Classification of Animal Kingdom on basis of Arrangement of cells

Every organism in Animal kingdom is multicellular.


The types of cellular organisations found in animals are:


1.      Cellular level of organization: The organisms are made of cells which are formed or arranged as loose lumps. This is mainly seen in Sponges.


2.      Tissue level of organization: A tissue refers to a group of cells performing a similar function. In this organisation cells cooperate with each other performing same function. It is mainly seen in coelenterate.


3.      Organ level of organization: In this organisation the tissues are organised into organs to perform specific functions. It is mainly seen in platyheliminthes.


4.      Organ system level of organisation: In this system of organisation, the organs associate and co-ordinate with each other to form functional systems. Each system is concerned with a specific physiological function. It is seen from Annelids to Chordates.


Patterns in circulatory, digestive and reproductive system:


1. Circulatory System:

·         Open type: Blood is pumped out of the heart and cells and tissues are bathed in it. E.g. Arthropods, Mollusca.

·         Closed type: Blood is circulated through series of vessels of different size and diameters. E.g. Vertebrates.


2. Digestive System:

·         Complete: There are 2 openings to the outside of the body, the mouth and anus. E.g. Arthropods, Chordates.

·         Incomplete: They have only one opening towards the outside of the body and it serves as both mouth and anus. E.g. Platyhelminthes.


3. Reproductive System:

·         Internal fertilisation: Fertilisation takes place inside the body of some organisms. E.g. Platyhelminthes.

·         External fertilisation: Fertilisation takes place outside the body of some organisms. E.g. Ctenophora.


1. Direct development: Embryo develops into a mature individual without involving a larval

stage. Metamorphosis is absent E.g. fishes, reptiles, birds etc.


2. Indirect development: Involves sexually immature larval stage, having different food requirements than adults. Metamorphosis is present. E.g. most of invertebrates and amphibians.


·         Oviparous animals: They lay fertilised or unfertilised eggs. The chances of survival of young one is less.

·         Viviparous animals: They give birth to young ones. The chances of survival of young one is more.

·         Ovoviviparous animals: They produce eggs, but instead of laying eggs, the eggs develop within the maternal body and hatch within or immediately after release from the parent. E.g. Some sharks, snakes etc.

Post By : Atul Sharma 10 Jan, 2019 3219 views Biology