Biology (Protist,fungi,etc)

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Stromatolite
(stroh–mat’–oh–lite)

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A columnlike rock that consists of many minute layers of prokaryotic cells, usually cyanobacteria.

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Serial Endosymbiosis

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The hypothesis that certain organelles such as mitochondria and chloroplasts originated as symbiotic prokaryotes that lived inside other, free–living prokaryotic cells.

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RNA World

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A model that proposes that during the evolution of cells, RNA was the first informational molecule to evolve, followed at a later time by proteins and DNA

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ribozyme
(ry’–boh–zime)

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A molecule of RNA that has catalytic properties.

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Protobionts
(pro”–toh–by’–ontz)

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Assemblages of organic polymers that spontaneously form under certain conditions. Protobionts may have been involved in chemical evolution.

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Proterozoic Eon

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The period of Earth’s history that began approximately 2.5 billion years ago and ended 542 million years ago; marked by the accumulation of oxygen and the appearance of the first multicellular eukaryotic life–forms.

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Prebiotic Soup Hypothesis

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The hypothesis that simple organic molecules that are the precursors of life originated and accumulated at Earth’s surface, in shallow seas or on rock or clay surfaces. Compare with iron–sulfur world hypothesis.

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Preadaptation

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A novel evolutionary change in a pre–existing biological structure that enables it to have a different function; feathers, which evolved from reptilian scales, represent a preadaptation for flight.

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Photosynthesis

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The biological process that captures light energy and transforms it into the chemical energy of organic molecules (e.g., carbohydrates), which are manufactured from carbon dioxide and water.

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Period

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An interval of geologic time that is a subdivision of an era; each period is divided into epochs

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Paleozoic era

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That part of geologic time extending from roughly 542 million to 251 million years ago.

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Ozone

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A blue gas, O3, with a distinctive odor that is a human–made pollutant near Earth’s surface (in the troposphere) but a natural and essential component of the stratosphere.

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Microsphere

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A protobiont produced by adding water to abiotically formed polypeptides

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Microfossils

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Ancient traces (fossils) of microscopic life

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Metabolism First Hypothesis

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An explanation of the origin of life, in which life began as a self–sustaining, organized system consisting of chemical reactions between simple molecules enclosed within a boundary.

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Mesozoic era

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That part of geologic time extending from roughly 251 million to 66 million years ago.

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Mass Extinction

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The extinction of numerous species during a relatively short period of geologic time. Compare with background extinction.

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Iron–Sulfur World Hypothesis

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The hypothesis that simple organic molecules that are the precursors of life originated at hydrothermal vents in the deep–ocean floor. Compare with prebiotic soup hypothesis.

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Index Fossils

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Fossils restricted to a narrow period of geologic time and found in the same sedimentary layers in different geographic areas.

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In Vitro Evolution

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Test tube experiments that demonstrate that RNA molecules in the RNA world could have catalyzed the many different chemical reactions needed for life. Also called directed evolution.

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Heterotroph
(het’–ur–oh–trof)

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An organism that cannot synthesize its own food from inorganic raw materials and therefore must obtain energy and body–building materials from other organisms. Also called consumer. Compare with autotroph. See chemoheterotroph and photoheterotroph.

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Era

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An interval of geologic time that is a subdivision of an eon; eras are divided into periods.

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Epoch

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The smallest unit of geologic time; a subdivision of a period.

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Eon

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The largest division of the geologic time scale; eons are divided into eras.

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Endosymbiont
(en”–doe–sim’–bee–ont)

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An organism that lives inside the body of another kind of organism. Endosymbionts may benefit their host (mutualism) or harm their host (parasitism).

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Cyanobacteria
(sy–an”–oh–bak–teer’–ee–uh)

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Prokaryotic photosynthetic microorganisms that possess chlorophyll and produce oxygen during photosynthesis.

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Chemical Evolution

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The origin of life from nonliving matter.

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Cenozoic era

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A geologic era that began about 66 million years ago and extends to the present.

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Cambrian Radiation

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A span of 40 million years, beginning about 542 mya, during which many new animal groups appeared in the fossil record.

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Autotroph
(aw’–toh–trof)

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An organism that synthesizes complex organic compounds from simple inorganic raw materials; also called producer or primary producer. Compare with heterotroph. See chemoautotroph and photoautotroph

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Archaean eon

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The period of Earth’s history from its beginnings approximately 4.6 billion up to 2.5 billion years ago; life originated during the Archaean.

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Anaerobic
(an”–air–oh’–bik)

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Growing or metabolizing in the absence of molecular oxygen. Compare with aerobic

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Anaerobe

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Organism that can grow or metabolize in the absence of molecular oxygen. See facultative anaerobe and obligate anaerobe. Compare with aerobe.

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Aerobe

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Organism that grows or metabolizes only in the presence of molecular oxygen. Compare with anaerobe.

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Adaptive Radiation

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The evolution of a large number of related species from an unspecialized ancestral organism.

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Actinopods
(ak–tin’–o–podz)

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Protists characterized by axopods that protrude through pores in their shells. See rhizarians.

