One of the least complicated of the endocrine control systems directly responds to changing blood levels of ions and nutrients. which of the following describes this mechanism?
a) protein synthesis
b) catabolic inhibition
c) the rapid oxidation of carbohydrates
d) humoral stimulation

Flock x flock y flock z total pieces of food eaten (from previous page) 147 93 60 food percentage* % % % simulated number of birds in flock for 3rd generation** * divide each flock's total pieces of food by 300, the total number of pieces of food eaten. ** multiply the food percentage for each flock by the total number of birds (30).

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

The law of thermodynamics states that energy can't be created or destroyed. to natural sources of energy on earth are the