Grade 11 Zoology Note

Kingdom Animalia

Important term:

1. Cellularity

The organisms are made up of cells. These are called as basic unit of organisms. These may be of following types:

a) Unicellular: The organism made up of only one cell is called unicellular or acellular e.g. Protozoans.

b) Multicellular: The organism made up of may cells. They are called as Metazoans. E.g. all organismsexcept the protozoans.

2. Body layer:

It is the cellular layer which forms the body. On the basis of body layer animals are two types:

a) Diploblastic: This term used for those animals which are derived from two germ layers i.e. outer ectoderm and inner endoderm. E.g. sponges, coelenterates.

b) Triploblastic: This term used for those animals which are derived from three germ layers i.e. outer ectoderm and inner endoderm and middle mesoderm. E.g. most of the animal is triploblastic except protozoans, poriferans and coelenterates.

3. Body organization:

a) Cellular grade organization-each cell perform all its vital activities independently. Tissue is absent. E.g. porifers

b) Tissue grade organization-when the group of cells which are similar in shape, structure, and origin, perform specific function collectively, this organization is tissue grade.e.g. Nerve cell of coelenteron

c) Organ grade organization-the different tissue combine to form organ which perform the specific function e.g. respiratory system, nerve system.

d) System grade organization-the different organ collectively function as a definite system. E.g. in all chordates.

Body surfaces-

a) Anterior end: The part of the body which moves forward called the anterior end.

b) Posterior end: opposite to the anterior end.

c) Dorsal surface: the upper surface is dorsal surface which faces towards the sky in natural posture.

d) Ventral surface: opposite to the dorsal surface.

e) Depressed body: Dorsoventrally pressed or filattened.

f) Laterally compressed: flattened laterally.

5. Symmetry:

a) Bilaterally symmetry: Body plan is in such a way that when the animal cuts into two exactly equal and similar halves cuts through longitudinally and medially. Each half is the mirror to one another. E.g. Platyhelminthes-chordates.

b) Radial symmetry (biradial): Body plan is cuts exactly two exactly or similar halves, when cut through any side passing the center. E.g. Echinoderms and some coelenteron.

c) Asymmetry: Body plan is such that it cannot cut into two equal halves.Eg Amoeba.

6. Habitat:

a) Aquatic: the animal live only in water. It is Fresh water and Marine water

b) Amphibious: animal both live in land and water.

c) Terrestrial: animal live only in land. It is aerial- those live in air e.g. birds and birds, Arboreal-those live on tree and hold the branches e.g.Monkey; Burrowing-animal makes the burrow in the sand and soil eg.snakes, fishes.

Other term related to the habitat:

a) Solitary- an animal live alone or individual, cat dog.

b) Colonial-that animal to form colonies to live together e.g.Bee, ants.

c) Sedentary: animal live in such a way that such attach themselves to the substratum. E.g. Obelia, sycon.

d) Free swimming: Those which can move freely here and there in water, e.g. Paramecium, larva of frog.

e) Sessile: Those which do notpossess stalk. E.g.Sycon

f) Stalked: Those which possess a stalk E.g. Vorticella

G) Pelagic: Theanimal occurs on the surface of water of sea.

h) Benthic: Marine species when members lead a sedentary life upon sea bottom.

I) Abyssal: The animals found in the deep sea.

J) Littoral: Those animals which live in the intertidal zone of seacoat.

K) Lentic: Organism inhabiting standing water bodies.

l) Lotic: The animal found in running water of river steam like reptiles and fishes.

7. Body temperature:

a) Cold blooded (Poikilothermic): Those animals which body temperature is variable according to the environment. The body temperature is not constant. For e.g. frog, fishes.

b) Warm blooded (Homothermic): Those animal which body temperature is notvariable according to the environment. The body temperature is constant.E.g-birds, mammals

Coelom or body cavity:

a) True coelom: it is the cavity between the body wall and gut is formed by the splitting of mesoderm. Found in annelids and other higher animal

b) Psedocoelom: it is the cavity filled with the Nematode, Rotifer.

c) Haemocoelom: It is the cavity which is filled with the blood. Eg Arthropod

d) Acoelomate: coelom is not found in body. E.g. Porifera, Coelenterate

9. Locomotion: It is the process of movement of organism from one place to other. Animal move with the help of locomotary organ. The locomotary organs:

a)Pseudopodia: these are the cytoplasmic processes found in amoeba, entamoeba.

b) Flagella: these are the long whip like cytoplasmic processes found in Euglena, Trypanosomaetc. they are called flagellates.

c) Cilia: These are small, cytoplasmic, minute hair like processes, found in paramecium, Balantidium

d) Para podia: These are the locomotary organ of Neries.

e) Appendage: These are the locomotary organ of Arthropods.

f) Muscular foot: These are the locomotary organ of Mollusca.

g) Setae: These are locomotary organ of earthworm.

h) Tube feet: These are locomotery organ of starfish.

i) Fins: These are the locomotery organ of fishes.

j) Limbs: these are locomotary organ of vertebrates.

