Animalia

Animalia (Multi-cellular Eukaryotes)

This kingdom includes all animals except the protozoans, which have been transferred to the kingdom Protista.

The members of this kingdom are multicellular, eukaryotic and without cell wall.

They show heterotrophic mode of nutrition.

Almost all the animals are mobile . They move about in search of food or for other needs. Spionges and corals are however sedentary.

Cell wall is absent.

The phylum under kingdom Animalia that shows the maximum diversity is Arthropoda and the second largest is Mollusca.

Basis of Classification of Animals:

1. Organization: Organization is the structural differentiation of animal body. It can be divided in to three levels :

(i) Cellular level: In cellular level of organization, tissues do not differentiate. However, different types of cells may occur. e.g. Porifera

(ii) Tissue level: In tissue level of organization, cells are organized in to tissues but organs are absent. e.g.Coelenterata

(iii) Organ level: In organ level of organization, cells are organized in to organs and organs into organ system. e.g.Nematheliminthes and higher animals.

2. Body Symmetry: Body symmetry is defined as similarity in arrangement of parts. It is of two types:

(i) Radial symmetry: In radial symmetry, the body can be divided in to two equal halves by any vertical plane passing through the central axis. It is found in Sponges, Coelenterates and Echinoderms etc.

(ii) Bilateral symmetry: In bilateral symmetry, body is divisible in to two equal halves by only one plane. It is found in platyhelminthes, nematode, annelida, mollusca, arthropoda and chodrata.

3. Germinal layers: Germinal layers are primarily layers that differentiate in embryo to form tissues and organs.It includes outer ectoderm, middle mesoderm and inner endoderm. On the basis of germinal layer, animals are of two types:

(i) Diploblastic animals: Animals that have two germinal layers-outer ectoderm and inner endoderm are called diploblastic.

(ii) Triploblastic animals: Animals that bear three germinal layers- ectoderm, mesoderm and endoderm is known as triplobalstic. It includes Plateyhelminthes to Chordate.

4. Coelom (Body Cavity) : Coelom is a mesodermal lined fluid filled cavity that occurs between alimentary canal and body wall. It provides shock proof environment to various body organs. On the basis of presence or absence of coelom, animals are divided in to three types:

(i) Acoelomate : Animals that lack coelom are acoelomate. Example Porifera, Coelentrata, Platyhelmithes.

(ii) Pseudocoelomate: Pseudocoelomate lacks true coelom. A cavity called Pseudocoelom is present, which is not lined by mesoderm. Example: Nemathelminthes.

(iii) Coelomate: A true coelom lined by mesoderm is present. Example: Annelida, Mollusca, Arthropoda, Echinodermata and chordata.

Sample Questions

(More Questions for each concept available in Login)

Question : 1

Which of the following kingdoms includes only heterotrophic organisms?
A. Monera	B. Plantae	C. Protista	D. Animalia
Right Option : D
View Explanation

Question : 2

Maximum diversity is seen amongst _________________
A. Monera	B. Animalia	C. Plantae	D. Protista
Right Option : B
View Explanation

Question : 3

Observe the picture of an earthworm drawn below. Find out the most characteristic feature on the basis of which the animal has been placed in its phylum