EvolInActionLEC13 Flashcards
What are the three different ways that natural selection is likely to change populations? (Modes of Selection)
Directional, Disruptive, and Stabilizing selection!
What is directional selection?
A selection that favors individuals at one end of the phenotypic range.
What is disruptive selection?
A selection that favors individuals at both extremes of the phenotypic range.
What is stabilizing selection?
A selection that favors intermediate variants and acts against extreme phenotypes.
The normal curve of a phenotypic range is?
Normal distribution! or the bell curve!
What is balancing selection?
Ex. leopards & cheetahs
What does it lead to?
A selection that occurs when natural selection maintains stable frequencies of 2 or more forms in a population.
Leads to balanced polymorphism
What maintains genetic variation in population in the form of hidden recessive alleles?
Diploidy!
What is a heterozygote advantage
What will natural selection tend to do
Ex. sickle-cells in humans
Heterozygote individuals have greater fitness than homozygotes for a certain gene. Natural selection tend to maintain two or more of these alleles in the population.
Those who are heterozygote are immune to sickle-cells.
What is frequency-dependent selection?
A selection that occurs when the fitness of a morph declines if it becomes too common in the population.
What is sexual selection?
What can this result in?
Ex. Jacana birds.
A selection where an individual’s (reproductive success) depend on mating success.
Can result in sexual dimorphism.
What is sexual dimorphism?
Distinct differences between the sexes in secondary sexual characteristics.
What is intrasexual selection?
Ex. Two fighting male gazelles
Direct competition for mates of the opposite sex.
What is intersexual selection?
Ex. Male’s peacock appeal to female ones.
A selection that occurs when individuals of one sex are choosy in selecting their mates.