10. Nutrition: It is process of taking food. It of following:

a) Holozoic nutrition: An organism which take food in solid form.

b) Holophytic nutrition: It is a plant like nutrition.  It can synthesize its own food by photosynthesis.

c) Saprozoic nutrition: The animal which feed the on dead organic matter. Eg Earthworm

d) Saprophytic nutrition: The plant which feed dead organic Fungi

e) Parasitic nutrition: The organism which live on other organism remain alive at the expanse of liver fluke, Leech

f)Mixotrophic nutrition:Those organisms that feed more than one method.Eg. Euglena

g) Carnivorous:  Those animal feed on animal flesh.

h) Herbivorous: Animal feed on plant.

11. Digestion: process of breaking down the complex food by chemically and mechanically. The digestion is;

a) Intracellulardigestion: digestion takes place inside the amoeba, Euglena

b) Extracellular digestion: digestion takes place outside the cells. E.g. Hydra, Earthworms.

12. Respiration:

a) Aerobic respiration: It takes pace in presence of oxygen.

b) Anaerobic respiration: It takes place in absence of oxygen.

13. Circulation: it is a process of flow of fluid\blood within the body. These are two types-

a) Open circulation: It is type of circulation in which blood remains in the large open sinuses. Blood vessel is absent.

b) Closed circulation: It is a type of circulation in which blood flow through closed blood vessel. E.g. annelid, vertebrates.

14. Excretion: it is the process of removal of waste product from the body. The excretory organs for different organism are.

A.Contractile Vacuole: It is found in the protozoans

b.Flame cell: It is found in the helminthes

c.Nephridia: It is founds in annelids.

D.Malpighain tubule: it is found in arthropods

e) Kidney: it is found in vertebrate.

15. Reproduction: It is a process of giving young ones. It is of following types-

a) Asexual reproduction: it is a type of reproduction in which sexes are not involved. It take place by one parent only.E.g. Binary fission, budding

b) Sexual reproduction: It is type reproduction in which both sexes are involved. Male and female fused to form the zygote.

Other term involves in reproduction:

Monoecious\Hermaphrodite\Bisexual-An individual of specious having both Male and female reproductive organ           s e.g. Pheretima, Taenia, Fasiola.

Unisexul or Dioecious: When the male and female reproductive organ are present in different Individual. For e.g.Man, pila.

Oviparous-Animal which lays eggs. E.g.fishes, birds

Viviparous: Animal which gives the birth to young man

Ovoviviparous: Animal which gives the birth of immature one.Eg Kangaroo.

Sexual dimorphism: When the male and female individual separated easily by te looking. Human, Ascaris

Protandry: In this condition male reproductive organ mature earlier than female one. E.g. earthworm

Protogyny: In this condition female reproductive organ mature earlier than the male one.

16. Fertilization: It is the process of fusion of male and female gametes result in formation of zygote. It of two types;

a) External fertilization: Fusion of male and female gametetakes outside the sycon, fish

b) Internal fertilization: When the fertilization takes place outside the body is called internal fertilization-birds, mammals

17. Development:

a. Metamorphosis: The larva undergoes the certain change to form the adult.

b. Progressive metamorphosis: When the larva is simple and become complex in adult stage-tadpole of frog change into adult one.

c. Retrogressive Metamorphosis: When the larva is complex and more advance than the adult. E.g. Ascidians

d. Direct development: It means when the adult change into young one without forming larva.

e. Indirect development: It means egg change into larva and then adult.


-Robert E. Grant (1836) coined the term porifera. John Ellis (1765) studied water canal system in Sponge. The study of sponge is called Para zoology.


General character of porifera

1) No definite symmetry. 
2) Body multicellular, few tissues, no organs. 
3) Cells and tissues surround a water filled space but there is no true body cavity. 
4) All are sessile, (live attached to something as an adult). 
5) Reproduce sexually or asexually, sexual reproduction can be either gonochoristic or hermaphroditic. 
6) Has no nervous system. 
7) Has a distinct larval stage which is planktonic. 
8) Lives in aquatic environments, mostly marine. 
9) All are filter feeders. 
10) Often have a skeleton of spicules.

11) Possess unique flagellated cells – choanocytes – thatcreate water flow through a water current system

12) Outer and inner cell layers lack a basement membrane

13) Outer and inner cell layers divided by a noncellular layer– the mesohyl – that contains some cells and skeletalmaterial

14) Body support (“skeleton”) provided by spicules

Composed of calcium carbonate or silicon

Classifications of protozoa:

Class I- Calcarea


1. All are marine, single in live in colony.

2. Endoskeleton is composed of spicules made of calcium carbonate.

3. Choanocyte cells are large.

4. Osculum small surrounded by spicules.

Examples- Clathrina, Petrobiona

Class II. Hexactinellida


1. Flowre-vase like body.

2. Spicules are composed of silica.

3. Choanocytes are restricted to flagellated chamber.

Example: Hyalonema

Class III. Demospongia


1. Endoskeleton may be formed by siliceous spicules or sponging fibres or both.

2. Choanaocytes are restricted to spherical chambers.

3. Spicules are having one to four rays.

Examples: Spongilla, Helichondra

Phylum: Coelenterata

Hatschek named the Cnidaria due to presence of stinging cell in their body. Leukart named the coelenterate. Study of coelenterate is called Cnidology.

