FEEDBACK & HOMEOSTASIS

vocabulary feedback positive feed back negative feedback homeostasis behavioral and physiological responses

Occurs within cells, organisms, populations, ecosystems . . .

FEEDBACK - response to a stimulus from the environment. NEGATIVE - response is change around a set point. (multi-directional) POSITIVE - change creates more of the same change (one direction)

Behavioral - response by whole organism RESPONSES TO STIMULI Behavioral - response by whole organism Physiological - response within an organism migration hibernation shivering sweating

POSITIVE OR NEGATIVE? Blood Glucose If sugar levels are too high: pancreas secretes insulin which lowers blood glucose levels. If sugar levels are too low: liver breaks down glycogen to release glucose

THERMOREGULATION

BIOTIC & ABIOTIC FACTORS

Homeostasis & Evolution Most animals have the same basic methods to excrete waste (homologous structures). Fish used gills to get dissolved oxygen out of water. Land animals use lungs (divergent evolution)

homeostasis examples within the human body temperature range (37.2 to 37.6 degrees Celsius) blood pH range 7.35 to 7.45 hormone levels regulate nutrition concentration, heart rate & more

SOME HOMEOSTATIC DISRUPTIONS NON-NATIVE INVASIVE SPECIES (ecosystem) DEHYDRATION (cells) DISEASE (population) SOME MUTATIONS (organism) REINFORCEMENT LECTURE

RELATE EVOLUTION BEHAVIOR GENETICS ECOSYSTEMS

Positive / negative? behavioral/physiological? A bus of screaming students causes the alpha bison at the Wichita Mountain Wildlife refuge to start running, which eventually results in a stampede of the herd.

Positive / negative? Plowing a field erodes the soil and reduces plant growth which then allows wind and water to further erode the soil.

Positive / negative? Combustion of more fossil fuels removes it from the earth and adds CO2 to the atmosphere, which affects climate change.

Positive / negative? Behavioral/physiological? The hormone oxytocin causes contractions of the uterus during childbirth. Each contraction stimulates the nerves & then hypothalamus to produce more oxytocin. Contractions become more frequent and intense

Positive / negative? During the industrial age, more people survived and therefore reproduced, causing a rise in the population, which also survived and reproduced.

What type of feedback is most closely associated with homeostasis?

ASSIGNMENT READ SECTION IN TEXT ON HOMEOSTASIS AND FEEDBACK. TAKE NOTES. DEFINE VOCABULARY