9th grade biology evolution vocab

divergent evolution

the accumulation of differences between groups that can lead to the formation of new species

analogous structures

body parts that share common function, but not structure

plication

a fold or corrugation

epoch

a period of time in history or in a person's life

convergent evolution

a process by which evolution produces similar structures and characteristics in distantly related organisms

genetic drift

a random change in allele frequency

orthogenetic

an obsolete biological hypothesis that organisms have an innate tendency to evolve in a unilinear fashion

punctuated equilibrium

an equilibrium that is interrupted by brief periods of more rapid change

phylogenic tree

an evolutionary diagram showing the evolutionary relationships among organisms

adaptation

any heritable characteristic that increases an organism's ability to survive and reproduce in it's environment

gene pool

consists of all the genes, including all the different alleles for each gene, that are present in a population

fitness

describes how well an organism can survive and reproduce in it's environment

genetic equilibrium

if a population is not evolving, allele frequencies in it's gene pool do not change

vestigial structure

inherited from ancestors but have lost much or all of their original function due to different selection pressures acting on the descendant

artificial selection

nature provides the variations, and humans select those they find useful

directional selection

occurs when individuals at one end of the curve have higher fitness than individuals at the middle or at the other end

disruptive selection

occurs when individuals at the outer ends of the curve have higher fitness than individuals near the middle of the curve

reproductive isolation

occurs when organisms stop breeding with original mates and start isolating and breeding with other mates, forming new species

geographic isolation

occurs when two populations are separated by geographic barriers such as rivers, mountains, or bodies of water

gradualism

slow and steady

homologous structures

structures that are shared by related species and have been inherited from a common ancestor

stabilizing selection

takes place when individuals near the center of the curve have higher fitness than individuals at either end

speciation

the formation of a new species

allelic frequency

the number of times an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene

fossil

the preserved remains or traces of ancient organisms

adaptive radiation

the process by which a single species or a small group of species evolves over a relatively short time into several different forms that live in different ways

natural selection

the process by which organisms with variations most suited to their local environment survive and leave more offspring

camouflage

the process in which an organism blends into it's environment to prevent danger or predator-ism

evolution

the process of change over time

mimicry

the process of imitating to entertain or ridicule