General character of Coelenterata:

1. They are aquatic, mostly marine and a few are fresh water

2. Tissue grade of organization: organs and organ system are absent.

3. They are diploblastic.

4. Body is formed of two layers of cells, viz., an outer ectoderm and an inner endoderm with a non cellular jelly like layers of mesoglogea in between.

5. Radial symmetry with oral and aboral ends no definite head.

6. A central cavity called gastro vascular cavity which opens to exterior by the mouth. Anus is absent.

7. Digestion is both intracellular and extracellular.

8. Presence of stinging cells or cnidoblast in the ectoderm. The cnidoblast cells possess a capsule called nematocyst containing poisonous fluid. The cnidoblast cells are defensive cells used to kill or paralyses other preys and enemies.

9. They are acoelomates. I.e. there is no separation between the digestive cavity and the general body cavity.

10. Respiration and excretion occur by diffusion through the body surface.

11. Nervous system is primitive and formed of a network of nerve cells and fibres throughout the body.

12. Reproduction is by both sexual and asexual means. Fertilized eggs may develop into a larva called planula.

13. An alternation of generations or metagenesis is found in the life history i.e. the asexual polyploid generation alternates with the sexual medusoid generation

Classification of coelenterate:


Solitary or colonial, with polyp as the dominant stage. Mesogloea is acellular. Cnidocytes are confined to epidermis. Gonads are epidermal. Ex. Hydra; Bougainvillea; Obelia; Millepora; Stylaster; Physalia; Vellela; Porpita.


Solitary marine animals, with medusa as dominant stage and without a velum. Mesogloea is highly enlarged with cells. Reproductive organs are gastrodermal. Sense organs are located on the bell margin. Ex.  Aurelia; Pelagia;Cyanea.


They occur only in polyp form. Medusa form is absent. Pharynx present with two ciliated grooves called siphonoglyphs. Mesogloea is cellular and gonads gastrodermal.e.g. Metridium, Pennatula

Phylum: Platyhelminthes

Gagenbaur suggested the name Platyhelminthes. Its study is called Helminthology.

General character of Platyhelminthes

1. Flat worms are triploblastic i.e. having three germ layers. They are the first organ grade of organization.

2. Body is dorsoventrally flattened and has a definite anterior end, differentiated as a ‘head’.

3. They are acoelomate animals. The space between the body wall and gut are filled with parenchyma composed of loose cell masses.

4. Body is devoid of true metameric segmentation.

5. Alimentary canal is usually highly branched; it opens out by a single opening the mouth. Anus is absent.

6. Circulatory and respiratory system is absent.

7. Nervous system is ladder like. It is formed of brain and two main longitudinal nerve cords connected at intervals by transverse commissures.

8. Excretion is performed by specialized cells called flame cells. They lead into tubules which open out by one or more excretory pores.

9. Reproductive system is well organized. Most of them are hermaphrodites.

(Hermaphroditism is a phenomenon of occurrence of both male and female sex organs in one animal.)

10. Life history often includes larval stages. In some forms asexual reproduction is transverse fission takes place. Many flat worms reproduce asexually from a part of their body by regeneration.

Classification of Platyhelminthes:

Class TURBELLARIA (Dugesia; Bipalium; Leptoplana; Notoplana).

They are free living eddy worms, with flattened body and mouth located on the ventral side. Suckers are absent and epidermal cells are multiciliated. They are hermaphrodite. There are 4500 species, most of which are marine. Most turbellarians are carnivores and prey on small invertebrates or protozoans or scavenge on dead animals. One pair of eyes is generally present. All turbellarians are hermaphrodite, having both female and male reproductive organs and fertilization is internal. They have a brain and central nervous system, a well-developed excretory system and a complex reproductive system.

Class TREMATODA (Fasciola; Schistosoma; Fasciolopsis; Opisthorchis; Paragonimus).

Commonly known as flukes, they are parasitic animals with suckers. Alimentary canal is highly branched, with mouth as the only opening. They are all internal parasites having leaf-like shape. They have suckers for attachment and the adults feed on the blood of host. This class is characterized by a complex hermaphroditic reproductive system and a life cycle that involves intermediate and main hosts. Like most internal parasites they have a very high reproductive rate, which is further increased by the larval stages which are also able to reproduce asexually, thereby creating even more new individuals.


Class CESTODA (Taenia; Phyllobothrium; Haplobothriium; Echinococcus).

They are commonly known as tapeworms. Body is long, flattened and tape-like, with large number of proglottids or sometimes without segmentation. No digestive, respiratory and circulatory systems. They have saprozoic method of nutrition uptake.


Fig; example of phylum Platyhelminthes


Gegenburg (1859) introduced the name Nemathelminthes. Grobben (1910) coined the term as helminthes in place of Nemathelminthes. Rudolphi introduced the term Nematoda. Study of nematodes is called Nematology.

General characters of Nemathelminthes:

1. Phylum Nemathelminthes comprises of animals commonly called nematodes or roundworms.

2. Nematodes are ubiquitous and are found in freshwater, marine, as well as terrestrial environments.

3. Most of the species of nematodes live a parasitic life, though a number of free-living forms are also present.

4. These are triploblastic, bilaterally symmetrical animals with organs system level of body organization.

5. Body is elongated, cylindrical, unsegmented and vermiform.

6. Size of the nematodes varies considerably in different species.

7. Body is covered by a resistant, inelastic and thick cuticle which is covered by a thin and lipoid epicuticle.

8. Epidermis is syncytial in nature and is invaginated into four longitudinal cords.

9. Body wall has thick muscle layer composed of only longitudinal muscles which are present between four cords.

10. The body cavity is a pseudocoel and is not lined by coelomic epithelium. It contains pseudocoelomic fliuid rich in proteins, and organic metabolites.

