Protista

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bilateral symmetry

—Body plan in which the left and right halves of the animal are mirror images of each other.

Bioluminescent

—A flashing of light that emanates from an organism.

Cilia

—Short projections consisting of microtubules that cover the surface of some cells and provide for movement.

Colonial

—A member of a localized population of organisms.

Contractile vacuole

—In some protistans, a membranous chamber that takes up excess water in the cell body, then contracts, expelling the water outside the cell through a pore.

Flagellum

—Tail-like motile structure of many free-living eukaryotic cells.

Food vacuole

—A membranous chamber that engulfs food and secretes digestive enzymes to break down the food into nutrients.

Gamete

—Specialized cells capable of fusion in the sexual cycle; female gametes are termed egg cells; male gametes may be zoospores or sperm cells.

Hypotonic

—A solution with a lower salt concentration than inside a cell.

Meiosis

—Two-stage nuclear division process that is the basis of gamete formation and of spore formation.

Mitochondria

—An organelle that specializes in ATP formation, the "powerhouse" of the cell.

Mitosis

—Type of nuclear division that maintains the parental chromosome number for daughter cells, the basis of bodily growth, and asexual reproduction.

Motile

—Able to move.

Multicellular

—More than one cell.

Nucleus

—A membrane-bound organelle that isolates and organizes the DNA.

Organelle

—An internal, membrane-bound sac or compartment that has a specific, specialized metabolic function.

Osmosis

—The diffusion of water from an area of high concentration to low concentration through a membrane.

Plankton

—Any community of floating organisms, mostly microscopic, living in freshwater and marine environments.

Plastid

—Of many bacteria, a small, circular molecule of extra DNA that carries only a few genes and replicates independently of the bacterial chromosome.

Radial symmetry

—An arrangement of the floral parts characterized by their radiation from the center of the flower, like spokes on a bicycle wheel.

Unicellular

—Single celled.

Zygote

—The cell resulting from the fusion of male sperm and the female egg. Normally the zygote has double the chromosome number of either gamete, and gives rise to a new embryo.