BIO SCI 94 Lecture Notes - Lecture 26: Compass, Circadian Clock, Lightdark
8 Mar 2019
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Document Summary
Proximate/ultimate mechanisms for migration(long distance movement of population after season change) - relates to questions of habitat selection. True navigation- locate specific place on earth. Little understanding about true navigation, piloting/compass orientation well understood. Some birds/mammals- offspring memorize route by following parents south in fall and north in spring. Birds/other organisms- multiple mechanisms for finding compass direction. Some use sun compass, star compass, magnetic compass. Sun difficult to use, position changes throughout day. Most animals- have circadian clock; maintains 24 hour rhythm of chemical activity. Clock set by light-dark transition of day and night tells animals about time of day animals use sun position to find magnetic north. Clear nights- migratory birds use north star to find magnetic north. Some species use earth"s magnetic field determine location on globe. Variation in earth"s magnetic field predictable gradient of intensity/angle. Experimenter- manipulate magnetic field artificially alter general direction sea turtles swim in circular pool. Benefit of migration- increase access to food.
