Learning Objectives:

2.C.1:  Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes.

2.C.2:  Organisms respond to changes in their external environments.

2.D.2:  Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments.

2.D.4:  Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis.

2.E.2:  Timing and coordination of physiological events are regulated by multiple mechanisms.

3.D.1:  Cell communication processes share common features that reflect a shared evolutionary history.

3.E.2:  Animals have nervous systems that detect external and internal signals, transmit and integrate information, and produce responses.