Part of the peripheral nervous system, the autonomic nervous system regulates involuntary activity in the heart, stomach, and intestines.

The biosphere is the global ecological system integrating all living beings and their relationships. This includes their interactions with the lithosphere (the rigid outer part of the earth, consisting of the crust and upper mantle), hydrosphere (all surface water), and atmosphere (the envelope of gases surrounding the planet).

Heat is always transferred from warmer to cooler environments through conduction, convection, or radiation.

Part of the peripheral nervous system, the somatic nervous system is made up of nerve fibers that send sensory information to the central nervous system and control voluntary actions.

Cumulus clouds are large, puffy, mid-altitude clouds with a flat base and a rounded top. These clouds grow upward and can develop into a cumulonimbus or thunderstorm cloud.