 Homeo: Similar  Stasis: State of Balance  Homeostasis is the process by which an organisms internal environment is kept stable during changes in its external environment.

 How do our bodies maintain a stable internal environment?  How do plants maintain homeostasis?

 Water  Temperature  Hormones  Oxygen/Carbon Dioxide

 Water: Human body is 98% water contained in our tissues. We use it during digestion, respiration, excretion of waste, muscle exertion, and maintaining our core temperature. If high, water moves from tissues to surface to dissipate heat, if low, triggers thirst)  Temperature: is 96.4 degrees. If high draws water to surface to dissipate heat, if low, triggers muscle contraction to generate heat.  Hormones: Stress causes adrenalin production which increases heart and respiratory rates, heightens senses.  Insulin: pancreas produces in response to blood sugar levels: Low blood sugar triggers hunger, high triggers insulin production.  O2/CO2: Build up of CO2 and demand for O2 to tissues, CNS elevates respiratory and heart rates to increase O2/CO2 exchange and move O2 to muscles and organs.

 Water: transpiration an perspiration  Temperature: transpiration an perspiration  O2/CO2: plants use CO2 as energy and excrete O2 and moisture as waste.

 What is a stimulus?  An example of an external stimulus is?  An example of an internal stimulus is?

 What is a tropism?

 Class discussion/lab: