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Biology: Classification And Diversity Of Living Organism,Organization And Acquaintance Of Animals

CLASSIFICATION OF PLANTS   The Creator created the world with various types of diversified plants.  There are such small plants, whic...


 The Creator created the world with various types of diversified plants. 
There are such small plants, which cannot be seen with the naked eyes, again 
there are also such big plants that can be seen from a long distance. There are 
many pants. whcih do not have flowers. Again there are such plants which 
cannot be differentiated into root, stem and leaf. There are some plants, which 
have got no chlorophyll. They are not green and cannot prepare their own food. 
The number of plants in this diversified plant world is innumerable. They are in 
lacs not in thousands. How can we know this great plant world? For this there 
needs a well thought and well organized system. This is the system of plant 
 Classification is a system of arrangement in which one can know the plant 
kingdom easily. Considering the characteristics of plants of the vast plant 
kingdom, plants having similar characteristics are arranged in groups, i.e., one kind of plant is placed in one group. Thus plants are successively arranged in 
groups and sub-groups namely: Division, Class, Order, Family, Genus and 
Species etc. This systematic arrangement is called classification. 
The main objective of classification is to know easily the vast plant kingdom in 
short time. 

Aim of classification : 

 1. To acquire knowledge about each group and sub-groups. 
 2. To focus on the diversity of plant kingdom. 
 3. To preserve properly the acquired knowledge. 
 4. To present the full knowledge in a nutshell. 
 5. To give a name to every unit. 
 6. To identify useful plants for the benefit of mankind.

Unit of classification and Taxa: 

 There are certain steps for classification of plant kingdom. These step are 
called Taxa and is singular Tax.on. Using the steps classification is to be done 
ICBN or International Code of Botanical Nomenclature is the International 
constitution for naming the plants. Seven main. steps are recognised by ICBN 
These are: 
1. Kingdom: The plant kingdom is composed of the whole number and types 
of plants present in the world. The plant kingdom is comprises of about 450000 
2. Division: Plant Kingdom is divided into seven Divisions. 
3. Class: Each division is divided into several classes. 
4. Order: Each class is divided into several orders. 
5. Family: Each order is divided into several families. 
6. Genus: Each family is divided into several Genera (PI. of Genus). 
7. Species: Each genus is divided into several species. 
There are aboqt 250000 fruit producing plants. The name of the species should 
be written in small letters. Usually several members comprises the higher step, 
e.g. several species constitute a genus and several genera constitute a family 
etc. Sometime only one member of a Taxon may constitute a higher Taxon. In 
case of necessity any unit may be splitted to sub-unit for which the term sub 
should be prefixed against the main unit (Taxa).e.g. Sub Order, Sub￾Family Sub-Genus, Sub-species etc.
Binomial Nomenclature: 
 Name of a plant consisting of two parts - Generic (Genus) Species. name 
(Species) together make a complete name of a plant. For example Artocarpus 
heterophyllus is the. scientific name. of jackfruit, the national fruit of 
Bangladesh. In this name there are two words, first one is Artocarpus and the 
second one is heterophyllus. This type of nomenclature, i.e. one name 
consisting of two words, is called Binomial Name and the method of naming 
plants by two words is called Binomial System of Nomenclature. ICBN 
formulate the regulations of giving a scientific name to a plant. According to 
ICBN a scientific name (Botanical name) of a plant:
1. Shall be binomial. 
2. Shall be in Latin. 
3. The first name, the generic name, should be started with a capital letter and
the second name, the specific name, should be written with a small letter. 
4. Shall be written in Roman letters. 
5. Shall be printed in Italic form i.e. bending at right. 
6. In case of hand writing names should be underlined. 
Swiss scientist Carolus Lidnaeus introduced the Binomial System of 
 The main principle of classification is to arrange all plants of a similar 
character (one type of character), in a group. Previously the entire living 
creatures were placed either in Plant or in Animal Kingdom. But as more and 
more information regarding characteristics of various living beings, there 
develops a controversy regarding these two kingdoms theory. There established 
a concept of five kingdoms. According to this concept: 
(1) The entire Prokaryotic creature is placed in the Kingdom Monera. As a 
result Virus and Bacteria are separated from Plant Kingdom. 
(2) There were some controversies regarding some uniCellular Eukaryotic 
organisms (e.g., Euglena), that whether they are plants or animals? 
Because they simultaneously possess some characters of plant and some 
characters of animal. To solve this controversy now all the unicellular 
prokaryotes are placed in the Kingdom of Protista or Protoctista. All the 
unicellular Algae and Protozoa are placed in this Kingdom. 
(3) Rest of the multicellular eukaryotic organisms are arranged in there 
different kingdoms depending on their nutrition and food habit. They are, 
(A) Plantae - Autotrophic, photosynthetic green creatures. (B) Fungi -
Saprophytic, those which intake (absorb) liquid food from organic bodies 
and (C) Animalia - Rest of the heterotropic creatures. As a result of this 
classification the range of Plant Kingdom. become reduced, as Algae, 
Fungi, Bacteria and Viruses are separated from Plant Kingdom.


There are various types of viruses in the world, As a representative of
viruses, T2 Phage is itroduced here with its importance.

Structure : T2 Phage is a cellular. Its body is divided into two parts- head and 
tail; the head is a hexagonal and the tail is rod shaped, a protein shell surrounds 
the body. Inside the shell there is a' double-strand DNA in its head. At the 
upper end of the tail there is a collar, and at the lower end there is a base plate, 
some spikes and attachment fibres. In Viruses there is no nucleus, cell 
membrane, cytoplasm and other organelles. 

 Viruses can multiply only inside some other living cells. T2 Phage
attacks a Bacterium. It keeps the protein shell outside; its DNA enters into the 
Bacterial cell. Later on it (the Viral DNA) makes the Bacterial DNA inactive and make many new Viruses. Ultimately the Bacterial cell is destroyed and new Viruses came out. 

(l) T2 Phage kills Bacteria, (2) Widely used m Genetic Engineering.

