| A | B |
|---|
| natural selection | process by which organism best suited to their environment are most likely to survive and reproduce |
| half life | the time it takes for one half of the radioactive atoms in a sample to decay |
| radioactive dating | measuring the age of an object by determining the amount of radioactive isotope |
| homologous structure | stuctures that have common ancestry |
| vestigial structure | structure that is a remnant of an organism's evolutionary past and has no function |
| adaptation | process by which a species becomes better suited to its environment |
| balancing selection | selection for an allele is balanced by selection against it |
| directional selection | selection for or against an allele in a population is unopposed |
| ecological race | population of a species that differs genetically from other populations of the same species because they have adapted to different environments |
| divergence | accumulation of differences between two or more species or populations |
| gradulaism | hypothesis that evolution occurs at a slow, constant rate |
| puctuated equilibria | hpothesis that evolution occurs at an irregular rate |
| eubacteria | group of bacteria thought to have evolved more recently than archaebacteria |
| archaebacteria | group of bacteria thought to have given rise to eubacteria |
| cyanobacteria | group of photosynthetic bacteria thought to be the first organisms to release oxygen |
| multicellularity | made up of more than one cell |
| phylum | a division of a kingdom |
| mass extinction | an episode during which large numbers of species became extinct |
| mutualism | ecologicalrelationship which benefits all organisms involved |
| continental drift | movement of the continents over geologic time |
| notochord | rod of cartilage that extends along the back in chordates |
| vertebrate | animal with a backbone |
| endotherm | animal that uses heat from metabolism to control its body temperature |
| ectotherm | animals that uses heat from the environment to control its body temperature |
| primate | order of mammmals to which humans, apes, mokeys and prosimians belong |
| opposable thumb | digit that can be bent toward the other digits |
| binocular vision | both eyes simultaneously view the same object |
| prosimian | member of a group of tree dweling primates |
| anthropoid | member of primate suborder that contains monkeys, apes and humans |
| hominid | two legged primates such as humans and austrolopithecines |
| bipedal | walking on two legs |
| ozone | unstable pale blue gas that absorbs ultraviolet radiation |
| mycorrhizae | mutualistic association of fungi and root cells of plants |
