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Protista - Beneficial Protists

organisms cell cells food

Members of the kingdom Protista can also be very beneficial to life on Earth. Many species of red algae are edible and are popular foods in certain parts of the world. Red algae are rich in vitamins and minerals. Carageenan, a polysaccharide extracted from red algae, is used as a thickening agent in ice cream and other foods. Giant kelp forests are rich ecosystems, providing food and shelter for many organisms. Trichonymphs are flagellates that live in the intestines of termites. These protozoans break down cellulose in wood into carbohydrates the termites can digest.

The kingdom Protista is a diverse group of organisms. Some protists are harmful, but many more are beneficial. These organisms form the foundation for food chains, produce the oxygen we breathe, and play an important role in nutrient recycling. Many protists are economically useful as well. As many more of these unique organisms are discovered, humans will certainly enjoy the new uses and benefits protists provide.


Resources

Books

Blaustein, Daniel. Biology: The Dynamics of Life. Westerville, OH: McGraw-Hill Companies, 1998.

Johnson, George B. Biology: Principles and Explorations. Orlando: Holt, Rinehart and Winston, 1998.

Solomon, Eldra Pearl. Biology. Orlando: Saunders College Publishing, 1999.

Starr, Cecie. Biology: Concepts and Applications. Belmont, CA: Wadsworth Publishing Company, 1997.

Tobin, Allan J. Asking About Life. Orlando: Saunders College Publishing, 1998.


Jennifer McGrath

KEY TERMS


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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.

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