. Around the houses betel nut, coconut, mango, jackfruit, banana, 
litchi, tamarind, plum, jamboline, bamboos, Barun, Pipul, Akondo (Calotropis)
etc. are the main plants.
Among the crop plants paddy (Oryza sativa), deep-water rice (a variety of 
paddy grown in deep water), and jute (Chorchorus sp.) are the main.
Animals: In this region there live different species of small and large animals. 
Among them, toad, frog, lizard, tortoise, different varieties of snakes, 
mongoose, sparrow, Shalik, Moyena, parrot, crow, kite, vulture, buffalo, cow, 
goat, sheep etc. are notable. Besides these, in the rivers of this region there is 
fresh water dolphin (Shushuk) and different species of fish. In ponds and other 
water reservoirs there are many species of small and big fishes, aquatic snakes, 
tortoise etc.
2. Haor and other Marshy lands:
These are formed by accumulation of water in the low-lying areas on the earth 
surface. Except rivers, ponds, and lakes the other marshy lands of Bangladesh 
may be classified into three categories: Haor, Baor and Beel.
A. Haor: Due to natural movements of the earth, beneath the earth 
crust, some times changes take place on the earth surface. As a result earth surface become deepen to form a basin like area where plenty of water is 
reserved. This vast water reservoir is called Haor. The greater Sylhet district of 
Bangladesh is known as 'Haor Basin' region. The eastern region of Kishorganj 
and Netrokona are also included in Haor region. Some worth-mentioning Haors 
are Hakaluki, Tanguar Hayil, Dubriar Haor etc.
B. Baor : The horseshoe shaped water reservoirs, which are formed naturally 
due to the change of river route, are known as Baor. There are several Baors in 
the southwestern region of Bangladesh. Among these some big ones are: Baro 
Baisdia. Choto Baisdia. Baluhar. Marjat. Joidia etc.
c. Beel : Water reservoir that originates by the side of the old river route is 
called Beel. There are many Beels in the greater districts of Bangladesh namely 
Rajshahi, Rangpur, Bogra, Pabna, Faridpur and Khulna. Among these, Chalan 
Beel, Patrail, Manda, Parul, Raktodoha. Dakatia, Gopalgonj Bakhra are 
Environmental Characteristics :
Almost throughout the year water remains present in the Haors, Baors and 
Beels, but in winter water become less and then paddy is cultivatad there. In 
some places there remain at least some water throughout the year.
Plants : Usually common aquatic plants are grown in aquatic environments of 
the Haor, Baors and Beels. Besides this, there grow specially reeds 
(Nalkhagra), Ikar, Hijal, Karoch, Gota, Gamar, Barun and wild roses. Thes are 
bushes of Hijal and Nalkhagra.
Animals : In these shallow water bodies there are different species of fishes 
like Lata, Meni, Baim etc. and various kinds of animals like toad, frog, tortoise, 
water snakes, heron, crane, Kadakhocha Pakhi, kite, eagle and Pankouri etc.
3. Pleistocene uplands : During Pleistocene era (25,000 years ago), many regions of 
the world became raised and formed uplands. These regions are called Pleistocene uplands. In Bangladesh, Barendro region, Modhupur Gorh and Lalmai hills are parts of these uplands. The environmental characteristics and flora and fauna of 
these regions are almost similar. But the large area of Shaalbon is noticeable.
A. Barendro : The region occupies the north-western region of Bangladesh 
including Chapainowabganj, Rajshahi, Nowgaon, Jaipurhat and part of 
Dinajpur. The total area of this region is about 9300 square kilometers and 
situated at about 6 -12 meters (20-40 feet) above sea level. In some area of this 
region the soil is terraced in steps.
B. Modhupur Gorh : Modhupur Gorh includes Modhupur of Tangail district, 
Jamalpur, Gazipur, and parts of Dhaka and Narsingdi district. Total area of this 
land is about 4100-square kilometers and situated at about 15 -30 meters (50 -
100 feet) above the sea level. Long ago there was a continuous Shaalbon of 160 
kilometers long from Jamalpur to Dhaka. Now this forest is scattered into 
pieces. Though Chandra, Rajendrapur or Bhawal is treated as separate forests 
but they are actually parts of Modhupur forest. Brahmmaputra and 
Shitalakshma rivers separate the eastern part of this forest from the main 
uplands. Egaro Sindhur, Shibpur, and Monohardi thana and part of Sonargaon 
are part of this separated region.
C. Lalmai Hills : Lalmai Hills is situated near Comilla town and is about 14.5 
kilometers (9 miles) in length and 0.8 -2.4 kilometers (0.5 -1.5 miles) in 
breadth. This is also a part of Pleistocene uplands. This hill is about 6 -12 meter 
(20 -40 feet) in height. Its highest pick is more than 46 meters (150 feet). 
