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| deoxyribonucleic acid: an extremely long macromolecule that is the main component of chromosomes and is the material that transfers genetic characteristics in all life forms, constructed of two nucleotide strands coiled around each other in a ladderlike arrangement with the sidepieces composed of alternating phosphate and deoxyribose units and the rungs composed of the purine and pyrimidine bases adenine, guanine, cytosine, and thymine: the genetic information of DNA is encoded in the sequence of the bases and is transcribed as the strands unwind and replicate. |
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| a variable retrovirus that invades and inactivates helper T cells of the immune system and is a cause of AIDS |
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| a T cell that participates in an immune response by recognizing a foreign antigen and secreting lymphokines to activate T cell and B cell proliferation |
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| a cell with a true nucleus; a cell with a nuclear membrane and organelles; cf. prokaryotic cell |
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a cell lacking a true membrane-bound nucleus; cf. {eukaryotic cell}
Example: Bacteria |
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| the chain from a food source to the ultimate consumer. |
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| a series of organisms related by predator-prey and consumer-resource interactions; the entirety of interrelated food chains in an ecological community. |
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| a complex biotic community characterized by distinctive plant and animal species and maintained under the climatic conditions of the region, especially such a community that has developed to climax. |
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| an atmospheric heating phenomenon, caused by short-wave solar radiation being readily transmitted inward through the earth's atmosphere but longer-wavelength heat radiation less readily transmitted outward, owing to its absorption by atmospheric carbon dioxide, water vapor, methane, and other gases; thus, the rising level of carbon dioxide is viewed with concern. |
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| an organism, usually a bacterium or fungus, that breaks down the cells of dead plants and animals into simpler substances. |
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| a type of relationship between two species of a plant, animal, fungus, etc., in which one lives with, on, or in another without damage to either. |
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| a relationship between two species of organisms in which both benefit from the association. |
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| a relation between organisms in which one lives as a parasite on another. |
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| diversity among and within plant and animal species in an environment. |
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| (especially in plants) the synthesis of complex organic materials, especially carbohydrates, from carbon dioxide, water, and inorganic salts, using sunlight as the source of energy and with the aid of chlorophyll and associated pigments. |
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| any organism capable of self-nourishment by using inorganic materials as a source of nutrients and using photosynthesis or chemosynthesis as a source of energy, as most plants and certain bacteria and protists. |
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| an organism requiring organic compounds for its principal source of food. |
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| a person or thing that consumes. |
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| any process of formation or growth; development: the evolution of a language; the evolution of the airplane. |
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| Homologous structures are body parts that are alike because the species in question share a common ancestor. These structures may serve the same or different functions. |
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| A structure in an organism that has lost all or most of its original function in the course of evolution, such as human appendixes. |
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| a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. |
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| the organ system that protects the body from damage, comprising the skin and its appendages(including hair, scales, feathers, and nails). |
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| the usual method of cell division, characterized typically by the resolving of the chromatin of the nucleus into a threadlike form, which condenses into chromosomes, each of which separates longitudinally into two parts, one part of each chromosome being retained in each of two new cells resulting from the original cell. |
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| part of the process of gamete formation, consisting of chromosome conjugation and two cell divisions, in the course of which the diploid chromosome number becomes reduced to the haploid. Compare mitosis |
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| a malignant and invasive growth or tumor, especially one originating in epithelium, tending to recur after excision and to metastasize to other sites |
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| the offspring of two animals or plants of different breeds, varieties, species, or genera, especially as produced through human manipulation for specific genetic characteristics. |
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| a mature sexual reproductive cell, as a sperm or egg, that unites with another cell to form a new organism. |
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| Adenine and guanine are also known as purine bases; cytosine and thymine are also called pyrimidine bases. Each deoxyribonucleotide will contain one of these four bases. |
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| a triplet of adjacent nucleotides in the messenger RNA chain that codes for a specific amino acid in the synthesis of a protein molecule. |
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| any of a class of organic compounds that contains at least one amino group, –NH 2 , and one carboxyl group, –COOH: the alpha-amino acids, RCH(NH 2 )COOH, are the building blocks from which proteins are constructed. |
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| the final shape and other properties of each protein being determined by the side chains of the amino acids and their chemical attachments |
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| a sudden departure from the parent type in one or more heritable characteristics, caused by a change in a gene or a chromosome |
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| Human intervention in animal or plant reproduction to ensure certain characteristics are represented in successive generations. |
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| the process by which forms of life having traits that better enable them to adapt to specific environmental pressures, as predators, changes in climate, or competition for food or mates, will tend to survive and reproduce in greater numbers than others of their kind, thus ensuring the perpetuation of those favorable traits in succeeding generations. |
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| English naturalist who formulated the theory of evolution by natural selection, expounded in On the Origin of Species |
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