When a hormone is present in excessive levels, the number of target-cell receptors my decrease. This is called . A. Receptor recognition B. Paracrine regulation C. Sensory adaptation D. Up-regulation E. Down-regulation

E. Down-regulation

Explanation:Cells typically up or down  regulate  depending on  the concentration of a hormone levels. When  there is a excessive  concentration of a hormone in the blood stream, the cell decreases the number of receptors reducing  the interaction  with that hormone, Also, when there is excessive  hormone reduction, the  target cells activate to increase their number of receptors.

Down  regulation occurs by the the deactivating or degrading of target cells to reduce the number of  receptors due to their sensitivity to a particular excess hormone.

answer: decrease

a limiting factor is the one which decrease the abundance, distribution and causes extinction of the population of species in a ecosystem. here, predators including hawks, owls and snakes are the limiting factor for the population of mexican free tailed bat.   although bats are nocturnal animals as they forge for food at night these predators also may remain active during night which can decrease the population of the mexican free-tailed bats. also, these bats eat only one type of insects that are moths. the food can also be a limiting factor as all 400 members are dependent upon same type of food needs that are moths. the decrease in the moth population can cause decrease in population size of the mexican free-tailed bats.

therefore, the scenarios will most likely to decrease the population size of the mexican free-tailed bats.  

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.