Eco Evo Unit 1: Intro to Evolution

adaptive evolution

increase in the frequency of beneficial alleles and decrease in deleterious alleles due to selection

allele frequency (gene frequency)

rate at which a specific allele appears within a population

bottleneck effect

magnification of genetic drift as a result of natural events or catastrophes

directional selection

selection that favors phenotypes at one end of the spectrum of existing variation

diversifying selection

selection that favors two or more distinct phenotypes

evolutionary fitness

individual’s ability to survive and reproduce

founder effect

event that initiates an allele frequency change in part of the population, which is not typical of the original population

frequency-dependent selection

selection that favors phenotypes that are either common (positive\`) or rare (negative)

gene flow

flow of alleles in and out of a population due to the individual or gamete migration

gene pool

all the alleles that the individual in the population carry

genetic drift

effect of chance on a population’s gene pool genetic structure distribution of the different possible genotypes in a populationge

genetic variance

diversity of alleles and genotypes in a population

good genes hypothesis

theory of sexual selection that argues individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease ha

handicap principle

theory of sexual selection that argues only the fittest individuals can afford costly traits

heritability

fraction of population variation that can be attributed to its genetic variance

honest signal

trait that gives a truthful impression of an individual’s fitness

macroevolution

broader scale evolutionary changes that scientists see over paleontological time

microevolution

changes in a population’s genetic structure

modern synthesis

overarching evolutionary paradigm that took shape by the 1940s and scientists generally accept today

population genetics

study of how selective forces change the allele frequencies in a population over time

population variation

distribution of phenotypes in a population

relative fitness

individual’s ability to survive and reproduce to the rest of the population

selective pressure

environmental factor that causes one phenotype to be better than another

sexual dimorphism

phenotypic difference between a population’s males and females

stabilizing selection

selection that favors average phenotypes

Causes of Evolution

Natural Selection

Genetic Drift

Migration

Mutation

4 postulates of natural selection

1. Variation exists among individual organisms in a population.
2. Some of that variation is heritable.
3. Survival and reproductive success is variable
4. Individuals best able to survive and reproduce is not random

Gregor Mendel

the father of genetics

* each parent passes a combination of discrete "‘factors” (alleles of genes)
* Each gamete carries only one factor
* factors segregate independently during gamete formation
* dominant and recessive factors

Selection pressure

environmental factor that causes one phenotype to be better than another; can be abiotic (not alive) or biotic (alive)

Hopi Hoekstra

Professor and curator at Harvard University

Specializes in the genetic basis of adaptation

fundamental asymmetry of sex

Females generally invest more resources into their offspring. Female fitness is limited by these resources. Male fitness is limited by access to mates. Predicts that females should be choosy, and males should compete with each other for mates.