The organisms, which are eukaryotic, multicellular, and heterotrophic, are categorized as Animalia kingdom.
The organisms of Animalia kingdom have no cell-wall.
Most of animals of Animalia kingdom are mobile.
Based on the extent and type of the body design differentiation, Animalia kingdom classified as −
Let’s discuss each of them in brief −
The literal meaning of ‘porifera’ is the organisms with holes.
The organisms of porifera are non-motile and attached to some solid support.
The examples of this group are Sycon, Spongilla, Euplectelia, etc.
Organisms of coelenterata group live in water.
The organisms of this group have cavity in their bodies.
Hydra and sea anemone are the common example of coelenterate.
The organisms of this group do not have true internal body cavity or coelom; so, they neither have well-developed organs.
The bodies of organisms of this group are flattened from top to bottom; therefore, they are also known as flatworms.
Planareia, liverfluke, tape worm, etc., are the typical examples of this group.
The organisms of nematode have cylindrical body.
The organisms have tissue, but as such no well-developed body (i.e. no real organ).
The filarial worms (causing elephantiasis disease), roundworm in the intestines, etc., are the common examples of nematodes.
The organisms of annelida group live almost everywhere including fresh water, marine water as well as on land.
Earthworms, nereis, and leeches are the familiar examples of annelida.
Arthropoda, probably, is the largest group of animals.
The animals of this group don’t have well defined blood vessels rather there is an open circulatory system.
The literal meaning of arthropod is jointed legs; so, they have jointed legs.
Prawns, butterflies, houseflies, spiders, scorpions, etc. are the typical examples of arthropod.
The organisms of mollusca are invertebrate.
Most of the organisms of Mollusca group live in water.
Snails and mussels are the typical example of Mollusca.
The organisms of Echinodermata have spiny skinned.
Echinodermata are free-living marine organisms.
The examples of echinodermata are starfish, sea urchins, feather star, etc.
The organisms of protochordata are normally marine. E.g. Balanoglossus, Herdemania, and Amphioxus
The organisms of protochordata show a typical feature of body design, called as notochord; however, it does present there throughout the life.
Vertebrata has been discussed in a separate chapter.