There are about 78 types or species of whales, though this number ranges from 78 to 90 depending on the source. This group, called cetaceans, includes dolphins and porpoises, as well as whales.
Of the 78 species of whales, 11 species are baleen whales, which means that they eat by straining small organisms into their mouth. The rest of the species fall under the category of toothed whales. All whales live in a marine environment, or the sea, except for four species of river dolphins that thrive solely in fresh water. Whales all share a few common features, like blowholes. Blowholes are the nostrils of the whale and are positioned on top of the head. They breathe in air through the blowholes when they surface and then close it up when they dive.
Regardless of their status, all types of whales are protected under the Marine Mammal Protection Act, the Office of Protected Resources says. The blue whale, the largest animal on the planet, is listed as endangered, along with beluga whales, humpback whales, sperm whales and killer whales. These animals are threatened by pollution and habitat loss from climate change, collisions with ships, entanglements with fishing nets and illegal whaling.