INTRODUCTION TO CLASSIFICATION
Have you ever thought of the multitude of life-forms that surround us? Each organism is different from the other to a lesser or greater extent. For instance, consider yourself and a friend.
* Are you both of the same height?
* Does your nose look exactly like your friend’s nose?
* Is your hand-span the same as your friend’s?
However, if we were to compare ourselves and our friends with a monkey, what would we say? Obviously, we and our friends have a lot in common when we compare ourselves with a monkey. But suppose we were to add a cow to the comparison? We would then think that the monkey has a lot more in common with us than with the cow.
Activity 7.1:
* We have heard of ‘desi’ cows and Jersey cows.
* Does a desi cow look like a Jersey cow?
* Do all desi cows look alike?
* Will we be able to identify a Jersey cow in a crowd of desi cows that don’t look like each other?
* What is the basis of our identification?
In this activity, we had to decide which characteristics were more important in forming the desired category. Hence, we were also deciding which characteristics could be ignored.
Now, think of all the different forms in which life occurs on earth. On one hand, we have microscopic bacteria of a few micrometre in size. While on the other hand, we have blue whale and redwood trees of California of approximate sizes of 30 metres and 100 metres respectively. Some pine trees live for thousands of years while insects like mosquitoes die within a few days. Life also ranges from colourless or even transparent worms to brightly coloured birds and flowers.
This bewildering variety of life around us has evolved on the earth over millions of years. However, we do not have more than a tiny fraction of this time to try and understand all these living organisms, so we cannot look at them one by one. Instead, we look for similarities among the organisms, which will allow us to put them into different classes and then study different classes or groups as a whole.
In order to make relevant groups to study the variety of life forms, we need to decide which characteristics decide more fundamental differences among organisms. This would create the main broad groups of organisms. Within these groups, smaller sub-groups will be decided by less important characteristics.
Questions
1. Why do we classify organisms?
2. Give three examples of the range of variations that you see in life- forms around you.
Source: This topic is taken from NCERT TEXTBOOK