Natural Selection Flashcards
Principles of Natural Selection
- natural selection depends on the environment. It does not favor the superior trait but favors the traits that are beneficial for survival and reproduction in a specific area.
- natural selection acts on the existing heritable traits. This heritable variance serves as a starting material for natural selection to act upon.
- heritable variations come from random changes or mutations in the genes.
Four fundamental principles of natural selection that Charles Darwin originally outlined in his book The Origin of Species
- Variation
- Inheritance
- High rate of population growth
- Reproductive advantage
variables which cause a certain phenotype of an organism to have a better chance of surviving and reproducing.
selective pressures
a particular way that genes are expressed in the physical traits or characteristics of an organism
phenotype
3 types of natural selection
- stabilizing selection
- directional selection
- Disruptive Selection
This type of natural selection occurs when there are selective pressures working against two extremes of a trait and therefore the intermediate or “middle” trait is selected for.
Stabilizing selection
This type of natural selection occurs when selective pressures are working in favour of one extreme of a trait.
Directional selection
This type of natural selection occurs when selective pressures are working in favour of the two extremes and against the intermediate trait. This type of selection is not as common.
Disruptive selection
External forces which affect an organism’s ability to survive in a given environment.
selective pressures
a measure of the extent to which natural selection is acting to reduce the relative contribution of a given genotype to the next generation.
selection coefficient
describes a difference in relative fitness between one genotype and another standard genotype.
selective coefficient
