Chapter 15 & 16- Biology
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Created by:
sunshine1194 on February 16, 2011
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29 terms
Terms | Definitions |
|---|---|
 gene pool | consists of all genes, including all of the different alleles, that are present in a population |
| relative frequency | number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur |
| single-gene trait | controlled by a single gene that has two alleles |
| polygenic trait | controlled by two or more genes |
| directional selection | when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end |
| stabilizing selection | when individuals near the center of the curve have higher fitness than individuals at either end of the curve |
| disruptive selection | when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle |
| genetic drift | random change in allele frequency |
| founder effect | a situation in which allele frequency change as a result of the migration of a small subgroup of a population |
| Hardy-Weinberg principle | states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change |
| genetic equilibrium | allele frequencies remain constant |
| speciation | formation of new species |
| reproductive isolation | when the members of two populations cannot interbreed and produce fertile offspring |
| behavioral isolation | occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior |
| geographic isolation | two populations are separated by geographic barriers |
| temperal isolation | when two or more species reproduce at different times |
| evolution | change over time |
| theory | well-supported testable explatnation |
| fossil | preserved remains of ancient organisms |
| artificial selection | when natural provides the variation, and humans select the variations that they find useful |
| struggle for existence | when members of each species compete regularly to obtain food, living space, and other necessities of life |
| fitness | how well suited an organism is to its environment |
| adaption | an inherited characteristic that increases an organism's chance of survival |
| survival of the fittest | when individuals that are better suited to their environment survive and reproduce most successfully |
| natural selection | survival of the fittest |
| descent with modification | when over long , over long periods, natural selection produces organisms that have different structures, establish different niches, or occupy different habitats |
| common descent | principle which states that all species were derived from common ancestors |
| homologus structure | structures that have a different mature form but develops from the same embryonic tissue |
| vestigal organ | when the organs of many animals are so reduced in size that they are just vestiges (or traces) of homologous organs in other species |
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