According to PAWS, animals live on every continent and in every ocean on Earth. Each region has distinct native wildlife species that are adapted to the local environment. Animals live in many areas that are completely inhospitable to humans, including the deep sea and natural boiling water springs. Many of these species are too tiny to be seen with the naked eye.
Rain forests are the world's most ecologically diverse biomes. According to Mongabay founder Rhett Butler, roughly half of all animal species reside in rain forests. These areas also contain more plant species than any other environment. Rhett Butler remarks that a hectare of rain forest contains up to 460 tree species, plus other flora such as ferns, flowering plants and vines.
Some of the most unusual animals live in ocean environments so deep that they receive no sunlight. The Smithsonian Institution reveals that some deep sea denizens are extremely difficult to see because they have transparent bodies. This is an important defense against predators. Other deep sea fish are bio-luminescent and use self-generated light to lure prey. Those that live in the deepest regions that still receive small amounts of sunlight have huge eyes mounted on long stalks. This enables the fish to take advantage of the scant light that reaches their environment.