In natural selection, the environment determines which traits are advantageous, leading to species that are well adapted to their environment.

In artificial selection, humans choose the traits, focussing on enhancing one or two characteristics and leading to species that are beneficial to humans in some manner.

Artificial selection (selective breeding) is the process by which humans breed organisms for specific genetic traits and determine which individuals reproduce.

Artificial selection changes allele frequencies by favouring certain traits, leading to these traits becoming more common over time.

Artificial selection is done to enhance desired traits in organisms. This produces a population of individuals that all show the desired characteristics and can be interbred to produce offspring with these characteristics.

For instance, breeders may want to breed horses that can run fast or cattle that produce more milk.

1. Select a population showing variation
2. Select individuals with desired traits
3. Breed these individuals together
4. Grow and test the offspring
5. Repeat this process until the desired traits are achieved

Inbreeding is the process of breeding closely related individuals.

An advantage of inbreeding is that it can be used in artificial selection to preserve desirable traits.

A disadvantage of inbreeding is that it limits genetic diversity and increases homozygosity and so the chance of harmful recessive alleles being expressed. This leads to inbreeding depression, which is a loss of the ability to survive and grow well.

For example, maize plants with inbreeding depression become progressively smaller.

Outbreeding is the process of breeding unrelated or distantly related individuals.

An advantage of outbreeding is that it can lead to hybrid vigour, an increased ability to survive and grow well due to increased heterozygosity, reducing the occurrence of harmful recessive traits.

For example, hybrid vigour in maize plants makes them healthier, grow taller, and produce higher yields.

Maize plants need to be somewhat inbred so they have desirable traits like uniformity for easier harvesting and selling.

Some outbreeding also needs to occur to achieve heterozygosity for better health and yield.

1. To produce many different varieties of rice and wheat
2. To produce wheat grains that are rich in gluten
3. To produce varieties that have resistance to diseases like those caused by fungal infection

Milk yield in dairy cattle is improved by selectively breeding cows that have the highest milk yields with bulls that have female relatives with high milk yields.