BIO RESPONSE 2

adaptation

a feature of an organism that helps it to survive and reproduce

adaptive advantage

the increased chance that an organism will survive, and reproduce due to characteristics that allow it to be more successful than other organisms.

circadian

activity with a period of about 24 hours

circalunar

activity with a period of about 29.5 days

circannual

activity with a period of about 365.25 days

circatidal

activity with a period of about 12.4 hours

crepuscular

active at dawn and dusk

day neutral plants

plants where flowering is not controlled by photoperiod

endogenous rhythm

rhythm that persists even in the absence of environmental cues

entrainment

resetting of internal biological clock by environmental cues

exogenous rhythm

a pattern that occurs ONLY in response to external cues, disappears when cues are removed

free running period

cyclic behaviour seen in the absence of external cues

innate behaviour

any genetically determined behaviour, not learned

internal biological clock

internal mechanism in organisms that controls the periodicity of activities

long day plants

flower when the night period is short, high levels of Pfr

noctoperiod

length of night

Pfr

the physiologically active form of phytochrome

phase shift

how much the period of activity is moved forward or back

photoperiod

day length

photoperiodism

any response of an organism to seasonal changes in day length

phytochrome

pigment in plants that regulates flowering

phytohormones

plant hormones

short day plants

flower when night period is long, low levels of Pfr

suprachiasmatic nucleus SCN

a cluster of neurons in the hypothalamus in the brain that governs the timing of circadian rhythms

zeitgeber

environmental cue that resets the biological clock