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Across 2. Variation in a trait within a population, as measured by the variance that is due to genetic differences among individuals. 7. The field of genetics that studies quantitative (continuously varying) characters. 9. A hypothesis that functionally related characteristics should be genetically correlated with one another. 10. Variation among individuals in a phenotypic trait that is caused by variation in the environment rather than by genetic differences. 13. A trait controlled by polygenic variation rather than by single loci. 15. The relationship shown between two phenotypic characters (e.g., body size and fecundity). 19. The degree to which two features in individuals with the same genotype vary in concert because both are affected by environmental factors (e.g., nutrition). 20. a chromosome region containing at least one gene that contributes to variation in a quantitative trait 21. The process of a character state that initially developed in response to the environment becoming genetically determined. 23. The ability, or potential, to vary. 24. The capacity of an organism to develop any of several phenotypic states, depending on the environment; usually this capacity is assumed to be adaptive. 25. The point at which response to selection (e.g., for a particular trait) ceases. Commonly observed in selection experiments. 26. An effect of the interaction between two or more gene loci on the phenotype or fitness whereby their joint effect differs from the sum of the loci taken separately.

Down 1. The proportion of the variance in a trait among individuals that is attributable to differences in genotype. Heritability in the narrow sense is the ratio of additive genetic variance to phenotypic variance. 2. Phenotypic variation arising from the difference in the effect of the environment on the expression of different genotypes. 3. That component of the genetic variance in a character that is attributable to additive effects of alleles. 4. The set of phenotypic expressions of a genotype under different environmental conditions. 5. Correlated differences among genotypes in two or more phenotypic characters, due to pleiotropy or linkage disequilibrium. 6. The difference (S) in mean trait between the population and the selected parents of the next generation. 8. Magnitude of fitness differences among genotypes/phyenotypes. 11. The evolution of internal factors during development that reduce the effect of perturbing environmental and genetic influences, thereby constraining variation and consistently producing a particular (usually wild-type) phenotype. 12. A table of values showing additive genetic variance and covariance between characters. Also called the genetic variance-covariance matrix, or simply G. 14. Heritability that can be estimated by a response to experimental selection. 16. The change in the mean value of a character over one or more generations due to selection. 17. Selection that favors some combination of genetically independent character states over others, usually because the characters are functionally related. 18. In a phenotypic trait, the sum of genetic variance and environmental variance. 20. a procedure for determining the map positions of QTL on chromosomes. 22. The existence of both a fitness benefit and a fitness cost of a mutation or character state, relative to another.