Importance of Viruses generally: 
 Deadly human diseases like Measles, Pox, Polio, Hydrophobia, Influenza, 
Harpies, Viral hepatitis etc. are caused by Viruses. Viruses cause about 300 
diseases of various plants and crops. Many diseases of domestic animals like -
Cow, Goat, Pig, etc. are caused by Viruses. Vrtises are also responsible for fatal 
diseases like - AIDS (Acquired Immune Deficiency Syndrome), Cancer etc. 
Vaccines of several diseases like -Pox, Polio, and Hydrophobia etc. are also produced from Viruses. 


 Innumerable Bacteria are surrounding us even inside our body. As a 
representative of Bacteria, the structure and importance of Closteridium IS 
described here. Structural features:
1. It is rod shaped and unicellular. 
2. They live in the intestine of human being,
 other animal or even in soil. 
3. They are without photosynthetic
4. They are prokaryotic, i.e. there is no 
 nuclear membrane and nucleolus in their
 cell . 
5. There are flagella around the cell wall. 
6. They are anaerobic, Gram positive and 
 Spore producing. 

Importance of Closteridium: 
Closteridium tetani is the causal 
bacteria of tetanus and Closteridium
botulinum is the causal organism for botulism (Food poisoning)

Importance of Bacteria : 
Structure : Deadly diseases of human being, like - Phthisis (Tuberculosis), 
Pneumonia, Typhoid, Cholera Diphtheria, Dysentery, Tetanus, H60ping cough, 
Meningitis etc are caused by different Bacteria. Besides Bacteria is also 
responsible for various plant diseases. Food putrification and food poisoning, 
water pollution and demannuring of soil etc. are also caused by Bacteria. Some 
antibiotics are prepared from Bacteria. Vaccines of Cholera, Typhoid, and 
Phthisis etc are also prepared from Bacteria. Besides Bacteria also perform the 
important works like; decomposition of rubbish, blending of tea, coffee, 
tobacco, 'preparation of butter, curd, cheese from milk, extractivn of Jute fibre, 
extraction of hairs from skin in tannery, preparation of some B-Vitamins, 
proper management of sewerage lines, and nitrogen fixation etc. 


 Thousands of Algal species are found
in this world. They have diversity in
shape, size and structure, but all of them
contain different photosynthetic pigments
and thus they are autotrophic.
 A short description of Spirogyra, as a.
representative of algae, is stated there.
Structure : They are green, un-branched
filamentous algae. Their chloroplasts are
band shaped, spirally arranged in the cell.
The name- Spirogyra comes from this
spiral chloroplast. 
There are pyrenoids in the chloroplasts.
The vegetative cell's are elongated and
each cell contains a well-organised
nucleus and a large vacuole. Their body is
slippery and the cell wall is three layered. 
 Sexual reproduction occurs by the process of conjugation. They also 
reproduce by fragmentations (Filament break up into short pieces and each part 
grown into a new filament) or by spore formation.

Importance of Spirogyra: 
 It is an important source of fish- food. It may .also be used for human food 
by special processing. It plays a great role in the natural food cycle. 


 Fungi (Sing: Fungus) are non-green;
there are no photosynthetic pigments in
their body. They depend on dead organic
substances or other living bodies for their
food. A short description of Agaricus- a
member of fungi is stated here: 
Structure: Agaricus is a well discussed
fungus. In BANGLA it is known as
'BANGER CHAATA' (Umbrella of frog).
The main vegetative body of Agaricus is very thin, thread like and branched. In the vegetative cells there are Nuclei (PI. of 
Nucleus), granular protoplasm, oil drops and vacuoles. Colourless thread like 
vegetative body usually lies under the soil surface and spread there. At last they 
interwove to form a special organ and rise above the soil. This special organ 
above the soil is called the Fruit body, which also known as Basidiocarp. A 
mature fruit body or an umbrella like body is known as Mushroom. It consists 
of an expanded umbrella like top, called Pileus and a stalk or stem like portion 
called the Stipe. Gills are arranged at the ventral surface of the Pileus from 
where spores are born. 
Reproduction: They reproduce by the formation of Basidiospores.
Importance: Agaricus campestris is well cultivated in home and abroad. They 
are marketed as 'Mushroom' and are served as a delicious food in luxurious 
hotels. There are different kinds of valuable food ingredients in it. In the fields 
there may have poisonous Mushroom too. So without being certain one should 
not eat it.


 There are about 23,000 species of Bryophyta in the world, of which Mosses 
constitute a major portion of this group. Mosses grow abundantly in  Bangladesh. Characteristics of Bryum moss are described here. Bryum grows 
on damp soil, on tree trunk and on the old walls etc. 
Characteristics : 
1. Plant body is divided into Rhizoid (instead of root), Leaf and Stem. 
2. There is no vascular tissue in its body. 
3. Male and female plants are different. 
4. Bi-flagellate sperms, grown in male plants, united with the non-motile egg. 
grown in the female plant, initiate the
5. Sporophytes are developed on the top of
the female plants. 
6. Spores produced in the capsules
germinate to produce algae like
filamentous Protonema. 
7. Moss plants develop from the Protonema. 

Importance of Moss plants : Mosses help to
grow soil on the stony surface. It helps to
hold water. Pit coal is develop from
Sphagnum (a Moss). 


 Pteridophyta is the first vascular plant (which Possesses vascular tissues). 
The number of species of pteridophyte is about 10,000 species. As a representative of Pteridophyta, the description of Pteris is given below. Pteris is also known as sun fern. 

1. Pteris plant is sporophytic. 
2. Plant body is divided into root stem and leaves. 
3. The stem is Rhizomatous and bears scales. 
4. Leaves are evergreen and pinnately compound. Leaves of fern are known as 
5. Vemation of young leaf is circinate. 
6. Sporangia (Sing: Sporangium) develop along the margin of the mature 
leaves. The swollen portion of a sporangium is called the capsule. Spores are borne in the capsule, 
7. The spores germinate and give rise to green heart-shaped gametophytes￾called Prothallus. Male and female sex organs develop on Prothallus, and by 
the union of the male and female gametes a new Pteris plant is born. Pteris are 
found to grow on old, broken walls and old bricks heap

Importance of Fern: 
Many ferns are planted in pots as ornamental plants 
Some ferns are taken as vegetables and some produce medicines. 


