B1.8 Evolution


B1.8.1 Theories of Evolution

Darwin's theory of natural selection

States that all living organisms have evolved fro simple life forms that developed more than 3bn years ago. Relatively rapid evolution can occur if a new form of gene occurs due to mutation and there is a large change in the environment.

  1. Within species there is genetic variation due to random mutations in individuals
  2. Individuals with characteristics best suited to the environment are more likely to survive and reproduce successfully
  3. The genes that have enabled these individuals to survive are then passed on to the offspring and the next generation
  • Conflicts with religious beliefs
  • Was no evidence at the time as it is a slow process
  • Didn't explain how variations within a species occur (was no knowledge of genes & DNA until 50 years later)

Lamarck's theory of evolution

Law of inheritence of acquired characteristic

  1. Environmental factor (e.g weight training) causes an acquired characteristic (bigger muscles)
  2. Acquired characteristic inherited by offspring (e.g. children have big muscles)
  • Acquired characteristics do not have a genetic basis
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B1.8.1 Classification and Evolutionary Trees

Organisms are classified as plant, animal or microorganism using the similarities and differences in their characteristics. Classification can show how organisms are related by evolution (evolutionary relationship) or by how they live (ecological relationship)

Evolutionary trees are models of the relationships between organisms. This tree shows that organisms G and E are more closely related than G and D, suggesting they evolved from the same ancestor more recently than G and D.


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B1.8.1 Selective Breeding

Selective breeding is the process in which somebody breeds together organisms in order to amplify a desirable trait in the species

  1. Choose individuals with desirable traits
  2. Breed together
  3. Select best offspring with traits
  4. Breed together
  5. Continue process for generations
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