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Lecture

BMEN 515 Lecture Notes - Opportunity Cost, Circadian Clock, Lightdark


Department
Biomedical Engineering
Course Code
BMEN 515
Professor
William Huddleston

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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
with, but by quality of genes received from mate, resources he controls, and assistance; may cause evolution of traits
males use tactics courtship behaviour signals good health, good provider, controls resources, good genotype
circadian rhythms: persistence of daily cycles in absence of environmental time cues suggests animals have internal clock; not exactly
24 hrs so must be p-a or p-d (below)
period of rhythm=length of cycles; phase=any point on cycle; when 2 rhythms match=in phase; if rhythm is shifted=phase-advanced or
phase-delayed
animal kept in constant conditions will be free-running: CR runs to natural period; genetically controlled
under natural conditions, environmental time cues entrain free-running rhythms to light-dark cycle of environment
nocturnal: active during night; depend on hearing, smell, tactile info (flying squirrels: rods)
diurnal: active during day; tend to be highly visual (ground squirrels: cones in eye)
most animals reproduce most successfully if reproductive behaviour coincides with most favourable time of year for survival of
offspring
change in day length (photoperiod) is reliable indicator of seasonal changes to come
hibernators and equatorial migrants have circannual rhythms, built in neural calendars that keep track of time of year
piloting: animals use this to find their way by knowing and remembering structure of environment (Grey whales)
homing: ability to return over long distances to nest site, burrow, location by piloting in a known environment (pigeons)
birds disappear and reappear seasonally migration
same birds and offspring often return to same breeding grounds year after year, and found at non-breeding season at locations very
far away from breeding grounds. 2 systems:
distance-and-direction navigation: knowing what direction and how far away destination is
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