This document discusses the environment and what constitutes life from a biological perspective. It explores the hierarchy of organization in nature from subatomic particles to the universe. Living things are defined by their complex organization, ability to maintain homeostasis, self-perpetuation, growth and development, interactions with their environment to obtain energy and matter, adaptation, and response. Humans are part of this biological hierarchy but are unique in that they can modify their environment to suit themselves, whereas other organisms adapt to the environment. The human environment consists of both natural spheres like the biosphere, atmosphere, lithosphere and hydrosphere, as well as man-made environments like anthropogenic ecosystems and physical structures.