The classification of organisms helps in the their study. A click train is a series of low-frequency clicks produced by an animal during echolocation. The two animals are called commensals. Commensalism is a type of symbiosis . A consumer is a living thing that eats other living things to survive.
Primary consumers eat producers, secondary consumers eat primary consumers, and so on.
There are always many more primary consumers than secondary consumers, etc. The land masses are hunks of Earth's crust that float on the molten core. The continental shelf is the part of the ocean floor next to each of the continents. For example, the wings of Pterodactyls, birds, and bats. They are the biggest source of protein in the oceans, a major constituent of plankton, and are found in all of the oceans and in many bodies of fresh water.