Major Animal Groups | Biology for Class 9 PDF Download

Kingdom animalia 

Characteristics :

(i) Cellular Nature : Members of kingdom animalia are wall less, eukaryotic and multicellular.

(ii) Nutrition : It is heterotrophic.

(iii) Locomotion : Most animals are mobile.

"Terminology" used in classification 

Grades of Body Organization -

(i) Cellular grade - e.g. Sponges

(ii) Cell-tissue grade - e.g. Coelenterates

(iii) Tissue - Organ grade - e.g. Flatworms

(iv) Organ- System grade - e.g. Aschelminthes to Chordates.

Body Plans -

(i) Cell aggregate - e.g. Sponges

(ii) Blind sac - e.g. Coelenterates , Flatworms

(iii) Tube within a tube - e.g. Aschelminthes to Chordates

Body symmetry - It is similarity in arrangement of body parts.

(i) Radial symmetry- Body can be divided into similar halves by any plane passing through centre axis.

(ii) Bilateral symmetry- Body can be divided along a median longitudinal plane into two mirrored portions right and left halves.

Germ layers -

(i) Diploblastic animals - having two germ layers i.e. ectoderm and endoderm.

(ii) Triploblastic animals - having three germ layers i.e. ectoderm, endoderm andmesoderm.

Metameric segmentation -

Body is divided into segments externally as well as internally (by septa).

Body Cavity [Coelom] -

A body cavity is a fluid-filled space between the gut and the outer body wall of an animal.

(i) Acoelomates : Animals without coelom e.g. Flatworms

(ii) Pseudocoelomates : In these animals, coelom is not lined by mesoderm. e.g. Nematodes.

(iii) True coelomates : In these animals, coelom is lined by mesoderm.

True coelom may be of two types :

(i) Schizocoelom : Coelom is originated by spliting of mesoderm. e.g. Annelids, Arthropods, Molluscs.

(ii) Enterocoelom : Coelom is originated by endodermal pouches. e.g. Echinodermates, Hemichoradates, Choradates.

Body temperature :-

(i) Ectotherm or Poikilotherm or Cold-blooded :

Their body temperature changes according to enviornmental temperature. e.g.Pisces, Amphibians, Reptiles.

(ii) Endotherm or Homeotherm or Warm- blooded :

Their body temperature cannot change according to environmental temperature. e.g.Mammals, Aves.

Phylum Porifera - Pore Bearing Animals

                                                      [Gk. porus - pore ; ferre - to bear]

Common name - "the sponges"

General Characters :

1. They live mostly in the sea (marine) but a few occur in fresh water.

2. They have cellular level organization with two germ layer i.e. diploblastic animals.

3. They are sessile or stationary.

4. Most of sponges are asymmetrical, some are radially symmetrical.

5. Sponges have pores on body and these pores are called ostia. Ostia open into a canal system and the canal opens to outside by a large opening ; named osculum present at top.

6. Skeleton of sponges is made up of minute calcareous or siliceous spicules or spongin fibres.

e.g. Sycon (Scypha) - Urn sponge

Euplectella - Venus's flower basket      Hyalonema - rope sponge

Cliona - boring sponge                        Euspongia - bath sponge

Spongilla Olynthus

Phylum Cnidaria or Coelenterata

[Gk. Knide = sting cells]

General Characters :

1. Aquatic animals mostly marine, some of live in colonies (corals) while other live solitary.

2. Body is radially symmetrical.

3. These are the first multicellular animals having tissue level organization with distinct labour of division.

4. Body has a central gastrovascular cavity- coelentron which lacks anus but has mouth which is surrounded by tentacles.

5. The body bears specialized cells-cnidoblasts, bearing stinging cell organelles called 'nematocysts'.

6. Nematocysts serve the function of paralysing the prey by injecting poison.

8. Nervous system is primitive, has only network of nerve cells (nerve net).

9. Coelenterates show two main forms, the polyp (asexual) and the medusae. (sexual)

e.g. Hydra : fresh water coelenterate

Obelia                                         Millepora-coral

Physalia -Portugese man of war   Aurelia -jelly-fish

Pennatula - sea-pen                   Metridium- sea-anemone

Corallium- red coral                  Gorgonia- sea fan

Phylum Platyhelminthes

 [Gk. platys = Flat ; helmin = worm]

Common name : Flatworms

General Characters :

1. Mostly parasitic animals, some are free-living (e.g. Planaria) and aquatic.

2. They are triploblastic animals showing bilateral symmetry and tissue organ grade of body organization.

3. The organisms are unsegmented, dorsoventrally flattened.

4. Body cavity (coelom) is absent i.e. acoelomate.

5. Suckers and hooks are usually present.

6. Alimentary canal has only one opening i.e. mouth, anus is absent.

8 Excretory system consists of blind tubules called protonephridia; having flame cells.

9. They are hermaphrodite i.e. male and female reproductive organs are present in same animal.

e.g. Planaria or Dugesia Microstomum- Energy of Hydra.

Fasciola- Liver fluke Schistosoma - Blood fluke

Taenia solium - Pork tape worm

PHYLUM NEMATODA OR ASCHELMINTHES
[Gk. nema = thread ; helmin = worm]

Common name - Thread worm or Round worm

1. They are parasitic, most are free living (in fresh or marine water or terrestrial).
2. They have narrow, elongated and cylindrical bodies. Body is covered by cuticle.
3. Triploblastic unsegmented animals with bilateral symmetry and organ system level of organization, having tube within tube body plan.
4. Pseudocoelom is present.
5. Alimentary canal straight and complete with mouth and anus.
6. Unisexual organisms.

e.g. Ascaris - round worm ; Enterobius - pin worm ; Wuchereria - filarial worm ; Ancylostoma - Hook worm.

