Grasses - Biology Encyclopedia
Grasses belong to one of the largest and most economically and ecologically important families of plants: the Poaceae, formerly called the Gramineae. There are over nine thousand species of grasses recognized by botanists.
Grassland - Biology Encyclopedia
Grasslands are environments in which grasses and grasslike plants dominate the vegetation. Grasslands once covered up to 25 to 40 percent of the earth's land surface, but many of these grasslands have been plowed for crop production.
Gray, Asa - Biology Encyclopedia
Asa Gray was one of the central figures in American botany in the nineteenth century. Through his writing, teaching, collection, and correspondence, he had a major influence on the study of plants in the United States.
Growth - Biology Encyclopedia
Growth implies development, from the time of emergence or birth to the time of maturity and for many species, beyond maturity to eventual senescence or death. Growth also implies increase in size resulting from cell multiplication and cell expansion, as well as maturation of tissues.
Gymnosperms - Biology Encyclopedia
Gymnosperms are a group of plants that share one common characteristic: they bear seeds, but their seeds do not develop within an ovary. For this reason, gymnosperms were long thought to be an evolutionary precursor to the angiosperms, which are seed plants that enclose their seeds in an ovary and that are vastly more diverse than gymnosperms.
Habitat - Biology Encyclopedia
In its simplest sense, a habitat is where an organism lives and thus is a concrete physical location like a stand of trees or a pool of water.
Hardy-Weinberg Equilibrium - Biology Encyclopedia
The Hardy-Weinberg equilibrium is the fundamental concept in population genetics (the study of genetics in a defined group). It is a mathematical equation describing the distribution and expression of alleles (forms of a gene) in a population, and it expresses the conditions under which allele frequencies are expected to change.
Harvey, William - Biology Encyclopedia
William Harvey was an English physician, a pioneer in the study of blood circulation and embryology, and the founder of experimental physiology. Educated in Cambridge, England, and Padua, Italy, he practiced medicine in London and was court physician to King James I and King Charles I.
Health - Biology Encyclopedia
For many years, health was defined merely as the absence of disease. However, it has become clear that health is an active process that depends on the supportive interaction of all the body's systems.
Health and Safety Officer - Biology Encyclopedia
Most companies, universities, and academic medical centers employ a health and safety officer (HSO). The HSO promotes the health and safety of employees and is in charge of the company's formal health and safety program.
Hearing - Biology Encyclopedia
Hearing is the process by which humans, using ears, detect and perceive sounds. Sounds are pressure waves transmitted through some medium, usually air or water.
Heart and Circulation - Biology Encyclopedia
"It is absolutely necessary to conclude that the blood in the animal body is impelled in a circle, and is in a state of ceaseless motion; that this is the act or function which the heart performs by means of its pulse." William Harvey's description of the circulation of the blood and the motive force of the heart in de Motu Cordis (1628) is considered the beginning of modern physiology. In the adult human body, the heart beats about 70 times per minute, or approximately 100,000 beats per day.
Herbal Medicine - Biology Encyclopedia
Using medicines derived from plants is a practice probably as old as humankind itself. Prehistoric peoples likely noted when consuming a particular plant part provided relief, such as willow bark "tea" lowering a fever.
Herbivory and Plant Defenses - Biology Encyclopedia
Herbivory is the consumption of plant tissues by animals. This usually has a negative impact on plant growth and reproduction, and so imposes natural selection on plants, thereby favoring the evolution of traits that reduce losses (defenses).
High School Biology Teacher - Biology Encyclopedia
Those with a broad knowledge of life science, strong interpersonal and decision-making skills, and an understanding of human development can become high school biology teachers. To prepare for this career, a student should have four years each of science and mathematics coursework, pursue outside interests in science and nature, and spend considerable time working with young people.
History of Agriculture - Biology Encyclopedia
Agriculture is the raising of domesticated animals and the planting, cultivation, and preservation of crops. Agriculture entails selective breeding of organisms with combinations of inherited characteristics that benefit humans (and not necessarily the organisms themselves), and so these practices have over time greatly influenced the course of evolution of these animals.
History of Biology: Biochemistry - Biology Encyclopedia
Biochemistry as a recognizably distinct discipline emerged at the beginning of the twentieth century. Initially it focused on the chemical changes of cellular metabolism.
History of Biology: Cell Theory and Cell Structure - Biology Encyclopedia
All living organisms are composed of cells, and all cells arise from other cells. These simple and powerful statements form the basis of the cell theory, first formulated by a group of European biologists in the mid-1800s.
History of Biology: Inheritance - Biology Encyclopedia
Heredity (colloquially synonymous with "inheritance") refers to the process by which certain features (heritable characteristics) are transmitted from parent to offspring. This process has long been a source of intense interest to scientists.
History of Evolutionary Thought - Biology Encyclopedia
Although Charles Darwin's name is virtually synonymous with the word evolution, he was not the first person to recognize the phenomenon of species change nor did he even use the word "evolution" in the original theory he set forth in On the Origin of Species (1859). In fact, only the very last word of his book was evolve The word evolution was introduced after Darwin published his book and by commentators like English biologist Thomas Henry Huxley (1825–1895) who borrowed the term from embryology.
History of Medicine - Biology Encyclopedia
Medical history reflects a gradual transition from supernatural to natural explanations of human diseases and disorders. Speculation with few facts characterized prehistoric medicine; that is, "supernatural" medicine men blending magic, religion, and social customs with variably effective herbal medicines.
History of Plant Physiology - Biology Encyclopedia
Plant physiology is concerned with the life processes of plants, and from the beginning has been focused largely on the higher green terrestrial plants, the autotrophic (self-feeding) plants that feed us animals. In part, plant physiology has roots in agriculture.