Living organisms are highly ordered, and maintaining order requires energy and materials from the environment. Individual organisms eventually die, but life continues via reproduction and heredity. Over long periods of time, life forms change due to evolution.
Science is a way of learning how nature functions.
Scientists perform tests that might rule out possible explanations for a particular phenomenon. Explanations that have been repeatedly tested and not disproven are tentatively accepted. The principles of biology can be applied to world problems such as overpopulation, disease, environmental degradation, famine, and drug addiction. Each structure or activity is in a specific relationship to all other structures and activities. Organized chemical steps break down and build up molecules, making energy available or building needed parts.