11. Nematodes exhibit undulating movement in dorso-ventral plane produced by alternate contraction and expansion of the longitudinal muscles.

12. Circulatory and respiratory system is absent.

13. Digestive tract is straight and complete with two openings, mouth and anus.

14. Flame cells are absent and excretory system consists of a few renette cells or a canal system.

15. Nervous system comprises of a circum-pharyngeal nerve ring surrounding the pharynx and four peripheral longitudinal nerves.

16. Sense organs are poorly developed and include amphids, phasmids, papillae, bristles and ocelli.

17. Sexes are separate with distinct sexual dimorphism.

18. Gonads are unpaired or paired and are tubular or coiled.

19. Sexual reproduction is the common form of reproduction.

20. Fertilized eggs are surrounded by a tough capsule.

21. Cleavage is determinate and development includes usually four larval stages.

22. Development of embryo takes place with or without intermediate hosts.

Classification of Nemathelminthes

Phylum Nemathelminthes is divided into two classes based on the presence or absence of phasmids.

a)  Aphasmidia

1.Phasmids, the sensory organs in the caudal end, are absent.

2. Amphids, the chemoreceptors are variably-shaped and are present behind the lips.

3. Excretory canals are absent.

4. Most species are free living and some are parasitic.

5. Free living species include almost all marine forms; and some terrestrial and freshwater forms.

A few examples are Xiphinema, Mermis and Enoplus.

b) Secerenentea or Phasmidia

1. Phasmids are present which open through minute pore on each side near tip of tail.

2. Amphids are pore-like and are present in the lateral lips.

3. Excretory canals are present.

4. Most of the species are parasitic in nature.

5. Free living species are soil inhabitants.

A few examples are Ascaris, Wuchereria, Oxyuris, Ancylostoma and Dracunculus

Fig: Example of Nemathelminthes

Phylum: Annilida

-Lamarck coined the term Annilida. K.N. (1926) thoroughly explained the earthworm.

General character of phylum Annelida

1. Body is metamerically segmented, each segment is known as annulus, generally external segment correspond with internal segmentation, annuli are arranged in a linear sequence from anterior to posterior direction.

2. Cuticle is soft and non chitinous.

3. Body cavity is a true coelom; coelom is filled up with a fluid known as coeliac fluid. Coelom is divided by septum into many chambers.

4. Body bilaterally symmentrical and triploblastic.

5. In most annelids sea or cheaeta and parapodia are locomotory are locomotory organs, some move by muscles, i.e., seta or parapodia absent.

6. Alimentary canal more or less straight, anus and mouth at opposite ends, digestion extracellular.

7. Well developed blood vascular system, blood vascular system closed.

8. Excretion by nephridia, each segment bears a pair of nephridium.

9. Most of them respire by body wall, some possess gills.

10. Well-developed nervous system with ganglia and nerve cords. A pair of supra esophageal ganglia, circum esophageal connective and ventral nerve cord constitute the nervous system. Ventral nerve cord gives off ganglia in each segment.

11. Most of them are hermaphrodite, some are unisexual, development direct or through larval stage, larva is known as trochophore larva.

Classification with reasons and examples:

Parker and Haswell classified phylum Annelida into 4 classes as-

1. Class-I: Polychaeta

2. Class-II:  Oligochaeta

3. Class-III: Hirudinea

4. Class- IV: Archiannelida

Class-I: Polychaeta


1. Most of them are marine, 5-10 cm. in length and variously coloured.

2. External segmentation and internal septum distinct.

3. Each segment bears a lateral fleshy outgrowth help in swimming. These appendages are known as parapodia and parapodium bears many setae.

4. Body is with a distinct head, head with eyes, pulp and tentacles.

5. Clitellum is absent.

6. Generally unisexual, fertilization external.

7. Development through trochophore larva.

Examples- Nereis, Aphrodite, Polynoe, Glycera, Syllus.




1. Either freshwater or terrestrial forms.

2. Head indistinct and without head appendages.

3. Parapodia and bristles absent and setae remain embedded in the skin.

4. Clitellum present.

5. Sexes united, gonads few, permanent, development direct

Examples- Tubifex, Dero, Pheretima, Megascolex etc.

Class-III: Hirudinea


1. Mostly aquatic forms, either fresh water or marine, but a few may be terrestrial.

2. Body dorsoventrally flattened, divides into definite number of segments which may be divided externally into segments.

3. Head distinct, without head appendages, may bear eyes.

4. Parapodia, Setae, tentacles absent.

5. Usually with two sucker, posterior one large and used for adhesion anterior one suctorial.

6. Coelom filled with vacuolated parenchyma and botryoidal tissue.

7. Blood vascular system haemocoelomic type.

8. Fertilization internal, development direct, and are hermaphrodite.

Examples- Acanthobdella, Pontobdella, Hirudo.


