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
Variation exists among individual organisms in a population.
Some of that variation is heritable.
Survival and reproductive success is variable
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.