Phylum- Annelida

                                                                           [Gk. annulus = ring ; lidos = form]

Common Name : Segmented worms

General Characters :

1. They occur in fresh water, sea water or moist soil. Some are free living, some are burrowing and a few are parasites.

2. Body is metamerically segmented i.e. body is divided externally by transverse grooves as well as internally by septa, these segments are called metameres.

3. They are the first animals with true body cavity i.e. coelom.

4. They are bilaterally symmetrical, triploblastic animals.

5. Body is covered by thin cuticle.

6. Locomotion by parapodia or Chitinous setae which are segmentally arranged.

7. Alimentary canal is complete.

8. Respiration is through the general body surface.

9. Excretion by nephridia.

10. Blood vascular system is closed. Blood is red due to the presence of the pigment " haemoglobin.

11. The nervous system consists of a dorsal "brain" and a ventral nerve cordhaving ganglia and lateral nerves in each body segment.

12. Sexes may be united (hermaphrodite) or separate.

e.g. Nereis - sand worm (clam worm)   Aphrodite - sea mouse

Pheretima - Earthworm                      Megascolex - Largest earthworm

Hirudinaria - India cattle leech           Bonellia

Hirudo - medicinal leech.

                                                                            Phylum Arthropoda

                                                                   [Gk. Arthron = joint ; Podas = foot]

Common Name : The animals with jointed feet.

The largest group of animals: General Characters :

1. They are found everywhere on earth- on land, in soil, in water and as parasites on plants and other animals.
2. Triploblastic, bilaterally symmetrical and metamerically segmented animals.
3. The body is segmented into 2 regions- head and thorax together and abdomen or 3 regions- head, thorax and abdomen. Anterior part of body forms a distinct head, bearing sense organs . Animals have jointed lags (3 or more pairs).
4. Arthropods have compound eyes, having many lenses to make mosaic vision.
5. Exoskeleton is made of chitin.
6. The body cavity is filled with blood i.e. haemocoel. Open circulatory system is present.

Blood may be colourless - Haemolymph (e.g. insects) or with copper contain pigment - Haemocycanin (e.g. prawn)

7.  Mouth parts adapated for biting, chewing, piercing and sucking.

8. Respiration occurs through general body surface, gills trachae or book lungs.

9. Excretion occurs by 'Malpighian tubules' or green glands or coxal glands.

10. Sexes are separate.

e.g. Peripatus Palaemon - (Prawn)

Cyclops - one eyed gaint Cancer - crab.

Scolopendra- Centipede Julus - Millepede

Lepisma - Silver fish Melanopus - grasshopper

Schistocerca - Locust Gryllus - house cricket

Periplaneta - Cockroach Musca - House fly

Apis - honey bee Anopheles - mosquito

Culex - mosquito Cimex - bed bug

Pieries - Butterfly Bombyx - silkmoth

Limulus - king crab Palamnaeus- scorpion

Arnea - spider Argus- ticks

Phylum- Mollusca

                                                                                  [L. Molluscs = soft]

Common Name : The Soft Bodied Animals

The second largest group of animals.

General Characters :

1. They are mostly aquatic, living in sea water, some of fresh water.

2. They are soft, unsegmented, triploblastic, coelomate animals with bilateral symmetry.

3. The body is divided into an anterior head, a ventral muscular foot and a dorsalvisceral mass of hump. Over the hump, a fold of thin skin called mantle orpallium is present, which secretes the shell.

4 The soft body is usually supported by a hard shell of calcium carbonate.

5. Locomotion is brought about by muscular foot.

6. Buccal cavity contain a rasping organ the 'radula' for feeding.

7. Respiration occurs through gills called ctendia.

8. Open blood vasuclar system. Blood is usually blue due to a blue pigment called"haemocyanin".

9. Excretion by a pair of kidneys or metanephridia, known as Kaber's organ orOrgan of Bojanus.

 e.g. Neopilina - Living fossils Chiton- Coat of mail shell Pila - apple snail

Aplysia - sea hare Helix - garden snail Dentalium - tusk shell

Unio - fresh water mussel Pinctada - Indian pearl oyster Sepia - cuttle fish

Octopus- devil fish Loliga - sea squid Nautilus

                                                                              Phylum - Echinodermata

                                                                   [Gk. echinos = spines ; derma = skin/covering]

Common Name : The Spiny Skinned Animals.

General Characters :

1. They are exclusively marine animals.

2. Body is triploblastic, coelomate and without segmentation with radial symmetry in adult and bilateral in larvae.

3. Body lacks head, but has oral and aboral surfaces. Oral surface of body has five radial areas called ambulacra.

4. Body cavity is modified into water vascular system. Tube like extensions called tube feet. Tube feet help in locomotion and food collection.

5. Digestive system is complete , mouth is on the lower surface and the anus is on the upper surface.

6. Respiration by gills, genital bursae, or respiratory trees.

7. Reproduction sexual, asexual or by regeneration. Sexes are separate.

e.g. Pentaceros - sea pentagen Asterias - star fish or sea star

Ophioderma - brittle star Ophiura

Echinus - sea urchin Holothuria - sea cucumber

Antedon - sea lily or sea feathers