Class-IV: Archiannelida


1. Body simple, elongated vermiform and threadlike.

2. Setae, parapodia, cirri absent.

3. External segmentation indistinct, internal septum present.

4. Hermaphrodite, gonads develop during reproductive season only.

Fig: Example of phylum Annilida

Phylum: Arthropoda

Von Siebod coined the term Arthropod. And its study is called entomology.

1) Bilaterally symmetrical (in most cases). 
2) Body has more than two cell layers, tissues and organs. 
3) Body cavity a true coelom. 
4) Most possesses a through straight gut with an anus (in most cases). 
5) Body possesses 3 to 400+ pairs of jointed legs. 
6) Body possesses an external skeleton (in most cases). 
7) Body is divided in 2 or 3 sections. 
8)Nervous system includes a brain and ganglia. 
9) Possesses a respiratory system in the form of tracheae and spiracles (in most cases). 
10) Possessesan open or lacunar circulatory system with a simple heart, one or more arteries, and no veins, (in most cases). 
11) Reproduction normally sexual and gonochoristic, but can be parthenogenetic. 
12) Feed on everything. 
13) Live everywhere.

Classification of arthropoda:

The major classes of living arthropods are as follows with one example each:

Class Arachnida- spiders

Class Crustacea- crabs


Class Insecta or Hexapoda– insects

Class Archnida: To be classified in the class Arachnida, an arthropod must have certain characteristics. Arachnid bodies are divided into two distinct regions, the cephalothorax and the abdomen. Four pairs of legs attach to the cephalothorax. Arachnids lack wings and antennae.

Class Crustacea: Despite such an extraordinary diversity of species, many crustaceans have a similar structure and way of life. The distinctive head usually bears five pairs of appendages (limb like attachments). Two pairs of these appendages are antennae that are used to detect food as well as to sense changes in humidity and temperature. Another pair of appendages is mandibles (jaws) that are used for grasping and tearing food. The final two pairs of appendages are maxillae, arm like projections used for feeding purposes.

Class Myriapods:  have a single pair of antennae and, in most cases, simple eyes. The mouthparts lie on the underside of the head, with an "epistome" and labrum forming the upper lip, and a pair of maxillae forming the lower lip. A pair of mandibles lies inside the mouth. Myriapods breathe through spiracles that connect to a tracheal system similar to that of insects. There is a long tubular heart that extends through much of the body, but usually few, if any, blood vessels

Class Insecta – true insects are the most important members of the
phylum Arthropoda. Typical adult insects have one pair of antennae, three
pairs of legs, and three body regions: head, thorax, and abdomen. The class
Insecta is divided into some 29 to 40 major orders. Insects make up more than
half of all living things in the world.

Fig: example of phylum Arthopoda

Phylum: Mollusca

Lamarck coined the term molluscus. Its study is called malacology and the study of cell of molluscan is conchology.

General character of Mollusca:

1. Free living aquatic forms (freshwater or marine), some amphibious.

2. Body is soft and unsegmented enclosed in a glandular mantle covered by usually a shell.

3. Coelom is reduced to a pericardial cavity around the heart.

4. Digestive system is complete.

5. Respiratory organs are in the form of gills called ctenidia.

6. Locomotor structure is represented by muscular foot.

7. They have soft-body, which is differentiated into three regions - head, visceral hump and foot.

8. Visceral hump is covered by a thin, fleshy fold called mantle.

9. Mantle secretes a calcarious shell, which may be external or internal.

10. Reproduction is sexual. Either unisexual or bisexual, development is direct.

Classification of Mollusca:

Phylum MOLLUSCA (feeding apparatus)

Phylum Mollusca divided into.

1. Class Amphineura
2.class Gastropoda
3. Class Bivalvia
4.Class Scaphopoda
5.Class Cephalopoda


Nervous system with double nerve cord with cross connections giving it a ladder-like look. Head is reduced and larva is trochophore. Ex. Neomenia


It is commonly known as elephant tusk shell that burrows in sandy bottom using a boat-like foot. Head, gills and eyes are absent and radula is simple. Excretion is done by nephridia and feeding by adhesive tentacles called captacula. Ex. Dentalium


They possess well-developed head, eyes and tentacles and a large foot attached on belly. Shell is present or absent.Ex. Pila, Cypraea, Patella


Body is enclosed in a two valve shell and bears no head, eyes, tentacles and jaws. Foot is hatchet-like, used for burrowing in sand by digging. Respiration is by gills and food capture by filter feeding with the help of gills.  Sexes are separate.Ex. Malletia, Sokemya, Acila


Foot is modified as head appendages with suckers. Radula is reduced and there is a pair of powerful jaws for feeding. A siphon is attached to mantle cavity for breathing and jet propulsion. There is no larval stage. Development is direct.Ex. Nautilus


Fig: Example of phylum Mollusca

Phylum: Echinodermata

Jacob Klein (1734) introduced the term Echinodermata.

General character of phylum Echinodermata

1. Free living exclusively marine forms.

2. Adults are radially symmetrical while larvae are bilaterally symmetrical.

3. Body is represented by a central disc covered by ossicles with spines called pedicellaria.

4. Disc may bear extensions called arms.

5.Digestive system is complete.