Gymnosperms produce flowers and seeds but do not bear any fruit. Once they 
were well spread around the world but at present their, number is becoming 
very limited. The total number of species of gymnosperms in the whole world 
is only 27. In Bangladesh only 3 gymnosperms are found to grow naturally in the forests. As a representative of gymnosperm the characteristics of Cycas is 
described here: 
Characteristics of Cycas: 
1. The Cycas plant is sporophyte. Their 
body is divided into root, stem and leaves.
2. They have vascular tissues. 
3. Leaves are compound, look like the
leaves of coconut tree, and are arranged
spirally as a crOWR on the top of the stem.
4. Vernation of the young leaves is
5. There are two types of root - (i) Primary
root or taproot and (ii) Coralloid root,
which resemble the sea corals. 
6. Female and male plants are different 
7. Female Sporophylls (Megasporophylls) are borne on the top of the female 
plant and the male Sporophylls (Microsporophylls) are on the top of the male plants. The male Sporophylls together form a cone like body, known as Male 
8. Seeds are developed after pollination and fertilization. New plants develop 
from the seed.

Importance : 
Cycas is planted in the garden only for beautification Cycas is found to grow wild in the forests of Chittagong. 

Monocotyledonous or Monocot plants: 

 Monocot plants bear one cotyledon in their seeds. Their roots are fibrous, leaves have parallel venation; flo:vers are trimerous (each floral parts being 3 in number). Examples of monocot plants are Paddy, Wheat, Sugarcane, Bamboo, Palm, Coconut, Betel nut and Date-Palm etc. As a representative of Monocot plants, here the characteristics ap.d importance of coconut tree is described briefly 
1. It is a tree without branch. 
2. Leaves are pinnately compound and are 
3. Arranged as a crown on the top of the
 stem. Flowers are in inflorescence, and
 the inflorescence is covered with a
 woody Bract. 
4. Flowers are unisexual; number of female
 flowers is less and is present at the base
 of the inflorescence stalk. Number of
 male flowers is more and is present at
 the top of female flowers. 
5. In flowers there are 3sepals, 3petals and
 6stamens in male flower and 3united 
 carpel in female flower. 
6. Fruits are fibrous and one seeded. 
Importance of Coconut plants: Green Coconut is a soft drink; the mature 
coconut is used in preparation of sweetmeat, treated with vegetables in curry. 
Again coconut oil also is obtained from it. Ropes, mats etc. are made from its 
coir. Leaves are used to make roof of hut or cottages. Brumes are made from the 
midrib of the leaflets. Leaves and stem are also used as fuel.

Dicotyledonous o,r Dicot Plants: 

 Dicot plants bear two cotyledons in their seeds. The root system is Tap
Root System; leaves are with reticulate venation, flowers are Tetramerous or
Pentamerous. In the world the number of dicotyledonous plant is more.
Examples of Dicot plants are: Mango, Jamboline (JAAM), Litchi, Jackfruit,
Shaal, Teak, Mehogoni, Garjan, and Sundari etc. As a representative of Dicot
plants, the characteristics and importance of Psidium guava (PEYARA) is described with a.diagram of a small twig of it.
Characteristics :
1. Psidium plants are sporophyte. The
 plant is a small tree with multiple
2. Leaves are simple and opposite.
3. Flowers are stalked, solitary. It develops
 from the axils of the leaf.
4. Ovary is situated below, the other parts
(whorls) of the 'flower is above the
5. Flowers are bisexual and
actinomorphic; sepals 5 free,
petals 5 free and white in colour; stamens many and free, carpels 5 syncarpous
Importance :
The fruits of Psidium are of great importance. The plant is cultivated for its
fruits. Ripe fruit is very tasty and the whole of it is edible. Jam, jelly etc. are
prepared from its fruit. Leaves are used in the treatment of diarrhoea and
dysentery. Water boiled with Psidium leaves is a good curative of gum pain.



Innumerable small and large plants and animals live in harmony in the diverse
geographical, environment and climatic conditions of the world. Organisms of
the same species living successfully under different environments become
modified or adopted differently. As a result, from a common ancestor with
diverse characters animals and plants evolve. This diversification of organisms
is called bio-diversity. So, the diversification found among the animals is
known as Animal diversity and the diversification among the plants is known
as Plant diversity.
To survive and disseminate successfully under various geographical regiotns
the diversities that have arisen among the animals through adaptations and
essential modifications of their external and internal morphology, size, shape,
behavior etC. is called animal diversity. Due to this diversification various species of animals have arisen in the world.
Due to diversification among the animals, the zoologists have categorized the
animal kingdom into the following criterions:
1. On the Basis of Shape and Size:
Animals are grouped into two categories on the basis of their shapes and sizes,
such as: .
a. Microscopic Animal
Light Microscopic: These animals can be seen well with the help of simple
light microscope.
Example: Amoeba, Hydra Cyclops Daphnia etc.
b. Large Animals: These are not microscopic. These can be seen by naked
eyes. Innumerable small, medium, large and very large animals belong to this
group. Example: Ant, Fly, Mosquito. Leech, Earthworm, Cockroach, Frog,
Turtle, Lizard Snake, Crocodile, Dog, Cat, Goat, Cow, Bat, Whale, Man etc.
2. On the basis of Symmetry:
Description of the relative proportion of the shape, structure, SIze etc. of
various organs of the animal body is called symmetry. The symmetry of
animals is mainly of three types.
a. Asymmetry: Not capable of being halved in any plane, e.g. Amoeba, snail
b. Bilateral Symmetry: Capable of being halved in one and only one plane,
e.g. Cockroach, Lizard, Frog, Fish, Man etc.
c. Radial Symmetry: Capable of being halved in many planes, e.g. Hydra,
Jelly fish, Star fish, etc.
3. On the basis of habitat: Animals are of different types such as:
a. Terrestrial: They live on land, e.g. Cockroach, Toad, Goat, Cow, Tiger
b. Aquatic: They live in water.
Aquatic animals are of two types:
i. Fresh water animal: Hydra, Singh, Kai, Frog, turtle, crocodile
ii. Marine animal: Lotia fish, Whale, Dolphin, Jellyfish, Shark, Starfish and
c. Flying: This animals can fly in the sky, e.g. Butterti.y, Bats and various
species of birds
d. Tree-living Or Arboreal: They live on trees, e.g. Tree frog, Python, various
species of Monkeys, Lemur and Leopard.
e. Desert dweller: They are animals of the desert, e.g. Camel, Dumba etc.
f. Boreal: Rat, Fox, Platypus, some species of snakes, Earth worms etc.
g. Polar: Some animals live in the Polar Regions, e.g. White bear, Antelope and
h. Forest dweller: Tiger, Bear, Monkey, Deer, Peacock, various species of
Snakes and Birds, Boar, wild Buffalo etc. They live in deep forest.
i. Mountain dweller: Gayal, Mountain goat, Elephant etc, are animals living in
mountain areas.
4. On the basis of habits:
On the basis of habits animals are of two types; mainly:
a. Diurnal: They are active during day timer e.g. Deer, Squirrel, Cow, Horse,
Duck, Hen, Vulture, Butterflies, Hoppers, Eagle and King stock.
b. Nocturnal: These animals are active during night time, e.g. Tiger, Fox, Owl,
Moths, Shrew, etc.
5. On the basis of feeding habits animals are mainly of three types:
a. Herbivorous: These animals eat grass or other plant materials, e.g. Goat,
Sheep, Cattle, Elephant, Horse, Rabbit, Guinea pig, etc.
b. Carnivorous: They are generally predacious and feed on animals, e.g. Tiger,
Lion, Jackal, Vulture, Hawk, Hyena, etc .
c. Omnivorous: Animals of this category eat all kinds of food, e.g. Cockroach,
Crow, domestic Dog, Cat and Man.
6. On the basis of nutrition:
a. Holozoic or heterotrophic or zootrophic:
For nutrition they depend upon plants or animals, because they cannot prepare
their own food. Heterotrophic animals are again mainly of three types:
i. Scavengers: They get their food from dead plants and animals, e.g.
Cockroach, Crow, Vulture, Hyena etc.
ii. Parasites: They take nutrients from other organisms i.e. the host's body.
They are smaller in size than the hosts. They live outside or inside the host body
e.g. Round worm is an internal parasite of human body and pediculus is an
external parasite.
iii. Predators: They are generally bigger in size than their prey animals. They
kill their hunts and eat their flesh e.g. Tiger, Lion, Jackal, Wolf, etc.

