17.3.1

Evolution by Natural Selection

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Principles of Natural Selection

Natural selection is the process that leads to evolution in a population. In order to understand how this process functions, it is important to learn the key principles of natural selection.

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Random mutation

  • Mutations are changes in the gene sequence of DNA.
  • Random mutations can arise spontaneously.
  • New mutations can result in new alleles of a gene.
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Variation in mutations

  • Most mutations are harmful because they alter the normal functioning of a gene.
  • But by chance, some mutations might confer a beneficial trait.
  • An individual with a beneficial mutation will be more likely to survive and reproduce than an individual without the mutation.
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Inheritance

  • When an individual reproduces, their offspring will inherit half of their genes.
  • When an individual with an advantageous mutation reproduces, the allele is inherited by their offspring.
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Change in allele frequency

  • Individuals in the next generation who have the advantageous mutation are also more likely to reproduce and pass on the allele.
  • Over many generations, the new allele will increase in frequency in the population.
  • The change in allele frequency over time is called evolution.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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