Biol 112 Test 1

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Evolution

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Descent with modification; the idea that living species are descendants of ancestral species that were different from the present day ones; also defined more narrowly as the change in the genetic composition of a population from generation to generation

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Catastrophism

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The principle that events in the past occurred suddenly and were caused by different mechanisms than those operating today
• Adaptation: Inherited characteristic of an organism that enhances its survival and reproduction in a specific environment

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Vestigial Structure

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A feature of an organism that is a historical remnant of a structure that served a function in the organism’s ancestors

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Convergent Evolution

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The evolution of similar features in independent evolutionary lineages

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Fossil

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A preserved remnant or impression of an organism that lived in the past

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Uniformitarianism

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The principle that mechanisms of change are constant over time

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Natural Selection

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A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits

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Homology

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Similarity in characteristics resulting from a shared ancestry

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Analogous Structures

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Having characteristics that are similar because of convergent evolution, not homology; similar function, but not from the same ancestry

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Biogeography

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The study of the past and present geographic distribution of species

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Strata

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A rock layer formed when new layers of sediment cover older ones and compress them

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Artificial Selection

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The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits

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Homologous Structures

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Structures in different species that are similar because of common ancestry

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Convergence

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Develop similar structures, yet no relation to one another

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Endemic

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Referring to a species that is confined to a specific geographic area

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Modern Synthesis

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Union of ideas from several biological specialties which provides a widely accepted account of evolution

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Average Heterozygosity

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The percentage, on average, of a population’s loci that are heterozygous in members of the population

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Point Mutation

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A change in a single nucleotide pair of a gene

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Gene Pool

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The aggregate of all copies of every type of allele at all loci in every individual in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population

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Hardy-Weinberg Principle

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

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Genetic Drift

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A process in which chance events cause unpredictable fluctuations in allele frequences from one generation to the next. Effects of genetic drift are most pronounced in small populations

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Gene Flow

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The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes

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Disruptive Selection

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Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes

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Sexual Dimorphism

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Differences between the secondary sex characteristics of males and females

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Population

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

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Geographic Variation

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Differences between the gene pools of geographically separate populations or population subgroups

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Founder Effect

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Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not relective of that of the original population

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Relative Fitness

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The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population

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Stabilizing Selection

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Natural selection in which intermediate phenotypes suvive or reproduce more successfully than do extreme phenotypes

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Heterozygote Advantage

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Greater reproductive success of heterozygous individuals compared with homozygotes; tend to preserve variation in a gene pool

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Microevolution

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Evolutionary change below the species level; change in the allele frequencies in a population over generations

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Cline

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A graded change in a character along a geographic axis

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Bottleneck Effect

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Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. Typically, the surviving population is no longer genetically representative of the original population

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Directional Selection

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Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals

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Sexual Selection

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

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Frequency-Dependent Selection

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

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Morphological Species

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A definition of species in terms of measurable anatomical criteria

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Biological Species

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Definition of a species as 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

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Ecological Species

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A definition of species in terms of ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment

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Reproductively Isolated

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The existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring

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Phylogenetic Species

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A definition of species as the smallest group of individuals that share a common ancestor, forming one brance on the tree of life

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Prezygotic Barrier

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A reproductive barrier that impedes mating between species or hinders fertilization if interspecific mating is attempted

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Allopatric Speciation

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The formation of new species in populations that are geographically isolated from one another

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Polyploidy

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A chromosomal alteration in which the organism possesses more than two complete chromosome sets. It is the result of an accident of cell division

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Punctuated Equilibrium

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In the fossil record, long periods of apparent statis, in which a species undergoes little or no morphological change, interrupted by relatively brief periods of sudden change

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Postzygotic Barrier

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A reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults

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Sympiatric Speciation

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The formation of new species in populations that live in the same geographic area

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Autopolyploidy

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An individual that has more than two chromosome sets that are all derived from a single species

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Hybrid

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Offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species

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Speciation

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An evolutionary process in which one species splits into two or more species

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Hybrid Zone

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A geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

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Allopolyploidy

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A fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combining their chromosomes

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Macroevolution

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Evolutionary change above the species level. Examples of macroevolutionary change include the origin of a new group of organisms through a series of speciation events and the impact of mass extinctions on the diversity of life and its subsequent recovery

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Exaptation

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Existing adaptation is modified for a different use

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Homeotic Gene

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Any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells

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Adaptive Radiation

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

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Heterochrony

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Evolutionaryy change in the timing or rate of an organism’s development

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Paedomorphosis

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The retention in an adult organism of the juvenile features of its evolutionary ancestors