Lesson 25 and 26: Natural Selection Flashcards
What is structural homology?
Traits that are similar in appearance and/or function between species who have matured past the embryonic stage
What is developmental homology?
When the traits of developing embryos of different species are similar
When can a comparison be deemed homologous as opposed to analogous?
When phylogenic evidence supports the hypothesis that similarities between two subjects results from a trait from common ancestor
What is convergent evolution?
Occurs when natural selection favors similar solutions to problems posed by a similar way of making a living
–I.E. streamlined bodies and elongated jaws filled with sharp teeth help any reptile or mammal regardless of common ancestor
Does convergent evolution result in homologous or analogous traits?
Analogous, because the shared traits were not present in the two subjects common ancestor
What are the three modes of natural selection?
Directional Selection
Disruptive Selection
Stabilizing Selection
What is directional selection?
When the mean frequency of a given trait to the right or left of the original mean
–The mean phenotype is shifted
What is disruptive selection?
When the mean of a trait decreases in frequency (but does not shift left or right) and the left and right frequencies of a trait increase in a bimodal distribution pattern
–Extreme phenotypes are favored
What is stabilizing selection?
When the mean frequency for a given trait is favored
What is sexual dimorphism?
Any trait that differs between males and females
What is sexual selection?
A form of natural selection based on ability to attract mates
What is lekking behavior?
When males congregate to perform a companion attracting ritual
Generally speaking what can exert naturally selection?
Any factor that influences survival and reproductive success
What governs sexual selection?
Female choosiness, and male-male competition
–These both result in traits which lead to mating success
