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Human Biology

53.1 • culture: set of behaviours shared by members of a population, transmitted through learning • when generations do not overlap, parental guidance is not factor is acquisition of behaviour • stereotypic: performed almost exactly the same way each time (ex spider spinning web) o stereotypic behaviour is often species-specific: individuals of given species perform it in same way • ethology: the study of animal behaviour from an evolutionary perspective o addresses behaviour patters, how and when to perform them o proximate mechanisms that underlie behaviour: neuronal, hormonal, anatomical o ultimate causes of behaviour: selection pressure that shaped evolution • most behaviours result from interactions btwn inherited anatomical and physiological mechanisms and the ability to modify behaviour as a result of experience • many animals’ behaviour is unlearned and highly stereotypic 53.2 • stereotypic behaviour tells biologists little about genes and experience in development • animal may fail to perform behaviour if the environmental conditions needed to stimulate it are absent; may perform behaviour if they imitate the same teacher • genes do NOT encode behaviours; gene products (enzymes) set in motion a series of gene- environment interactions that underlie development of proximate mechanisms that enable individuals to make certain behavioural responses • experiments help distinguish btwn genetic and environmental influences • deprivation experiment: rears a young animal so its deprived of all experience relevant to behaviour; if it exhibits behaviour, it can be developed without learning o heredity underlies food-storing behaviour of tree squirrel species, but behaviour was expressed only when environment provided situations that stimulated behaviour • genetic experiments: alters genomes by o interbreeding closely related species  selective breeding: means of genetic manipulating; used to select for both anatomical traits and behaviours; approach is applied and not theoretical, but does provide insight about effect genes have on behaviour o comparing individuals that differ in few genes  interbreedingwhen Lorenz crossbred ducks, hybrid offspring had some elements of each parents courtship display in new combinations. Hybrids exhibited display elements characteristic of other species; motor patterns of courtship displays are inherited; sexual selection has shaped these genetically determined behaviours o by knocking out/inserting gene sequences  fosB is involved in stimulating neural changes in hypothalamus of mother’s brain, possibly odor clues upon initial inspection of pups. It plays a part in motivating mother to retrieve and care for pups; neural changes do not occur if fosB gene is inactivated • without role models and opportunities for learning, individuals might fail to acquire appropriate behaviour, if genes didnt exert strong influences on development of behaviour • inherited behaviour is also adaptive when mistakes are costly or dangerous • patterns used to avoid predators is adaptive • some behaviours are expressed only under certain conditions (Red feathers of Robins) o releaser: object, event, condition required to elicit behaviour • complete stereotypy may not be adaptive (spiders adjust details of web for objects) • critical period: learning takes place only at specific time • imprinting: an animal learns a set of stimuli during a limited critical period; requires only brief exposure but its effects are strong and can last a lifetime (ex recognizing call of chicks) o critical period may be determined by brief developmental or hormonal state (ex at birth, mother goat must lick newborns neck to recognize it later on) • species-specific song in territorial displays and courtship is learned (birds hear it as nestlings, form a song memory in nervous system; matches his stored song memory when mature. If he is deafened after he sings SSS, he can sing it normally but if deafened before he sings before he learns it, he will not develop SSS2 critical stages: nestling, approaching sexual maturity) • deprivations experiments demonstrate that young male sparrows do not learn songs of other species, but exposure to few songs of their own is enough for imprinting o genes make it difficult to learn songs of other species • in multicellular organisms, all behaviour depends on nervous system for initiation, coordination, execution o hormones of endocrine system determine when behaviour is performed and when they can be learned • male birds use song to claim and advertise breeding territory, compete with other males, and declare dominance, attract females (females recognize song of species) • female birds injected with testosterone develop SSF just as males did. Females form SSS memory when nestling, but lack hormonal stimulation to express it • increase in testosterone causes certain parts of males brain for learning song to grow larger • hormones can control behaviour by changing brain structure and function, developmentally and seasonally 53.3 • old animals made decisions thru life as it matured (settle, eat, associate) • all decisions made in environment that varies in space and time • habitat: environment in which an organism lives; seeks food, rest, nest sites, escape routes in habitat • suitable habitats: good predictors of conditions suitable for future survival+reproduction • chemosensory cue of red abalone larvae settles on surface that has potential of supplying food for future survival and reproductive success • visual info provides useful cues; presence of already settled individuals is indication • flycatchers assess quality of habitat by seeing how well neighbours are doing; (settle in areas where broods (abundant food) artificially enlarged) • some highly social animals vote on quality of habitats (worker bees dance to communicate location, site that excites most workers is chosen) • animals compete for high-quality habitats; may improve its fitness by establishing exclusive use of habitat • may do this by establishing territory which excludes conspecifics (same species) by advertising it owns area and chasing others away (but advertising and chasing takes energy) • cost-benefit approach: assumes an animal has only a limited amt of time and energy to devote to activities; [costs must not outweigh benefits]; ecologists can make predictions, design experiments, and make observations explaining why patterns evolve the way they do • benefits of behaviour are improvements in survival and reproductive success; 3 costs • energetic cost: difference btwn energy at rest and energy used to perform behaviour • risk cost: increased change of getting killed/injured when performing behaviour • opportunity cost: sum of benefits the animal forfeits by not performing other behaviours • Moore and Marler: male lizards with more testosterone spent more time patrolling territories, doing advertising displays, used 1/3 more energy than control males. They had less time to feed, got fewer insects, stored less energy, died at higher rate • some animals defend all-purpose territories that include all resources (tigers, songbirds) • food supplies cannot be defended if widely distributed or fluctuate a lot (ex oceans) • some animals defend territory used only for mating (male grouse congregate on display grounds, defending small area. Males often use so much energy that less tired males eventually evict them) • foraging theory: helps us understand survival (ultimate) value of feeding choices; benefits = nutritional value, and costs similar to those for territorial defense • more rapidly an animal captures food, more time+energy it will have for other things • characterize each type of available food item in 2 ways: time it takes animal to pursue, capture, and consume item; and by amt of energy an item contains • most valuable food type is one that yields most energy per unit of time expended o can determine rate at which an animal would obtain energy given foraging strategy o animal gains most energy by taking only most valuable type and ignoring all others; but as that type depletes, it adds less valuable types (ex fish would ignore small water fleas if there are large ones) • for bluegills, only energy content of water fleas mattered; some animals travel great distances for nutrients • some ingest food for other reasons. Frogs get poisons from eating ants that have evolved poisons as defense mechanisms b/c frogs are immune to poisons • spices in food preparation protects ppl from contaminated food; most commonly used spices inhibited growth of some food-borne bacteria; perhaps spices disguise taste/smell of spoiled food. But eating spoiled food could be dangerous, and natural selection is not likely to have favored ppl who ate rancid food, no matter how tasty • most animals associate with others for mating partners and/or for resources it controls • males initiate courtship, hardly reject receptive females, fight for females • females seldom fight and often reject males o b/c sperm are small and cheap to make, very large # of offspring, males can increase reproductive success by mating with females o b/c eggs larger and expensive than sperm, females cannot increase reproductive output by increasing # of males she mates wit
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