LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Behaviors Governed by Circadian Rhythm Chapter 39 & 40

Circadian Rhythm Physiological cycles that are about 24 hours long and are governed by an internal “clock” –Entrained to exactly 24 hours by the day/night cycle © 2011 Pearson Education, Inc.

Suprachiasmatic Nucleus (SCN)

© 2011 Pearson Education, Inc. Bobtail Squid & Vibrio fisheri How Bacteria “Talk” – Bonnie Bassler

Photoreceptors in Plants Blue-light photoreceptors –Stomatal opening –Phototrophism Phytochromes –Seed germination © 2011 Pearson Education, Inc.

Plant Response to Seasons Photoperiod –Relative lengths of night and day –Photoperiodism  physiological response Short-day plants –Flower when light period < critical length Long-day plants –Flower when light period > critical length Day-neutral plants –Controlled by plant maturity, not photoperiod © 2011 Pearson Education, Inc.

Figure hours Light Flash of light Darkness Critical dark period Flash of light (b) Long-day (short-night) plant (a)Short day (long-night) plant