BIO202H5 Lecture 9: 9. Internal Balance
Document Summary
Bio202 lecture 9: internal balance: march 25, 2019. Internal balance is affected by the external environment through biochemical or chemical signaling. Bioluminescence in hawaiian bobtail squid: bacteria colonize specialized organs in the squid, while the predatory squid can blend in with the environment and thus improve camouflage when catching prey. Growth, metabolism and sexual development of animals is complex and depends on specific environmental and ecological cues. Thyroid hormone (thyroxine / t4) accelerates the growth of the pelvic fins in axolotl: more t4 the fin development was larger than the control group. Amphioxus postembryonic development reveals the homology of chordate metamorphosis (internal response to external cues balances by the endocrine system) Iop has an opposite effect of t4 & no effect on t3. Iop and control takes the longest for metamorphosis advancement: premetamorphic amphioxus: gill slits and mouth. Thyroid hormones stimulate growth: metamorphic amphioxus: cirri, gut, u-shaped gill slits, folds. Intracellular example: heat shock protein response (not on exam)
