Evolution by Natural Selection

When do scientists believe that life first developed on Earth?

3 billion years ago. These first life forms were very simple. All species of living things have now evolved from these simple life forms.

What is there among a population of species?

Genetic variation.

Every organism will have a slightly different combination of alleles that it inherited from its parents.

What is natural selection?

The process by which organisms with advantageous traits or characteristics are more likely to survive and reproduce, passing on their advantageous traits.

For example, a fox approaches some rabbits. Rabbits with alleles for better eyesight or hearing have an advantage, what does this mean?

These rabbits are more likely to detect the fox as it approaches than those who do not have those traits. They are more likely to survive and reproduce.

Beneficial alleles may be passed onto offspring. Over generations, these alleles will be widespread in the rabbit population.

What is evolution?

The change of the inherited characteristics of a population over time through a process of natural selection.

What can happen if 2 populations of one species become so different in phenotype?

They can no longer interbreed to produce fertile offspring. The 2 populations have now become 2 separate species.