B2.13: Evidence And Examples Of Evolution

Question 1

Summarise Darwin’s theory.

Answer 1

STEP 1 – there is in variation within any species
STEP 2 – organisms produce much more offspring than will survive, so there is competition for limited resources like food
STEP 3 – Only those best adapted will survive (this is known as ‘survival of the fittest’)
STEP 4 – Those that survive pass on successful adaptations to the next generation in their genes
Over time, the process of natural selection can mean that new species evolve:
- This ONLY happens if different groups of organisms cannot mate for a long time
- The organisms may be restricted from mating because of geographical isolation, this means they live in completely different areas. They may also be prevented from mating because of behavioural isolation
- If each group evolves differently they may (over an extended period of time) become different enough to be classified as a different species

Question 2

Lamark’s theory?

Answer 2

He said that a characteristic used by an organism more would become stronger and bigger, and that this would be passed on to offspring. Any characteristics that were NOT used would simply disappear.