Natural selection:

Process where certain inherited traits make it easier for some individuals to thrive and reproduce, changing genetic makeup of population over time

Adaptation:

Way in which organisms seem to be ideally shaped to enhance their survival and reproductibility in their environment

Fitness:

Relative ability to survive and create offspring

Principles of natural selection:

1.Different members of a population have various variations
2.Many of these are inheritable
3.Populations can have way more offspring than resources, leading to "The struggle for existence"
4.Favourable traits are more likely to come out on top and spread in a population because more offspring

These lead to change in both phenotype and genotype.

Some types of selection:

Directional selection:

Favoured trait is at one extreme. ex:short to tall

Stabilising selection:

Selection against extreme phenotypes. ex: medium is premium

Disruptive selection:

Favouring extremes at both extremes, selecting against common traits.
ex: political parties

Sexual selection:

Make oneself attractive to the opposite sex or intimidate the same sex for the production of more offspring

Artificial selection:

Humans select traits and breed for them in animals/plants