Definitions chapter 5: Adaptation and natural selection Flashcards
Natural Selection
Differential success (reproduction and survival) of individuals that results in elimination of maladaptive traits from a population
Evolution
Change in gene frequency through time resulting from natural selection and producing cumulative changes in characteristics of a population
Adaptation
A genetically determined characteristic (behavioral, morphological, or physiological) that improves an organism’s ability to survive and reproduce under prevailing environmental conditions
Gene
Unit material of inheritance; more specifically, a small unit of a DNA molecule, coded for a specific protein to produce one of the many attributes to species
Allele
One of two or more alternative forms of a gene that occupies the same relative position or locus on homologous chromosomes
Genome
The collective term for all the DNA in the cell
Chromosomes
One of a group of threadlike structures of different lengths and sizes in the nuclei of cells of eukaryote organisms
Locus
Site on a chromosome occupied by a specific gene
Homozygous
Containing to identical alleles of a gene at the corresponding loci of a pair of chromosomes
Heterozygous
Containing to different alleles of a gene, one from each parent, at the corresponding loci of a pair of chromosomes
Genotype
Genetic constitution of an organism
Phenotype
Physical expression of a characteristic of an organism, determined by both genetic constitution and environment
Qualitative Traits
Phenotypic characteristics that fall into a limited number of discrete categories
Quantitative Traits
Phenotypic characteristics that have a continuous distribution
Phenotypic Plasticity
Ability to change form under different environmental conditions
Norm Of Reaction
The set of phenotypes expressed by a single genotype across a range of environmental conditions
Developmental Plasticity
Differences in phenotypic traits for a given genotype under different environmental conditions that reflect differences in the allocation of biomass to different tissues (leaves, stem, and roots) during the growth and development of the individual plant
Acclimation
Reversible phenotypic changes in an individual organism in response to changing environmental conditions - a form of phenotypic plasticity
Genetic Differentiation
When genetic variation occurs among subpopulations of the same species
Gene Pool
The sum of all the genes of all individuals in a population
Allele Frequency
The proportion of a given allele among all the alleles present at the locus in the population
Genotype Frequency
The proportion of various genotypes in a population; compare gene frequency
Target Of Selection
The phenotypic trait that natural selection acts directly upon
Selective Agent
The environmental cause of fitness differences among organisms within a population with different phenotypes
Directional Selection
Selection favoring individuals at one extreme of the phenotype in a population
Stabilizing Selection
Selection favoring the middle in the distribution of phenotypes
Disruptive Selection
Selection in which two extreme phenotypes in the population leave more offspring than the intermediate phenotype, which has lower fitness
Mutations
Transmissible changes in the structure of a gene or chromosome
Genetic Drift
Random fluctuation in allele frequency over time, due to chance alone without any influence by natural selection; important in small populations
Migration
Intentional, directional, usually seasonal movement of animals between two regions or habitats; involves departure and return of the same individual ; a round-trip movement
Gene Flow
Exchange of genetic material between populations
Hardy-Weinberg Principle
The proposition that genotypic ratios resulting from random mating remain unchanged from one generation to another, provided natural selection, genetic drift, and mutation are absent
Assortative Mating
When individuals choose mates non randomly with respect to their genotype, or more specifically, select mates based on some phenotypic trait
Positive Assortative Mating
Occurs when mates are phenotypically more similar to each other than expected by chance
Negative Assortative Mating
Occurs when mates are phenotypically less similar to each other than expected by chance
Inbreeding
Mating among close relatives
Inbreeding Depression
Detrimental effects of inbreeding
Cline
A measurable, gradual change over a geographic region in the average of some phenotypic character, such as size or colorization; or it can be a gradient in genotypic frequency
Ecotype
Subspecies or race adapted to a particular set of environmental conditions
Geographic Isolates
Groups of populations that are semi-isolated from one another by some extrinsic barrier; compare subspecies
Subspecies
Geographical unit of a species population, distinguishable by morphological, behavioral, or physiological characteristics
Adaptive Radiation
Evolution from a common ancestor of divergent forms adapted to distinct ways of life
Selective Breeding
Selecting individuals that exhibit a desired trait, and mating them with individuals exhibiting the same trait (or traits)