6. A unique ambulacral or water vascular system is present.

7. Tube feet are present for locomotion and respiration. Tube feet are extended and retracted by variation in hydraulic pressure of the fluid in them and contraction of their muscles.

8Nervous system has a central nerve ring with five radiating nerves.

9.Reproduction is sexual. Sexes are separate. Development is indirect.

10. Show very high power of regeneration

Phylum Echinodermata is divided into

1. Subphylum  ASTEROZOA

Free living echinoderms with pentaradial arms. The group includes star fishes and brittle stars.


They are commonly called star fishes or sea stars because of star-like pentamerous shape of body. Ambulacral groove is present. Locomotion is by tube feet and respiration by dermal branchiate. Pedicellariae are present. Ex. Asterias, Altering, Astropecten.


No pedicellariae, dermal branchiae, ambulacral grooves, intestine and anus. Visceral organs are confined to the central disc. Stomach is sac-like and pouched. Podia are used for feeding and respiration and not for locomotion. Madreporite is located on the oral side. Ex.Ophiothrix, Gorgonocephalus,Ophioderma.


Commonly known as sea daisies, they have disc-shaped body and are less than 1.0 cm in size. They show pentaradial symmetry, without arms.  Podia are located on the margin. Madreporite present on the aboral side. Digestive system consists of a blind sac-like stomach, without intestine or anus. Ex. Xyloplax.

2. Subphylum CRINOZOA

Echinoderms with radial symmetry and sedentary nature. Mouth and anus on the same side and facing upward.


Sedentary or almost so, attached to substratum by aboral cirri. Body consists of small pentamerous central disc called calyx. Mouth and anus located on the same side. Ex.Antedon, Diplocrinus, Heterometra, Lamprometra, Decametra, Capilaster.

Phylum chordate:

1. Bilaterally symmetrical. 
2. Body has more than two cell layers, tissues and organs. 
3. Body cavity a true coelom. 
4. Most possesses a through gut with a non-terminal anus. 
5. Body monomeric with no head or jaws. 
6. Possess at some stage of their life a hollow dorsal nerve tube. 
7. Possess at some stage of their life a dorsal cartilaginous rod called a notochord. 
8. Possess at some stage of their life gill slits in the parangeal region. 
9. Has a partially open circulatory system. 
10. without excretory organs. 
11. Reproduction normally sexual and gonochoristic. 
12. Feed on a variety of organic materials. 
13. All live marine environments.

The phylum chordate are further classified as

Sub phylum hemichordate: It includes about 80 species.
1. Bilaterally symmetrical. 
2. Body has more than two cell layers, tissues and organs. 
3. Body cavity a true coelom. 
4. Body possesses a through gut, straight or U-shaped, with an anus. 
5. Body divided into three sections, a proboscis, a collar and a trunk. 
6. Nervous system normally diffuse, but variable. 
7. Has a partially open circulatory system. 
8. Possesses glomerulus as an excretory organ. 
9. Reproduction normally sexual and gonochoristic. 
10. Feeds on fine particles in the water. 
11. All live marine environments.

Sub phylum: Urochordata: it includes 2100 species.

1. Body shows variation in size and form.

2. The body is un-segmented and has no tail

3. The body is covered by a test. It is formed by tunicine which israllied to cellulose. Hence the name Tunicata.

4. Body wall shows one-layered epidermis, dermis is made by connective tissue and muscles, and atrial epithehum.

5. Celome is absent.

6. Atrial cavity surrounds the pharynx, into this cavity the gill slits,anus and genital ducts will open. It opens through atrial aperture.

7. Larva has notochord in the tail. It disappears during metamorphosis.

8. Respiratory system contains gills in the pharyngeal wall.

9. Ciliary mode of feeding is common.

10. Open type of Circulatory system is seen.

11. The heart is ventral and it periodically reverses its function.

12. Nervous system is represented by a single dorsal ganglion in the adult.

13. Excretion is carried on by nephrocytes.

14. Asexual reproduction is by budding.

15. Bisexual animal and cross fertilisation is favored.

16. Fertilization is external.


Sub phylum: Cephalochordata: it includes 15 species.

1. Body is fish -like and is useful for burrowing and swimming.

2. Appendages are absent.

3. Dorsal, caudal and ventral fins are present.

4. Body- wall shows one- cell thick, non-ciliated epidermis, dermis, connective tissue, striated muscle and parietal peritoneum.

5. Notochord extends from the anterior end to posterior end.

6. Enterocoelic coelom is present. However, reduced in the pharyngeal region by atrium.

7. Alimentary canal is long. It includes a large pharynx with many gill-slits  ciliary mode of feeding is developed.

8. Gillss will perform respiration.

9. Circulatory system is closed.

10. Heart and respiratory pigments are absent.

11. Hepatic portal system is present.

12. Excretory system shows paired protonephridia with solenocytes.

13. Brain is not present

14. Two pairs of cerebral and several pairs of spinal nerves are present.

15. Sexes are separate. Gonads are metamerically arranged and without gonoducts.

16. Asexual reproduction will not take place.

17. Fertilization is external.

Sub Phylum Vertebrata (Craniata)

1.Vertebrates have a well developed brain.

2.Brain is set inside a bony box, known as cranium.

