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1.3 - Evolution I.pdf

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McMaster University
Joe Kim

Arnav Agarwal 2011 Evolution I Module 1: Introduction Introduction: - Biology is the science of life, so psychology is a biologically science - Unifying theory of all biology is the theory of evolution - Biological sciences goal: elucidate adaptive designs of living things o Includes functional systems, subsystems, working parts, etc. Module 2: Adaptations Adaptations: - Definition: biological traits/characteristics that help an individual survive and reproduce in its habitat - Always “for” something; they function to make the organism better suited to the environment - Examples of adaptations that allow the organism to interact with a complex physical environment: o Eyes recognizing and responding to surroundings by analyzing the reflected light o Racoons having front paws they can “see” with (through touch) while scavenging o Bat’s echolocation: able to discriminate between different objects and movements, even at night Adaptationists: - Psychological traits can be evaluated in the same way as biological traits aren’t just morphological, but encompass perceptual processes and behaviors - Scientists form questions that form sub-tasks of the actual task that is done, and then for processes capable of accomplishing them - Adaptationists: describe how hypotheses about adaptive function guide investigations o Includes psychologists studying development, behavior or perceptual processes Is the job any different for “higher” mental processes? - Cognitive psychologists are also adaptationists, breaking a problem into adaptive problems and then finding adaptations that solve those problems - In assessing “higher mental processes”, cognitive psychologists assess the jobs the mind needs to do (attention, retrieval, etc.), and then which adaptive functions of mental activity it uses o Focus: selective attention o Encoding: memory encoding o Retrieval: memory retrieval o Identification: word recognition Arnav Agarwal 2011 Adaptive conclusions - Many more adaptive functions of the mind, involving movement, language, attractions, etc. - These all evolved through natural selection Recap - What is true about adaptations? o They perform a specific function o They help an individual survive and reproduce Module 3: Evolution by Natural Selection How do adaptations arise?: - In development: due to the activation of relevant genes in interaction with relevant environmental aspects - Natural selection explains how they arise, become differentiated in species and maintain complex functionality despite mutations Three essential components to their insight: - Natural selection: differential survival and reproduction of organisms as a result of the heritable differences between them - Four basic mechanisms of evolution: natural selection, migration, genetic drift and mutation - Natural selection discovered by Charles Darwin and Alfred Wallace (independently) - Three aspects to the theory: o Significant individual differences:  Variation among individuals for a given characteristic within a population o Differential reproductive success:  The variation in the characteristic causes variation in survival and reproduction rates; some will have more offspring than others o Heritability of the trait:  The trait causing differential success is heritable, and can be passed on to the offspring of successful reproducers, so that the child may resemble the parent in terms of the trait Selective transmission: - Example of natural selection (fish colors): o Population of fish in a blue ocean; some are blue, some are red  Red fish are more visible to predators, blue fish are able to camouflage o Blue fish therefore survive and reproduce better o The surviving blue fish tend to have blue-colored offspring Arnav Agarwal 2011  Body color is a heritable trait o Selective transmission of heritable parental traits will occur over time:  The population will be mostly blue o Breakdown of aspects:  Variation in traits: body color  Differential reproduction: blue > red  Heredity: body color is able to be passed on to offspring of survivors - Selective transmission of heritable parental traits occurs because the specific characteristics best adapted for survival and reproduction are going to be reproduced at higher rates Recap: - Which of the following is not an essential component of natural selection? o Individuals do not reproduce at the same rates as one another o Individuals of a population are not identical to one another o Homogeneity of traits within a population  Natural selection cannot act in a population where everyone is identical; variation is a requirement o Heritability of traits that give rise to differential reproduction Module 4: Natural Selection in the Wild Stabilizing selection: - The usual observation made by researchers measuring natural selection in wild populations - Definition: selection against any sort of departure from the species-typical adaptive design - This type of selection keeps traits stable over generations Arnav Agarwal 2011 - A certain trait will stay stable for long as it is adaptive in some way - However, any environmental change might make an atypical trait favored over the typical trait, causing evolutionary change, which can even be rapid Darwin’s finches: - Classic example of rapid evolutionary change (within one generation) in beak size and shape in Daphne Island finches in the Galapagos - 1977: severe drought led to vegetation decimation -> food was scarce and small (normal) seeds were eaten up -> birds with big, heavy beaks could eat the hard seeds left -> survived over birds with small beaks (died of starvation) - 1976-1978 (2 years): average beak size increased from 9.4 to 10.2 mm - Once breeding conditions were favorable, the large-beaked finches reproduced and had survived more, and passed on the heritable beak size trait; therefore, change persisted Natural selection in the wild (conclusions): - Average beak size returned to pre-drought sizes after the drought, once small seeds returned - Natural selection examples observed in a lifetime tend to be small, subtle and reversed over time; natural selection takes place more significantly over long periods of time - Other changes due to natural selection are permanent and allow for species diversification; evolutionists often test hypotheses of larger, slower evolutionary change by comparing species Module 5: Reproductive success = fitness - Natural selection: “survival of the fittest” Arnav Agarwal 2011 o not just those who are best at surviving, but also those who are best at reproducing - “Fitness” is used as an abstract property’s label, that natural selection tends to maximize o Refers to how good a particular genotype is at leaving copies of its genes in the next generation relative to other genotypes; doesn’t refer to being the best in a certain trait - Darwinian fitness: average reproductive success of a genotype relative to alternative genotypes DNA, alleles and evolutionary biology: - Fitness: competition between genotypes to leave copies of themselves in the next generation - Evolution: change in gene frequencies over generations Module 6: Sexual Selection Evolution by natural selection in nature: - Most familiar organisms produce sexually, where their gametes fuse - There is often competition for mates - Sexual selection: natural selection acting on mate-finding and reproductive behaviors Peacock courtship display: - Male peacocks often grow elaborate tail feathers and develop elaborate behaviors to persuade the female pe
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