Zoology 101 – McIntyre – Natural Selection - 20 Apr 2012Nature Notes #1 essay assignment: detail in handout on course websiteAspects of the puzzle: WHY is life so diverse? 1. Many species, each consistently different2. Slight variation within a species (the same one)3. Bizarre PhenotypesThe development of evolutionary theory:- Linnaeus – Swedish physician and botanist who created the term “taxonomy” (domain, kingdom, etc.). He developed the binomial format or naming species (i.e. Homo sapiens for humans).- Lamarck – stated that species change over time- Malthus – economist that argued that as population goes up resources become morelimited; “resource bottleneck” effect- Lyell – incorporated James Hutton’s principle of unifomitarianism (which stated that mechanisms of change are constant over time). Lyell proposed that the same geologic processes are operating today as in the past, and at the same rate. - Darwin – Charles Darwin (England) went on the voyage of the HMS Beagle. He wanted to be a clergyman at Cambridge University. He travelled on the HMS Beagle to South America and other areas of the world, and he returned England. He went onboard as a naturalist. The Galápagos Islands were the basis of his thinking. - Wallace – Albert Russell Wallace (also from England) went to SE Asia. He studied insects (collect them too). He noticed the same thing that Darwin saw when he studied mainland fauna compared to island faunaKey observations by both Darwin and Wallace:- Endless forms most beautiful: Many species including fossils that resemble modern species including fossils that resemble modern species (Darwin said “fossils”)- Geographical gradients: shifts in which species are found especially on islands, compared to mainlands- Fit to environment: match between organism traits & challenges of lifeAdaptations: inherited characteristics of organisms that enhance their survival & reproduction in specific environments Natural Selection (Darwin & Wallace’s hypothesize): a) Variation – among organismsb) Differential – survival & reproduction (bird is predator and it eats green beetles, leaving the orange beetles; orange beetles thrive)c) Inheritance – inheriting traits from parent/ancestor….result in: Mechanism of Evolutionary ChangeEvolution: heritable change in a population through time- Pattern – species diversity in space & time- Process – “descent with modification” vianatural selection - Darwin’s finches had different beaks(different diet preferences). Evolutionarychange occurred due to adaptive radiation.- Darwin made a phylogenetic tree (the 1st one ever). Wallace didn’t do this- Evolution via “descent with modification” is driven largely by natural selection (not exclusively, but it’s one of the main factors of it). - CLICKER QUESTION: At what level of biological organization does evolution occur?o Biosphereo Ecosystemo Communityo Population (evolution does not occur in higher levels nor does it occur in individuals)o IndividualLimits of adaptations:a) Natural selection acts only on existing variations a. Constrained by the past, can’t account for the futureb) Selection pressures vary in time & spacea. Temporal: in the same place, some years are harsher than othersb. Spatial: in the same year, some habitats are harsher than others (sun vs. shade)c) Selection is not the only evolutionary processes (genetic drift)d) All traits are subject to trade off (i.e. loud singing of a male frog can attract females, but it can also attract predators)e) Natural selection takes time to give rise to evolutionary changea. Changes in the environment may outpace the rate of adaptationf) Selection sometimes acts on variation that’s not heritableEvidence for Evolution:- Artificial selection – the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traitso Observations of Darwin: Observation #1 – Members of a population often vary in their inherited traits Observation #2 – All species can produce more offspring than their environment can support, and many of these offspring fail to survive and reproduceo Inferences of Darwin: Inference #1 - Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals Inference #2 – This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations- Direct observations of evolutionary changeo Animals that eat plants, herbivores, often have adaptations that help them feed efficiently on their primary food sources. Evolution in the length of the beaks of soapberry bug population has occurred; their beaks have grow longer. There is also an evolution occurring in bacteria. Bacteria and viruses are becoming drug-resistant. (pp.461-462)- Fossil record- Homology – similarity in characteristics resulting from a shared ancestry o Homologous structures – structures in different species that are similar because of common ancestry o Vestigal structures – a features of an organism that is a historical remnant of a structure that served as a function in the organism’s ancestorso Evolutionary tree – a diagram that reflects evolutionary relationships among groups of organismso Convergent evolution – the independent evolution of similar features in different lineageso Analogous – having characteristics that are similar because of convergent evolution, not homologous- Biogeography – the study of the past and present geographic distribution of species (i.e.continental drift)Big-Picture Conclusions:1) Natural selection links the process of evolutionary change with patterns of diversity observed in nature2) Darwin & Wallace converged on the same inference of parallel observations3) Adaptations of organisms to their environment results from descent with modificationEvolutionary traps: (Qu’est-ce que
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