The humpback whale is a large marine mammal that lives wide spread throughout the North Pacific Ocean. Barnacles are small marine crustaceans that will attach themselves to the bodies of humpback whales. Though the barnacles grow on the skin of whales to filter feed, they are too small to harm the whale. This example best defines which of the following commensalism

mutualism

parasitism

predation

commensalism

Explanation:

the barnacles benefit from the whale while the whale doesn't but the whale isn't harmed either

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.