Origins of life on Earth

  • Earth is 4500 million years old
  • Life began 3500 million years ago
  • Debate whether life developed due to the conditions on Earth or simple life forms arrived from another planet
  • Fossils are found in rocks
  • Can date when the different organisms existed
1 of 3

Theories of evolution

  • Lemarck thought that acquired characteristics were passed on to the next generation
  • Darwin's theory thought that small changes took place over time
  • Natural selection meant that organisms vary and are more likely to survive
  • Best adapted breed will pass on their characteristics
2 of 3

Natural Selection & Extinction

Natural Selection

  • Survival of organisms with the best characteristics is known as the survival of the fittest
  • The best adapted plants and animals survive due to natural selection
  • Organisms of a species all vary from one another


  • means that a species that once existed has been completely wiped out
  • always involved a change in circumstances
  • a new disease may kill all members of the species
  • climate change can make it too hot, too cold, too wet for a species and reduce food supply
  • a new predator could kill and eat all the new species
  • a new competitor may evolve and the original species will be left with nothing to eat
  • the habitat that the species live in may be destroyed
3 of 3


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Evolution, extinction and natural selection resources »