Evolutionary Biology Lecture 7
Order by
28 terms
Terms | Definitions |
|---|---|
 Microevolution | -processes that occur within species |
| Macroevolution | -evolution above the species level -patterns of origination, extinction, diversification of higher taxa -rates of evolution (gradualism, saltation), origin of novel features, evolutionary trends |
| do all individual character evolve at the same rate | -no, individual characters vary in evolutionary rates |
| how do evolutionary rates vary | -through time -within species -between species |
| example of how evolutionary rates vary | -murid rodents(mice and rats) arose in the Miocene and doubled in species number in about 1.98 myr -colubrid snakes arose in Miocene and doubled in species number in about 1.24 myr |
| punctuated equilibrium | -long periods of little change (stasis) followed by short period of rapid change -long term average rates mask the short periods of change and even periods of "stasis" may mask rapid fluctuations that have no net direction |
| character mean | -average of the trait we are discussing |
| fluctuating character mean | -might change drastically over time, but averages out to no change -something radical could happen causing a rapid change -this is masked by our gaps of knowledge in the fossil record |
| hypotheses for stasis | 1) internal genetic or developmental constraints 2) stabilizing selection for a constant optimum phenotype 3) brief and local divergence that did not leave evidence |
| gradualism | -that change occurs over a long period of time, with slow moving forces -darwin proposed that evolution proceeds gradually |
| saltation | -sudden evolutionary changes that happen in single generation, rather than gradually -some darwin supporters argued that even if characters evolved in leaps, darwin's theory would be just as valid -richard goldschmidt (1940): species and higher taxa arise in single evolutionary steps due to major chromosomal changes -"hopeful monsters" |
| saltation vs. punctuated equilibrium | -punctuated equilibrium: evolutionary changes in morphology were continuous, but were so rapid and localized they were not preserved -saltation: fixation of a single mutation of large effect -gaps among higher taxa may be explained by extinction of intermediates |
| what is the ultimate fate of all species | -extinction |
| what are the most extreme periods of extinction | -mass extinction |
| mass extinction | -when a large percentage of species go extinct in a short period of time |
| how many times has mass extinction occured | -5 -end ordovician (440 mya) -late devonian (365 mya) -end permian (250 mya) -end triassic (215 mya) -cretaceous-tertiary or K-T (65 mya) |
| end ordovician | -may have been proportionally the second largest extinction -100 families (49% of genera went extinct) -corresponds with a drop in temperature and drop in sea level due to glaciation |
| late devonian | -may have been multiple extinction pulses of up to 15 my in duration -22% of marine families, 57% of genera, about 75%of species went extinct |
| end permian | -most severe extinction event -52% of families, up to 96% of all marine invertebrates, 70% of terrestrial species -caused by massive volcanic eruption -almost instantaneous -caused global warming -anoxia in ocean currents -altered ocean currents -released vast amounts of methane |
| end triassic | -one of least intense mass extinctions -20% of marine families, all non-dinosaurian archosaurs, and many large amphibians lost -several hypothetical mechanisms (explanation) -global climate change (doesn't explain suddenness) -asteroid impact (no evidence of crater) -massive volcanic eruptions -released massive amount of CO2 or SO2 and contributed to climate change |
| cretaceous-tertiary | -about 50% of all species became extinct -evidence for impact of a large, extraterrestrial body (meteor or asteroid) |
| were mass extinctions selective | -yes |
| did all taxa have the same survival rate | -no |
| what made a species more likely to survive | -wide geographic ranges - broad ecological distributions (in different types of environments) -more diverse genera -ecological characteristics (feeding mode) were less important |
| what percentage of extinctions were background extinctions | -96% -they happened gradually throughout the history of life |
| what is the background extinction rate | -about 1 extinction per million species per year |
| how long does a typical species survive before going extinct | 5-10 my |
| causes of extinction | -failure to adapt to environmental changes -habitat destruction -introduced predators, diseases, and competitors |
First Time Here?
Welcome to Quizlet, a fun, free place to study. Try these flashcards, find others to study, or make your own.