On-Line Biology Book: GLOSSARY

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calcitonin  A hormone produced by the thyroid that plays a role in regulating calcium levels.

calcium carbonate Chemical that also occurs in limestone and marble.

Calvin cycle (aka Calvin-Benson Cycle or Carbon Fixation) Series of Biochemical, enzyme-mediated reactions during which atmospheric carbon dioxide is reduced and incorporated into organic molecules, eventually some of this forms sugars. In eukaryotes, this occurs in the stroma of the chloroplast.

cambium A lateral meristem in plants. Types of cambiums include vascular, cork, and intercalary.

Cambrian Geologic period that begins the Paleozoic Era 570 million years ago. Marked in its beginning by a proliferation of animals with hard, preservable parts, such as brachiopods, trilobites, and archaeocyathids. PICTURE

campodactyly  A dominant trait in which a muscle is improperly attached to bones in the little finger, causing the finger to be permanently bent.

capillaries  Small, thin-walled blood vessels that allow oxygen to diffuse from the blood into the cells and carbon dioxide to diffuse from the cells into the blood. PICTURE

capillary bed  A branching network of capillaries supplied by arterioles and drained by venules.

capsid The protein "shell" of a free virus particle. This definition is from the Glossary at the UCMP site at http://www.ucmp.berkeley.edu/glossary/gloss4cell.html

capsule 1. Structure produced around certain bacteria; 2. Structure produced by the bryophyte sporophyte that contains spores produced by meiosis.

carbohydrates  Organic molecules composed of carbon, hydrogen, and oxygen that serve as energy sources and structural Materials for cells of all organisms.

cardiac cycle  One heartbeat; consists of atrial contraction and relaxation, ventricular contraction and relaxation, and a short pause.

cardiac muscle  The type of muscle that is found in the walls of the heart. Cardiac muscle is striated but branched, unlike the straight-shaped striated skeletal muscle cells. PICTURE

cardiovascular system  The human circulatory system consisting of the heart and the vessels that transport blood to and from the heart. PICTURE

carnivores Term applied to a heterotroph, usually an animal, that eats other animals. Carnivores function as secondary, tertiary, or top consumers in food chains and food webs.

carotenoids Major group of accessory pigments in plants; includes beta carotene. PICTURE

carpals  The bones that make up the wrist joint.

carpels  The female reproductive structures of a flower; consisting of the ovary, style, and stigma. PICTURE

carrageenan Chemical extracted from red algae that is added to commercial ice creams as an emulsifying agent.

carrying capacity  The maximum population size that can be regularly sustained by an environment; the point where the population size levels off in the logistic growth model.

Casparian strip  In plants, an impermeable waxy layer between the cells of the endodermis that stops water and solutes from entering the xylem, except by passing through the cytoplasm of adjacent cells. PICTURE 1 PICTURE 2

cast Type of fossil preservation where the original material of the fossil has decayed and been replaced later by another material, much the way a plaster cast is made in a mold.

catabolic reactions  Reactions in cells in which existing chemical bonds are broken and molecules are broken down; generally produce energy, involve oxidation, and lead to a decrease in atomic order.

catastrophism Once-popular belief that events in earth history had occurred in the past a sudden events and by processes unlike those operating today. Periods of catastrophic change were followed by long periods of little change. A subgroup, the Diluvialists, contended that Noah's Flood was the last of many floods which had occurred throughout earth history.

cell body  In a neuron, the part that contains the nucleus and most of the cytoplasm and the organelles. PICTURE 1 PICTURE 2

cell cycle  The sequence of events from one division of a cell to the next; consists of mitosis (or division) and interphase. PICTURE