Class Notes (785,637)
Canada (481,693)
Biology (6,616)
Biology 1002B (1,323)
Tom Haffie (863)

Lecture 24.docx

3 Pages
Unlock Document

Western University
Biology 1002B
Tom Haffie

Lecture 24: Biological Timekeeping  Circadian clock  Diurnal Phenomena o Reoccurs daily  Foraging/predatory behaviour  Sleep-wake cycles  Body temperature  Hormone secretion  Photosynthesis o It acts like a sine function, goes up and down  The value of keeping track of time o What if organisms could anticipate environmental change?  Know when sun goes up and down  Think of advantage  Conserve energy o Lhcb2 mRNA  Photosynthetic gene, light antenna around PSII  There’s no transcript during the night, only appears during the day  Measure transcript abundance, using northern blot  Transcription vs. mRNA decay  This is not a response to light, because it begins to synthesis when it is still dark  It anticipate that light is going to come on  The transcript abundance start when it is still dark o It is continued under constant light  The cycle continues with constant light o How can you explain this?  Not just response to light  Endogenous biological clock  Circadian rhythm  Question: what is the advantage of anticipation (check online)  Circadian rhythms o Circadian rhythm – biological rhythm with a period of “around” a day (24 hours) sometimes more sometimes less o Based on internal clock o Two major criteria  Can be set by the external time (environment)  Can be set of what is going on outside, can be based on the sun  Free-running  Not slaved to the external time  So when environment is constant, the cycle continues, it runs by itself  Eventually, the free-running clock can get out of whack, must be trained again  E.g. body temperature and hormone under circadian control, even under constant environment  Circadian phenomena o Diurnal phenomena  Circadian  Non-circadian o Photosynthesis (the process) (light depended, not circadian) vs. photosynthetic gene expression (under circadian control) o Thousands of genes are under circadian control  Questions about the clock o Has a clock o Input  How is the clock synchronized with astronomical time? o Output  How is molecular time linked to changes in physiology/behaviour o What is the biochemical basis of the clock o Every clock oscillators, moves between two extremes passing an equilibrium  The period is very constant  Circadian rhythm have a genetic basis o Drosophila melanogaster o Eclosion mutants (when larva turns into a fly)  The mutants
More Less

Related notes for Biology 1002B

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.