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Complex organisms only evolved from and began as simple organisms - 3 billion years ago.

EVOLUTIONARY Similarities and Differences

!) Similar genes and common ancestors = closely related organisms.

These similar organisms look alike and have similar habitats (e.g. whales and dolphins)

2) HOWEVER genetically different species can also look alike and share similar habitats - although evolved from different ancestors.

EVOLUTIONARY TREE - The more recent the common ancestor - the more closely related the two organisms/species.

ECOLOGICAL Similarities and Differences

1) Organisms in the same environment with similar characteristics could suggest competition between species (e.g. for a food source)

2) Differences in the same environment can show predator-prey relationships

Natural Selection

Charles Darwin invented the idea of Natural Selection.

1) Individuals within a species show variation due to differences in their genes.

2) Those better adapted to the environment due to their characteristics and features, have a better chance of survival.

3) Those who survive continue on to breed and reproduce so that all useful and adapted genes are passed on throughout generations - therefore, the entire species within an

environment have a better survival chance.

Mutations

1) Mutation = Change in organism's DNA.

2) Usually, mutations have no effect. But they can be beneficial when they do - they can produce useful characteristics which increase chances of surviving and reproducing.

3) If so - this can be passed on to future generations through natural selection.

4) Over time, the mutation will accumulate in population e.g. some bacteria become resistant to antibiotics due to mutation.

Darwin

- It went against religious beliefs and the idea that our existence was due to God.

- Darwin had no good explanation because he didn't know anything about genes or mutations.

- Not enough evidence to convince scientists.

Lamarck

- He believed that if a characteristic was used more frequently by an organism in their lifetime, it would become more developed.

- These characteristics would then be passed on to the next generation.

Scientists

- They often created different hypotheses to explain similar observations because of different beliefs or influences from different peoples.

- HOWEVER, a hypotheses can be decided based on evidence to support or disprove it.

- For example,

- Lamarck's theory was rejected because experiments disproved the idea.

- Darwin's theory was accepted because there was evidence to support his ideas.

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