Biology Ch. 15, 16. Evolution

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Fossil

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trace of a long-dead organism

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sediment

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dust, sand, mud

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mold

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imprint in rock in the shape of an organism

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cast

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when molds are filled with hard minerals in the shape of the organism

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law of superposition

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the successive layers of rock or soil were deposited on top of one another by wind or water. (lower=older, higher=newer)

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startum

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lowest layer in the Earth

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relative age

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can tell if a fossil is older or younger by using the law of superposition(lower=older, higher=newer)

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absolute age

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age of a fossil in years, can be sound by carbon dating

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mass extinction

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brief periods during which large numbers of species disappeared

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biogeography

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study of the the geographical distribution of fossils anf living organisms

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acquired trait

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a trait that is not determined by genes

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natural selection

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organisms best suited to their environment reproduce more successfully than other organisms. this leads to there being a greater population of the organisms with the favored trait.

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population

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interbreeding single-species group

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Charles Darwin

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created the idea of natural selection

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Lamarck

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believed that organisms acquired traits and passed them onto their offspring. (not true)

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uniformitarianism

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the geographical structure of the earth resulted from cycles of observable processes and that these same processes operate continuously through time.
(ex- volcanoes erupt the same way now as they did 1000 years ago.)

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The Origin of Species

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book, written by Charles Darwin. About natural selection

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descent with modification

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new forms of animals are the changed forms of past animals

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adapt

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to change to be better fit to its environment

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fitness

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ability to successfully reproduce

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adaptive advantage

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a favorable trait

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homologous structure

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similar features that originated in a shared ancestor

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analogous structure

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serves similar functions, looks somewhat alike, but the organisms are NOT from a common ancestor

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vestigial structure

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features useful to an ancestore, but are not used by the modern organism
(ex-appendix, not used by humans, but is still in the body)

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conserved

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remained unchanged

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co-evolution

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change of two or more species in close association with each other
(ex-bee and flower(pollen))

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convergent evolution

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when organisms look similar, but are not related

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divergent evolution

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two or more related populations or species become more and more dissimilar

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adaptive radiation

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many related species evolve from a single ancestral species

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artificial selection

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when divergent evolution is sped up artificially

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population genetics

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the study of evolution from a genetic point of view

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bell curve

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when the middle values of a trait are most common, with few organisms at the extremes

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evidence of evolution

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fossils
homologous structures
embryonic similarities
macromolecule similarities
vestigial structures

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causes of variation in traits

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influenced by environmental factors, such as amount/quality of food available, and heredity

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variations in genotype

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mutations
genetic recombination (during meiosis)
random fusion of gametes

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gene pool

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total genetic information available in a population

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allele frequency

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determined by dividing the number of a certain allele, by the total number of alleles in a population

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phenotype frequency

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equal to the number of individuals with a particular phenotype divided by the total number of individuals in a population

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5 assumptions of the Hardy Weinberg genetic equilibrium

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1. no net mutations occur
2. no immigration of emigration
3. large population
4. random mating
5. natural selection does not occur

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gene flow

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process of genes moving from one population to another

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genetic drift

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when allele frequencies change due to a random event, or natural disaster.
effects small populations more

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assortative mating

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selection of a mate due to similarity of characteristics

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stabilizing selection

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(may be form of graph)
individuals with the average form of a trait have the highest fitness

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directional selection

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(may be form of a graph)
individuals that display a more extreme form of a trait have a greater fitness

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disruptive selection

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(may be form of a graph)
individuals with either extreme variation of a trait have a greater fitness

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sexual selection

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when animals choose their mates based on certain traits

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speciation

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process of species formation.
resulted in many related populations of organisms

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morphology

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internal and external appearance of an organism

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biological species concept

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an organism is a member of any population is can successfully interbreed with, but cannot breed with other groups

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geographic isolation

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physical separation of members of a population

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reproductive isolation

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results from barriers to successful breeding between population groups in the same area
(sometimes arises through disruptive selection)

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prezygotic isolation

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reproductive isolation that occurs before fertilization

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postzygotic isolation

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reproductive isolation that occurs after fertilization