Evo Bio ch9-10

Quantitative Traits

each phenotype is determined by many genes

population genetics

examines discrete genotypes

quantitative genetics

examines continuously distributes phenotypes.

• mean and variance of populations

Uses for Quantitative Genetics?

1. measure heritable variation

2. measure differences in fitness

3. predict evolutionary response to selection on quantitative traits

QTLs - Quantitative Trait Loci

identifies a particular region of the genome as

containing a gene associated with the trait of interest

______ percentile of this distribution is used as a significance threshold

95th

Formula for predicting evolutionary response

R=h² S

R = predicted response

h² = heritability

S = selection differential

Directional Selection

Phenotype shifts to one extreme

• fitness increases with the value of the trait

Stabilizing Selection

intermediate phenotype have highest fitness

Disruptive Selection

both phenotypic extremes have highest fitness

Pratt and Anderson

classified social status of male giraffes

Simmons & Scheepers

challenged notion that giraffes have long necks in order to reach leaves on tall trees

Zonosemata tephritid flies

found that these flies mimic jumping spiders to deter other jumping spiders

Ray Huey

conducted observational study of garter snakes and where/why they chose to sleep at night

Garter Snake night retreats

found that snakes choose medium rocks to heat and cool

Comparative Method

purpose is to remove the effects of evolutionary history from an analysis. testing the adaptation by itself

Hosken

hypothesized that bigger testes in bats evolved for sperm competition.

Joe Felsenstein

developed a way to evaluate cross-species correlation among traits. this method helped Hosken come to conclusion about bat testes

Fuchsia excoricata

green phase: 5.5 days

intermediate phase: 1.5 days

red phase: 5 days

Delph & Lively

had two hypothesis for why Fuchsia drops its flower after red phase.

determined that a physiological constraint keeps Fuchsia from dropping flowers sooner