Chapter 11 Zoology

Evolution

evolution

population changing over time

Charles Darwin

developed natural selection as a mechanism that causes populations to change over generation

natural selection

advantageous traits become more common over generations

individuals within a population must vary

variation must be heritable

organsisms

produce more offspring than resources can produce

mutations and sexual reproduction

genetic variations came from,,,

mircoevolution

small-scale

genetic changes within a population

macroevoltion

large-scale evolutionary changes that can lead to the formation of new species or higher taxonomic groups

adaption

heritable characteristics that improves an organisms ability to survive

dont directly change the environemt, but can influence environmental conditions indirectly by altering low organisms interact with and modify their surroundings

allele frequency

the proportion of specific allele among all copies of a gene in a population

divergent evolution

related organisms becoming increasingly different after evolving from common ancestors

homologous characteristics

homologous characteristics

similar becuase of common ancestory

divergent evolution

convergent evolution

unrelated or distantly related organisms independently evolve similar traits because they experience similar environmental structures

analogous structures

analogous structures

similar function but evolved independately

natural selection, mutation, genetic drift, migration

mechanisms of evolution

natural selection

Depending on environmental conditions, phenotype may be advantageous or disadvantageous

each person carries two alleles → determines phenotype

If advantageous, frequency increases in the subsequent generation

mutation

source of new alleles in a population

change in allele frequency resulting from this is very small

genetic drift

the effect of chance

bottleneck and founder effect

bottleneck effect

disaster ruins frequency

founder effect

small group leaves to start a new population in a new location

migration/gene flow

flow of alleles in and out of a population resulting from the migration of individuals

Hardy-Weinberg assumptions

no natural selection

no mutation

no migration/gene flow

very large population (small effect of genetic drift)

random mating

Hardy-Weinberg equilibrium

p + q = 1

homozygous dominant = p²

homozygous recessive = q²

heterozygous = 2pq

p² + 2pq + q²

fossil records, comparative anatomy, embryology, biogeography

evidence of evolution

comparative anatomy

Homologous structures have same underlying anatomical organization

biogeography

location of species often reflect their evolutionary history

vestigeal structures

a feature inherited from an ancestor that has become reduced or nonfunctional due to changes in selective pressures

Provides strong evidence for common ancestry among species

speciation

function of a new species

adaptive radiation

multiple species arrive simultaneously

theory

a broad explanation that has been extensively

sympatric speciation

occurs when populations become reproductively isolated without geographic seperation

purposeful

Evolution is not …