Class 9 Biology Diversity In Living Organisms Classification and Evolution

Classification and Evolution

Organizing the living organisms into groups according to a certain set of characteristics is called classification.

The features belonging to a particular organism is called characteristics.

We need classification due to following reasons:

  • It is not possible to study about each existing living organism in details.
  • Classifying organisms into groups makes it easier to know about the different life forms.
  • It helps us to understand the evolution of all life forms to a large extent.
  • It also forms the basis for the giving scientific names to the living organisms in order to universalize their names so that people around the world can recognize the organism irrespective of their local word for the organism.

Organisms can be classified on the basis of their characteristics:

  • Size: The size of the organisms.
  • Cellularity: Whether the organism is multicellular or unicellular.
  • Habitat: This classification is done on the basis of whether the organism lives on land, air or water.
  • Body organization: The way in which the cells are organized in the body of organisms.

Aristotle classified the organism on the basis of their habitat.

  • The animals living on land were called terrestrial animals.
  • The animals living in water were called aquatic animals.
  • The animals living on air were called aerial animals.

But this strategy couldn’t work because the plants weren’t considered here.

Some animals except one characteristic did not share any other characteristics in common. For example, fish and octopus both are aquatic animals but except living in water they don’t share any other common characteristics.

The process of development of complex organisms from simpler one with time is called evolution.

Fig. Evolution in Human beings

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