The term "hard bottom" refers to the ocean region close to shore, where wave action prevents the accumulation of muddy sediment that will create a soft bottom. Plants and animals living on or in the seafloor are called benthos.
The realm of open water, called the pelagic zone, has the greatest volume and vertical range of any life zone. It includes the region above the continental shelf, called the neritic province, and the region beyond, called the oceanic province.
Where water movements are not strong enough to wash them away, sediments coat much of the benthic environment. Soft bottoms are common along coasts, along continental margins, and in the deep sea.
Cancers are a collection of diseases that result from loss of control over cell division (mitosis). Because the cell cycle is controlled by proteins, and proteins are encoded by genes, cancers are genetic diseases.
An organ is a structure composed of two to four types of tissues working to perform functions that are beyond the scope of an individual tissue type. A set of related organs working cooperatively toward the performance of even more complex functions constitutes an organ system.
An organelle is a specialized cellular structure in eukaryotic cells analogous to an organ in the body. Organelles are discrete structures within the cell that perform a specialized function.
Organic agriculture uses the principles of diversity and nutrient cycling found in nature to raise crops and livestock. All kinds of food are grown using organic practices, from fruits and vegetables to grains and dairy products.
How did life begin on Earth? The fact is that no one knows the answer yet, and it remains one of the primary unsolved questions of biology.
Osmoregulation means the physiological processes that an organism uses to maintain water balance; that is, to compensate for water loss, avoid excess water gain, and maintain the proper osmotic concentration (osmolarity) of the body fluids. Most humans are about 55 to 60 percent water by weight (45 percent in elderly and obese people and up to 75 percent in newborn infants).
Glycolysis and the Krebs cycle both generate the high-energy compound adenosine triphosphate (ATP) directly, by substrate-level phosphorylation, but this represents only a small fraction of the energy in each glucose that passes through these pathways. Much more of the energy in glucose is conserved in the form of high-energy electrons carried in pairs by the electron "shuttles" NADH and FADH2, which are generated in glycolysis and the Krebs cycle.
Pain is experienced by humans and animals in response to excessive pressure, heat, or chemicals. Although humans often view pain as undesirable, pain helps protect them from injury by alerting them to its presence.
Paleontology is a broad field of study that focuses on the history of life on Earth. Fossils, which are the material remains (bones, teeth, shells) or traces (physical or chemical) of ancient organisms, are what paleontologists study.
The pancreas is a soft oblong organ located in the upper central region of the abdominal cavity, just behind the lower surface of the stomach. It has three portions: an expanded medial portion called the head, a central portion called the body, and a tapering lateral portion called the tail.
A parasite is typically an organism that lives in or on the body of another living organism, the host, and harms it by feeding on its tissues or stealing nutrients. In the broad sense, parasites include certain bacteria, fungi, protozoans, worms, arthropods, and a few vertebrates.
Louis Pasteur was a French microbiologist who made major discoveries about the biology of bacteria; invented techniques to prevent the spoilage of milk, wine, and beer by microorganisms; and pioneered the prevention of infectious disease through vaccination.
Whether an organism is a worm or a human, virtually all its characteristics are influenced by its genetic makeup. Since Gregor Mendel's pioneering studies of inheritance in the mid-nineteenth century, enormous strides have been made in understanding the molecular basis of inheritance.
Linus Carl Pauling, American chemist, is the only person to have won two undivided Nobel prizes (in chemistry in 1954 and the Nobel Peace Prize in 1962). He is best known for his work on molecular structure, the nature of the chemical bond, and the effects of various chemical agents on the human body.
A pedigree is a diagram that depicts the blood relationships of family members, as well as which individuals express the trait or disorder under study. Construction of a pedigree is often the first step in the identification of a gene variant that causes a particular disease or trait.
The peripheral nervous system (PNS) refers to all the neurons (and their supporting cells, or glia) of the body outside the brain and spinal cord (central nervous system [CNS]). The brain is the organ that decides how a person responds to what happens in the surrounding world.
Peroxisomes (microbodies) are cytoplasmic organelles involved in metabolism of hydrogen peroxide, H2O2. The peroxisome is about 0.5 microns in diameter, and is surrounded by a membrane.
The people who tell others about new medicinal preparations usually work for pharmaceutical manufacturing companies as pharmaceutical sales representatives. To keep informed about new products, pharmaceutical sales representatives are continuously learning as part of their jobs.
A pharmacologist practices the science of pharmacology, which is the study of drug, hormone, and chemical actions on biological systems. A pharmacologist must have knowledge in the sources, chemical properties, biological effects, and therapeutic uses of drugs.