BIL 330 Lecture Notes - Lecture 16: Ultraviolet, Senescence, Arctogadus Glacialis
Document Summary
Senescence is an inevitable consequence of natural wear and tear: senescence might reflect the accumulation of molecular defects that fail to be repaired (e. g. , from ultraviolet radiation). The right timing of life history events is critical so behavior and physiology match changing environmental conditions. Photoperiod: the amount of light that occurs each day; provides a cue for many events in the life histories of virtually all organisms. Example: in michigan, water fleas (daphnia) enter diapause in mid-september when the photoperiod declines to less than 12 hours of sunlight. Related species in alaska enter diapause in august when the photoperiod declines to less than 20 hours of sunlight. These photo-sensitivities are related to environmental temperature; the photoperiod is related to decline of temperatures below a hospitable threshold. Fluctuations in resource availability often determine the timing of life history events. Metamorphosis occurs when a larva changes into a juvenile or an adult. Like many amphibians, the barking treefrog undergoes metamorphosis.
