They move with by squirting water through a siphon, a type of jet propulsion. Many also squirt ink to help escape predators. There are 75 species of whales, dolphins, and porpoises. They have a hollow nerve cord that ends in a brain. They show the distribution and origins of shared characteristics.
Cladograms are testable hypotheses of phylogenetic relationships.
In classification, a class is a group of related or similar organisms. A class contains one or more orders. A group of similar classes forms a phylum. 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.