Theory of evolutions

• Lamarck's theory;

  He suggest that organisms could acquire new traits during their lifetime, and they could be then passed on to their offspring.
• According to Lamarck's theory giraffes have long necks because;

  1. Giraffes started off with short necks and adapted to lower vegetation.
  2. They then started to stretch their necks to reach higher branches for food. This caused then to get longer necks over their lifetime.
  3. This trait is then passed to offspring.
• Lamarck's theory was proved wrong by modern genetics. Because we know that characteristics acquired by an organism during its lifetime do not affect their DNA, so can't be passed on.
• Darwin's observations;

  1. Individual organisms within a species show a wide range of variation for a specific trait.
  2. Observed variations between species adapted to different environments.
  3. Older layers of rocks contained fossils with less complex organisms, whereas recent layers of fossils contained more complex organisms.
• Both Darwin and Wallace independently propesed the theory of natural selection.
• According to Darwin and Wallace's theory giraffes have long necks because;

  1. A random genetic mutation occurred within species causing them to have longer necks.
  2. Giraffes with longer necks adapted better to the environment, so had a higher chance of surviving and reproducing, so trait of long necks were passed onto offspring.
• A first Darwin's and Wallace's theory wasn't accepted because;

  • Religious reasons
  • Lack of evidence
  • DNA wasn't discovered yet