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Anthro Exam 2 2


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Traits *
Characteristics of organisms.
Balanced Polymorphism
Maintenance in a population of different alleles of a particular gene in proportion to the advantages offered by each.
Biological Species Concept
A species is a group of interbreeding organsims that are reproductively isolated from other organisms.
Ecological Species Concept
Natural selection, not reproductive isolation, plays the important role in maintaining differences between species.
Allopatric Speciation
Speciation that occurs when two or more populations of a single species are geographically isolated from each other and then diverge to from two or more new species.
Character Displacement
Members of different species become morphologically or behaviorally more differnt from each other as the result of competition over limited resources.
The process in which selection acts against the likelihood of hybrids occurring between members of two phenotypically distinctive populations leading to the evolution of mechanisms that prevent interbreeding.
Parapatric Speciation
A two-step process of speciation that occurs when (1) selection causes teh differentiation of geographically separate, partially isolated populations of a species, and (2) then subsequently the populations become reprouctively isolated as a result of reinforcement.
Sympatric Speciation
A hypothesis that speciation can result from selective pressures favoring different phenotypes within a population, without positing geographical isolation as a factor.
The evolutionary relationships among a group of species descended from a common ancestor.
Branch of biology concerned with the use of phylogenies for naming and classifying organisms.
Comparitive Method
A method for establishing the function of a phentoypic trait by comparing different species.
A branch of biology that is concerned with the procedures for constructing phylogenies.
Analogous Traits
Traits that are similar because of convergent evolution, not common descent.
Homologous Traits
Traits that are similar because of common ancestry, not convergence.
Ancestral Trait
A trait that appears earlier in the evolution of a lineage or clade, one that characterizes a common ancestor.
Derived Trait
A trait that appears later in the evolution of a lineage or clade, one that has evolved since th etime of the last common ancestor.
Taxonomic groups that are related to the group of interest and can be used to determine which traits are ancestral and which are derived.
Cladistic Systematics
A system for classifying organisms in which patterns of descent are the only criteria used in classification.
Evolutionary Systematics
A system for classifying organisms in which both patterns of descent and patterns of overall similarity are used in classification.
Pleiotropic Effects
Phenotypic effects created by genes that influence multiple characters (traits).
Correlated Characters
Traits that are statistically associated in a population, e.g., beak depth and width are both controlled by genes that influence overall size.
Point Mutation
A common type of mutation in a single codon, causing the substitution of one amino acid for another in a protein sequence.
Fitness *
A measure of an individual's genetic contribution to subsequent generations.
Blending Inheritance
A widely-held nineteenth-century theory that a child is an intermediate between maternal and paternal characteristics, as the result of the mixing of their bloods.
A unit of inheritance carried on a chromosome, transmitted from generation to generation by the sex cells, and controlling some trait or character.
Alternative forms of a gene.
The genetic makeup of an organism, its total genetic material.
The observable characteristics of an organism.
Genes exist on paired chromosomes; at meiosis the pairs are segregated so that a gamete has only one of the pair.
Independent Assortment
Genes on one chromosome do not influence the distribution of genes on other chromosomes; they separate independently from one another during meiosis and are randomly asorted in the gametes.
The creation of novel genotypes as a result of the random segregation of chromosomes and of crossing over.
A spontaneous change in the chemical structure of DNA.
Determined by more than one gene.
All of the genetic information carried by the organism.
Population Genetics
The branch of biology dealing with the processes that change the genetic composition of populations through time.
A community of potentially interbreeding individuals, usually at a given locality or within a limited geographical region.
Gene Pool
All of the genes found in the members of a population.
Change in a population's gene pool from generation to generation.
Small-scale changes in gene frequencies within a population over a short period of time.
Large-scale, long-term changes in gene frequencies resulting ni the formation of new species.
Environmental Variation
Phenotypic differences between individuals that exist because individuals developed in different environments.
Gene Flow
The movement of genes from one population to another, as the result of interbreeding.
Mate Guarding
A form of mating in which the male defends his mate after copulation to prevent other males from mating with her.
Describes traits that are very sensitive to environmental conditions during development, so that different phenotypes are produced in different environments.
Describes a trait that is very insensitive to environmental conditions during development, resulting in similar phenotypes in a wide range of environments.
Genetic Drift
Random change in gene frequencies due to sampling variation that occurs in any finite population.
A state that occurs when all of the individuals in a population are homozygous for the same allele at a particular locus.
The process of growth and differentiaion from zygote to adult.
The evolution of similar adaptations in unrelated species.
Equilibrium *
A steady state in which either gene or genotype frequencies do not change.
Stabilizing Selection
Selection pressures in a stable habitat that favor average traits by eliminating the extreme variations in a continuous distribution.
Directional Selection
Selection pressures in a changing habitat that favor one extreme variation in the distrubution of a trait.

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