Negative feedback mechanisms are common among plants and animals while positive feedback mechanisms are very rare. Why are negative feedback mechanisms so much more prevalent?
A) Positive feedback mechanisms have a higher energy cost.
B)Negative feedback mechanisms provide energy for cell growth.
C)Positive feedback mechanisms evolved much later than negative feedback mechanisms.
D)Only negative feedback mechanisms lead to homeostasis, important for life.

Aresearcher designed an investigation to test what effect eating different types of food would have on blood insulin levels. she selected 10 male subjects who were all 25 years of age and in good health. the experiment took place over 3 days. at 8: 00 a. m. on each day, the subjects ate a meal consisting of only 1 type of food. they had their blood insulin levels measured after consuming the meal. on day 1 they ate a high fat diet, on day 2 they ate a high protein diet, and on day 3 they ate a high sugar diel what is the independent variable in this experiment? a the age of the subjects b the blood insulin level c the type of food consumed d the time of day the meal was consumed