7. On the basis of the presence or absence of vertebral column:
Depending on the presence or absence of vertebral column in animal body,
animals can be divided into two principal groups. Such as:
Invertebrates: Earthworm, Cockroach, Roundworm, Jelly fish, Starfish,
Octopus, Snail, Oyster, Hookworm etc, are the animals without backbones.
Vertebrates: Embryonic notochord (an identifying character of the phylum
chordata) of these. animals transforms into vertebral column. When fully
formed, e.g. Fishes, Amphibians, Reptiles, Birds and Mammals. Vertebrate
animals have been placed in the subphylum vertebrata under the phylum
chordata ..
8. On the basis of economic importance animals can be divided into two
main groups: .
Beneficial animals: There are many worms, insects, birds and beasts in the
world which benefit man in various ways directly or indirectly, e.g. Bee, Silk
worm, various species of fresh water and marine Fishes, Dog, Cat, Goat, Cow,
Horse, Ass, Elephant, various species of birds etc.
Harmful Animals: Many animals do harm to man directly or indirectly, e.g.
Mosquito, Fly, White ant, Ribbon worm, Round worm, Snakes. Rat, Tiger,
Lion etc.
Though apparently, they are harmful to man, in the animal world all animals in
one way or the other are necessary. All animals have a particular role in'
keeping the natural balance, food chain etc. So to preserve the existence of
animals including the human being, no organisms should be killed
unnecessarily. For that the balance of ecosystem may be disturbed, which
ultimately will have direct or indirect harmful effects on human society. To
understand the beneficial role of animals, every body should have at least a
first hand knowledge about the animal kingdom. Animals are valuable and
essential resource of a country. It is the duty of all conscious people to be
sympathetic towards them and to conserve them. Otherwise many of the animal
resources will vanish from the surface of the earth. In the long run the future
human society will adversely be affected.


In the world there are numerous plants and animals of diverse nature. It is not
possible for anyone to know about each of them separately. So the organisms
(that is the plants and animals) are scientifically arranged into various taxon
(plural taxa), based on the similarities and dissimilarities among them. The
process. of arranging the organism into various taxa is known as classification.
The science of classification is called Taxonomy.
There are different basis of classification. The natural or modern classification
is more applicable compared to others. Swedish naturalist, Carolus Linnaeus,
introduced the rules of modern natural classification.


a. With the help of classification we can learn scientifically with less labour and
time about the plants and animals of the world.'
b. When the classification of an organism (plant/animal) and the identifying
characters of the taxa of that classification are known, we can easily get an idea
about the features of that particular organism.
c. Unfamiliar organism can easily be marked and identified by comparative
studies of the similar and dissimilar characteristics. Harmful and beneficial
organisms can be identified.
Through comparative studies, particularly of the structural characteristics of any
plant or animal, placing that organism under a phylum, class, order, family;
genus and species is the object of classification. Species is the unit and
lowermost taxonomic category.


 Classification of cockroach
 Kingdom : Animalia
 Phylum : Arthropoda
 Class : Insecta
 Order : Dictyoptera (in Britain & Europe)
 Orthoptera (in America)
 Family : Blattidae
 Genus : Periplaneta
 Species : P. americana


