Biology · Both
Evolution & Natural Selection
Darwin’s theory of natural selection, adaptation, speciation and evidence for evolution.
Evolution is the change in inherited characteristics of a population over generations. Natural selection is the main mechanism.
Natural selection
1. Variation exists in a population (mutation and sexual reproduction)
2. Some variants are better suited to the environment (advantage)
3. Those individuals are more likely to survive and reproduce
4. Advantageous alleles are passed on and become more common
This is **survival of the fittest** in a scientific sense (best adapted to reproduce).
Speciation
New species can form when populations become isolated (e.g. geographic isolation).
Different selection pressures → different adaptations → eventually cannot interbreed successfully.
Evidence
• Fossils – changes over geological time
• Antibiotic resistance in bacteria – evolution observed in real time
• Comparative anatomy and genetics
Practice questions
Try these without looking at the answers first.
Q1.What causes variation that natural selection can act on?
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Mutation / sexual reproduction
Q2.What is speciation?
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Formation of new species (often after isolation)
Q3.Give one modern example of evolution.
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Antibiotic resistance in bacteria