Unit 8 Flashcards
Artificial Selection
The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits
Allopathic speciation
A mode of speciation induced when an ancestral population becomes segregated by a geographic barrier or is itself divided into two or more geographically isolated subpopulations
Adaptive radiation
The emergence of numerous species from a common ancestor introduced into an environment that presents a diversity of new opportunities and problems
Biogeography
The study of the past and present distribution of species
Bottleneck effect
Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population
Balancing selection
Natural selection that maintains stable frequencies of two or more phenotypic forms in a population (balanced polymorphism)
Balanced polymorphism
The ability of natural selection to maintain diversity in a population
Catastrophism
The hypothesis by Georges Cuvier that each boundary between strata corresponded in time to a catastrophe, such as a flood or drought, that had destroyed many of the species living there at that time
Cline
A graded variation in a trait that parallels a gradient in the environment
Descent with modification
Darwin’s initial phrase for the general process of evolution
Directional selection
Natural selection that favors individuals at one end of the phenotypic range
Disruptive selection
Natural selection that favors individuals on both extremes of a phenotypic range over intermediate phenotypes
Evolutionary adaptation
An accumulation of inherited characteristics that enhance organisms’ ability to survive and reproduce in specific environments
Evolution
All the changes that have transformed life on earth from its earliest beginnings to the diversity that characterizes it today
Founder effect
Genetic drift that occurs when a few individuals become isolated from a population, with the result that the new population’s gene pool is not reflective of the original population
Fitness
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals
Gradualism
A view of earth’s history that attributes profound change to the cumulative product of slow but continuous processes
Gene pool
The total aggregate of genes in a population at any one time
Genetic drift
Unpredictable fluctuations in allele frequencies from one generation to the next because of a population’s finite size
Gene flow
Genetic additions to or subtractions from a population resulting from the movement of fertile individuals or gametes
Genetic polymorphism
The existence of two or more distinct alleles at a given locus in a population’s gene pool
Homology
Similarity in characteristics resulting from a shared ancestry
Homologous structures
Structures in different species that are similar because of common ancestry
Hardy-Weinberg Theorem
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
Hardy-Weinberg equilibrium
The condition describing a non-evolving population (one that is in genetic equilibrium)
Heterozygote advantage
Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools
Microevolutuon
Evolutionary change below the species level; change in the genetic makeup of a population from generation to generation
Mutations
A change in the DNA of a gene, ultimately creating genetic diversity
Natural Selection
Differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Evolution occurs when natural selection causes changes in relative frequencies of alleles in the gene pool
Population genetics
The study of how populations change genetically over time
Population
A localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring)
Phenotypic polymorphism
The existence of two or more distinct morphs (discrete forms), each represented in a population in high enough frequencies to be readily noticeable
Prezygotic barriers
A reproductive barrier that impedes mating between species or hinders fertilization of ova if interspecific mating is attempted
Postzygotic barriers
Any of several species-isolating mechanisms that prevent hybrids produced by two different species from developing into viable, fertile adults
Punctuated equilibrium
In evolutionary theory, long periods of apparent stasis (no change) interrupted by relatively brief periods of sudden change
Relative fitness
The contribution of one genotype to the next generation compared to that of alternative genotypes for the same locus
Reproductive isolation
The existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids
Sexual selection
Natural selection for mating success
Sexual dimorphism
A special case of polymorphism based on the distinction between the secondary sex characteristics of males and females
Stabilizing selection
Natural selection that favors intermediate variants by acting against extreme phenotypes
Taxonomy
Ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences, leading to a classification scheme; the branch of biology concerned with naming and classifying the diverse forms of life
Vestigial organs
A structure of marginal, if any, importance to an organism. Vestigial organs are historical remnants of structures that had important functions in ancestors
