Unit-1: REPRODUCTION
UNIT-2 GENETICS AND EVOLUTION
UNIT-3 BIOLOGY IN HUMAN WELFARE
unit-4 biotechnology
Unit-5 ECOLOGY

13.0 Introduction

If an alien from a distant galaxy were to visit our planet Earth, the first thing that would amaze and baffle him would most probably be the enormous diversity of life that he would encounter. Even for humans, the rich variety of living organisms with which they share this planet never ceases to astonish and fascinate us. The common man would find it hard to believe that there are more than 20,000 species of ants, 3,00,000 species of beetles, 28,000 species of fishes and nearly 20,000 species of orchids. Ecologists and evolutionary biologists have been trying to understand the significance of such diversity by asking important questions- Why are there so many species? Did such great diversity exist throughout earth’s history? How did this diversification come about? How and why is this diversity important to the biosphere? Would it function any differently if the diversity was much less? How do humans benefit from the diversity of life?

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