1. Kingdom, Phylum, Class, Order, Family, Genus and Species names are to be
written one below the other in definite order.
2. Names of the step can be written either in English or in BangIa. But the
Phylum name must be written in English, e.g. in the case of writing the
classification of man. Man is a.n animal of the phylum Chordate. Here at the
time of writing, general name of the taxon can be written in English or in
BangIa but the Phylum name chordata must be written in Roman alphabet
never to be written in BangIa.
3. When writing in hands, in both the cases of plants and animals, the generic
and specific names must be underlined individually. For example, in case of
Man when writing in hand, Genus: Homo, Species: Homo sapiens. This can
also be written as H.sapiens:
4. When printed Genus and species names are to be printed in italics. as:
Genus: Homo and Species: Homo sapiens, H sapiens ..
5. Excepting the generic and species names, no other taxon should not be
6. For the name of family of all animals there should be an ending of four
letters 'idae', such as: Hominidae (family of human) Bufonidae (family of
7. In case of invertebrate animals, it is enough to write seven taxonomic
categories in English, namely kingdom, Phylum, Class, Order, Family, Genus
and Species. But in case of the vertebrate animals like Man, Frog, Snake Fish
etc. you are to write the taxon subphylum, under ,the phylum chordata. For
example the classification of Man is given below.
 Classification of Man
 Kingdom   Animalia
 Phylum     Chordata
 Subphylum    Vertebrata
 Class        Mammalia
 Order       Anthropoidea
 Family     Hominidae
 Genus      Homo
Specie      H.sapiens

8. You must write in full the scientific or species name of any animal, such as
scientific name of toad: in print you are to write Bufo melanostictus but while
classifying species names can be printed both as B. melanostictus or Bufo
melanostictus and in hand B. melanostictus. But it never can be printed
melanostictus or written melanostictus.
9. Scientific name is to be written in combination of two parts. Of these two
parts, the first one is the genus part of the scientific name and the other is the
species part, e. g. scientific ,name of Toad is Bufo melanostictus. Here Bufo is
the genus part and melanosticutus is the species part. This system of naming the
animals was approved by the ICZN (International commission on
Zoological Nomenclature) in 1961.
So, the process of scientific naming of organisms (plants and animals) with the
combination of two words using the genus name first and species name thereafter is called Binomial Nomenclature.

Like animals, unicellular organisms were placed into phylum protozoa. But
now they are separated from the animal kingdom and placed in protista or
protoctista of 5-kingdom classification. However, as phylum protozoa were a
part of the animal kingdom, previously therefore they are still taught in
zoology. In the last decade, about the 80's, the International Protozoologist
Committee decided that the unicellular protozoans are of vast variety and that
they should be included in a single phylum. Thus they have classified
protozoans under 7 phyla. In this classification, protozoa is a subkingdom of
protista or protoctista kingdom. Among them the amoeba is included in-the
phylum Sarcomastigophorea and malarial parasite is in Apicomplexa. The
names of nine major phyla of animal kingdom are mentioned below with their
identifying characteristics and examples:
1. Plylum - Sarcomastigophorea Kingdom - Protista
Habit and habitat: The organisms of this phylum are cosmopolitent. Some
members of these phyla are free living but some are colonial, some lives on
damp and wet soil, many species lives in fresh water and marine water. Many
members are external or internal parasite of plants or animals, such as
(Amoeba) free-living organism of fresh water.

Identifying Characters: 

a. Animals of this phylum are unicellular, mic~oscopic. All of functions are
perforn1ed by the single cell.
b. They have no cell wall (outside the cell membrane); in the cytoplasm there is a centriole, one vacuole is present, no plastid.
c. They locomote with the help of pseudopodia:
d. They live singly or in colonies.
e. They are free living animals. Example: Amoeba proteus.

Kingdom Animalia: 

Habit and habitat: Animals of this phylum are generally known as sponge.
They are of different sizes, shape and colour. They are distributed worldwide. In
adult stage they live under water. attached with some objects. They live in
colonies. They look like a plant. Major members are marine but some live in
fresh water.
Identifying Characters:
a. These are simplest multi-cellular animals.
b. There are many small pores or ostia in their bodies
c. Internal circulation is maintained by canal system.
d. There is no separate well-formed tissue, organ or system.

Example: Scypha gelatinosum (Marine sponge). spongilla fragilis (Fresh water sponge) 

2. Phylum - Cnidaria 

Habit and Habitat: Many members of this phylum live in worldwide in fresh
water, drain, canal, river, lake, stream etc. But maximum are marine species.
They are of different colour, shapes and sizes; they are the beauty of sea they
are attached with floating wood, leaves or something else or free swimming.
Some species are free living and some are colonial. As: Hydra (fresh water
animal) Jelly fish (Marine water animal) and Corals (Marine).

Identifying Characters: 

a. They are two layered animals; body is formed of two embryonic cell
layers ectoderm and endoderm. Between these two layers there is a non￾cellular layer called mesoglea.
b. A body cavity named coelenteron or gastrovascular cavity takes part both in
digestion and water circulation.
c. In the ectoderm there are specialized cnidoblast cells. Example: Hydra
Example : Hydra vulgaris, Aurelia aurita.

3. Phylum Platyhelminthes: 

Habit and habitat: Members of this
phylum are mainly ectoparasite or
endoparasite of other organisms but a few
species are free living. They live in fresh
water, drain; stream etc. and some species
live in saline water, some member of this
phylum live in damp and moist soils.
Identifying Characters:
a. They are flat bodied, worm like diocious and mostly endoparasitic animals.
b. Body is covered by a thick cuticle.
c. Sucker or hooks are present.
d. Flame cell is the excretory organ.
e. Digestive system incomplete or absent.
Example: Taenia solium Tape worm Fasciola hepatica liver fluke.

4. Phylum Nematoda. 

Habit and habitat: Most members are
parasitic. Some of them lives as
parasites of plant roots or grains
(Wheat. paddy) Intestine, blood and
other organs of different animals. some
are free living they live in soil and
water. On the basis of number they are
second largest phylum of animal

Identifying characters: 

a. Body cylindrical, covered with thick cuticle and bilaterally symmetrical.
b. Complete digestive system (Mouth and anal opening present).
c. Body cavity uncovered, there is no true coelom.
d. Circulatory and respiratory system absent.
e. They are generally unisexual.
Ascaris lumbricoides (Round worm)
Ancylostoma duodenale (Hook worm)
Enterobius vermicularis (pin worm)
Rhabditis- free living, Live in soil.

5. Phylum Annelida: 

Habit and habitat: Majority of the annelid
animals live in temperate and tropical counties of
the world. They show wide diversity in their
structure, habit and habitats. Many live in fresh
water, saline water. Some occur in moist soil,
some members lives in seashore, some in bottom
of shallow sea, some species live in grooves on
stone and soil.

