We all know that living organisms need food to survive. Life forms, however, do not all eat the same things. Autotrophs, known as *self-feeders* are organisms which create "food" using energy from the sun, thermal energy from the Earth, or other such means to feed themselves. All members of the kingdom plantae are autotrophs. Heterotrophs, known as *other-feeders* are beings which feed themselves by eating other creatures, plants, or foods which exist outside of themselves. All members of the kingdoms animalia and fungi are heterotrophs. On Earth, nature provides the following three mechanisms for living creatures to be supplied with energy.

• Photosynthesis
• Respiration
• Chemosynthesis