Organisms: a living thing, such as an animal, a plant, a bacterium, or a fungus. (NCI1) An organized living body, especially the material structure of an individual animal, plant, bacterium, etc. All living things. Organisms maintain an internal order that is separated from the environment. Life began on Earth as primitive cells about 3.5 to 4 billion years ago. (Brooker, 3)

Animals: living organisms having sensation and voluntary motion, without rigid cells walls, and dependent on organic substances for food. (Oxford) "Unicellular" or "multicellular" organisms that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, ‘Animalia’ was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the “domain eukaryota.” (MeSH) Animals are multicellular organisms whose cells do not possess cell walls. They obtain their food by taking it into a “digestive” “cavity” in a process known as ‘ingestion.’ Once inside the digestive cavity, food is digested and absorbed. (Indge, 17)

Invertebrate: an animal without a backbone or "spinal column." (Oxford) An animal lacking a “vertebral column.” This group consists of 98% of all animal “species.” (NCIt)

Vertebrate: animals having a "vertebral column," members of the “phylum” “chordata,” subphylum ‘craniata.’ (MeSH) Includes fish, amphibians, reptiles, birds, and mammals. (Oxford) A “subphylum” of animals consisting of those having a bony or cartilaginous vertebral column. (NCIt) Characterized by the possession of a brain enclosed in a skull, ears, "kidneys," and other organs. (Lawrence)

Mammals: animals having a "vertebral column," members of the “phylum” “chordata,” subphylum ‘craniata.’ (MeSH) Includes fish, amphibians, reptiles, birds, and mammals. (Oxford) A “subphylum” of animals consisting of those having a bony or cartilaginous vertebral column. (NCIt) Characterized by the possession of a brain enclosed in a skull, ears, "kidneys," and other organs. (Lawrence)

Primates: the ‘taxonomic’ order of mammals that includes man, monkeys, and lemurs. (NCIt) Known from the 'Paleocene' era, includes tree shrews, lemurs, monkeys, apes and humans. Largely 'arboreal' with limbs modified for climbing, leaping, or swinging. Have large brains in relation to body size, a shortening of the 'snout' and elaboration of the 'visual apparatus,' often with "stereoscopic vision." (Lawrence)

Great Apes: members of the family ‘pongidae’ which includes gorillas, chimpanzees, bonobos (pigmy chimpanzees) and orangutans, and is characterized by absence of a tail and cheek pouches. (Oxford) Also simply referred to as ‘apes.’

Bacteria: single-celled “prokaryote,” typically without a discrete, membrane-bound “nucleus.” (HGPIA) Small single-celled organisms. Found almost everywhere on Earth and vital to the planet's “ecosystems.” Some “species” can live under extreme conditions of “temperature” and “pressure.” The human body is full of bacteria, and in fact is estimated to contain more bacterial cells than human cells. Most bacteria in the body are harmless, and some are even helpful. A relatively small number of species cause disease. (NHGRI) Found in soil, water, and even our digestive tracts. (Brooker, 64) They generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round, rodlike, and spiral. (MeSH) Differ from "archaea" in gene “sequences” and types of molecules in their membranes. (Lewis, 18) Some cause infections and disease in animals and humans. (NCI1) Singular - ‘bacterium.’ Also referred to as ‘eubacteria.’

Deinococcus Radiodurans: found in the soil and is highly resistant to “radiation,” especially “ionizing radiation.” (MeSH) Tolerates 1,000 times the radiation level that a person can. It can live amidst the radiation of a nuclear reactor. It realigns its radiation-shattered pieces of “DNA.” Then “enzymes” bring in new “nucleotides” and assemble the pieces. (Lewis, 228)

E. coli (escherichia coli): common bacterium that has been studied intensively by geneticists because of its small genome size, normal lack of "pathogenicity," and ease of growth in the laboratory. (HGPIA) A species of rod-shaped bacteria commonly found in the lower part of the intestine of warm-blooded animals. It is usually (not “pathogenic”). (MeSH) A normal resident of the human small intestine, but under certain conditions can produce a “toxin” that causes severe diarrhea (food poisoning) and can damage the kidneys. (Lewis, 326) Common intestinal bacterium that adjusts the rate of “transcription” of particular genes in response to environmental cues. (Kandel, 258)

