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BIOL 4150 (48)
Lecture

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Department
Biology
Course
BIOL 4150
Professor
Scott Brandon
Semester
Fall

Description
Responses to the environment must be timed appropriately  CIRCADIAN RHYTHMS CONTROL THE DAILY CYCLE OF BEHAVIOUR: o The persistence of daily cycles in the absence of environmental time cues suggests that animals have an endogenous clock (seldom exactly 24 hours)  circadian rhythms. o When two rhythms completely match, they are in phase, and if a rhythm is shifted, it is phase-advanced or phase-delayed. o Since the period of circadian rhythm is not exactly 24 hours, it must be phase-advanced or phase-delayed to remain in phase with the daily cycle of the environment; rhythm has to be entrained to the cycle of light and dark in the animal’s environment. o Animal kept in constant conditions will not be entrained to the cycle of the environment, and its circadian clock will run on its natural period free-running. o The free-running circadian rhythm is under genetic control. o Animals that are active at night are nocturnal and have different sensory capabilities than those that are diurnal. Diurnal animals tend to be highly visual, whereas nocturnal animals depend more on their abilities to hear and small and use tactile information. o Diurnals have retinas made up entirely of cone cells and nocturnal retinas are composed entirely of rods (highly sensitive to light stimuli, but do not provide info about colour).  PHOTOPERIOD AND CIRCANNUAL RHYTHMS CONTROL SEASONAL BEHAVIOURS o Most animals reproduce most successfully if they time their reproductive behaviour to coincide with the most favourable time of year for the survival of their offspring. o A change in day length—photoperiod—is a reliable indicator of seasonal changes to come. o Hibernators and equatorial migrants have circannual rhythms. Animals must find their way around their environment  PILOTING: ORIENTATION BY LANDMARKS—most animals find their way by knowing and remembering the structure of their environment  piloting.  HOMING: RETURN TO A SPECIFIC LOCATION—the ability to return over long distances to a nest site, burrow, or other specific location homing.  MIGRATION: TRAVELLING GREAT DISTANCES o Distance-and-direction navigation: requires knowing in what direction and how far away the destination is. With a compass to determine direction and a means of
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