3.Notochord is present in all chordates during sometime of development, it is formed on the dorsal side of the primitive gut in the early embryo stage.

4.Most vertebrates possess guts with a non-terminal anus.

5.The mouth cavity and the oesophagusis connected by the pharyngeal gill slits to a muscular tube pharynx, which opens to the exterior.

6. They possess a dorsal hollow nerve tube at some stage of their life.

7.Possess a dorsal cartilaginous nerve rod known as the notochord.

8.At some stage of their life possess gill slits in the pharyngeal region.

9.  Have partially open circulatory system.

10.Possess two pairs of appendages.

11.The endoskeleton is made of cartilage or bone.

12.The first vertebrates were jawless fishes with single caudal fin.

13.The advancement of vertebrates with a hinged jaw which opened new food options and jawed fishes became the dominant creatures in the sea.

14.All vertebrates have a heart and closed circulatory system.

15.Reproduction is normally sexual.

16.Feed on variety of organic materials.

17.Unisexual animals, have one pair of gonads.

It consist of two division,

Division 1: Agnatha (jawless Vertebrates)

Class: Cyclostomata

1. They have cartilaginous skulls and tooth-like structures composed of keratin.

2. Hagfish have no true fins and have six or eight barbels around the mouth and a single nostril.

3. Hagfish eyespots when present can detect light, but as far as is known none can resolve detailed images.

4. Some hagfish species are thought to be hermaphroditic, having both an ovary and a testicle.

5. True jaws are absent.

6. Paired fines are absent.

7. The nostril is single and median.

8. Notochord present through life.

9. Heart is two chambered.

e.g. Petromyzon

Fig: Petromyzon

Division Gnathostomata

1. Jaw present

2. Notochord is usually replaced by vertebral column.

3.  Pairs appendages present.

4. Paired nostrils are present

They are divided into two superclass, i.e. Pisces and tetrapoda.

Super class- Pieces

General character of pieces

1. They are completely aquatic found in fresh water and marine water.

2. Body is streamlined or boat shaped and laterally compressed. It helps the fishes to swim.

3. Body is covered the cycloid and placoid scales.

4. It is cold blooded in nature.

5. Locomotion takes place by paired and unpaired fins.

6. Lateral line system is receptor organ which can detect the vibration or change in temperature.

7. Digestive system is well develops

8. Respiration takes place through gills. Gills may or may not be covered by operculum.

9. Excretion takes place by mesonephric kidney, no urinary bladder.

10. Circulatory system consist of heart, its two chamber

11. Nervous system consists of ten pairs of cranial nerves

12. Vertebrae are amphicoeloes type.

13. Sexes are separated. Fertilization is external.

14. Development is direct.

Super class pieces divided into following class

1. Chondrichthyes -

a. marine, 2 pairs of fins (pectoral & pelvic)

b.sharks (body fusiform)

c.rays (flat, plated teeth, tail spine)

d.skates (flat, sharp teeth)

e.ratfish (aberrant, dorsal spine)

2. Osteichthyes –

a. bony fishes, marine & freshwater

b.30k species, most diverse & abundant class

c.coelacanth - pair of lungs, muscular fins

d.led to evolution of amphibians

e.lungfish - single lung, fleshy fins

f. ray-finned fishes - all other fishes

g.Swim bladder, membranous fins

Difference between the cartilaginous and bony fishes


1. Endoskeleton is cartilaginous.

2. Mouth is ventral in position.

3. Operculum is absent.

4. Caudal fin is heterocercal.

5. Body covered with placoid scales.

6. Pelvic fins are modified into intromittant organs in males called claspers.

E.g. Scoliodon, Torpedo, saw fish.

Bony Fish Teleostomi:-

1. Endoskeleton is bony.

2. Mouth is terminal or sub-terminal in position.

3. Operculum is present.

4. Caudal fin is homocercal.

5. Body covered with cycloid, ctenoid, rhomboid scales.

6. Claspers are absent.

E.g. Labeo, Clarius, Anabas, Catla.

Super class: Tetrapoda

It has four classes:





General character of class Amphibia

1) The representatives of class Amphibialive  both on land and in water i.e. amphibious.

2) Amphibians are cold-blooded or exothermic animals.

3) The skin is smooth, thin, hairless, porous and rarely scaled. The skin contains both mucus glands and poison glands.

4) A bone endoskeleton with varying numbers of vertebrae; ribs present in some, absent or fused to vertebrae in others.

5) Four limbs which may vary in size with the forelimbs of some being much small  than the hind limbs; some are legless.

6) Limbs have varying numbers of digits and webbed feet are often present; no true nails or claws.

7) The mouth is usually large with small teeth in upper or both jaws; two nostrils open into the anterior part of the mouth cavity.

8) Respiration is accomplished either separately or in combination by lungs, skin, and gills; some larval types possess external gills and these may persist throughout life.

9) A three-chambered heart consisting of two atria and one ventricle.

10) Body temperature regulation is exothermic in nature. That is, the body is heated from without rather than from within.

11) Separate sexes with internal fertilization via spermatophore a sperm packet on a stalk in salamanders and caecilians, but external fertilization in frogs and toads.

12) Ten pairs of cranial nerve are present.

