16 Darwin made a key association between his observations and Malthus’ observation: “Individuals that possess superior physical or behavioral attributes are more likely to survive than those that are not so well endowed.”
21 Scientists now know that genes are responsible for inherited traits Scientists now know that genes are responsible for inherited traits. Therefore, certain traits become more common in a population because more individuals in the population carry the genes for those traits.
22 Fossils provide some of the most significant evidence for evolution. Transitional fossilsDerived traitsAncestral traits
23 Comparative Anatomyhomologous structures: similar structures in different organisms -Vertebrate limb structurevestigial structures: structures in an organism that are reduced in size or function – human appendix, eyes on a blind ratanalogous structures: similar structures in unrelated organisms – bat vs. butterfly wings
25 Comparative Biochemistry *amino acids*DNA* The fewer differences in two organisms DNA or amino acid sequences, the more closely related they are.
26 Other evidenceComparative embryology – many related organisms have similar embryonic developmentBiogeography – how organisms are distributed on earth – provides evidence that similar environments lead to similar organisms
28 The changing of a species that results in its being better suited to its environment is called an adaptation.
29 Examples of Adaptations Fitness - # of offspring with one trait as compared to the # of offspring without the traitCamouflage – allows an organism to blend in with its surroundingsMimicry – allows an organism to look like another speciesAntibiotic resistance – bacteria become resistant to the drugs that once treated them
31 The Hardy-Weinberg Principle The frequency of alleles in populations does not change unless the frequencies are acted on by some factor that causes changeGenetic equilibrium – when the frequency of alleles remains the sameOnly if – large population, no movement, random mating, no mutation, no natural selection
33 Punctuated equilibrium Gradualism vs.Punctuated equilibriumFor a long time, scientists thought that evolution was a continuous, gradual process. Many now think that there are long periods of no change, alternating with period of rapid change.