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TNPSC Free Notes Biology – Animal Kingdom

இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான  முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.

Animal Kingdom

 Basis of Classification
 We can divide the Animal kingdom based on the
1. level of organization (arrangement of cells)
2. body symmetry,
3. Germ layers and
4. Nature of coelom.
Level of organization:
 Animals are grouped as unicellular or multicellular based on cell, tissue,
organ and organ system level of organization
 It is a plan of arrangement of body parts.
 Radial symmetry and bilateral symmetry are the two types of symmetry.
Radial symmetry:
 In radial symmetry the body parts are arranged around the central Axis.
If the animal is cut through the central axis in any direction, it can be divided into
similar halves. e.g. Hydra, jelly fish and star fish
Bilateral symmetry:
 In bilateral symmetry, the body parts are arranged along a central axis.
If the animal is cut through the central axis, we get two identical halves
Germ layers:
 Germ layers are formed during the development of an embryo.
 Organisms with two germ layers, the ectoderm and the endoderm are called
diploblastic animals. e.g Hydra.
 Organisms with three germ layers, ectoderm, mesoderm and endoderm are
called triploblastic animals. e.g Rabbit.
 It is a fluid-filled body cavity.
 A true body cavity or coelom is one that is located within the mesoderm.

Based on the nature of the coelom, animals are divided into 3 groups.
1. Acoelomates do not have a body cavity e .g Tapeworm.
2. Pseudocoelomates have a false body cavity e.g Roundworm.
3. Coelomates or Eucoelomates have a true coelom e.g Earthworm, Frog.
 Animal Kingdom is further divided into two groups based on the presence
or absence of notochord as below.
1. Invertebrata
2. Chordata-Prochordata and Vertebrata
 Animals which do not possess notochord are called as Invertebrates or
Non- chordates. Animals which possess notochord or backbone are called
as Chordates.

 A protozoan (in Greek protos = first and zoon = animal)
 Is a single-celled eukaryote.
 They are included under the kingdom Protista.
 The study of protozoa is called Proto zoology.
 They are found in ponds, ocean, in moist soil, and in the cells and tissues of
plants and animals causing diseases.
 Protozoans have specialized organelles.
 These organelles are used for movement, feeding, and other functions
The types of protozoans are as follows:
 Ciliates – presence of cilia for locomotion (e.g. Paramecium)
 Flagellates – presence of flagella for locomotion (e.g. Euglena)
 Pseudopods – presence of pseudopodia for locomotion (e.g. Amoeba )
 Sporozoans – parasites (e.g. Plasmodium)
 Common Protozoans Plasmodium, Paramecium, Euglena
Phylum: Porifera (L. poros-pore; ferre-to bear)
 These are multicellular, non-motile aquatic organisms, commonly called as
 They exhibit cellular grade of organization.

 They are aquatic, mostly marine, an asymmetrical and a few species live in
 They possess a water transport system or canal system where water enters
through minute pores called ostia
 Nutrition is holozoic and intracellular
 They also reproduce asexually by fragmentation or gemmule formation
and sexually by the formation of gametes.
1. Sycon (Scypha)
2. Spongilla(fresh water sponge)
3. Euspongia (bath sponge)
4. Euplectella (Venus flower basket)
Phylum Coelenterata (Cnidaria) (G. knode -needle or sting cells)
 Coelenterates are aquatic organisms, mostly marine and few fresh water
 They are multicellular, radially symmetrical animals, with tissue grade of
 Body wall is diploblastic with two layers. An outer ectoderm and inner
 They have a central vascular cavity or coelenteron (serves both digestion
and circulatory function)
Cnidarians exhibit two basic body forms, polyp and medusa
1. Physalia (Portugese man of war)
2. Adamsia (Sea anemone)
3. Pennatula(Sea pen)
4. Meandrina (Brain coral)

Phylum Platyhelminthes (Flat worms) (G. Platy -broad or flat; helmin-
 They have a dorso ventrally flattened body and hence called flatworms

