BIO 201 Lecture Notes - Lecture 8: Stabilizing Selection, Disruptive Selection, Directional Selection

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peardeer516

8 Mar 2018

School

Stony Brook University

Department

Biology

Course

BIO 201

Professor

True

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Document Summary

A (cid:272)ha(cid:374)ge i(cid:374) the distri(cid:271)utio(cid:374) of ge(cid:374)eti(cid:272) (cid:448)ariatio(cid:374) i(cid:374) a populatio(cid:374) is . Evolutionary change is both a pattern and a process. Stabilizing selection - variance decreases, mean stays the same. Directional selection - mean value of the character changes. Disruptive selection - variance increases, mean remains similar. Sexual dimorphism - elaborate characters evolved in one sex in a way that increases their attractiveness to mates. Sexual selection results from differences in mating success among individuals in a population, not merely from differences in survival and reproduction. Sexual selection and natural selection are happening at the same time. Sexual selection can work in the opposite direction as natural selection resulting in (cid:272)hara(cid:272)ters a(cid:374)d (cid:271)eha(cid:448)iors that redu(cid:272)e sur(cid:448)i(cid:448)al (cid:271)(cid:455) . Often female preference for elaborate male characteristics. There may be no genetic variation for the extra long tail feather phenotype. Natural selection may limit the length of tail feathers in this species.

Related Questions

A population that is variable in fur color phenotypes changes its distribution over time, such that the average color stays the same but the variance (spread of values) decreases in the population. Which mode or combination of modes of selection would explain this?

A. directional selection only;

B. disruptive selection only

C. stabilizing selection only

D. two of these would explain this

E. any of A, B or C would explain this

yellowhare287

(SLO 2) In a single population of locusts, the mean wing length is 47 mm, the selection gradient on wing length is Î² = 0.12/mm, the phenotypic variance for wing length is P = 3.6 mm², and the heritability of wing length is h² = 0.27. In addition, we know that the additive genetic covariance between wing and leg length is 0.60 mm².

Define selection gradient, variance, and heritability using your own words, as if you are explaining these to a freshman biology study.

What is the expected evolutionary change in mean leg length due to selection on wings?

What is the expected evolutionary change in mean leg length due to selection on both wings and legs?

Repeat these calculations to predict what will happen to wing length as a result of the selection on both wings and legs. What do you predict the average wing and leg lengths will be in the next generation?

Why do your predictions in b, c, and d differ? Explain, using evolutionary language.

Is evolution occurring? Describe and explain, using evidence from your calculations.