Probably the name 'Moinamoti Shaalbon Bihar' originates because of the 
presence of Shaal forest here.
Environmental Characteristics : Soil of Pleistocene uplands is unproductive, 
acidic and reddish or somewhere grayish. Rainfall is insufficient, less than 2000 
m.m. in a year. Climate is to some extent extreme, high temperature in summer, 
dry winter, less humidity in air; these are the characteristics of this region. This 
climatic condition has contributed in creating deciduous forest. In Modhupur 
region forests develop in elevated land (Chala) and places in between raised 
lands (Chala) are known as BAID (Low land). In low land Areas paddy Is 
Major Plants : One of the characters of this upland is the presence of Shaal 
forest. Shaal forest is said to be a deciduous forest. Because in winter all the 
trees of this forest become leafless. In some places Shaalbon is also known as 
GAJARI GORH. 97% tree of this forest is Shaal tree (Shorea robusta) from 
which the name Shaal forest originates. Among other trees, there are wild 
Chalta, Gachhi Gajari, Koroi, Kumvi, Gamari, Palash, Vela, Bahera, Haritaki 
etc. Almost all of these are deciduous plants. Many jackfruit trees have been 
cultivated in Modhupur and Bhawal region. Shaalbon has reduced in large scale 
in Barendro region. There are still some Shaalbon in Phulpur and Ghoraghat of 
Dinajpur and Dhamarhat of Nowgaon. The Shaalbon of Dhamarhat is a 
continuous part of Indian Shaalbon. In Chapainowabganj and Godagari of 
Rajshahi, Shaalbon is almost nil. Besides a very few Shaal trees, some Pora￾Shaal, Koroi, and Sinuri etc. are present here.
Major Animals : Monkeys, squirrel, jackals Langoor, several species of 
snakes, mongoose and different kinds of birds are the major animals of 
Barendra region. In Modhupur region the major animals are monkeys, entellus, 
jackals, lizards, woodpeckers, owls, kites, mongoose, water monitor, squirrels 
and tree frogs. Once leopard and deer were abundant here but now they are 
very scanty.
4. Tertiary hilly region : The hilly regions of north-eastern and south-eastern 
part of Bangladesh have originated during the elevation of the Himalayans in 
Tertiary period They are similar to Lusai of Asam and Arakan hills of 
Mayanmar. These hills are situated in greater Sylhet, Chittagong and 
Chittagong Hill Tracts.
A. Hills of Sylhet : In Moulavibazar, Habiganj and north-eastern part of Sylhet 
there are hills or hillock covered with grassland and trees. Usually these are 
situated at 30 -60 meter (100 -200 feet) above sea level. In these hills tea 
cultivated. The highest hill of Sylhet region is the Patharia Hill. Its height is 240 
meters (800 feet).
B. Hills of Chittagong : In the northern region of Chittagong there are some 
small hills situated parallal with the seashore and are extended north to south 
The hills of Sitakunda and Chandranath are one of them. The highest peak here 
is 350 meters (1155 feet). In the south there are some small hilly range in 
between Cox's Bazar and Teknaf.
C. Hills of Chittagong Hill Tracts: There are many hills in the hilly district of 
Rangamati, Bandarban and Khagrachhari. These hills are extended from north 
to south. Normal height of these hills is not more than 600 meters (200 feet). 
Among the hills of Chittagong Hill Tracts the highest one is Tajingdong 
(Bijoy), which is 1231 meters (4039 feet) in height. Other high hills are: 
Moudok Muyal -about 1000 meters (3292 feet), Reng Tiyang -about 920 meters 
(3141 feet), and Pyramid hill -about 920 meter (3016 feet).
Environmental Characteristics: Hilly lands are elevated with heavy rainfall 
and it rains almost throughout the year. Air in this region is saturated with 
humidity. In Sylhet region the amount of rainfall is more than 5000 m.m. in a 
year, in Chittagong -about 3000 m.m. and in Chittagong Hill Tracts to 2500-
2750 m.m.
Plants: Presence of forest is the characteristic features of hilly region. In these 
forests there grow various types of plants - climbers, bushes, bamboos, canes 
and grasses. Formerly this region was covered with dense forests. But due to 
overgrowth of population and collection of forest resources in excess these 
forests are decreasing gradually.
Management of forests of Bangladesh is of two types. (1) Reserve forest under 
the management of the forest department of Bangladesh and (2) Unclassed 
State forest under the management of Local district administration. The second 
type of forests has suffered much loss. Most of these areas are now barren.
The management of forest department causes the damage of most of the forest 
area. In natural forest there grow many species of plant. But for the production 
of more valuable timber, in many regions the naturally growing plants are being 
cut down and many trees of a single species have been planted. This is called 
monoculture. This type of forest is called Plantation Forest. In these forests 
valuable species of plant like Teak, Gamar, Rubber etc are planted, thus the 
diversity of plants in this forest is much lesser.
