When an evolutionary biologist designs an experiment to test a hypothesis, which term is used to describe the variable that the scientist changes among his/her groups of study organisms.

Explanation:

Controlled experiment=An experiment in which only one variable is changed

Independent variable=The variable that is deliberately changed in an experiment

Dependent variable=The variable this is observed and changes in response to the independent variable

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.