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Alternation of Generations

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A type of life cycle characteristic of plants and a few algae and fungi in which they spend part of their life in a multicellular n gametophyte stage and part in a multicellular 2n sporophyte stage

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Alveolates

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Protists that have alveoli, flattened vesicles located just inside the plasma membrane; include the dinoflagellates, apicomplexans, and ciliates. See chromalveolates.

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Alveolus
(al–vee’–o–lus) (pl., alveoli)

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(1) An air sac of the lung through which gas exchange with the blood takes place. (2) Saclike unit of some glands, e.g., mammary glands. (3) One of several flattened vesicles located just inside the plasma membrane in certain protists

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Amoeba
(a–mee’–ba) (pl., amoebas)

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A unicellular protist that moves by means of pseudopodia

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Apicomplexans

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A group of parasitic protists that lack structures for locomotion and that produce sporozoites as infective agents; malaria is caused by an apicomplexan

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Archaeplastids

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A monophyletic supergroup of eukaryotes with chloroplasts bounded by outer and inner membranes; include red algae, green algae, and land plants

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Axopods
(aks’–o–podz)

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Long, filamentous, cytoplasmic projections characteristic of actinopods

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Bikonts

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One of two main clades of all eukaryotes that had a common ancestor with two flagella. Compare with unikonts

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Blade

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(1) The thin, expanded part of a leaf. (2) The flat, leaflike structure of certain multicellular algae.

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Brown Alga

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One of a group of predominantly marine algae that are multicellular and contain the pigments chlorophyll a and c, and carotenoids, including fucoxanthin

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Cell Signaling

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Mechanisms of communication between cells. Cells signal one another with secreted signaling molecules, or a signaling molecule on one cell combines with a receptor on another cell. See signal transduction.

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Cellular Slime Mold

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A group of funguslike protists whose feeding stage consists of unicellular, amoeboid organisms that aggregate to form a pseudoplasmodium during reproduction

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Chromalveolates

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A supergroup composed of diverse protists with few shared characters; most are photosynthetic, and heterotrophic chromalveolates, such as the water molds and ciliates, probably descended from autotrophic ancestors. Divided into two main groups, alveolates and stramenopiles.

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Ciliate
(sil’–e–ate)

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A unicellular protist covered by many short cilia.

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Cilium
(sil’–ee–um) (pl., cilia)

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One of many short, hairlike structures that project from the surface of some eukaryotic cells and are used for locomotion or movement of materials across the cell surface

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Coenocyte
(see’–no–site)

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An organism consisting of a multinucleate cell, i.e., the nuclei are not separated from one another by septa.

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Colony

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An association of loosely connected cells or individuals of the same species.

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Commensalism
(kuh–men’–sul–izm)

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A type of symbiosis in which one organism benefits and the other one is neither harmed nor helped. Compare with mutualism and parasitism.

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Conjugation
(kon”–jew–gay’–shun)

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(1) A sexual process in ciliate protists that involves exchange or fusion of haploid nuclei with another cell. (2) A mechanism for DNA exchange in bacteria that involves cell–to–cell contact

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Diatom
(die’–eh–tom”)

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A usually unicellular alga that is covered by an ornate, siliceous shell consisting of two overlapping halves; an important component of plankton in both marine and fresh waters.

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Dinoflagellate
(dy”–noh–flaj’–eh–late

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A unicellular, biflagellate, typically marine protist that is an important component of plankton; usually photosynthetic.

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Diplomonads

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Small, mostly parasitic zooflagellates with one or two nuclei, no functional mitochondria, and one to four flagella

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Euglenoids
(yoo–glee’–noidz)

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A group of mostly freshwater, flagellate, unicellular algae that move by means of an anterior flagellum and are usually photosyntheti

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Flowing–Water Ecosystem.

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A river or stream ecosystem

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Foraminiferan
(for”–am–in–if’–er–an)

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A marine protist that produces a shell, or test, that encloses an amoeboid body. Also called foram. See rhizarians

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Fucoxanthin
(few”–koh–zan’–thin)

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The brown carotenoid pigment found in brown algae, golden algae, diatoms, and dinoflagellates.

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Gametangium
(gam”–uh–tan’–gee–um)

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Special multicellular or unicellular structure of plants, protists, and fungi in which gametes are formed.

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Golden Alga

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A member of a group of algae, most of which are biflagellate, are unicellular, and contain pigments, including chlorophylls a and c and carotenoids, including fucoxanthin

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Green Alga

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A member of a diverse group of algae that contain the same pigments as plants (chlorophylls a and b and carotenoids)

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Holdfast

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The basal structure for attachment to solid surfaces found in multicellular algae.

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Hypha
(hy’–fah) (pl., hyphae

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One of the threadlike filaments composing the mycelium of a water mold or fungus.

