Which statements best describe natural selection? Check all that apply.

Populations must have genetic variation.
Genetic mutations do not produce advantageous traits.
Natural selection occurs when the environment changes.
Evolution works independently of natural selection.
Organisms best suited for the environment survive and reproduce.

Describe how an electric generator works

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.

Some substances but not other can cross the (blank) membrane of a cell