 They are bilaterally symmetrical, triploblastic, acoelomate (without body
cavity) animals.
 Most of them are parasitic in nature.
 Suckers and hooks help the animal to attach itself to the body of the host.
 Excretion occurs by specialized cells called flame cells.
 These worms are hermaphrodites.
 Having both male and female reproductive organs in a single individual.
e.g- Liver fluke, Tapeworm.
1. Taenia solium (Tape worm)
2. Fasciola hepatica (Liver fluke)
3. Schistosoma (Blood fluke)
Phylum Aschelminthes (Round worms)
 (G. Askes –cavity; helminths – worms)
 Previously called Nematoda, this phylum is now named as Aschelminthes.
 The bodies of these worms are circular (round) in cross section and hence
are called round worms.
 Aschelminthes are bilaterally symmetrical, triplo blastic animals.The body
cavity is a pseudocoelom.
 They exist as free-living soil forms or as parasites
 It is un segmented and covered by thin cuticle.
 Sexes are separate.
1. Ascaris lumbricoides (Round worm)
2. Enterobius vermicularis (Pin worm)
3. Wuchereriabancrofti (Filarial worm)
Phylum Annelida (Segmented worms):
 (L. annulus -a ring, and G. edios- form)
 Annelids were the first segmented animals to evolve. They are aquatic or
terrestrial, free living but some are parasitic.
 Setae and parapodia are locomotor organs.

 Sexes may be separate or united (hermaphrodites). e.g. Nereis, Earthworm,
 Their elongated body is metamerically segmented and the body surface is
divided into segment or metameres
 This phenomenon is known as metamerism.
1. Lampitomauritii (earthworm)
2. Neries (sand worm)
3. Hirudinaria (leech)
Phylum Arthropoda (Animals with jointed legs):
 (G. arthros- jointed; podes- feet)
 Arthropoda is the largest phylum of the animal kingdom.
 They are bilaterally symmetrical, triploblastic and coelomate animals.
 Exoskeleton is made of chitin and is shed periodically as the animal grows.
 The casting off and regrowing of exoskeleton is called moulting or ecdysis.
 Circulatory system is of open type.
 Sensory organs like antennae, eyes (compound and simple), statocysts
(organs of balance/ equilibrium) are present.
 Excretion occurs by malphigian tubules or green glands.
 Sexes are separate.
1. Limulus (King crab, a living fossil)
2. Palamnaeus (Scorpion), Eupagarus (Hermit crab),
3. Apis (Honey bee), Musca (House fly)
4. Vectors- Anopheles, Culex, Aedes (mosquitoes)
5. Economically important insects- Apis- (Honey bee), Bombyx (Silk
worm), Laccifer (Lac insects), Gregarious pest – Locusta (Locust)
Phylum Mollusca (Soft Bodied Animals)
 (L. molluscs –soft bodied)
 This is the second largest animal phylum. Molluscs are terrestrial and
aquatic (marine or fresh water) and exhibit organ system level of body

 They are bilaterally symmetrical (except univalves eg. apple snail)
triploblastic and coelomate animals.
 The sense organs are tentacles, eyes and osphraidium
 Excretory organs are nephridia.
 Open type of circulatory system is seen except for cephalopods such as
squids, cuttle fishes and octopus.
 Blood contains haemocyanin, a copper containing respiratory pigment.
 Pila (Apple snail),
 Lamellidens (Mussel),
 Pinctada (Pearl oyster)
 Octopus (Devil fish)
 Octopus is the only invertebrate that is capable of emotion, empathy,
cognitive function, self awareness personality and even relationships with
humans. Some speculate that without humans.
 octopus would eventually take our place as the dominate life form on earth.
Phylum Echinodermata (Spiny Skinned Animals):
 (G. Echinos – spiny; dermos –skin)
 They are exclusively free-living marine animals.
 These are triploblastic and true coelomates with organ-system grade of
 Adult animals are radially symmetrical but larvae remain bilaterally
 Locomotion occurs by tube feet.
 Body wall is covered with spiny hard calcareous ossicles
 These animals have a mesodermal endoskeleton of calcareous ossicles and
hence the name Echinodermata (spiny skin)
 The most distinctive feature of echinoderms is the presence of the water
vascular system or ambulacral system with tube feet or podia.

 The circulatory system is open type.
 Sexes are separate. Reproduction is sexual and fertilization is external.
 Asterias (Starfish or Sea star)
 Echinus (Sea-urchin),
 Antedon (Sealily)
 Cucumaria (Sea-cucumber)


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