Many scientists suggest that billions of years ago,
life on earth began with
(1) simple, single-celled organisms
(2) simple, multicellular organisms
(3) complex, single-celled organisms
(4) complex, multicellular organisms

Which are forms of nitrogen that are usable by humans

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

Scientists discover two populations of mice on either side of a major river. the two populations have almost identical genes but the mice from one side cannot breed with mice from the other. this is most likely because