An organism?s environment includes nonliving, or abiotic, features, such as temperature, sunlight, precipitation, rocks, ponds, and so forth. abrasion: particles moved by water, ice, and air can be effective in wearing away rock. active transport: the movement of a substance against its concentration gradient (from low to high concentration).
Al2O3 (aluminum oxide)
O ------ Al ----- O ------- Al --------- O
A version of a gene.
Alternating current (AC). is electric current that repeatedly reverses its direction; the electric charges vibrate about relatively fixed positions. In the United States, the vibrational rate is 60 Hz
Amino Acid (Organic or Inorganic?)
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When we vomit, the acidic nature of our stomach contents becomes immediately apparent both from the taste and from the burning sensation in our throats. The purpose of this acidity is to kill any bacteria we swallow with our food. In the stomach, digestive enzymes and a muscular churning action combine to reduce our food to a thick liquid called chyme. Chyme exits the stomach through a second sphincter and enters the small intestine. Typically, it takes the stomach about 4 hours to process a meal. The small intestine is about 20 feet long. In the duodenum, the first foot of the small intestine, digestion continues with the breakdown of proteins, fats, carbohydrates, and nucleic acids. Some of the digestive enzymes at work in the duodenum are made by the small intestine itself. Others are made by the pancreas. Pancreatic enzymes play an important role in neutralizing food, which arrives from the stomach in a highly acidic condition. In addition, the small intestine receives bile, a substance that is produced in the liver and stored in the gall bladder. Bile is an emulsifier?it breaks fats into tiny droplets that are more easily attacked by enzymes. Beyond the duodenum, the rest of the small intestine functions primarily in absorbing nutrients into the body. In order to be able to do this efficiently?that is, rapidly?the small intestine has a huge surface area. It is covered with numerous fingerlike projections called villi, each of which is in turn covered with tiny little projections called microvilli. Flattened, the small intestine would fill the area of a tennis court! Digested nutrients are absorbed across the surface of the small intestine into capillaries found inside each villus.