For Predominance of certain species, forests are given various names. 
Such as in cane forest mainly canes are grown. In the similar way in bamboo forest various types of bamboos are grown. Teak and Gamar are already mentioned. Besides. in many treeless hills there grows different types of grasses, particularly Chhon grass (Imperata cylindrica) are grown. These are 
called Chhon forest.
In Bangladesh the hily forests are of two types :
1. Tropical Evergreen Forest: In these forests the large trees do not shed their
leaves in winter as the Shaal forest do. Thus their canopy or tops of the trees
look evergreen throughout the whole year.
2. Mixed Evergreen Forest: Some of the plants of this forest are evergreen
and some species shed their leaves in winter. As there is a mixer of evergreen
and deciduous plants this forest is known as mixed evergreen forest.
Height of the trees of this forest is not equal. As a result their tops are seems to
be arranged in 2/3 strata or layers. The tallest trees are up to 60 meters (200
feet) in height, e.g. Garjan, Chapalish, Civit. Telgu etc. They are said to be the
first layer trees. Trees having a medium height make the second layer, e.g.
Chikrashi and Gamar. Trees of the third layer are shorter than those of the
second layer, e.g. Jarul, Uriaam (Mangifera longipes) etc.
Forest region of Sylhet: They are a combination of tropical evergreen and
mixed evergreen type. Among the first layer trees, Chapalish, Deowa,
Chamrata, Aamra, Padak and Banchalta are prominent. In the second layer
Bhuikadam, Champa, Panidumur, Bandarhola, Chikrashi and Gamar are
prominent. Among bamboos Muli, Khang, Parua are notable. There are some
Garjan in Patharia region. In some areas some Teak, Ironwood, Malacca and
Koroi have been planted. A large number of orchids, various types of
Colocasia, ferns and epiphytes are found to grow in the forests of Sylhet. Canes
also grow in Sylhet forest.
Forests of Chittagong region are evergreen and mixed evergreen type. Here
among the first layer plants Garjan, Chapalish, Chandul, Koroi, and Coconut
are prominent. Second layer is comprised of mainly Chikrashi, Jarul, Bahera,
Toon, Dhenkijaam etc. Bamboos and Chhon grow in open forests.
Forest of Chittagong Hill Tracts comprises of evergreen, mixed evergreen,
deciduous, canes and bamboo forests. The major plants of this region are Civit,
Garjan, Chandul, Nageshwar, Batna, Taali, Pitraj, Punail, Koroi, Gamar, Vadi
Bandarhola, Chapalish, Udal, Aamra, Shilvadi, etc. Among these Gamar Koroi
Vadi, Shilvadi, Udal and Aamra are deciduous tree. Bamboo and Chhon forests
are in abundance in this region. Canes are also available. There are many Teak
but they are all planted.
Main Animals:
Sylhet Region: Among the mammals monkey and entellus (Honuman) are
prominent. Besides these there are various kinds of birds.
Chittagong Region: Notable animals of this region are elephant, leopard, deer,
gibbon and different kinds of snakes and birds.
Chittagong Hill Tracts: Amphibians like tree frog, toad, python, cobra,
monitor lizard are found in the forests. Among mammals big rat, bat, monkey,
entellus, leopard, gibbon, bear, elephant, gaur are found to live here. Elephant is
the largest mammal amongst the terrestrial animals. In forest, birds like
Moutusi, Doyel (Copsychus saularis) [the national bird of Bangladesh], parrot,
woodpecker and some others.
5. Coastal Forest or Mangrove forest:
Environmental Characteristics: In the coastal region of the Bay of Bengal the
soil is saline, muddy and water logged. Besides daily high and low tides is an
important factor. All these environmental factors are unfavourable for plants.
To overcome these adverse conditions, plants, those grow here, develop certain
adaptations such as: (1) Due to salinity of the soil their root cannot enter very
deep in the soil. So to protect from wind and storm many plants (e.g. Sundari)
develop root buttresses.
(2) Many plants (e.g. Boro) develop stilt roots.
(3) Due to inadequate oxygen supply in the soil many plants e.g. Sundari,
Keora, etc. develop Pneumatophores or respiratory roots, originate from the
underground horizontal branch roots lying parallel with the soil surface. There
are air pores and air spaces in these respiratory roots, which help the exchange
of gasses.
(4) As seeds are washed out by tides, in some plants there occurs viviparous
germination. Hence seed germinates when it is in the fruits and fall on the earth
when the root become elongated and heavy. Viviparous germination found in
plants such as Boro, Khosi, Hargoja etc. Sundari and Geowa do not have
viviparous germination.
