Chapter 9: Annual Cycles Flashcards
What are the three main efforts?
- reproduction
- molt
- migration (often)
The annual cycles of birds coincide with _____ _____ and ______.
seasonal resources and opportunities
Birds that are permanent residents undergo three main sequential tasks:
- breeding
- molt
- survival until the next breeding season
Tropical birds base their annual cycles on __ and ___ seasons
wet and dry
Migratory birds face an additional annual challange of
needing to increase body mass for nutrient supply during the migration
All plants and animals exhibit self-sustained oscillations called ______ ______
endogenous rhythms.
Through use of the nervous system and through release of hormones (endocrine system), these biological clocks regulate daily cycles of metabolism, physiology, and behavior. These are called _____ _____
circadian rhythms
Some clocks measure day length and govern events that are tied to an annual cycle (e.g. egg laying, molt, premigratory fattening, migratory restlessness, etc.). These are called______ _____
circannual rhythms.
Circadian rhythms in birds are tied to the activities of two important structures
- the pineal gland
- the suprachiasmatic nucleus of the hypothalamus
The pineal gland is located
on the top of the brain
The pineal gland includes photosensitive cells that direct the rhythmic release _____
melatonin
melatonin regulates …
daily rhythems in accordance with the light-dark cycle
Removal of the pineal gland in House Sparrows causes
normal 24-hour cycles to disappear
One affect of the melatonin is
to regulate the circadian activity of the suprachiasmatic nuclei
All birds have an intrinsic circadian rhythm that is about ___ hours in length
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