AP Bio Unit 7: Evolution

homologous structures

homologous structures

structures in different species that are similar because of common ancestry

vestigial structures

remnants of features that served important functions in the the organism's ancestors

convergent evolution

the independent evolution of similar features in different lineages

Hardy-Weinberg

the frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work

gene pool

the combo of all of the alleles for all of the loci in individuals in a population

population

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

natural selection

a process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are organisms with other characteristics

genetic drift

changes in the gene pool due to random events

founder effect

when a individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population

bottleneck effect

when there is a severe drop in population size, certain alleles may be overrepresented among the survivors, others may be underrepresented, and some may be absent altogether

gene flow

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

directional selection

when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting the frequency curve for the phenotypic character in one direction or the other

disruptive selection

when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes

stabilizing selection

acts against both extreme phenotypes and favors intermediate variants

sexual selection

a form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates

sexual dimorphism

marked differences between the two sexes in secondary sexual characteristics, which are not directly associated with reproduction or survival (differences in size, color, ornamentation, and behavior)

heterozygote advantage

when individuals who are heterozygous at a particular locus have greater fitness than do both kind of homozygous

speciation

the process by which one species splits into two or more species

microevolution

changes over time in allele frequencies in a population

macroevolution

the broad pattern of evolution over long time spans

species

a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring- but do not produce viable, fertile offspring with members of other such groups

reproductive isolation

the existance of biological barriers that impede members of two species from producing viable offspring

prezygotic barriers

impede mating or hinder fertilization if mating occurs (five types: habitat, temporal, behavioral, mechanical, gametic)

post zygotic barriers

prevents hybrid zygote from developing into a viable fertile adult through reducing hybrid viability, reducing hybrid fertility, or hybrid breakdown

allopatric speciation

gene flow is interrupted when a population is divided into geographically isolated subpopulations

sympatric speciation

speciation occurs in populations that live in the same geographic area (usually occurs due to polyploidy, habitat differentiation, and sexual selection)

punctuated equilibrium

the theory that in the evolution there are long periods of little morphological change punctuated by relatively short periods of significant change

adaptive radiation

Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill vacant ecological roles in their communities

homeotic genes

master regulatory genes that determine such basic features as where a pair of wings and a pair of legs will develop on a bird or how a plant's flower parts are arranged

phylogeny

the evolutionary history of a species or group of species

phylogenetic tree

evolutionary history of a group of organisms represented in a branching diagram

analogy

similarity due to convergent evolution

homology

similarity due to shared ancestry

clade

a group of species which includes an ancestral species and all of its descendants

outgroup

a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes the species we are studying

Darwin's Theory (five parts)

1. Variation 2. Overproduction 3. Competition 4. Survival of the fittest 5. Overtime, emergence of new species (new alleles)