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differentiation

(Encyclopedia)differentiation, in biology, series of changes that occur in cells and tissues during development, resulting in their specialization. This, in turn, permits a greater variety of organisms. In plants, ...

hydra, in zoology

(Encyclopedia)hydra hīˈdrə [key], common name for freshwater organisms in the phylum Cnidaria, which includes jellyfish, sea anemones, and corals. Hydras are widely distributed in lakes, ponds, and sluggish stre...

annual rings

(Encyclopedia)annual rings, the growth layers of wood that are produced each year in the stems and roots of trees and shrubs. In climates with well-marked alternations of seasons (either cold and warm or wet and dr...

Warburg, Otto Heinrich

(Encyclopedia)Warburg, Otto Heinrich ŏtˈō hīnˈrĭkh värˈbo͝orkh [key], 1883–1970, German physiologist. He was director (1931–53) of the Kaiser Wilhelm Institute (now Max Planck Institute) for cell physi...

Temin, Howard Martin

(Encyclopedia)Temin, Howard Martin, 1934–94, American virologist, b. Philadelphia, Ph.D. California Institute of Technology, 1959. A professor at the Univ. of Wisconsin in Madison, Temin began his cancer research...

liver

(Encyclopedia)liver, largest glandular organ of the body, weighing about 3 lb (1.36 kg). It is reddish brown in color and is divided into four lobes of unequal size and shape. The liver lies on the right side of th...

cattail

(Encyclopedia)cattail or reed mace, any plant of the genus Typha, perennial herbs found in almost all open marshes. The cattail (also called club rush) has long narrow leaves, sometimes used for weaving chair seats...

ovum

(Encyclopedia)ovum ōˈvəm [key], in biology, specialized plant or animal sex cell, also called the egg, or egg cell. It is the female sex cell, or female gamete; the male gamete is the sperm. The study of the ovu...

Zernike, Frits

(Encyclopedia)Zernike, Frits, 1888–1966, Dutch physicist, Ph.D. Univ. of Amsterdam, 1915. He was on the faculty at the Univ. of Groningen from 1915 until his retirement in 1958. Zernike received the 1953 Nobel Pr...

actin

(Encyclopedia)actin, a protein abundantly present in many cells, especially muscle cells, that significantly contributes to the cell's structure and motility. Actin can very quickly assemble into long polymer rods ...