Mycoplasma: any of a group of almost sub-microscopic bacteria of very simple internal structure. They lack the typical rigid bacterial cell wall, occur in a variety of "morphological" forms, and are responsible for several animal diseases. (Lawrence)

M. genitalium (mycoplasma genitalium): a species of bacteria originally isolated from urethral specimens of patients. (MeSH) The smallest microorganism know to be able to reproduce. (Lewis, 431)

M. pneumonia (mycoplasma pneumonia): closest relative of M. genitalium. Has a genome size of 816,000 base pairs. Causes extensive infection of the lungs and bronchi, particularly the lower lobes of the lungs in humans. (MeSH) Editor’s note - studied by J. Craig Venter in his search for the minimal number of genes required for life.

Disease Vectors: invertebrates or non-human vertebrates which transmit infective organisms from one host to another. (MeSH) An invertebrate animal (e.g., tick, mite, mosquito, bloodsucking fly) capable of transmitting an "infectious" agent among vertebrates. (NCIt)

Eukaryote: organism or cells with a nucleus separated from the cytoplasm by a two-membrane nuclear envelope. (NCIt) Organisms that have larger cells with internal compartments that serve various functions. Have a cell nucleus in which the "genetic material" is surrounded by a “membrane. (Brooker, 8) Eukaryotic cells also have an extensive "cytoskeleton" of protein "filaments" and "tubules," and many cellular functions are 'sequestered' in membrane-bounded "organelles" in the cytoplasm. (Lawrence) Adjective - ‘eukaryotic.’ Editor’s note - from “domain eukarya.”

Extremophiles: "prokaryotic" microorganisms that grow in extreme conditions (e.g. very high or very low temperature, high salt concentration, very acid) that other microorganisms cannot survive in. (Lawrence) Live in marginal environments. Single-celled life has diversified to occupy a vast range of environments, from the freezing deserts of Antarctica to hot acidic springs. (Venter, 57)

Fungi: any of a large division of organisms, including mushrooms, toadstools, moulds, rusts, yeasts, which lack "chlorophyll," and grow on and obtain nutriment from organic matter. (Oxford) A plant-like organism that does not make ‘chlorophyll.’ Mushrooms, yeasts, and molds are examples. (NCI1) They reproduce either sexually or asexually, and have life cycles that range from simple to complex. (MeSH) Singular - ‘fungus.’

Saccharomyces Cerevisiae (S. cerevisiae): this yeast is single-celled with only about 6,000 genes, but a third of them have counterparts among mammals, including at least seventy genes implicated in human diseases. (Lewis, 432) Most yeast genes have only one “exon.” On average each (human) gene has about 9 exons. (Batista, 69) Also referred to as ‘baker’s yeast.’

Genetically Modified Organism: organism whose genome has been changed by a genetic engineering technique. (MeSH) An organism whose genetic characteristics have been altered by any of the techniques of "genetic engineering." (NCIt) Plants, animals or microorganisms that have been genetically altered by means other than conventional breeding, usually by the introduction of a gene from another species. (Lawrence)

Genetically Modified Crops: commercial varieties of crop plants such as maize, sugar-beet, cotton and soybean that have been produced by genetic engineering rather than conventional crop breeding. (Lawrence)

Germ(s): any microorganism, especially one that causes disease. (OxfordMed)

Host: an animal or plant on or in which a parasite lives. (Oxford) Any organism in which another organism spends part or all of its life, and from which it derives nourishment or gets protection. (Lawrence) An organism that nourishes and supports another but does not benefit by the association. (Also), a recipient of transplanted tissue or organ from a donor. (NCIt)

Microorganisms: an organism too small to be seen except with the aid of a microscope. (Oxford) Microorganisms include bacteria, protozoa, algae, and fungi. Although viruses are not considered living organisms, they are sometimes classified as microorganisms. (NCI1) Editor’s note - includes “viruses.”  Also referred to as ‘microbes.’