Distribution of coastal forests:
Plants those are adapted in adverse coastal
environment are known as mangrove. The
forests, which develop by them, are called
mangrove forest. In local language some
times they are called 'Para-Bon' Sundarban in the southern part of Bangladesh and
Chokoria Sundarban in the south-eastern
region are natural forest. Besides these, for
the protection of coastal area from cyclone and tidal zone
Environmental Characteristics: Calcium enriched soil, moderate rainfall,
and moderate temperature is the main environmental features. Saline water
enters in the mangrove forest at the time of high tides and recedes at low tides.
 Plants: In the sandy shore of the island Jhau (Casuarina), Nishind (Vitis
nigunda), Bhat, Nata, Chhagalkhurilata are found to grow. They are the plants
of sandy heaps. Around the island there are large varieties of screw pine
(Pandanus). There are aquatic plants in the marshlands of Zinzira. There is a
small mangrove forest in the south, but there is no Sundari tree. Crepa, Khalshi
Shoilkanta, Hargoja etc. are found to grow here. Among the planted plants
mango, jackfruit, Peyara, betel nut, pomelo (Jambura), plum (Kul) and at
abundance of coconut are prominent. Around the homestead Chalta, Koroi
Ipomia, Udal, fig etc. are found to grow. In the island usually Paddy Coriander,
Onion, Chili, Garlic, Sweet potato etc. are cultivated. There are various brown
and red alga growing on corals and stones. At presen afforestation process is
going on in this island.
 Main Animals: Large marine turtles are found in the island. They come on
the land for laying eggs. They lay many eggs at a time. Besides, in the lowlying
area of the southern part there are innumerable red crabs and abundant of
marine birds. Around the island there are various kinds of marine fishes in the
sea. Several corals, different species of marine snails, bivalves and poisonous
snakes are present around the island.
The inhabitants of this island usually live on fishing. Population is increasing
very rapidly in the northern part of the island. Children collect and sell stone
and corals of sandy beach to the tourists. As a result soil is eroding from the
entire coastal area. Thus hampering the environment of the island.
Importance of Forest Regions for the Conservation of Environment and
maintaining the Ecological Balance: Plants, animals, water, light, air.
temperature and soil etc. are the components of Natural Environment. These Factors collectively form the natural environment of a particular region. From
the beginning the Almighty Creator has established a balance in these elements.
Any single notable change in any element of nature of any particular area affects the established balance among the total elements. Ultimately it causes adverse reaction on environment as a whole. As a result. the natural
environment is destroyed and gradually it becomes inhabitable. The flora,
particularly the forest of a region or of a country plays a direct role in
maintaining the natural environment and protecting a balance because the
plants are the Primary Producer. For example, if there is no plant in any water
reservoir (or marshy land), then no fish will survive there and in absence of
fish, the fish dependent cranes, other birds and snakes will not be able to live
there. If the forests of an area are destroyed, the water holding capacity of soil
will be decreased rainfall will be less, degradation of land will increase, rivers
will be silted up, and in rainy season the area will be flooded easily. And due to
the lowering of the water level in the dry season draught will appear. The yield
of crops will decrease and deficiency will increase. Again all the inhabiting
animals, birds, frogs, snakes will perish or they will come to the cropland or
locality in search of food. If the number of plant is decreased the amount of
CO2 will increase in the atmosphere and the natural balance will be destroyed.
So for leading a normal healthy life for ourselves and our next generation we
shall have to give adequate protection to our present forest resources and raise
more and more forests and fruit trees to increase the plant resources according
to the additional demand of the growing population.
Conservation of endangered plants and animals: The land area is limited
on the earth but population is increasing. New houses are being made for this
additional population to live. Schools and colleges are being built for the
education of their children, hospitals for treatment; new roads are being made
for their movement. More cultivable land are being procured for producing
additional food for them. For all these reasons forest land are being destroyed
every moment. It is learnt from different survey report that at present in
average 50 acres of forestland are being destroyed in every minute. Due to
destruction of forest areas, many plant and animal species dependent on them
have already been perished and many more species are on the way to be
extinct. The endangered plants and animals are inseparable components of the
environment. So to save the environmental balance they must be protected
from the extinction, so that we can get valuable life saving medicine and valuable gene for the development of the crops. By this time many plants and
animals ar going to be perished. They must be protected from extinction. The
endagered plants are Ashwagandha, Latakasturi, wild onion, and Montesia etc.
and among the endagered animals are Ghorial, Green tortoise, Python, King
cobra, hilly Moyena and stripped tiger. In order to save them the natural
environment, where they grow, is to be conserved as it was before. The
destruction of forest area must be stopped totally. No uncontrolled procurement
of plant from nature will be allowed. The use of insecticides, fungicides or
weedicides should be minimized as much as possible.



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