Severe flooding in an area caused a population of minnows to become split into two separate ponds. Prior to the separation, the male minnows all had a moderate number of spots. Following the separation, the first pond was filled with larger fish that fed on minnows, so male minnows with fewer spots were better able to avoid detection by predators. The minnows in the second pond, however, had very few predators, and female minnows in this pond preferred to mate with males that had the most spots. After many generations, the two minnow populations evolved into different species and could no longer interbreed.

Which of the following describes a negative feedback loop? when the heart rate is too high, the body sends hormones that continually increase the heart rate higher. when a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones. when blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows. when a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs.

Read this summary of a scientific theory: "cells are the most basic structural and functional units of life. all living organisms are made up of one or more cells. all cells that are alive in the world today came from pre-existing cells." which of the following would require this theory to be modified? -a.) a survey finds that a majority of people believe viruses carry out the basic processes of life. -b.) a prominent scientist says she feels strongly that one day the theory will be challenged by life on other planets. -c.) the dna of unicellular and multi-cellular organisms is shown to have many fundamental similarities. -d.) scientific observations show that microscopic organisms living in the deep ocean are not made up of cells.

Polar zones are cold and tend to be dry because of a pressure system of cold. low high