BIO202H5 Lecture 9: BIO202 WINTER 2016 LECTURE 9
Document Summary
Lecture 9: reproduction (1) external cues and timing of reproduction. Interaction initiated by melatonin biosynthesis in pineal gland or photoreceptors in retina. Circadian and circannual rhythms are coordinated and interactive. Bodies react to different annual amounts of daylight by circadian rhythms. Pineal glands are sensitive to changes in photoperiod (daily amount of light vs. amount of darkness) Once photoperiod beings to change animal"s body starts to do things differently (e. g. mammals winter shuts down metabolism earlier) Bats attempt to copulate with females when system slowed down. Females do not become pregnant adaptation of fsh delays pregnancy until ready. Special fsh receptor helps female delay fertilization until spring (reduced affinity of fsh to fshr delays ovulation) advantage in winter, disadvantage other times in year! Homeostatic loop controlled by hypothalamus and pituitary gland but hormones released from thyroid and adrenal gland (gonadotropins affected by temperature and photoperiod) (4) external cues and mate condition mating in birds (honesty)