Identifying characters: 

a. Body metamerically segmented, body covered with thin cuticle.
b. Ciliated, glandular, coiled tubules named nephridium acts as excretory
c. Generally setae are used as accessory organ for locomotion.

Example: Pheretima posthuma (Earthworm), Tubifex (Live in fresh water,used as food of aquarium fish Hirudo madicinalis (leech). 

6. Phylum Arthropoda: 

Habit and habitat: This phylum is. the largest.
in animal kingdom. About 60-65% of the known
animals belong to this phylum. They are -
universally distributed and are adapted to live in
almost all types of environments. 
Many species are either ecto or endoparasite.
They are terrestrial or aquatic. Many of them are
capable of flying like cockroach, butterflies,
Bagdaprawn, king crab, spider etc are members
of this phylum. 

Identifying characters: 

a. Body is divisible into different regions, namely head, thorax and abdomen of 
cephalothorax and abdomen or head and trunk. 
b. Appendages of the animals of this phylum
are jointed or formed by many segments. 
c. Body is covered by cuticle enriched with
d. In the head there is a pair of compound
eyes and antenna. 
e. They have blood filled body cavity named

Example: periplaneta americana
(Cockroach) Bombyx mori (Silkworm)
Carcinoscorpius (King crab -a living fossil). 

7. Phylum Mollusca: 

Habit and habitat: Member of this phylum shows a great variety in structural 
organization, habit and habitat. Most of the members have shells. They are 
marines and some occur in hilly region and in forest or in plain land. Some 
species live in different types of fresh water, e.g. snail, octopus and bivalve.

Identifying characters:

a. Body is soft, generally covered by hard shell.
b. Muscular foot present on the ventral side of the body for locomotion.
c. Respiration by gills or lung.

Example: Pila globosa (Apple snail) lamellidens (Bivalve) Octopus vulgaris

8. Phylum Echinodermata:

Habit and habitat: All members of this phylum are marines. None occurs on 
land or fresh water. Different species of Echinodermata are found in all seas of 
the world. Majority of them are free living, but some are at the adult stage lead 
a stationary life.

Identifying characters:

a. Integument spinous
b. Body radially symmetrical or can be divided into five similar parts
c. Water vascular system controls the locomotion and respiration
d. In adult animal, head, dorsal and ventral side is not marked clear, oral and 
aboral surfaces are present.

Example: Asterias rubens (Star fish) Echinus esculentus (Sea urchins)

9. Phylum chordata: 

Habit and habitat: Animals of this phylum are found in almost all habitats of
world. Some species live in land. Among the aquatic chordates some live in
fresh water and some in marine water. Many species are arboreal, desert
dweller, polar, cave dweller and carsorial. Some members of phylum chordate
are ectoparasite on other animals.

Identifying characters: 

Through out life or only at the embryonic stage animals of the phylum chordata
have four principal characteristics:
1. Notochord: They have in the middle of the dorsal side of the body a soft.
flexible. rod shaped, firm, un-segmented structure called notochord, throughout
the life or only in embryonic condition. In higher chordates, it.is replaced by
bony vertebral column.
2. Nerve cord: A single medium, hollow nerve cord on the dorsal side of body
is present.
3. Throughout life or at any stage of the life-cycle there are lateral pharyngeal
gill slits.
4. In case of aquatic chordate body behind the anus modified into a muscular
tail which is accssory organ of locomotion.

Example: Bufo melanostictus (Toad) Crocodylus porosus (saline water
crocodile) Homo sapiens (Man) Bubo bubo (owl) Catla catla (catla fish)
Ascidia (Ascidia) Scoliodon (shark) Tenualosa ilsha (Hilsa fish) Mus musculus
(Small rat) Bandicota indica (Large rat)


Amoeba: Amoeba proteus is a simple one celled animal. It is so small in size
that it cannot be seen clearly without a microscope. Amoeba is an excellent
example of Subkingdom Protozoa, Kingdom Protista or Protoctista. Though
they are members of protista at present, they are discussed with animal.
Following that tradition, they will be discussed along with. the living beings.
Though the body of Amoeba is formed of a single cell, the functioning of this
cell is not so simple. Within the cell of Amoeba, many physiological functions
like respiration, nutrition, reproduction, excretion, stimulation etc. are
Habit and Habitat: Amoeba is found throughout the world. It lives in pond,
river, and 'other freshwater pools. Soft wet soil, leaves and stems of aquatic
plants or any hard surface may harbour Amoeba, It is a free living animal. By
producing finger like pseudopodia they move and intake their food.
Body structure: Amoeba appears as a colourless and transparent drop of jelly
when viewed under a microscope. It lacks a definite body shape because it
changes its shape by producing the pseudopodia every moment. So, it is not
possible to describe its definite shape, anterior or posterior ends, dorsal and
ventral surfaces. Moreover, as Amoeba's shape is changeable, its body cannot
be divided into two similar parts. This condition is called ,asymmetry. In size, a
full grown Amoeba generally may be from 1/20 mm to. 1 mm. The body of
Amoeba can be divided into two main parts, Plasmalema and Protoplasm.
A. Plasmalema or Plasma membrane: The body of Amoeba is covered with
plasmalema formed by the combination of protein and lipid. This membrane is
extremely thin, living, semi-permeable and elastic.

1. Plasmalema of Amoeba gives its shape.
2. It holds the various organelles inside the protoplasm.
3. The membrane being elastic it can produce pseudopodia easily.
4. By the process of diffusion, through the plasmalema it takes oxygen and
water. It also discharges carbon dioxide and excretory materials through the
5. It helps the Amoeba to become attached to any solid surface.
B. Protoplasm: The thick jel1y like substance surrounded by the plasmalema is the protoplasm. It can be divided into two parts, Cytoplasm and Nucleus.
1. Cytoplasm: Without the nucleus, the rest of the protoplasm is cytoplasm. It
is divisible into two parts, such as Ectoplasm and Endoplasm.
Ectoplasm: The part of cytoplasm immediately behind the plasma membrane is known as ectoplasm. This part is thick, transparent, non-granular and contractile.
1. Ectoplasm protects the organelles inside the body.
2. It helps to maintain the shape of the body.
3. It assists the Amoeba in producing pseudopodia

