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Psych 1XX3 Lecture Evolution .pdf

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McMaster University
Joe Kim

Psych 1XX3 Lectures ▯ ▯ EVOLUTION▯ Adaptations: biological traits that help an individual survive and reproduce in its habitat, help an organism to be better suited to their environment. serve a specific function▯ ❖ EX: your eyes allow you to properly see your surroundings by detecting and analyzing reflected light▯ ❖ EX: raccoons are primarily nocturnal, and their paws are so sensitive they can practically “see” with them to scavenge for food▯ - adaptations are always for something. identifiable changes that enable organisms to interact with a complex physical environment▯ - behaviors are also biological adaptations▯ - how do we detect edges? how do we assess the speed of an object?▯ - once these steps have been identified, you can look for processes capable of accomplishing those tasks… or the relevant adaptations▯ ▯ Adaptationists▯ - describe how hypotheses about adaptive function guide their investigations.▯ - scientists who study development, behaviours or perceptual systems in the same manner are also adaptationists▯ - is the job really difference for “higher mental processes?”▯ ❖ cognitive psychologists are also adaptationists as they identify processes and how we have adapted to them.▯ ▯ Evolution by Natural Selection▯ - discovered by Charles Darwin and Alfred Russel Wallace and is one of the 4 basic mechanisms of evolution (mutation, genetic drift, and migration)▯ Natural Selection: the differential survival and reproduction of organisms as a result of the heritable differences between them▯ ▯ 3 Essential Components:▯ 1. Individual Differences▯ ❖ within any population there is variation among individuals for any given characteristic▯ 2. Differential reproduction▯ ❖ these differences affect individuals chances of surviving and reproducing▯ 3. Heritable▯ ❖ the traits that give rise to differential reproduction have a genetic basis▯ ❖ the offspring of successful reproducers will resemble their parents - with respect to variable characteristics▯ SELECTIVE TRANSMISSION▯ 1. Variation in Traits▯ ❖ blue fish blend well in the water, red fish stand out▯ 2. Differential Reproduction▯ ❖ since the red fish stand out they get eaten more, which leads to more blue fish on average surviving and reproducing▯ 3. Heredity▯ ❖ body colour is a heritable trait therefore more fish end up being blue because of their parents▯ 4. Selective Transmission▯ Psych 1XX3 Lectures ❖ over successive generations there will be selective transmission of heritable parental traits and the population will be mostly blue▯ ❖ this is bc the specific characteristics that are best adapted for survival and reproduction are going to be reproduced at higher rates.▯ ❖ eventually… the entire fish population will be blue▯ ▯ Stabilizing Selection: selection against any sort of departure from the species-typical adaptive design▯ ❖ keeps traits stable over generations▯ ❖ blue would remain the most common color because its adapted and reduces predation▯ ❖ however… sometimes when there has been a significant change in the environment, selection favours traits that are atypical, and evolutionary change can be observed, sometimes even quite rapid▯ EX of rapid evolutionary change▯ MEDIUM GROUND FINCH - living on the Galapagos▯ ❖ in 1977 a severe drought hit the island and decimated the vegetation▯ ❖ this caused all the small seeds to be quickly eaten up leaving only the large tough seeds that most birds ignored▯ ❖ the birds that had the unusually large beaks could eat the hard seeds and survived▯ ❖ the birds that could not died from starvation▯ ❖ 1976-1978 the average beak depth increased from 9.4mm to 10.2mm. ▯ ❖ the large-beaked ones survived and reproduced, and their offspring had large beaks as well▯ - most examples involve small, subtle changes that can be reversed over time. once the drought ended and plants produced smaller seeds the average beak size went down again.▯ ▯ “Survival of the Fittest”▯ - this isn’t the whole story, natural selection isn’t just involved with individuals who are the best at surviving, it’s also those who are best at reproducing▯ ▯ Darwinian FItness▯ - average reproductive success of a genotype relative to alternative genotypes▯ - not the same thing as physical fitness▯ - competition between genotypes▯ - some evolutionists describe evolution as: the change in gene frequency over generations▯ ▯ Sexual Selection▯ the component of natural selection that acts on traits that influence an organism's ability to obtain a mate▯ - often competition for mates, natural selection acts on mate finding and reproduction.▯ - peacocks will use their tail courtship display as a way to attract a female mate.▯ - ability to be chosen by the opposite sex▯ - defeating same-sex rivals in mating competition▯ Peacock’s Tail: energetically expensive to produce, makes them more conspicuous to predators, makes it harder to get away from predators▯ ❖ does not help with physical survival▯ ❖ they shed their tail at the end of the breeding season▯ ❖ increases their fitness because it increases their chances of mating▯ Psych 1XX3 Lectures - as well, stag’s are more vulnerable than females in order to have their antlers, however they have them so they can fight for a mate. this negative weaponry is simply to get a mate▯ Sexually Selected Traits▯ - both traits have a negative effect on survival▯ - for the elk: antlers are used in combat▯ - for the peacock: tail feathers are used in courtship.▯ - peacocks don’t fight with their tails, solely there to dazzle the females▯ Selective Force▯ - peacocks —> female choice▯ - Elk —> success in combat▯ Mate Competition▯ - peahens respond to peacock’s tail▯ ❖ the tails contain eyespots, females discriminate based on how many eyeshots▯ ❖ they also prefer symmetry on the tails▯ Mate choice Preferences▯ - female choice picks out males with best resistance to genes and chance at good health▯ ▯ Species Typical Behavior - The Comparative Approach▯ - behaviors are evolved, species specific adaptations▯ - we need to test hypotheses about adaptive functions▯ ▯ Species: Sandpiper (3 types)▯ 1. sanderling 2. semipalmated 3. dunlin▯ - can be differentiated by their vocalizations, dietary and habitat preferences▯ - they all have a signature way of foraging▯ ▯ Species Typical Behavior▯ ❖ physical form (typography) - how an animal moves▯ ❖ Habitat preference - where do they go to eat? how do they hunt?▯ ❖ group size - when do they choose to be alone or in a flock?▯ ❖ Social system - do they mate anonymously or in polygamy? how do they choose mates▯ - how old are the kids when they head out on their own?▯ - animal species differ in all of these things, these things can evolve▯ Behavior Genetics▯ - by keeping animals in captivity you can selectively breed them to change their typical behaviour in a few generations.▯ - people have created different breeds of dogs for certain purposes▯ - in order to complete experiments you must do ones that have short generations ▯ ❖ the fruit fly - ideally used by researchers▯ ▯ Evolution is the common ground shared by all the life sciences. it contributes to understanding of psychology neuroscience and behavior.▯ ▯ The Selfish Gene: natural selection will favor the genes that best serve their own interest, ie replication. ▯ ▯ WHY DO WE HELP EACH OTHER?▯ Cooperation: helps both people▯ S
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