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Hypotrichs

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A group of dorsoventrally flattened ciliates that exhibit an unusual creeping–darting locomotion

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Index Fossils

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Fossils restricted to a narrow period of geologic time and found in the same sedimentary layers in different geographic areas

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Kinetoplastid

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A single mitochondrion with an organized deposit of DNA; characteristic of trypanosomes

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Macronucleus

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A large nucleus found, along with one or several micro nuclei, in ciliates. The macronucleus regulates metabolism and growth. Compare with micronucleus

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Micronucleus

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One or more smaller nuclei found, along with the macronucleus, in ciliates. The micronucleus is involved in sexual reproduction. Compare with macronucleus

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Monophyletic Group
(mon”–oh–fye–let’–ik)

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A group of organisms that includes a recent common ancestor and all its descendants; a clade. Compare with polyphyletic group and paraphyletic group.

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Mutualism

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In ecology, a symbiotic relationship in which both partners benefit from the association. Compare with parasitism and commensalism.

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Mycelium
(my–seel’–ee–um) (pl., mycelia)

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The vegetative body of most fungi and certain protists (water molds); consists of a branched network of hyphae

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Nanoplankton

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Extremely minute (<10 μm in length) algae that are major producers in the ocean because of their great abundance; part of phytoplankton

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Oospore

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A thick–walled, resistant spore formed from a zygote during sexual reproduction in water molds.

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Parabasilids

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Anaerobic, flagellated excavates that often live in animals; examples include trichonymphs and trichomonads

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Paraphyletic Group

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A group of organisms made up of a common ancestor and some, but not all, of its descendants. Compare with monophyletic group and polyphyletic group

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Parasitism
(par’–uh–si–tiz”–m)

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A symbiotic relationship in which one member (the parasite) benefits and the other (the host) is adversely affected. Compare with commensalism and mutualism

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Pellicle

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A flexible outer covering consisting of protein; characteristic of certain protists, e.g., ciliates and euglenoids

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Phagocytosis
(fag”–oh–sy–toh’–sis)

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Literally, “cell eating”; a type of endocytosis by which certain cells engulf food particles, microorganisms, foreign matter, or other cells.

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Phycocyanin
(fy”–koh–sy–ah’–nin)

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A blue pigment found in cyanobacteria and red algae.

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Phycoerythrin
(fy”–koh–ee–rih’–thrin)

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A red pigment found in cyano bacteria and red algae

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Plankton

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Free–floating, mainly microscopic aquatic organisms found in the upper layers of the water; consisting of phytoplankton and zooplankton. Compare with nekton.

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Plasmodial Slime Mold
(plaz–moh’–dee–uhl)

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A funguslike protist whose feeding stage consists of a plasmodium.

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Plasmodium
(plaz–moh’–dee–um)

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A multinucleate mass of living matter that moves and feeds in an amoeboid fashion.

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Protist
(pro’–tist)

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One of a vast informal group of eukaryotic organisms, primarily unicellular or simple multicellular; mostly aquatic

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Pseudopodium
(sue”–doe–poe’–dee–um) (pl., pseudopodia)

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A temporary extension of an amoeboid cell that is used for feeding and locomotion.

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Radiolarians

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Those actinopods that secrete elaborate shells of silica (glass)

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Red Alga

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A member of a diverse group of algae that contain the pigments chlorophyll a, carotenoids, phycocyanin, and phycoerythrin.

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Red Tide

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A red or brown coloration of ocean water caused by a population explosion, or bloom, of dinoflagellates

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Rhizarians

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A diverse supergroup of amoeboid cells that often have hard outer shells, called tests, through which cytoplasmic projections extend; include forams, actinopods, and certain shell–less amoebas

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Serial Endosymbiosis

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The hypothesis that certain organelles such as mitochondria and chloroplasts originated as symbiotic prokaryotes that lived inside other, free–living prokaryotic cells.

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Sessile
(ses’–sile)

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Permanently attached to one location, e.g., coral animals.

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Sporangium
(spor–an’–jee–um) (pl., sporangia)

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A spore case, found in plants, certain protists, and fungi

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Sporozoite

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The infective sporelike state in apicomplexans

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Stipe

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A short stalk or stemlike structure that is a part of the body of certain multicellular algae.

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Stramenopiles

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Protists that have motile cells with two flagella, one of which has tiny hairlike projections off the shaft; include water molds, diatoms, golden algae, and brown algae. See chromalveolates.

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Test

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A shell

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Triple–Gene Fusion

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The fusion of three separate genes into a single unit early in the course of eukaryote evolution; provides evidence of a bifurcation; characteristic of unikonts.

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Ultrastructure

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The fine detail of a cell, generally only observable by use of an electron microscope.

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Unikonts

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One of two main clades of all eukaryotes that had a common ancestor with a single posterior flagellum. Compare with bikonts.

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Water Mold

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A funguslike protist with a body consisting of a coenocytic mycelium that reproduces asexually by forming motile zoospores and sexually by forming oospores.

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Zoospore
(zoh’–oh–spore

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A flagellated motile spore produced asexually by chytrids, certain algae, water molds, and other protists.

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zooxanthellae
(zoh”–oh–zan–thel’–ee) (sing., zooxanthella)

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Endosymbiotic, photosynthetic dinoflagellates found in certain marine invertebrates; their mutualistic relationship with corals enhances the corals’ reef–building ability

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Zygosporangium
(zy”–gah–spor–an’–gee–um)

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A thick–walled sporangium containing a zygospore.