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EVOLUTION 101

Introduction

Patterns

Mechanisms

Microevolution

Speciation

Macroevolution

The big issues

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Natural selection

Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift.

Darwin's grand idea of evolution by natural selection is relatively simple but often misunderstood. To find out how it works, imagine a population of beetles:

  1. There is variation in traits.
    For example, some beetles are green and some are brown.
Color variation in these beetles

  1. There is differential reproduction.
    Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do.
Differential reproduction
  1. There is heredity.
    The surviving brown beetles have brown baby beetles because this trait has a genetic basis.
Heredity of the traits of the beetles who survive
  1. End result:
    The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown.
Eventually, the advantageous trait dominates

Download this series of graphics from the Image library.

If you have variation, differential reproduction, and heredity, you will have evolution by natural selection as an outcome. It is as simple as that.


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Genetic drift

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Natural selection at work

Mechanisms
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See how the simple mechanisms of natural selection can produce complex structures, learn about misconceptions regarding natural selection, or review the history of the idea of natural selection.


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