Zoology Exam 1

evolution

defined by Darwin’s phrase descent with modification

fossils

remains or traces of organisms from the past, found in sedimentary rock

strata

sedimentary rock layers

paleontology

the study of fossils

adaptation

inherited characteristics of organisms that enhance their survival and reproduction in specific environments

natural selection

process in which individuals with favorable inherited traits are more likely to survive and reproduce

artificial selection

process in which humans have modified other species by selecting and breeding individuals with desired traits

homology

similarity resulting from common ancestry

homologous structures

anatomical resemblances that represent variations on a structural theme present in a common ancestor

vestigial structures

remnants of features that served a function in the organism’s ancestors

evolutionary trees

diagrams that reflect hypotheses about the relationships among different groups

convergent evolution

the independent evolution of similar features in different lineages

analogous

share similar function, but not common ancestry

biogeography

the scientific study of the geographic distribution of species, provides evidence of evolution

pangaea

large continent where the earth’s continents were formerly united

endemic species

species that are not found anywhere else in the world

microevolution

a change in allele frequencies in a population over generations

genetic variation

differences among individuals in the composition of their genes or DNA sequences

natural variation

differences in DNA sequences that do not confer a selective advantage or disadvantage

population

a localized group of individuals capable of interbreeding and producing fertile offspring

gene pool

consists of all the alleles for all loci in a population

hardy-weinberg equilibrium

a population where gametes contribute to the next generation randomly and Mendelian inheritance occurs, allele and genotype frequencies remain constant from generation to generation

adaptive evolution

a process in which traits that enhance survival or reproduction increase in frequency over time

genetic drift

describes how allele frequencies fluctuate unpredictably from one generation to the next

founder effect

when a few individuals become isolated from a larger population

bottleneck effect

when there is a drastic reduction in population size due to a sudden change in the environment

gene flow

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

relative fitness

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

direction selection

favors individuals at one extreme end of the phenotypic range

disruptive selection

favors individuals at both extremes of the phenotypic range

stabilizing selection

favors intermediate variants and acts against extreme phenotypes

sexual selection

a process in which individuals with certain inherited characteristics are more likely to acquire mates than other individuals of the same sex

sexual dimorphism

a difference in secondary sexual characteristics between males and females of the same species

intrasexual selection

direct competition among individuals of one sex (often males) for mates of the opposite sex

intersexual selection (mate choice)

when individuals of one sex (usually females) are choosy in selecting their mates

balancing selection

when natural selection maintains stable frequencies of two or more phenotypic forms in a population

frequency-dependent selection

the fitness of a phenotype depends on how common it is in the population

heterozygote advantage

when heterozygotes have a higher fitness than both homozygotes