ap bio -- unit 1: evolution

i love you natural selection, i didn't know how good i had it

population

a total number of species in the same place at the same time

allele

alternative forms (arise by mutation) of a gene that codes for protein

allele frequency

how often an allele appears in a population

evolution

change in heritable characteristics (traits) in a population over successive generations

species

organisms capable of interbreeding + producing viable, fertile children

population

group of organisms of the same species living in the same place at the same time

natural selection

survival of the fittest; individuals w/ most fit trait survives >> produces more

adaptation

any characteristic that helps an organism survive its environment

fitness

reproductive success of an individual

selective pressure

environmental factor that influences who has greater fitness

viable

able to survive

mutation

change in DNA sequence of an organism’s genome >> variation in traits

gene pool

all alleles present in a population

phenotype

physical appearance of a trait

genotype

combination of alleles that are inherited

how do mutations happen?

dna replication errors or mutagens/environmental factors

directional selection

one extreme of a trait has highest fitness

stabilizing selection

moderate forms of a trait have highest fitness

disruptive selection

both extreme of a trait have highest fitness

artificial selection

human breeding animals and plants for favorable traits

sexual selection

#1. one sex competes with others for a mate

#2. one sex chooses mate based on other sex’s trait

genetic drift

chance events change allele frequency in population

(bottleneck + founder effect)

bottleneck effect

chance event (like natural disaster) happens >> population dies by chance >> changes allele frequency

founder effect

population moves to uninhabited land >> gene pool/trait variation decreases

gene flow

individuals bring in new alleles or take their alleles w/ them while leaving >> changes allele frequency

hardy-weinberg equilibrium (HWE)

population experiences no allele change

large population, random mating, no gene flow, no genetic drift, no natural selection

p

frequency of dominant allele (A)

q

frequency of recessive allele (a)

p²

frequency of homozygous dominant genotype (AA)

2pq

frequency of heterozygous genotype (Aa)

q²

frequency of homozygous recessive genotype (aa)

microevolution

changes in allele frequency w/in population

caused by natural selection, sexual selection, artificial selection, genetic drift, gene flow, and/or mutations

speciation/macroevolution

formation of new species from accumulation of microevolutionary changes (change in allele frequency)

species

group of organisms that can make + product viable, fertile offspring

how does speciation occur?

single population (of one species) becomes reproductively isolated via reproductive barrier (prevents gene flow) and populations genetically diverge

zygote

fertilization of 2 gametes

prezygotic

barriers that prevent sperm + eggs from combining to form a zygote or prevents mating from occurring

postzygotic

zygote has formed/mating has occurred + barriers prevent zygote from developing or offspring isn’t viable or fertile

geographic isolation

physical environmental barrier (ex. river)

behavioral isolation

different mating signals + behaviors prevent populations from recognizing others as mates

temporal isolation

the populations mate at different times (ex. seasons or night)

mechanic isolation

the bodies and/or reproductive organs don’t fit together

gametic isolation

mating occurs but gametes can’t combine (usually b/c incompatible chromosome numbers)

hybrid inviability

hybrid forms but not viable

hybrid infertility

hybrid is formed but not fertile

low hybrid fitness

hybrid lives to childhood/adulthood but unlikely to survive and/or reproduce

allopatric speciation

population splits into 2 diff. species b/c of geographic barrier + accumulate microevolutionary differences + can’t mate w/ each other

sympatric speciation

population splits into 2 diff. species (b/c of microevolutionary reproductive barrier) in the same environment + can’t mate w/ each other

gametes

sperm + eggs

fossil

preserved remains or traces of ancient organisms, such as bones, shells, or imprints, found in rock layers

fossil evidence

assigns fossils to relative chronological age w/ rock layers

transitional fossil

“in between” fossils — have characteristics of species that are hypothesized to be ancestral + characteristics of descendent species

biogeographical evidence

supports evolution by showing how species are distributed across different geographical areas + species in isolated environments evolve

vestigal structures

structures that are no longer used but may have been in ancestors (ex. tail bone)

homologous structures

organs or bones that, due to their similarity, suggest their connection to a common ancestor

divergent evolution

occurs when 2 or more species that share a common ancestor evolve diff. traits. often due to environmental pressures, leading to increased diversity between species

analogous structures

similar in different species that share a common function, but do not demonstrate common ancestry/relatedness

convergent evolution

occurs when unrelated or distantly related species independently evolve similar environmental pressures or ecological roles, despite not sharing a common ancestor w/ those traits

embryological evidence

structural similarities between development of embryos

dna/molecular evidence

dna code is the same in all organisms + sequence of dna and/or sequence of amino acids in proteins can be compared to determine relatedness

phylogeny

the evolutionary history of a species or group of species

how are phylogenies determined?

using fossil evidence + morphological + molecular homologies

morphology

refers to body structure

molecular

refers to DNA or protein strcutures/sequences

derived traits

traits that a homologous group shares that are not found in the common ancestor of the group

phylogenetic trees/cladograms

diagrams that organize species by evolutionary relationships — graphs both share the same information

node

divergent point

darwin’s postulates of natural selection

1. all individuals in populations must have different traits

2. heritable traits are genetic characteristics passed from parent to offspring via DNA

3. some individuals have characteristics better suited for survivable than others

4. trait/allele frequency refer to how common different versions of a gene (allele) are within a population