The habitat of a land animal might be on the ground, in the air or even below the ground. Birds spend a great deal of time in the air. Rodents, rabbits and snakes actually build nests in the ground, below the surface. Bears and bats inhabit caves at least some of the time. Bears, elephants, cows and many other animals live on the ground. Some land animals live in the water and on the land, i.e. turtles, alligators and crocodiles. Freshwater animals do live in a watery environment, but not every freshwater animal lives in the same environment. For instance, some freshwater animals live on the bottom, actually burrowing into the ground, while others inhabit the surface. Some prefer the deeper parts of a freshwater environment.
All animals depend, at least indirectly, on the sun as an energy source. Through the process of photosynthesis, the sun provides energy that plants store. Herbivores (plant eaters) eat the plants and then there is a transfer of the stored energy from the plant to the herbivore. Carnivores (meat eaters) benefit from the sun as an energy source by eating the herbivores. Again, a transfer of energy takes place -- from herbivores to carnivores. The process of securing a life-sustaining diet is essentially the same for freshwater animals. The sun is at the center of the energy cycle, providing sunlight that is transformed into plant food. In freshwater, microscopic plants, algae as well as other freshwater plants provide a food source for some small freshwater animals (minnows). These animals are then eaten by larger freshwater animals (amphibians, reptiles), and in the process transfer energy to even larger animals to maintain the energy cycle.
Land and freshwater animals range from microscopic to very large in size. It may be easier for humans to see the very large animals, but small animals are represented on earth and in freshwater in great numbers. The largest freshwater animal is the arapaima fish. The arapaima is native to the waters of the Amazon and can grow up to 10 feet long. The largest land animal that exists today is the African elephant, which can grow to weigh between 2 and 7 tons.
The length of time an organism lives is called life span. There are some land and freshwater animals that live longer than humans. A giant tortoise can live as many as 150 years or more, and a turkey buzzard can live as many as 118 years. However, the gastrotrich, a freshwater organism, lives only three days. Most land and freshwater animals live between the extremes of three days and 150 years.