Darwin-Wallace Theory of Natural Selection
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23 terms
Terms | Definitions |
|---|---|
 1831-1836 | The years in which Darwin sailed on The Beagle as the ship's naturalist |
| 1837 | when darwin began his first notebook on transmutation |
| two principles darwin gained from malthus | - biotic potential -environmental resistance |
| reverend william paley | arguably influenced darwin to ideas of "superfecundity" and "struggle for existence" because he read his book before reading malthus' |
| relative adaptation | that natural selection was operating continuously - darwins ideas shifted to this after reading malthus |
| alfred russel wallace | independently came to the same conclusions as darwin in 1858, based on observations in Malay Archipelago |
| november 24 1859 | darwin published "on the origin of species by means of natural selection, or the preservation of favored races in the struggle for life" - intended to be an abstract of a larger publication including all of his work (never published the intended follow-up) |
| principle of natural selection | generally referred to as the darwin-wallace theory of natural selection in honor of the ideas both darwin and wallace developed |
| artificial selection | used this concept by breeders as a metaphor and example of natural selection |
| biotic potential | when favorable environmental conditions allow the survival of all offspring, the number of individuals in a population will increase exponentially - Observation #1 |
| environmental resistance | a population rarely realizes biological potential for growth due to factors (limited food, competition, disease, predation, etc) - a strong and constantly operating check on population growth - Observation #2 |
| deduction #1 | from the facts of biological potential and environmental resistance, darwin deduced that many progeny die as a result of a "struggle" to survive and reproduce |
| observation #3 | - based on knowledge of domestic breeding and observation of natural history - individual variations existing in al pops and spp. some differences is inherited, but darwin did not know how (the mechanism) |
| deduction #2 | the process resulting in deaths of progeny is selective (=natural selection) b/c variants best suited to environment are ones that survive and reproduce. also, success of individuals is in terms of FITNESS, = capacity for leaving offspring |
| observation #4 | environmental change is SLOW and GRADUAL - from lyell's Principles of Geology - d also observed the gradual variation among individuals, varieties, subspecies, and spp in the galapagos islands |
| deduction #3 | evolution occurred through gradual change in the hereditary composition of a species based on his observations of gradual variation among individuals, varieties, spp, subspp,. - speciation as a simple extention of the gradual (microevolutoinary) process of selection, with divergence and branching of lineages |
| darwin's philosophical contributions | - first consistently MECHANISTIC hypothesis for evolution of organic diversity thru natural selection (contra earlier vitalistic ideas) - contrary to any TELEOLOGICAL theory (no final causes) - based on POPULATION THINKING (variation in individuals not of great importance) - GRADUALIST, UNIFORMITARIAN - emphasized ADAPTATION (paley) to ENVIRONMENT (lamarck) -explained UNITY OF NATURE |
| unity of nature | e.g., homologous traits result from descent from common ancestor, analogous result from natural selection |
| the modern synthesis | 1900-1940 - result of controversy btwn mendelian geneticists and darwinian evolutionists - forged from contributions of a number of geneticists, systematists, and paleontologists who integrated darwin's theory of natural selection w/ mendelian genetics |
| mendelian beliefs | typological thinking, natural pop's are uniformly "wild type" - variation is discrete, inheritance is particulate - variation arises at random - geographic variation is a phenotypic response only, therefore unimportant - species are real, discrete, and arise by saltation |
| naturalist beliefs | - population thinking, natural populations are extremely variable - variation is continuous, changes are small and gradual - variation is adaptive, showing influences of environment - geographic variation is genotypic (and important) - species are variable, transitional forms can sometimes be found btwn named species - new spp arise gradually |
| Dobzhansky | -observed both field and lab work - huge contribution to the modern synthesis - made strong arguments for mutation as original basis of variation, w/ the adaptive force in evolutoin being natural selection |
| Darwin's 5 Theories | 1. evolution as such- idea that characteristics of organisms in lineages change through time (significantly) 2. common descent - d was first to argue that all spp diverged from common ancestors and that all life should be seen as a large branching tree (ie the PRINCIPLE OF DIVERGENCE). contrary to lamarck's idea of organic progression 3. Gradualness (gradualism) - diff characteristics among org's evolve thru innumerable small steps involving intermediate forms (vs. saltation) 4. Populational Speciation - changes in proportions of individuals differing in one or more inherited trants w/in one population, called populational or VARIATIONAL change (vs. transformational evolution of lamarck) 5. Natural Selection - entirely novel concept explaining processes that cause the changes in proportions of variant individuals - others realized the "struggle for life" could result in spp extinction, but D and W realized that the process operated w/in species to cause the evolution of adaptations |
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