Why are predators necessary to maintain the balance in an ecosystem

In which case would a scientist choose to use a dissecting microscope rather than a compound microscope

Elephants in the savanna regions of africa dig holes in dried up river beds to reach water lying just below the surface. these holes provide drinking water for other animals as well. so, without the elephants, many animals might otherwise die from lack of water during the dry season. the location in which the elephants live is an example of a/n and the role they play in creating water holes is an example of a a) ecosystem; habitat b) community; niche c) habitat; niche d) niche; habitat

Identify two examples of chemical reactions that you have encountered during the last week. identify an exothermic and endothermic reaction. explain.