C, Proteins is the correct answer
Answer:
controlled experiments
Explanation:
Experiments in which all variables are identical except for one are called controlled experiments. This where an observer tests his hypothesis by looking on changes that were brought about by one variable. The results are always dependent on one adjusted variable.
Blood flow through most organs in the systemic circuit is regulated primarily by increasing or decreasing the sympathetic activity to arterioral smooth muscles in the organ. Another form of regulation called active hyperemia, depends upon the ,metabolic activity of the organ. Increased activity leads to increased interstitial fluid metabolites, which cause dilation of the arterioles, the former is a type of extrinsic regulation of blood flow; the latter is an example of intrinsic regulation.
Because natural selection acts directly only on phenotypes, more genetic variation within a population usually enables more phenotypic variation. Some new alleles increase an organism's ability to survive and reproduce, which then ensures the survival of the allele in the population.
