Environmental Science

Organic compounds made up of atoms of carbon, chlorine, and fluorine. An example is Freon-12 (CCl2F2), used as a refrigerant in refrigerators and air conditioners and in making plastics such as Styrofoam. Gaseous CFCs can deplete the ozone layer when they slowly rise into the stratosphere and their chlorine atoms react with ozone molecules. Also used Freons chromosome Grouping of various genes and associated proteins in plant and animal cells that carry certain types of genetic information. See genes.

Process in which certain organisms (mostly specialized bacteria) extract inorganic compounds from their environment and convert them into organic nutrient compounds without the presence of sunlight. Compare photosynthesis.

Formation of the earth and its early crust and atmosphere, evolution of the biological molecules necessary for life, and evolution of systems of chemical reactions needed to produce the first living cells. These processes are believed to have occurred about 1 billion years before biological evolution. Compare biological evolution.

One of the millions of different elements and compounds found naturally and synthesized by humans. See compound, element.

Smallest living unit of an organism. Each cell is encased in an outer membrane or wall and contains genetic material (DNA) and other parts to perform its life function. Organisms such as bacteria consist of only one cell, but most of the organisms we are familiar with contain many cells. See eukaryotic cell, prokaryotic cell.