Unit 5-6

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Prokaryotes

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An organism of the kingdom Monera (or Prokaryotae), comprising the bacteria and cyanobacteria, characterized by the absence of a distinct, membrane-bound nucleus or membrane-bound organelles, and by DNA that is not organized into chromosomes.

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bacteria

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ubiquitous one-celled organisms, spherical, spiral, or rod-shaped and appearing singly or in chains, comprising the Schizomycota, a phylum of the kingdom Monera

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spirochetes

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Any of various slender, spiral, motile bacteria of the order Spirochaetales, many of which are pathogenic, causing syphilis, relapsing fever, yaws, and other diseases.

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cyanobacteria

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a widely distributed group of predominantly photosynthetic prokaryotic organisms of the subkingdom Cyanophyta, resembling phototrophic bacteria, occurring singly or in colonies in diverse habitats: some species can fix atmospheric nitrogen.

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autotrophs

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An organism capable of synthesizing its own food from inorganic substances, using light or chemical energy. Green plants, algae, and certain bacteria are autotrophs.

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extremophiles

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An organism adapted to living in conditions of extreme temperature, pressure, or chemical concentration, as in highly acidic or salty environments.

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thermophiles

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Requiring high temperatures for normal development, as certain bacteria.

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halophiles

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An organism that requires a salty environment

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methanogens

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Any of various archaea that are capable of producing methane from the decomposition of organic material.

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Protists

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Any of a group of eukaryotic organisms belonging to the kingdom Protista according to some widely used modern taxonomic systems. The protists include a variety of unicellular, coenocytic, colonial, and multicellular organisms, such as the protozoans, slime molds, brown algae, and red algae.

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Algae

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any of numerous groups of chlorophyll-containing, mainly aquatic eukaryotic organisms ranging from microscopic single-celled forms to multicellular forms 100 ft. (30 m) or more long, distinguished from plants by the absence of true roots, stems, and leaves and by a lack of nonreproductive cells in the reproductive structures

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dinoflagellates

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Any of numerous minute, chiefly marine protozoans of the order Dinoflagellata, characteristically having two flagella and a cellulose covering and forming one of the chief constituents of plankton. They include bioluminescent forms and forms that produce red tide.

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ciliates

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Any of various protozoans of the class Ciliata, characterized by numerous cilia.

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diatoms

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Any of various microscopic one-celled or colonial algae of the class Bacillariophyceae, having cell walls of silica consisting of two interlocking symmetrical valves.

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bryophytes

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A plant of the Bryophyta, a division of photosynthetic, chiefly terrestrial, nonvascular plants, including the mosses, liverworts, and hornworts.

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Gymnosperm

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a vascular plant having seeds that are not enclosed in an ovary; a conifer or cycad.

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angiosperm

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a plant having its seeds enclosed in an ovary; a flowering plant.

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monocot

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a monocotyledon.

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dicot

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A flowering plant with two embryonic seed leaves or cotyledons that usually appear at germination.

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Cnidaria

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an alternative name for the invertebrate phylum Coelenterata, giving emphasis to the stinging structures as characteristic of the phylum.

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Deuterostomes

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Any of a major group of animals defined by its embryonic development, in which the first opening in the embryo becomes the anus. At this stage in their development, the later specialized function of any given embryonic cell has not yet been determined. Deuterostomes are one of the two groups of animals that have true body cavities (coeloms), and are believed to share a common ancestor. They include the echinoderms, chaetognaths, hemichordates, and chordates.

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parenchyma

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Botany. the fundamental tissue of plants, composed of thin-walled cells able to divide.

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collenchyma

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a layer of modified tissue consisting of cells that are thickened at the angles and usually elongated.

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sclerenchyma

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supporting or protective tissue composed of thickened, dry, and hardened cells.

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Xylem

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a compound tissue in vascular plants that helps provide support and that conducts water and nutrients upward from the roots, consisting of tracheids, vessels, parenchyma cells, and woody fibers.

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tracheids

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An elongated, water-conducting cell in xylem, one of the two kinds of tracheary elements. Tracheids have pits where the cell wall is modified into a thin membrane, across which water flows from tracheid to tracheid. The cells die when mature, leaving only their lignified cell walls. Tracheids are found in all vascular plants

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transpiration

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the passage of water through a plant from the roots through the vascular system to the atmosphere.

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Phloem

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the part of a vascular bundle consisting of sieve tubes, companion cells, parenchyma, and fibers and forming the food-conducting tissue of a plant.

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plasmodesmata

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any of many minute strands of cytoplasm that extend through plant cell walls and connect adjoining cells.

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meristem

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embryonic tissue in plants; undifferentiated, growing, actively dividing cells.

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apical

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of, at, or forming the apex.

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meristems

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The undifferentiated plant tissue from which new cells are formed, as that at the tip of a stem or root.

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cork cambium

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A lateral ring of meristematic tissue found in woody seed plants, producing cork on the outside of the ring and parenchyma on the inside of the ring. Also called phellogen.

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periderm

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the cork-producing tissue of stems together with the cork layers and other tissues derived from it.

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Cortex

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the portion of a stem between the epidermis and the vascular tissue; bark.

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palisade

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the upper layer of ground tissue in a leaf, consisting of elongated cells beneath and perpendicular to the upper epidermis and constituting the primary area of photosynthesis.

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auxin

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a class of substances that in minute amounts regulate or modify the growth of plants, esp. root formation, bud growth, and fruit and leaf drop.

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gibberellins

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Any of several plant hormones, such as gibberellic acid, used to promote stem elongation.

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cytokinins

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Any of a class of plant hormones that promote cell division and growth and delay the senescence of leaves.

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ethylene

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a flammable colorless gaseous alkene; obtained from petroleum and natural gas and used in manufacturing many other chemicals; sometimes used as an anesthetic

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abscisic acid

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a growth-regulating plant hormone, C15H20O4, that promotes dormancy and the aging and abscission of leaves.

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multicellular sporophyte

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the form of a plant in the alternation of generations that produces asexual spores.

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sepals

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One of the separate, usually green parts forming the calyx of a flower.

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cotyledons

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A leaf of the embryo of a seed plant, which upon germination either remains in the seed or emerges, enlarges, and becomes green.

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hypocotyl

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the part of a plant embryo directly below the cotyledons, forming a connection with the radicle.

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radicle

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the lower part of the axis of an embryo; the primary root.

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auxin

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a class of substances that in minute amounts regulate or modify the growth of plants, esp. root formation, bud growth, and fruit and leaf drop.

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statolith

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an inclusion, as a starch grain, that by a change in position within the cells of an organ or part is assumed to cause a corresponding change in position of the organ or part.

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Thigmotropism

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oriented growth of an organism in response to mechanical contact, as a plant tendril coiling around a string support.

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Photoperiodism

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the response, as affecting growth or reproduction, of an organism to the length of exposure to light in a 24-hour period.

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Phototropism

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phototropic tendency or growth.

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circadian rhythm

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A daily rhythmic activity cycle, based on 24-hour intervals, that is exhibited by many organisms.

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florigen

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A plant hormone that promotes flowering.

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Embryo

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the rudimentary plant usually contained in the seed.