Endoplasm: The granular portion of cytoplasm which is surrounded by the
ectoplasm is known as the endoplasm. This part is semi transparent and less
The relatively thick outer part of endoplasm is called plasmagel and inner
liquid part plasmasol. The granules of plasmagel generally always remain
stable. But the granules present in plasmasol show active movement. The
difference between plasmagel and plasmasol is .not consistent because one can be transformed to other.
1. Endoplasm contains the organelles of the cell,
2. It assists in various physiological functions.
3. Frequent change in the density of the plasmagel and plasmasol helps in
producing pseudopodia.
2. Nucleus: At the middle of the endoplasm the translucent round body seen is
the nucleus. It cannot be clearly seen in the body of living Amoeba. There is
only one nucleus in Amoeba., The nucleus is covered by the nuclear membrane
made of protein and lipid. Inside there remain chromatin fibres and the
nucleolus. The amount of nucleoplasm is scanty in the nucleus of Amoeba.
1. Nucleus conducts the functions of the Cell body.
2. Nucleus takes active part in reproduction.
Cytoplasmic organelles:
(A) Pseudopodia: Froml any part of the body of living Amoeba finger like
growth are produced continuously. These are known as pseudopodia.
Pseudopods are made of plasmalema, ectoplasm and endoplasm. These are
unstable outgrowths of the body and disappear soon. The anterior part of
pseudopods is round and blunt.
1. Pseudopods help in capturing the food materials.
2. They play an important role in locomotion.
3. Pseudopods indicate the anterior part of the Amoeba at the time of locomotion.

(B) Vacuoles: There are several types of vacuoles in Amoeba. Presence of the
vacuoles is an important characteristic of Amoeba. The nature of formation of
these vacuoles is rather simple. The vacuoles help in various physiological
functions. There are three types of vacuoles in Amoeba.
1. Contractile Vacuole: In the endoplasm of Amoeba some bubble like
vacuoles are seen. These vacuoles are transparent and fast growing. In the body
of the living Amoeba these vacuoles can continuously be contracted or
expanded, so, these have been named as contractile vacuoles.
1. Contractile vacuoles store the watery substance of the body.
2. They-help in the removal of excess water and excretory products.
3. They help in the expulsion of carbon dioxide produced during respiration.
2. Food Vacuole: In the body of Amoeba food vacuole is formed surrounding
the food material. There may be one or more of this vacuole. Size, shape and
number of these depend on the size, shape and number of food materials.
1. Food vacuoles store the food material.
2. They help in the digestion of food.
3. They have also roles in excretion of faecal materials.
3. Water vacuole: The smallest transparent, round water filled vacuole in the
body of Amoeba is the water vacuole. In number it can be one or more. Water
vacuole is noncontractile.
Functions: Water vacuole contains water and keeps the balance of water
constant of the body. If an Amoeba is examined under high-powered
microscope some organelles are seen as.
Goigi bodies: Within the'stained body of Amoeba some structures are seen
which looks like small tubules and vesicles. These are known as Golgi bodies.
Function: Golgi bodies help in secretion and excretion of food.
Mitochondria: Around the contractile vacuoles some rod or dot like structures
are seen. These are mitochondria.
Function: They take part in respiration and in energy generation.

Reserve food: In the endoplasm of the body of Amoeba food particles remain
stored as fat and starch. When necessary these stored food materials provide
nutrition to Amoeba.
Crystals: Crystal particles of different shapes and sizes are found in the body
of Amoeba. It is assumed that these crystals are simply the faecal substances
produced during metabolism.
Locomotion: Animals move from one place to another for food, self-defense
and in search of favourable environment. Such voluntary movement of animal
is known as locomotion. Amoeba move very slowly and its locomotion is
irregular. Amoeba move with the help of special type of finger-like out growth
known as pseudopodium (Plural-pseudopodia).
The meaning of pseudopodium is "false foot"(pseudo means False and podos
means foot). Amoeba at the time of locomotion, produce pseudopodia from
different parts of the body and these again disappear within the body. This
particular type of locomotion of Amoeba is called Amoeboid movement.
At the time of locomotion pseudopodia come out from any part of the body and
the animal advances in that direction. Simultaneously with the formation of
pseudopodia, the protoplasm of the body of Amoeba flows in that direction and
with that other parts of the body move that way. In this way Amoeba advances
towards its target. It can form pseudopodia at any part of its body and always
move at the direction of pseudopodia. When new pseudopodia are formed on
one side of the body, the old pseudopodia disappear. In this way, Amoeba
moves by rolling.

