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BIOL 1500
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Biology Chapter 9 Notes: Evolution and Biology • Clear and consistent preference for sweet and fatty foods; animals have taste preferences because they cannot create their own food • Will examine cooperation, conflict, communication, mating and parenting; the evolution Behaviour: encompasses any and all of the actions performed by an organism, often in response to its environment or to the actions of another organism, warblers singing; feeding is one of many behaviours influenced by natural selection; mutated genes that reduce child care does not increase in population Innate Behaviours (instincts): does not require any environmental input to develop; present in all individuals in a population; do not vary much from one individual to another or over the lifespan of the individual; fixed action pattern and triggered under certain conditions; requires no learning and runs to completion; egg-retrieval in geese (egg shaped objects that are bigger), aggressive displays and attacks by stickleback fish (in response to red colour) • Some behaviours require a degree of learning; rhesus monkeys are afraid of snakes and even the site of snakes will engage monkeys in fear related responses; captive monkeys will view another monkey expressing fear towards snakes in real life or on video and then express fear towards snakes • Behaviours learned easily and by nearly all individuals are called prepared learning; language is a dramatic example; underscores the fact that organisms don't learn everything with equal ease; well prepared to learn behaviours that have been important to ancestors and reproductive success; takes time to adjust to modern society • Natural selection produces organisms that exhibit relatively simple behaviours in response to certain situations or environmental conditions • Pleasure from sex has the incentive to seek out additional opportunities to experience that pleasure; behaviours that lead to a specific outcome that increases the animal's relative reproductive success will be favoured by natural selection; this can trick animals sometimes (egg retrieval by geese); avoiding incest among humans like kibbutzim in Israel Kindness & Altruism • Altruistic behaviours: behaviour that come at a cost to the individual performing them while benefiting a recipient; seems that way in the animal world; must define costs and benefits in terms of their contribution to an individual's fitness • Puzzled Darwin because natural selection typically supported selfish behaviour instead of altruistic-appearing behaviours (social spider giving birth to spiderlings) • Virtually all of apparent acts of altruism in the animal kingdom prove to be not truly altruistic; have evolved as a consequence of either kin selection or reciprocal altruism Kin Selection: kindness toward close relatives; lead to the evolution of apparently altruistic behaviour toward close relatives; with a potential K allele, it can increase the behaviour in a way that increases fitness of a close relative of yours while decreasing your own fitness; thus, an increase market share of allele K; increases the fitness of the relatives you help might compensate for own reduced fitness because allele K will, overall, increase its frequency in the population when helping relatives increase their reproductive output • ground squirrels are prey to birds; some squirrels see the predators and make alarm calls while other squirrels keep their mouth shut • 80% of squirrels making alarm calls are female and usually older females • increases relative's fitness; likely it was that the alleles being propagated by the recipient of the altruistic-like behaviour were the same alleles found in the altruistic individual; benefits to relatives are greater than the personal cost • the more closely related, the stronger the chance of kin altruism • in an unrelated colony, the older female would still be as likely to make a call; programmed • dividing wealth to relatives are another example; 46% to children, 37% to spouses • individual's fitness is not just measured by his or her total reproductive output (direct fitness); also includes the reproductive output that individuals bring about through their seemingly altruistic behaviours towards their close kin (indirect fitness) • Inclusive fitness: sum of an individual's indirect and direct fitness • since no two individuals are identical there will be conflict (women and fetuses); at some point, it is in the mother's best interest to reduce the amount of glucose and other nutrients given to the fetus; step-parents vs. biological parents abuse to preschool children Reciprocal & Apparent Altruism: can lead to evolution of apparently altruistic behaviour towards unrelated individuals; the carrier of a allele R causes you to help unrelated individuals and allele R might still increase its market share and the individual might be more likely to return the favour • vampire bats may vomit up a blood meal for an unrelated individual; bats only do this for individuals that will return the favour or have previously done so; their own survival is improved in the long run and the behaviour is favoured by natural selection • the acts that seem altruism may be selfish in actuality • both individuals in reciprocal altruism give up something of relatively low value in exchange for getting something of great value at a later time when they need it Reciprocal altruism can evolve if certain conditions are met: 1. Repeated interactions among individuals, with opportunities to be both the donor and the recipient of altruistic-appearing acts 2. Benefits to the recipient that are significantly greater than the costs to the donor 3. The ability to recognize and punish cheaters, individuals that are recipients of altruistic- appearing acts but do not return the favour • selfishness is expected to be the norm among unrelated individuals; conditions for evolution of reciprocal altruism are not satisfied in many species and that may cause it to be rare but with exceptions; smaller fish may be allowed to swim into the mouth of a larger fish and clean parasites by eating them; you scratch my back and I'll scratch yours • reciprocal altruism is very common among humans; interactions and relationships Behaviours and Natural Selection • natural selection can lead to fitness-reducing behaviours; fitness not only is an individual's reproductive success but also depends on the specific environment in which the organism lives; certain behaviours have been favoured by natural selection over others • adaptation to a new environment takes time and the more quickly an environment changes, the more likely it is that the evolved behaviours of a population will no longer be appropriate • Selfish genes win out over group selection; behaviours that reduce an individual's reproductive output are not likely to evolve; natural selection favours individuals producing more offspring relative to those producing fewer offspring • the selfish offspring will pass on the selfish allele at a higher rate than the alternative allele is passed and reproduce more • group selection: describes the evolution of a trait that is beneficial for the species ore population while decreasing the fitness of the individual exhibiting the trait; almost never seen in nature Sexual Conflict • there are big difference in how much males and females must invest in reproduction; males and females hinges on a physical difference between the sexes; female is defined as the sex that produces the larger gamete • Reproductive investment: material and energetic contribution to the offspring; energy expended in the growth, feeding and care of the offspring • the number of offspring a male can produce increases with the more females the males find; additional mating result to additional offspring; this does not work for females • internal fertilization in most mammals takes place in females • lactation occurs in females and not in most males; nuturing during both pregnancy and lactation can only be accomplished by the female; early investment in reproduction is much greater for females than males; • investments may become more equally divided after fertilization; birds after fertilizing the eggs; mal
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