The cell possesses an extraordinary array of enzymes, each specialized to carry out an important function in the cell. However, in many cases it is critical that the enzymes only be active at certain times and not others.
Convergent evolution is the process by which unrelated or distantly related organisms evolve similar adaptations. Organisms displaying these similarities usually live in similar environments, and the force driving convergence is natural selection.
A coral reef is a living community built around the accumulated mineralized remains of coral animals, which belong to phylum Cnidaria. The hardened calcium carbonate secretion from coral animals, with mineralized algal cells and other secretions, create nooks and crannies that shelter up to sixty thousand species, including hundreds of types of corals, as well as eels, lobsters, sea slugs, sea horses, sea urchins, turtles, and a huge variety of fishes.
In the broad sense, creationism is the belief that the universe and life were created by God. Within this definition are a broad range of beliefs.
Francis Harry Compton Crick, a British biophysicist, was co-winner of the Nobel Prize in physiology and medicine in 1962, for his work in genetics. This award was shared with American biologist James D.
The class Crocodylia consists of twenty-two species of alligators, caimans, gharials, and crocodiles worldwide, and is most closely related to birds (class Aves). Like birds (and mammals), crocodilians have the ventricle of their heart divided into left and right compartments (unlike amphibians, turtles, and reptiles, whose ventricles have but a single, undivided compartment).
The Crustacea are a subphylum of the animal phylum Arthropoda. This is a large and diverse group with more than forty thousand species, including crabs, shrimp, lobsters, crayfish, barnacles, and many near-microscopic members of the zooplankton community.
Cyanobacteria (blue-green algae) are microorganisms that structurally resemble bacteria (they lack a nucleus and organelles). However, unlike other bacteria, cyanobacteria contain chlorophyll a and conduct oxygenic photosynthesis.
Cytokinesis is the process by which a cell divides its cytoplasm to produce two daughter cells. As the final step in cell division after mitosis, cytokinesis is a carefully orchestrated process that signals the start of a new cellular generation.
The cytoskeleton is responsible for cell shape, motility (movement) of the cell as a whole, and motility of organelles within a cell. There are three types of filaments in the cytoplasm of most vertebrate cells: microfilaments, microtubules, and intermediate filaments.
Charles Darwin was the founder of modern evolutionary thought, and the developer, along with Alfred Russel Wallace, of the theory that natural selection is a principle driving force in evolution. Darwin is generally recognized as the single greatest thinker in the history of biology, whose contributions provided the basis for understanding the immense diversity that characterizes the natural world.
Nicolas de Saussure was an early pioneer in plant physiology. He was born and lived in Geneva, Switzerland, and later became professor of mineralogy and geology at the Geneva Academy.
A dentist is a medical professional who cares for the oral health of his patients. Dentists administer both prophylactic (preventative) care and corrective treatments for teeth and gums.
Deserts are environments shaped by aridity, or dryness. Aridity reflects the balance between precipitation and potential evapotranspiration (PET), or the air's ability to absorb water (determined by temperature and water content).
Desertification is the degradation of grasslands, savannas, and woodlands to a more desert-like condition, with resulting decrease in plant production and the land's ability to support livestock grazing or other human uses. Vegetation becomes sparse; exposed soil becomes more vulnerable to erosion; and yields from cropland or grazing are reduced.
Reproduction and development are integral factors of life. Multicellular organisms arise through a process that begins with the fertilized egg and ends with a new individual.
Differentiation in plants refers to the processes by which distinct cell types arise from precursor cells and become different from each other. Plants have about a dozen basic cell types that are required for everyday functioning and survival.
Digestion breaks down foods into nutrient molecules that are small enough to be absorbed into an animal's circulatory system. Following digestion, nutrients are delivered to cells, where energy is extracted from their chemical bonds.
The human digestive system is responsible for food ingestion and digestion as well as the absorption of digested food molecules and the elimination of undigested molecules. It consists of a long tube called the gastrointestinal tract or GI tract (alimentary canal) and several accessory organs.
Disease (or "lack of ease") is any damage or injury that impairs an organism's function. Diseases (sometimes called deviations from the norm) can be classified in numerous ways.
DNA (deoxyribonucleic acid) is the molecule that stores genetic information in living systems. Like other organic molecules, DNA mostly consists of carbon, along with hydrogen, oxygen, nitrogen, and phosphorus.
The genome of an organism is the sum total of its genetic information. The genome is not only a blueprint for the organism it also contains historical notes on the evolution of the organism.