Types of Selection Flashcards
Continuation from Methods of Evolution.
What’s stabilizing selection?
Genetic diversity decreases and the population stabilizes on a specific trait.
The environmental selective pressure will eliminate individuals with on the upper or lower ends of a trait, and a particular trait will stabilize around the middle value.
What’s Directional Selection?
Either the lower or upper limit of a trait is preferred, and there is selective pressure against the other extreme.
In time, the allele frequency will shift in the direction of the favoured trait.
EX: The fastest cheetahs are fittest for their environment, there is selective pressure against the slowest cheetahs.
What’s Disruptive selection?
The upper or lower values of a particular trait have competitive advantages, and the selective pressure is against the mean trait.
Allele frequency will shift towards both extremes, results in creation of two new species and eliminating the middle (speciation).
EX: Light butterflies are camouflaged during the day, and dark butterflies are camouflaged at night. Grey butterflies are not camouflaged in either scenario.
What’s Coevolution?
Many species evolve symbiotic relationships with other species.
These species occasionally evolve together to the point that they are both dependant on one another.
What’s Altruism?
Some species display behaviour that will decrease their fitness, to help or cooperate with another. increasing the fitness of the other being.
What does Altruism lead to in nature?
leads to the increased fitness of the individual indirectly.
By protecting or helping those who are closely related to you, there is a greater number of your own genes passed onto the next generation
