"Los animales que viven encima y debajo de la superficie del agua de un gran río, de un estanque, del mar abierto, de una costa oceánica, de un bosque de manglares"--T.p.
Compares how animals vary in the same environment when day turns to night, such as the shrikes, locusts, and sand vipers of the North African desert that give way to scorpions, desert hedgehogs, and jerboas at nightfall.
Compares how plants and animals vary when their environments are essentially the same except that one is hot and dry and the other cold, such as a hot river in India versus a cold river in Canada.