Terms to Know
Decomposer- A consumer that feeds on organic matter from the bodies of dead organisms. These microorganisms feed from all levels of the food pyramid and are responsible for recycling elements (also called saprobes). The breakdown of dead matter and wastes into simple compounds that can be directed back into the natural cycles of living things
Prokaryote- Any of a wide variety of one-celled organisms of the kingdom Monera (or Prokaryota) that are the most primitive and ancient known forms of life. Prokaryotes lack a distinct cell nucleus and their DNA is not organized into chromosomes. They also lack the internal structures bound by membranes called organelles, such as mitochondria. At the molecular level, prokaryotes differ from eukaryotes in the structure of their lipids and of certain metabolic enzymes, and in how genes are expressed for protein synthesis. Prokaryotes reproduce asexually and include the bacteria and blue-green algae.
Pathogen- Any agent—usually a virus, bacterium, fungus, protozoan, or helminth—that causes disease. Pathogens are parasitic microbes whose relationship with a host results in infection and disease. The type and severity of infection depend on both the pathogenicity of the organism and the condition of the host. Pathogenicity, you will recall, is a broad concept that describes an organism’s potential to cause infection or disease and is used to divide pathogenic microbes into one of two general groups. True pathogens (primary pathogens) are capable of causing disease in healthy persons with normal immune defenses. They are generally associated with a specific, recognizable disease, which may vary in severity from mild (colds) to severe (malaria) to fatal (rabies). Examples of true pathogens include influenza virus, plague bacillus, and malaria protozoan.
Eukaryote- An organism whose cells contain a nucleus surrounded by a membrane and whose DNA is bound together by proteins (histones) into chromosomes. The cells of eukaryotes also contain an endoplasmic reticulum and numerous specialized organelles not present in prokaryotes, especially mitochondria, Golgi bodies, and lysosomes. The organelles are enclosed in a three-part membrane (called a unit membrane) consisting of a lipid layer sandwiched between two protein layers. All organisms except for bacteria and archaea are eukaryotes.
Fermeter- Process that allows respiration to occur in the absence of oxygen. Biologically, it allows cells to obtain energy from molecules (e.g., glucose) anaerobically. Glycolysis, the breakdown of glucose, is a form of fermentation. Alcoholic fermentation occurs when yeast cells convert carbohydrate sources to ethanol and carbon dioxide. Fermentation reactions are common in muscle cells, yeasts, some bacteria, and plants.
Helminth- Any parasitic worms. Tapeworms, flukes, and roundworms are collectively called helminths, from the Greek word meaning “worm.” They have been included among microorganisms because of their infective abilities and because the microscope is necessary to identify their eggs and larvae. Multicellular animals equipped to some degree with organs and organ systems.
Protozoan- Comprise a large, diverse assortment of microscopic or near-microscopic organisms that live as single cells or in simple colonies and that show no differentiation into tissues. Formerly classified in the animal kingdom, they are now generally divided into five protist phyla: Mastigophora (the flagellates), Sarcodina (the amebas), Ciliophora (the ciliates), Opalinida, and Sporozoa. Most are motile, and most ingest food, as do animals, rather than produce it themselves. Found in freshwater and at all depths in the ocean; some live in soil. Some are parasites in the bodies of humans or other animals, sometimes causing diseases.
Mold- A conspicuous mass of mycelium and fruiting structures produced by various fungi. Molds of the genera Aspergillus, Penicillium, and