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Animal Kingdom

- A quick revision tool for the grip on the chapter.

Kingdom Animalia

1. Animals are eukaryotic, multicellular and heterotrophic organisms.
2. They have multiple cells with mitochondria and they depend on other organisms for food.
3. Habitat - Most of the animals inhabit seas, fewer are seen in fresh water and even fewer on land.
4. Animal bodies - Bodies of animals are made of cells organized into tissues that perform specific functions.
5. Cell structure - The animal cell contains organelles like the nucleus, mitochondria, Golgi complex, ribosomes, endoplasmic reticulum, lysosomes, vacuoles, centrioles, cytoskeleton.
6. Organ systems are skeletal system, muscular system, digestive system, respiratory system, circulatory system, excretory system, reproductive system, immune system and the endocrine system. 

Phylum Porifera

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The word Porifera means organisms with holes.


1. Non-motile (meaning they are attached to solid support), mostly asymmetrical, diploblastic animals mainly found in marine habitats.

2. There are holes or pores all over the body called as Ostia and the opening at the upper free end is called Osculum.

3. The body is supported by skeleton called spicules or spongin fibres.

4. Reproduction is carried out sexually and asexually.

5. For example, Sycon, Euspongia, Spongilla, Euplectella etc.


Difference between Platyhelminthes, Nematoda and Annelida


Members of the phylum Platyhelminthes are commonly called flatworms. There are both parasitic (dependent on a host organism for survival) and free-living forms of this group.

All roundworms, phylum Nematoda, are very similar in appearance: they have a cylindrical body with tapering ends.  Most Nematodes are free-living, but some are important parasites of plants and animals.
They include segmented worms. One group is entirely marine (the polychaetes), while the other two groups are either terrestrial or live in freshwater.
They are acoelomate.
They are pseudocoelomate.
They are coelomate.
They do not have a respiratory system or a circulatory system. They have complete alimentary canal and excretory tubes for removing wastes from the body cavity. They have a circulatory system and a digestive system.


Phylum Arthropoda

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1. Triploblastic, segmented, bilaterally symmetrical animals having jointed appendages for locomotion. 

2. Blood-filled true coelom and body is protected with chitinous exoskeleton.

3. Body segments are divided into head, thorax and abdomen.

4. Reproduction is sexual and gonochoristic, but can be parthenogenetic.

5. For example, prawn, spider, scorpion, housefly, cockroach, centipede, butterfly.


Phylum Mollusca

1. Hard, calcareous shell, triploblastic, unsegmented, bilaterally symmetrical or asymmetric as in Pila.

2. They exhibit organ system level of organization.

3. The body is divided into head, visceral mass, muscular foot and mantle.

4. Open circulatory system and nephridia for excretion.

5. Muscular foot for locomotion.

6. Reproduction: Sexual and gonochoristic.

7. For example Chiton, Octopus, Pila, Unio, Loligo.



1. Non-chordates are animals without a notochord.
2. They are the most abundant and diversified of all animals living or extinct.
3. Non-chordata includes a number of phyla.
4. The major ones are Porifera, Coelenterata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, and Echinodermata.

Urochordata and Cephalochordata

Phylum Chordata is divided as Urochordata, Cephalochordata and Vertebrata
1. Also called Tunicata
2. Possess notochord at larval stage (larval tail)
3. Marine animal and mostly sessile
4. Lives as a solitary individual and can form colonies as well
Examples: Ascidia, Salpa,

1. Notochord present throughout the life
2. Notocord present from head to tail region
3. Segmented marine animals
Example: Branchiostoma



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1. These fishes have teeth-like scales, denticles, which include the sharks, rays, skates and ratfishes.
2. Their mouth is usually located ventrally. 
3. These were the first fishes to have paired fins (pectoral and pelvic fins) for more efficient swimming.
4. They contain a cartilaginous endoskeleton, the deposits of calcium salts provide strength to them.
5. They have 5 to 7 gill slits per side and no swim bladder.
6. The notochord is present throughout life.
7. They are predatory fishes, they feed on other fishes, crustaceans and molluscs. They filter food particles like planktons from the water current that passes through the mouth, pharynx and gills
8. The heart is two-chambered, contains one auricle and one ventricle.
9. Male and females are separate and fertilization is internal.