Classification of Animals, Biology Assignment Help

Biology Assignment Help >> Classification of Animals

1-Symmetry- The arrangement of body parts of an organism in relation to one another and it is the similarity of body parts in different directions or regions of the body. On the basis of type of the symmetry, animals can be divided into following types:

(A) Asymmetrical-When the body of an animal is not divisible into two equal halves by any plane it is named as asymmetrical. It is found in sponges.

(B)Symmetrical- This type of animals are as follow:

(a)Spherical- In this type the body parts of an animal are arranged in a sphere thus the sides of the body are not distinguishable. The body is divisible into two similar halves from any plane passing through the centre .It is found in the Volvox.

(b)Radial-This type of animal is divisible into two equal halves by any plane that passes through the centre from top to the bottom e.g. Hydra.

(c)Biradial symmetry-When the body of an animal is cut into two similar halves through only two vertical planes its called biradial symmetry. For e.g. sea anemone.

(d)Bilateral symmetry- In this type body is divisible into two equal left or right halves that is cut in a vertical plane passing through the median longitudinal body axis e.g. frog

Body temperature-Based on the body temperature the individuals may be divided into following types. These are as following:

a) Poikilothermous or cold blooded animals- Animals whose body temperature is varies with that of the surrounding enviroment are named as cold blooded. Example fish, invertebrates, amphibians or reptiles.

b) Homoiothermous or warm blooded animals- Animals whose body temperature remains constant or does not change with the change of environmental temperature. Example mammals or birds.

Germ layers

Germ layers are found in animals, layer at the gastrulation stage. These layers give rise to all the organs/tissues of the fully formed individual. Based on the number of the germ layers animals can be divided into following types;

1-Diploblastic – The embryos of coelenterate or porifera have two germ layers the ectoderm or endoderm. These animals are called the diploblastic.

2-Triploblastic-The embryos of all other animals from phylum platyhelminthes to phylum chordata have three germ layers, the ectoderm, mesoderm and the endoderm. These animals are called as triploblastic.


Coelom is the body cavity which is lined throughout by mesoderm.It is filled with coelomic fluid in which different internal organs are suspended. The coelomic fluid acts as a simple circulatory system for transportation of food material. Based on the type of coelom animals are classified into following types:

a)-Acoelomate-These does not have any cavity in the body except digestive tract. example flatworms

b)-Pseudocoelomate-In these

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