B1.8:Evolution

The theory of evolution - More than 3 billion years ago, life on Earth began as simple organisms from which all the more complex organisms evolved.

NATURAL SELECTION - The process by which species evolved

Charles Darwin was a scientist who came up with the natural selection idea in the 1800s.

• Individuals within a species show variation because of the differences in their genes.
• Individuals with characteristics that make them better adapted to the environment have a better chance of survival so will breed more succesfully.
• The genes responsible for the useful characteristics are more likely to be passed on to the next generation.
• The gene for the useful characteristic will become more common in a population leading to the gradual changing a species over time - evolution.

MUTATION - A change in an organism's DNA

• A mutation can be beneficial as it can produce a useful characteristic giving the organism a better chance of surviving and reproducing.
• The beneficial mutation is more likely to be passed on to future generations by natural selection.
• The beneficial mutation will become more common in a population, sometimes changing a whole species.

Charles Darwin's idea was very controversial at the time because:

• went against common religious beliefs that God was the creator of the Earth
• couldn't give a good explanation for why the useful characteristics appeared or how they were passed on because genes were not discovered till 50 years later
• not enough evidence to convince many scientists as not many other studies had been done into how organisms change over time

Jean-Baptiste Lamarck's idea was that:

• A characteristic used more and more by an organism would become bigger and stronger.
• One that is not used disappears eventually.
• The acquired characteristic used the more will be passed on to its offspring.

CLASSIFICATION - The process of sorting organisms into groups based on their similarites and differences

e.g. plants make their own food by photosynthesis and are fixed in the ground

e.g. animals move about the place annd can't make their own food

e.g. microorganisms are different to plants and amimals (bacteria are single-celled)

Evolutionary relationships - how all living things are related

Species with similar characteristics often have similar genes because they share a recent common ancestor making them closely related. They often look alike and tend to live in similar types of habitat.

Evolutionary trees show common ancestor and relationships between organisms. The more recent the common ancestor, the more closely related the two species.

Ecological relationships - how living things interact with each other

Organisms in the same environment with similar characteristics suggest they might in competition (may compete for food sources).

Differences between organisms in the same environment can show predator-prey relationships.