AP Bio Unit 7: Natural Selection

biogeography

the geographic distribution of species

evolution

change in the genetic makeup of a population overtime; descent with modification

natural selection

a process in which individuals that have certain traits tend to survive and reproduce at higher rates than other individuals because of their traits

artifical selection

the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits

population

a group of individuals of the same species that live in the same area and interbreed to produce fertile offspring

gene pool

a population genetic makeup; consists of all copies of every type of allele

microevolution

small scale genetic changes in a population

genetic drift

chance events that cause a change in allele frequency

bottleneck effect

when a large population is drastically reduced by a non-selective disaster

founder effect

when a few individuals become isolated from a large population and establish a small population with a gene pool that differs from the large population

gene flow

the transfer of alleles into or out of a population due to fertile individuals or gametes

relative fitness

the number of surviving offspring that an individual produced compared to others left in population

directional selection

selection on the extreme towards one phenotype

stabilizing selection

selection towards the mean away from extremes

disruptive selection

selection against the mean and towards the extremes

sexual selection

a type of natural selection that explains why many species have showy unique traits; selection for mating based on certain traits (affects fitness)

Hardy-Weinberg Equilibrium

a model used to assess whether natural selection or other factors are causing evolution at a particular locus

Hardy-Weinberg principle

frequency of alleles and genotypes in a population will be remain constant from generation to generation provided that ONLY Mendelian segregation and recombination of alleles are at work

five conditions of Hardy-Weinberg equlibrium

• No mutation
• No gene flow
• No natural selection
• Random mating
• Large population size

fossils

remains or traces of past organism

fossil record

gives a visual of evolutionary change overtime

comparative morphology

analysis of the structure of living and extinct organisms

homology

characteristics in related species that have similarities even if structures differ

vestigial structures

structures that are conserved even though they no longer have a use

molecular homology

similarities in DNA and AA sequencing between species

homologous structures

characteristics that are similar in 2 species because they have a common ancestor

convergent evolution

similar adaptation that have evolved in distantly related organisms due to similar selection presures

analogous structures

structures that are similar but have separate evolutionary origins

biogeography

the distribution of animals and plants geographically

systematics

classification of organisms and determining their evolutionary relationships

taxonomy

naming and classifying species

phylogentic trees

diagrams that represent the evolutionary history of a group of organisms

node

branching point; represents common ancestors

sister taxa

two clades that emerge from the same node

bassal taxum

a lineage that evolved from the root and remains unbranched

synapomorphy

a derived trait shown by clade member

derived charateristic

similarly inherited from the most recent common ancestor of an entire group

ancestral characteristic

similar trait that arose prior to common ansestor

outgroup

a lineage that is least closely related to the rest of the organisms

monophyletic group

includes the most recent common ancestor of the group and all its descendants (clade)

paraphyletic group

includes the most recent common ansestor but not all of it’s desendents

polyphyletic group

does not include most recent common ancestor of all members of the group

species

a group able to interbreed and produce viable offspring

speciation

formation of a new species

allopatric speciation

physical barrier divides population or a smaller group of the population is separated from the main population preventing gene flow

sympatric speciation

a new species evolved while still inhabiting the geographic regions of the ancestral species, usually due to the exploration of a new niche

2 types of reproductive isolation

prezygotic and postzygotic barriers

prezygotic barriers

prevent mating or hinder fertilization

habitat isolation

species live in different areas or occupy different habitats in the same area

temporal isolation

species breed at different times of the day, year or season

behavioral isolation

unique behavioral patterns and rituals separate species (sexual selection)

mechanical isolation

the reproductive anatomy of species does not fit the anatomy of another

genetic isolation

proteins on the surface of gametes do not allow for sperm and egg to fuse

reduced hybrid viability

the genes of different parent species many interact in a way that impair the hybrids development or survival

reduced hybrid fertility

a hybrid can develop into a healthy adult but is sterile

hybrid breakdown

the hybrid of the first generation may be fertile, but when they mate with a parent species or one another, their offspring will be sterile

microevolution

change in allele frequencies within a single species or population

macroevoltion

large evolutionary patterns

stasis

no change over long periods of time

punctuated equilibrium

when evolution occurs rapidly after long periods of statis

gradualism

when evolution occurs slowly over hundreds, thousands or millions of years

divergent evolution

groups with the same common ancestor evolve and accumulate differences resulting in the formation of new species (homologous traits)

adaptive radiation

if a habitat or niche becomes available, species can diversify rapidly

convergent evolution

two different species develop similar traits despite having different ancestors (analogus traits)

extinction

the termination of a species