Biological warfare (previously called germ warfare) is the use of diseasecausing microorganisms as military weapons. One of the earliest recorded uses of biological weapons occurred in the fourteenth century.
Biology (from the Greek bios, meaning "life") is the scientific study of all forms of life, including plants, animals, and microorganisms.
A biome is an ecosystem containing plant and animal species that are characteristic to a specific geographic region. (An ecosystem is the community of plants and animals in an area considered together with their environment.) The nature of a biome is determined primarily by climate, including a region's annual average temperature and amount of rainfall.
Biophysics is the application of the principles of physics (the science that deals with matter and energy) to explain and explore the form and function of living things. The most familiar examples of the role of physics in biology are the use of lenses to correct visual defects and the use of X rays to reveal the structure of bones.
The biosphere is the space on or near Earth's surface that contains and supports living organisms. It is subdivided into the lithosphere, atmosphere, and hydrosphere.
Biotechnology is the application of biological processes in the development of products. These products may be organisms, cells, parts of a cell, or chemicals for use in medicine, biology, or industry.
Birds are warm-blooded vertebrate (having a backbone) animals whose bodies are covered with feathers and whose forelimbs are modified into wings. Most can fly.
Birth, or parturition (pronounced pahr-chuh-RIH-shuhn), in mammals is the process during which a fully developed fetus emerges from the mother's uterus (or womb) by the force of strong, rhythmic muscle contractions. The birth of live offspring is a reproductive feature shared by mammals, some fishes, and certain invertebrates (such as scorpions), as well as some reptiles and amphibians.
Birth defects, or congenital defects, are abnormalities that are present at birth. They may be the result of genetic factors such as an inherited disease or a chromosomal abnormality.
A black hole, among the most mysterious elements in the universe, is all that remains of a massive star that has used up its nuclear fuel. Lacking energy to combat the force of its own gravity, the star compresses or shrinks in size to a single point, called a singularity.
Blood is a fluid connective tissue that performs many functions in the body. It carries oxygen and nutrients to the cells, hormones (chemical messengers) to the tissues, and waste products to organs that remove them from the body.
Blood supply refers to the blood resources in blood banks and hospitals that are available for use by the health care community. The blood supply consists of donated blood units (in pints) that are used in blood transfusions.
Boolean algebra is a form of mathematics developed by English mathematician George Boole (1815–1864). Boole created a system by which certain logical statements can be expressed in mathematical terms.
Botany is a branch of biology that deals with plant life. It is the study of the structure and the vital processes of plants, including photosynthesis, respiration, and plant nutrition.
The brain is a mass of nerve tissue located in an animal's head that controls the body's functions. In simple animals, the brain functions like a switchboard, picking up signals from sense organs and passing the information to muscles.
Brewing is the multistage process of making beer and other alcoholic malt beverages. Brewing has taken place around the world for thousands of years, and brewed beverages are staples in the diets of many cultures.
Bridges are structures that provide a means of crossing natural barriers, such as rivers, lakes, or gorges. Bridges are designed to carry railroad cars, motor vehicles, or pedestrians.
Brown dwarfs—if they indeed exist—are celestial objects composed of dust and gas that failed to evolve into stars. To be a star, a ball of hydrogen must be large enough so that the pressure and heat at its core produce nuclear fusion, the process that makes stars bright and hot.
Buoyancy is the tendency of an object to float in a fluid, such as air or water. The principle of buoyancy was first discovered by Greek mathematician Archimedes (c.
A burn is damage to an area of the body caused by excessive heat, chemicals, electricity, or the Sun. Burns caused by heat can be the result of contact with fire, scalding water, or hot surfaces.
Butterflies are popular, well-known insects with large, colorful wings covered with tiny scales. Together with moths, butterflies make up the order Lepidoptera, which contains over 150,000 species or kinds.
CAD/CAM is an acronym for computer-aided design and computer-aided manufacturing. The use of computer software programs makes it possible to remove much of the tedious manual labor involved in design and manufacturing operations.
The calculator is a computing machine. Basic calculators perform basic mathematical functions (addition, subtraction, division, and multiplication).
Calculus is a field of mathematics that deals with rates of change and motion. Suppose that one nation fires a rocket carrying a bomb into the atmosphere, aimed at a second nation.
A calendar is a system of measuring the passage of time for the purpose of recording historic events and arranging future plans. Units of time are defined by three different types of motion: a day is one rotation of Earth around its axis; a month is one revolution of the Moon around Earth; and a year is one revolution of Earth around the Sun.
A calorie is a unit of heat measurement in the metric system. It is defined as the amount of heat needed to raise one gram of pure water by 1°C under standard conditions.
A canal is a human-made waterway or channel that is built for transportation, irrigation, drainage, or water supply. Although canals are among the oldest works of civil engineering, they continue to play a major role in commerce, as they are the cheapest form of inland transportation yet devised.
Cancer is a disease of uncontrolled cell growth caused by exposure to carcinogens (cancer-causing substances), genetic defects, or viruses. Cancer cells can multiply and form a large mass of tissue called a tumor.