Biomass: organic matter that can be used as an energy source. (ex: wood, crops, and animal waste) Conservation: a careful preservation and protection of something; especially planned management of a natural resource to prevent exploitation, destruction, or neglect. Fossil Fuels: a natural fuel formed in the past from the remains of living things. (ex: coal, oil, natural gas) Geothermal Energy: heat energy from within the earth. Hydropower: energy that comes from the force of moving water. Nonrenewable: an energy source that cannot be replaced by natural means at the same rate that it is consumed. Nuclear Energy: energy stored in the nucleus of an atom. Renewable: energy from a source that is not depleted when used Solar Energy: energy radiated from the sun. Wind Energy: energy harnessed from air in motion.