Anthro Exam 2 2
Terms
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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.
- Reinforcement
- 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.
- Phylogeny
- The evolutionary relationships among a group of species descended from a common ancestor.
- Taxonomy
- 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.
- Systematics
- 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.
- Outgroups
- 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.
- Genes
- A unit of inheritance carried on a chromosome, transmitted from generation to generation by the sex cells, and controlling some trait or character.
- Alleles
- Alternative forms of a gene.
- Genotype
- The genetic makeup of an organism, its total genetic material.
- Phenotype
- The observable characteristics of an organism.
- Segregation
- 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.
- Recombination
- The creation of novel genotypes as a result of the random segregation of chromosomes and of crossing over.
- Mutation
- A spontaneous change in the chemical structure of DNA.
- Polygenic
- Determined by more than one gene.
- Genome
- 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.
- Population
- 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.
- Evolution
- Change in a population's gene pool from generation to generation.
- Microevolution
- Small-scale changes in gene frequencies within a population over a short period of time.
- Macroevolution
- 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.
- Plastic
- Describes traits that are very sensitive to environmental conditions during development, so that different phenotypes are produced in different environments.
- Canalized
- 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.
- Fixation
- A state that occurs when all of the individuals in a population are homozygous for the same allele at a particular locus.
- Development
- The process of growth and differentiaion from zygote to adult.
- Convergence
- 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.