Life Processes
This content is part of NCERT Solutions for Class 10 Science Chapter 6 Life Processes
INTRODUCTION :
All living organisms have arisen through the evolutionary process and show diversity, yet some similarities exist among them. e.g. Amphibians, reptiles and mammals have limbs for locomotion in water, fishes have fins for swimming in water and birds have wings for flying.
• A close examination reveals that the limb, fins and wings are formed on the same basic structural plan.
• All such examples can be explained if we consider that the diverse groups of organisms share a common ancestor from who they have diverged and formed two different species. Such process of change in biological system is called as evolution.
• The Doctrine of the Organic Evolution state that the organisms existing at present are the descendants of much simpler ancestors.
16.2 EVOLUTION :
The term ‘Evolution’ means “unrolling or unfolding” change from one condition to another. It means members of a species change generation after generation with environmental requirements to turn into better organized and more complex new species. The changes in the properties of population of organisms or groups of such populations over the course of generations are considered as organic evolution. It is a process of cumulative change of living populations and in the descendant populations of organisms. In other words, it is “descent with modifications.” Evolution is a change in the genetic composition of a population. There is an inbuilt tendency of variation during reproduction, both because of errors in DNA copying and as a result of sexual reproduction.
