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Evolution I & II.rtf

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Karen Mc Garry

Evolution I Introduction to Adaptations The biological sciences, including psychology have a shared agenda: their goal its to elucidate the adaptive designs of living things. Adaptation = biological traits, or characteristics, that help an individual survive and reporduce in its habitat. Adaptations perform a specific function that make an organism better suited to its environment. Examples: Eyes enable you to recognize and respond effectively to things around you by detecting and analyzing the reflected light. Raccoons primarily nocturnal and have good night vision, their front paws are so sensitive they can "see" with them through touch as they scavenge for food. Some bat species have evolved yet another adaptation that enables them to nagivate through their environment at night (echolocation) *Note: Adaptations are always for something; they serve identifiable functions in the life of an indvidual. Biological traits aren't semply morphological; perceptual processes and behaviours are also biological adaptations. Cognitive Psychologists study "higher" mental processes: - Selective attention - Memory encoding - Memory retrieval - Word recognition These mental proceesses refer to tasks that the mind needs to accomplish to do its jobb. In other words, they refer to the adaptive functions of mental acitivy. So cognitive psychologists aer also adaptationists: they find it helpfl to analyse their subject matter into adaptive their subject matter into adaptie problems or tasks, and to then look for the adaptations that solve those problems. There are many more adaptive functions that are served by our brain/minds. The adaptive functions that are served by our minds evolved like all other adaptations - through natural selection. Evolution by Natural Selection How do adaptations arise? Adaptations emerge in development as a result of the activation of relevant genes in interactionwith relavent aspects of the environment. - How do they arise - How do they become differentiated in related species - How do they maintain their complex functionality in spite of the destruve force of random genetic mutations Ans: Natural Selection Natural Selection Discovered by Charles Darwin and Alfred Russel Wallace 4 basic mechanisms of evolution; a) Natural Selection b) Mutation c) Genetic drift d) Migration Natural Selection = differential survival and reproduction of organisms as a result of the heritable differences between them. 3 Essential Components: 1. Significant Individual Differences - Within any population, there is variation among individuals for any given characteristic. Second, these differences affect individuals' chances of surviving and reproducing (causing).. 2. Differential Reproduction - Some indviduals will have more offspring than others. Lastly, the traits that give rise to differential reproduction have a genetic basis (meaning they are).. 3. Heritability - The offspring of successful reproducers will resemble their parents will respect to these variable characteristics. Selective Transmission The blue fish are well camouglaged in the blue ocean water and the red fish are much more visible to predators. Therefore, the red fish get eaten more often and so, on average, the blue fish survive and reproduce better than the red fish. Blue fish tend to have blue coloured offspring because body coloure is a heritable trait. -> Over successive generations, there will be selective transmission of heritable parental traits and the population will be mostly blue. This is because the specific characteristics that are best adapted for survival and reproduction are going to be reproduced at higher rates. Eventually, tif the process continues, the entire fish population will be blue. Natural selection cannot act in a population where everyone is identical - variation amongst the population is required. Natural Selection in the Wild Stabilizing Selection = Selection against any sort of departure from the species-typical adaptive design This sort of selection tends to keep traits stable over generations. Example: Blue would remain the most common colour in our fish population bc it is adaptive and minimizes the rish of predation. But in some cases (esp. if sig. change in environ) then selection favours traits that are not typical and evolutionary change can be observed, sometimes quite rapid evolutionary change. Darwin's Finches "The Medium Ground-Finch" which lives on Daphne island in the Galapagos. Peter and Rosemary Grant who studies these birds, along with their students, were able to observe natural selection in action - within only a generation! Beak size and ability to crack seeds: In 1977, a severe drought hit the island and decimated the vegetation. Food was scarce adn all of the small seeds were quickly eaten up, leaving only the large touch seeds that the finches usually didn't bother with. The birds that had unusually big, heavy beaks, were able to eat the hard seeds that remained and so survived the drought whereas the birds with small beaks died from starvation. Between 1976 and 1978 the average beak depth increased from 9.4mm to 10.2mm. The large beaked surivors went on to reproduce when the conditions were again favourable for breeding, and bc break size is heritable their offspring inherited large beaks as well. The mean beak size inc bc only individuals w/ larger beaks were able to eat the hard seeds. These large-beaked individuals survived and had offspring that inherited large beaks from their parents. Most examples of natural selection that can be observed within the lifetime of a scientist tend to involve fairly small, subtle changes like this, which can be reversed over time (ex. when the drought ended and plants again produced smaller seends, the average beek depth of the finches returned to pre-drought sizes). But other changes that arise through natural selection are more permanent and form a potential foundation for diversification of rela
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