13) Amphibians are the only vertebrates to undergo complete metamorphosis.

14) Eggs are usually laid in water or in a moist environment and fertilized externally. They change from an aquatic larval stage to a terrestrial form on reaching adulthood.

15) Larvae develop in water or very moist environments and undergo complete metamorphosis. Examples

Frog ,toad ,tree frog etc

Class reptilian

-General characteristic of class reptilian

1) Class reptilian (L. Reptilia= creeping) includes animals which are cold blooded.

2) The skin has a few cutaneous glands and high levels of keratin, which prevents water loss through the skin.

3) The scales and scutes are formed from the epidermis and are also made of keratin, to protect the body.

4) Reptiles are considered as tetra pods with two sets of paired limbs. Most of these animals have five clawed toes on each limb.

5) All reptiles have spinal columns and a strong skeletal system with a rib cage. They have a well-developed brain and a central nervous system.

6) Unlike amphibians, reptiles do not pass through an embryonic stage with gills. These animals breath with well-developed lungs, right from birth. Most of them have two lungs, except some snakes.

7) All reptiles have three-chambered hearts, except crocodiles, which have four-chambered hearts (2 atria, 2 ventricles), like mammals and birds.

8) Reptiles have a digestive system which has a muscular opening at the base of the tail.

9) In case of reptiles inhabiting arid regions, water is further absorbed into the body and only the remaining waste is excreted.

10) Twelve pairs of cranial nerve.

11) These amniotic eggs can survive without water, as they have protective shells and membranes that allow oxygen and other gases to enter.

12) Respiration by lungs only.

13) The offspring of reptiles resemble the adults at the time of birth itself. There is no metamorphosis, as in the case of amphibians.

14) Lateral sense organs are absent.

15) They are the first animals with amniotic eggs, that can be laid on land and not in wate.Eg Wall lizard,Garden lizard

General character of class Aves:

1) The members of class aves are commonly known as birds. They are worm-blooded with an exoskeleton of feathers.

2) Body usually spindle shaped, with four divisions: head, neck, trunk, and tail; neck disproportionately long for balancing and food gathering.

3) Limbs paired; forelimbs usually modified for flying; posterior pair variously adapted for perching, walking, and swimming; foot with four toes.

4) Epidermal covering of feathers and leg scales. Thin integument of epidermis and dermis.

5) No sweat glands. Oil or preen gland at base of tail.

6) Pinna of ear rudimentary. Fully ossified skeleton with air cavities.

7) Skull bones fused with one occipital condyle. Each jaw covered with a keratinized sheath, forming a beak.

8) No teeth; ribs with strengthening, uncinate processes. Posterior caudal vertebrae reduced and fused as the pygostyle.

9) Pelvic girdle a synsacrum.

10) Aerythrocytes sternum usually well developed with keel.

11) Single bone in middle ear.

12) Fused bones in pelvis, feet, hands, and head

13) Lightweight bones (bones that are either hollow or spongy/strutted)

14) Endothermic

15) Possess a four-chambered heart and in general exhibit high metabolic rates

16) Adept navigational abilities in many species

17) Extraordinary communication and song production

18) Nervous system well developed, with 12 pairs of cranial nerves and brain with large cerebellum and optic lobes. Circulatory system consists of four-chambered heart with two atria and two ventricles.

19) Sexes separate; testes paired, with the vas deferens opening into the cloaca.

20) Females have left ovary and oviduct only. Prental care is well developed.

Example: Sparrow, pigeon, parrot

Class Mammilia

General character of Mammalia are

1) Warm blooded. Possess hair which is made of keratin. The evolution of mammalian keratin is believed to be independent of reptilian keratin. Hair provides insulation .

2) Endothermic. The majority of the heat energy is used to maintain their high body temperature. Four chambered heart.

3) Mammary glands are used to produce milk to nourish their young. Female glands are the only functional glands.

4) Thediaphragm is a muscle that separates the thoracic cavity from the abdominal cavity. Seven cervical vertebrae (neck bones) are present in most mammals.

5) Most are viviparous though some are oviparous. An extended gestation period uterine development is common in most placental mammals.

6) Teeth are imbedded in the jaw bone and come in a variety of forms. Well developed brain.

7) Mammals developed from the therapsid ancestors during the Triassic period.

8) Mammals are heterodontic, meaning that their teeth are different shapes, except those with no teeth at all.

9) Reptiles and fish have teeth that are all basically the same, though they can vary in size throughout the mouth. See image above.

10) The Buccal Cavity (the mouth) has a false palate as a roof, meaning that the nostrils do not lead directly into his mouth.

11) The body is maintained at a constant temperature they generate heat within their bodies metabolically and also have special cooling mechanisms. Highly developed neopallium.

12) Tectum reduced to corpora quadrigemina: functions mainly as a relay center for auditory information and to control visual reflexes.

13) Corpus callosum in eutherians provides additional communication Smell acute except whales and higher apes.

14) Eye typical of amniotes. Tapetumlucidum well developed in nocturnal mammals.

15) Touch- most have vibrissae that are controlled by facial muscles.

16) Lateral movement of jaw during mastication.

17) Viviparous except monotremes which are egg lying.

18) Parental care well developed.

Example: Rabbit, Bat, Human.

Go Top