Ch. 1.1 Notes Homeostasis

Characteristics of Living Things Must have ALL of these: Orderly structure (cells & DNA) Reproduces (species) Grows & develops (needs food & water) Adjust to surroundings (stimulus/response & homeostasis) Adapt & evolve due to changes in the environment This should be a review for you

What is homeostasis? Homeostasis: the process of maintaining a stable internal environment (in your body/cells) (without homeostasis, organisms would die!)

What does homeostasis keep stable? Body temperature Heart rate Blood pressure Blood sugar levels

Homeostasis Video Homeostasis video clip about body temperature (7 mins) https://ca.pbslearningmedia.org/res ource/tdc02.sci.life.reg.fevervid/fev er/#.Wata1FWGPcs

How does it keep things stable? Negative feedback tends to stabilize a system, bringing things back to normal Example: shivering in response to body cooling off during cold weather Example: sweating in response to body heating to cause evaporation & body cooling.

Negative Feedback Negative feedback controls sugar levels in the bloodstream as well. Video clip on how sugar levels are regulated in the body: http://health.howstuffworks.com/human -body/systems/endocrine/adam- 200092.htm

Regulation of Blood Sugar Levels

Positive Feedback Positive feedback: when the feedback causes the change to continue increasing in the same direction. (i.e. we want the condition to continue) Ex: hormone (oxytocin) that causes contractions during pregnancy. Contractions trigger more hormone production, which causes more contractions, etc. Non Example: if the thermostat's response to a dropping temperature was to switch off the heater or to switch on the air conditioner (chiller) to continue making it even colder! (This is NOT what happens!) Environmental/Ecological problems.

Homeostasis Lab Overview