Lecture 7

Lecture 7 - Biological Timekeeping and introduction to...

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Biological Timekeeping and introduction to Migration, Orientation and Navigation Biological Timekeeping - Rhythms o Activities and behavior patterns are linked to environmental features with regular frequencies Tides Days Seasons o Biological clocks are internal mechanism that keep time o Physiological pacemakers and the environment work together to run the clock o Characteristics of biological rhythms (KNOW 3 features of bio rhythms) Activity vs time Sinusoidal wave Cycle is peak activity to peak activity Amplitude difference between a baseline and a peak activity Rhythms are temperature compensated Chemical reactions rates often double with each 10 degree C increase Rhythms are set (entrained by external factors Biological rhythms usually occur with the same frequency as an environmental feature… …But are approximately self-sustaining even in the absence of the feature o Types of rhythms Tidal rhythms: 12 hours Fiddler crabs: o Feed when tide is low o Return to burrows at high tide Bivalves: o Open when tide is high o Close when tide is low o Circadian rhythms: daily Daily cycle = 24 hours Diurnal: peak activity is during daylight hours Nocturnal: peak activity is at night Crepuscular: peak activity is at dusk and/or dawn o What adaptations are needed for each lifestyle? o Lunar rhythms: Monthly-ish Lunar rhythms are often related to tidal rhythms E.g. for some fish species, spawning is timed with tides Grunion spawning on the beach occurs during Spring tides Many insects also co-ordinate eclosion (hatching or emerging from the pupal case), mating and egg-laying with lunar cycles o Circannual rhythms: yearly Hibernation Migration
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Diapause: period of dormancy in insect species – sort of like hibernation in mammals - The Clock
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Lecture 7 - Biological Timekeeping and introduction to...

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