All animals are heterotrophs. Blue whales feed on crustaceans. Lions eat mammals such as wildebeest, zebras and antelope. Atlantic puffins eat fish such as sandeel and herring. Green sea turtles eat seagrasses and algae. Many species of corals are nourished by zooxanthellae, tiny algae that live within the corals' tissues. In all of these cases, the animal's carbon comes from ingesting other organisms.
In contrast, an autotroph is an organism that obtains its carbon from carbon dioxide. Autotrophs need not feed on other organisms, since they can synthesize the carbon compounds they need for energy using sunlight and carbon dioxide.