Nutrition: Energy is required for physiological function. Food is the source of this energy. Nutrition is a process, By this process Amoeba performs its food
ingestion, digestion, absorption, assimilation and excretion of faecal materials
Body reorganization and growth also occur through this process.
Food: Amoeba takes small algae, bacteria, diatom and various micro
organisms as its food.
Process of intake of food: Amoeba has no digestive system. For the intake of
food there is no mouth or any other fixed organ. At the time of food intake
Amoeba becomes attached to a surface and with the help of pseudopodia ingest
food by various methods. It can select organic and inorganic foods. It takes
about 2 to 3 minutes to ingest the food. Amoeba intakes food mainly by the
following five processes:
1. Circumvallation
2. Circumfluence
3. Import
4. Invagination
5. Pinocytosis
1. Circumvallation: In this process Amoeba takes mobile and solid food
substances. With the help of pseudopodia it surrounds the food material.
Without touching the food material, the edges of the pseudopodia come close
together and with the ectoplasmic membrane form the food vacuole along with water. When the pseudopodia surround the food material it looks like a cup. It is called "Food cup". The ectoplasm transforms into endoplasm and protects
the protoplasm
2 Circumfluence: In this process Amoeba takes immobile food materials.
Immediately after coming in contact with the food material, amoeba forms a
"food cup" and by stretching the pseudopodia it brings the enclosed food in
direct contact with the body. In this way, Amoeba takes the food material inside
the body.
3. Import: If any food material comes on its body, by being motionless and
without stretching any pseudopodia, Amoeba makes the food inactive. Then the
inactive food material is taken inside the body. This is called import process.
4. Invagination: When the body of amoeba comes in contact with any food
particle it secretes sticky substance and fixes it with the body surface. Besides Amoeba secretes a
kind of toxic juice from the body which kills the living food material. The
ectoplasm along with the food enters the endoplasm in the form of a tube. Then
the plasma membrane disappears and forms a food vacuole. In this process no
pseudopodium is required to receive the food material.
5. Pinocytosis: In this process Amoeba takes liquid food materials. At many
times in different parts of the body surface of Amoeba the plasmalema gets
folded and enters into the endoplasm,"as a result of which a tube like structure
is formed. This tube is called pinocytic tube. With liquid food materials the
tube forms pinosome or small cavities, which later on is taken within the
Digestion: The cytoplasm of the body cannot absorb directly the food materials
which Amoeba intakes. Reacting with various enzymes these food materials
are converted into simple components for assimilation. This is digestion
Digestion occurs in two process-acidic and alkaline. Amoeba has no digestive
system. Food is digested inside the food vacuoles. Along with the body
movements the food vacuoles are brought well inside the endoplasm. Inside.
the endoplasm, hydrochloric acid from the inner membrane of the vacuoles
works on the food. It kills the living food materials and makes the contents
acidic. Thus the acidic process is finished. Next alkali is secreted from the
neighboring cytoplasm which brings the partly digested food material into the
alkali media. At this time, various types of enzymes are secreted from the
endoplasm enters the food vacuole along with the food. In the digestion of food
more than one enzyme participates. It is however not known definitely which
enzymes take part and what their order is. It is assumed that there is a
possibility of the presence of protease, lipase and carbohydrates enzymes. The
enzyme named protease is secreted when food remains in an acidic medium
inside the food vacuole. It converts the complex protein food into simple
When the food vacuole becomes alkaline, the enzyme peptidase becomes
active. Due to this reaction peptide is transformed into amino acids. Lipase
transforms the fat portion of the food into fatty acid and glycerol. The enzyme
amylase acts on the carbohydrate part of the food and transforms it into
glucose. As the digestion process continues, the form of the food material is
gradually changed.
Absorption: Through the actions of enzymes complex food materials are
converted into simple materials. These simple food components inside the food
vacuole are absorbed by the endoplasm.
Egestion : Inside the endoplasm of amoeba, the digested food is absorbed and
the remainder is stored in the food vacuole. The food vacuole gradually
approaches to the cell membrane of the body opposite to pseudopodia. At one
stage the contents of the vacuole are thrown outside the body through the
plasma membrane.
Respiration: There is no definite structure for respiration in Amoeba. They
respire through aerobic process. In absence of any definite organ, there
respiration is accomplished by the plasmalema. Respiratory work mainly occurs through diffusion. The amount of dissolved oxygen of water where Amoeba
lives is higher than the oxygen content of cytoplasm. As a result, oxygen can
easily enter the body of Amoeba by diffusion process. Oxygen is required for respiration. To meet this requirement diffusion continuously
occurs in the body of Amoeba. Carbon dioxide produced due to chemical
reaction, is eliminated from the body in the same manner. This process can
easily happen as the amount of carbon dioxide is more in the cytoplasm of
Amoeba than in the water.
Excretion: The process by which the nitrogenous waste materials are collected
and removed from the animal body is called excretion. The excretory material
of Amoeba is mainly ammonia. In dissolved condition these excretory
materials are discharged outside through the plasmalema by the process of
Reproduction: Reproduction is one of the most important characteristics of
organisms. The biological process by which an organism, to check its
extinction, either singly or with the help of the opposite sex of the same
species, produces progeny is called reproduction. Amoeba mainly produces its
progeny by asexual process. Asexual reproduction process is of two types,
Binary fission and Sporulation.
1. Binary fission: Growth of the body is an important characteristic of
organisms. With suitable environment and proper food, the amount of
cytoplasm of the body of Amoeba increases also with the volume of body. The
growth of the body reaches to such an extent that its cytoplasm cannot perform
the metabolic activities smoothly. At this stage Amoeba starts to multiply by
binary fission. In this process one mother Amoeba divides into two daughter
The process is described below:
At the beginning of the division, Amoeba withdraws its pseudopodia. The body
then takes a circular shape. Its nuclear membrane disappears and the nucleus
becomes larger and conspicuous. Gradually the nucleus takes a long shape and
the mid-section contracts. At this time the endoplasm around nucleus becomes
slightly loose. The chromosomes situated in the nucleus divide longitudinally.
The two daughter chromosomes move towards the two opposite poles and the
mid-section becomes narrow. As a result the nucleus takes the shape of a
The cytoplasm then deposits surrounding the nucleus. About the same time
plasmalema being folded enters towards the interior. Next the nucleus is
divided into two parts and the plasmalema folds meet together. As a result
the mother Amoeba transforms into two daughter Amoeba. In the meantime
the cytoplasm surrounding the nucleus which is being divided approaches the
fold. At this stage, the nucleus is divided into two parts to form two
daughter nuclei. Finally the cytoplasm surrounds each nucleus. Next the
plasmalema is formed outside the cytoplasm. As a result, the mother Amoeba
becomes transformed into two new small Amoebas. Then these new daughter
Amoebas begin their own free life.
To survive under unfavourable environment Amoeba produces a thick wall around its body. This is called cyst wall. This stage is known as cystic stage.
2. Sporulation: Surrounded by an cyst wall in unfavourable condition, the nucleus of Amoeba is divided by multiple divisions and forms numerous spores.

This process is known as sporulation.

In this process first nuclear membrane of Amoeba disappears and the nucleuos 
is divided into several chromatin segments by repeated divisions. They remain 
in free state inside the endoplasm. These chromatin parts then become encloses 
by nuclear membrane.
Later on cytoplasm surrounds these small parts and finally plasmalemma is 
formed around them. Next the spore membrane is formed outside the 
plasmalema. In this way in the body of an Amoeba more than hundred spores may be formed. Breaking the plasmalema, next these spores come outside. In a favorable condition, daughter Amoeba comes out from the spores.



Undisputegists : Biology: Classification And Diversity Of Living Organism,Organization And Acquaintance Of Animals
Biology: Classification And Diversity Of Living Organism,Organization And Acquaintance Of Animals
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