Archaea: unicellular organisms that are less common than bacteria. Some live in extreme environments such as hot springs. (Booker, 9) Single-celled organisms lacking nuclei, similar to prokaryotes in most aspects of cell structure and metabolism. However, their genetic transcription and translation do not show the typical bacterial features, but are extremely similar to those of eukaryotes. (NCIt) They are characterized by the presence of characteristic "tRNAs" and "ribosomal RNAs," the absence of cell walls, and their occurrence in unusual habitats. While archaea resemble bacteria in morphology and genomic organization, they resemble eukarya in their method of (DNA replication). (MeSH)

Methanococcus Jannaschii: single-celled organism (that) lives in hydrothermal vents where hot mineral-rich liquid billows out of the deep seabed. In these hellish conditions the cells withstand crushing pressures of 3,700 pounds and temperatures of around 185 degrees Fahrenheit (85 degrees centigrade). Generates its cellular energy by converting “carbon dioxide” into "methane." (When sequenced by J. Craig Venter), almost 60% of its genes were new to science and of unknown function. (Venter, 55-56)

Protozoa: a group of microscopic single-celled organisms. Most protozoa are free-living but some are important disease-causing parasites of humans. (OxfordMed) Group of... non-photosynthetic, aquatic, unicellular eukaryotes. (Lawrence) Eukaryotes from the “kingdom protista.” (NCIt)

Multicellular Organisms: a single organism composed of more than one cell. Multicellular organisms came into being approximately 1 billion years ago. (Brooker, 191) Eukaryotic organisms (e.g. plants and animals) consisting of large numbers of cells specialized for different functions and organized into a cooperative structure. (Lawrence)

Organic: of, pertaining to, or derived from a living organism; having the characteristics of a living organism. Of, pertaining to, or designating carbon compounds. (Oxford) A substance relating to or containing elemental carbon or carbon compounds. (NCIt)

Parasite: any living thing that lives in another living organism. Some parasites cause irritation and interfere with bodily functions, others destroy host tissues and release "toxins" into the body. Human parasites include fungi, bacteria, "viruses," protozoa, and worms. (OxfordMed) An animal or plant that gets nutrients by living on or in an organism of another species. A 'complete parasite' gets all of its nutrients from the host organism, but a 'semi-parasite' gets only some of its nutrients from the host. (NCI1) Invertebrate organisms that live on or in another organism (the host), and benefit at the expense of the other. Traditionally excluded from definition of parasites are pathogenic bacteria; fungi; viruses; and plants; though they may live (like parasites). (MeSH) Adjective - ‘parasitic.’

Plant: a living organism, other than an animal, able to subsist wholly on inorganic substances, and moving chiefly by growth. (Oxford) Plants share the following features: cells have cell walls, of which the main component is "cellulose," they are photosynthetic and their "chlorophyll" is found in special "organelles" known as 'chloroplasts.' (Indge, 210)

Plastids: a general name given to organelles found in plant cells, which are bound by two membranes and contain DNA and large amounts of chlorophyll, “carotenoids,” or “starch.” (Brooker, G-28)

Prokaryotes: simple organisms without nuclei in their cells. Includes bacteria. (Indge, 153) Organisms without a cell nucleus or any other membrane-bound organelles. Most prokaryotes are bacteria but the group includes both the bacteria and the archaea. Eukaryota, Bacteria, and Archaea are now considered the top nodes of a three-domain “taxonomy” system. (NCIt) Adjective - ‘prokaryotic.’

Transgenic: experimental organism whose genome has been altered by the transfer of a gene or genes from another species or breed. (NCIt) One or more "DNA sequences" from another species have been introduced by artificial means. Animals usually are made transgenic by having a small sequence of foreign DNA injected into a fertilized egg or developing embryo. Transgenic plants can be made by introducing foreign DNA into a variety of different tissues. (NHGRI) An experimentally produced organism in which DNA has been... incorporated into the organism's germ line. (HGPIA

Unicellular Organisms: organisms composed of one cell. (Brooker, 3)