Part 3 Flashcards
two species evolving together
ex: hummingbird and flower
coevolution
Two factors that essential for natural selection to occur
variability and selective pressure
when individuals of one extreme phenotype have the advantage over others. causes natural selection to favor the trait.
directional selection
type of selection where the highest survival is at the intermediate level and lower at extremes.
stabilizing selection
type of selection when traits of either extreme are favored over the intermediate. least common selection
disruptive selection
fossil that is evidence of a common ancestor
transitional fossil
a feature that gives and individual an improved function in a competitive environment.
ex: whales have thick bones to help them dive
adaptive trait
traits that have the same structure, but a different function
ex: human hand-whale fin- bat wing
homologous traits
traits that no longer have a function
ex: hipbone in whales, tail bone in humans
vestigial traits
a measure of how closely related two DNA molecules are to each other
DNA sequence similarity
a change in the overall inherited characteristics of a group of organisms over multiple generations
evolution
a group of individuals of the same species living in a defined area
population
an evolutionary process by which a populations becomes better matched to its environment over time through natural selection
adaptation
when two species look very similar but have vastly different genes (no common ancestor)
ex: dolphins and sharks
convergent evolution
traits with very different structures but the same function
ex: birds and butterflies
analogous traits
exchange of alleles from one population to another
ex: one bird traveling to another flock + changing gene pool
gene flow
when a random decrease in population causes a change in allele frequency
ex: tornado kills off some fish
genetic drift
decrease in a population that can cause extinction (more extreme version of genetic drift)
ex: flood drowns all but some birds
bottleneck effect
when location or geographic difference causes speciation
ex: two squirrels on different sides of the Grand Canyon
allopatric speciation
when geography isn’t a factor, yet two species can’t reproduce, leading to speciation
ex: two types of fish one live birth and one lays eggs
sympatric speciation
branch on evolutionary tree? split of ancestors on tree? most immediate ancestor?
clade, node, most recent common ancestor
three major domains of life
bacteria, archaea, eukarya
form the highest, most inclusive hierarchical level in the organization of life
classifies into bacteria, archaea, eukarya
domains
domain of single-celled prokaryotes, often extremophiles
archaea
