Carbon: a chemical element with symbol C and atomic number 6. Carbon is known and has been used since antiquity. In nature it occurs both in its elemental and chemically bonded forms. Most of carbon is found in bonded form as carbonate mineral (e.g. limestone, magnesite, dolomite). In water it is present as dissolved carbonate and bicarbonate. Natural carbon is mostly organic. Coal is not an elemental carbon but rather a diverse mixture of carbon compounds. Crude oil and natural gas are primarily made up of various hydrocarbon compounds. A diamond is a carbon arranged in a crystal structure found in volcanic rocks. Carbondioxide is present in the atmosphere in large amounts. Carbon is also a component of the organic matter of living organisms.
Photosynthesis: the life processes inside plants, algae and certain bacteria that convert inorganic matters into organic matter by the light energy from the Sun.
Autotrophs: organisms that produce organic compounds from inorganic matter (carbon dioxide, water, ions). Autotrophs include plants, which utilize atmospheric carbon dioxide by photosynthesis.
Heterotrophs: living organisms that obtain organic matter to produce their own organic matter. Heterotrophs include the kingdoms of Animalia and Fungi.
Greenhouse effect: the retention of heat in the atmosphere. Solar radiation is re-radiated from the surface into the atmosphere. A part of the re-radiated energy cannot escape the atmosphere since a 'wall', the atmosphericgreenhouse gases, do not let it escape. This energy portion is therefore re-radiated to the planetary surface. Without this phenomenon the average temperature on Earth would be around 40 °C (104 °F) cooler. Due to human activities, carbon dioxide levelsincrease, which contributes to greenhouse gas emission and may cause global warming.