Darwin, Wallace & Mendel [Biology only]

Darwin's theory

• Charles Darwin, after observations on a round-the-world expedition, years of experiment and discussion, and developing knowledge of geology and fossils, proposed the theory of evolution by natural selection:
  • Individuals in a species show a wide range of variation
  • Those with characteristics most suited to the environment are more likely to survive and breed
  • The characteristics that helped them survive are passed on
• He published On the Origin of Species in 1859. It was controversial, and only gradually accepted, because:
  • It challenged the idea that God made all living things
  • There was insufficient evidence at the time to convince many scientists
  • The mechanism of inheritance and variation (genes) was not known until 50 years later
• Lamarck's alternative theory said that changes that occur in an organism during its lifetime can be inherited (a giraffe stretching its neck has long-necked offspring). We now know this cannot happen in the vast majority of cases: acquired characteristics do not change the genes in gametes