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Glossary of Terminology: G

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Number of records found : 181


G1 - phase in the cell cycle between the completion of cell division and the initiation of DNA synthesis

G2 - phase in the cell cycle between the completion of DNA synthesis and the next cell division

Gaia theory - a model in which the organisms on the Earth have radically altered its composition. A stronger position is that the Earth's biosphere effectively acts as if it is a self-organizing system, which works in such a way as to keep its systems in some kind of equilibrium that is conducive to life

gale - a storm with wind speeds between 34 to 40 knots

galeiform - helmet-shaped

gall - an abnormal outgrowth caused by infection or irritation by certain fungi or bacteria

game species - species of animals that are hunted or fished, for purposes of sport, recreation, and food capture

gamefish - a species of fish considered to possess sporting qualities on fishing tackle

gamete - a sex cell, e.g., a spermatozoan or egg cell, produced by sexually reproducing orgnaisms

gamete bundle - in coral sexual reproduction, the polyps of many species release bundles of eggs and sperm cells, called gamete bundles, that float to the sea surface. The layers surrounding the egg and sperm bundles soon rupture, releasing the gametes at the surface, where fertilization occurs

gametocyte - a reproductive cell capable of dividing by meiosis to produce gametes, e.g., a spermatocyte or oocyte

gametogenesis - the development and maturation of gametes (sex cells) through meiosis. The process is termed 'spermatogenesis' in the development of sperm cells and 'oogenesis' in the development of egg cells

gametophyte - a life cycle stage in certain algae that produces male and female reproductive organs

gamma ray - an electromagnetic wave or photon emitted from the nucleus

gamodeme - a deme forming a more or less isolated local intrabreeding community

ganglion - a structure containing an aggregation of cell bodies of nerve cells (neurons)

gap analysis - a Geographic Information System (GIS) methodology to identify the distribution of biodiversity over large spatial areas. It was developed in 1988 by the U.S. Geological Survey in an effort to ensure that regions rich in species diversity are conserved with the hope that this will eliminate the need to list species as threatened or endangered in the future. The gap analysis approach uses maps of vegetation and predicted animal distributions to locate centers of species richness outside areas currently managed for biodiversity protection. These are considered the "gaps" of gap analysis. Thus far, its use primarily has been in the terrestrial sphere

gap phases - the phases of the cell cycle known as G1 and G2, during which relatively less obvious cellular activity is visible

garden eel - a family of eels (Heterocongridae) that occur in colonies in the sandy bottoms adjacent to coral reefs, where they live individually in burrows from which they protrude to feed on plankton. From a distance these eels resemble a field of seagrass. They are very shy and disappear into their burrows at the approach of a potential predator

gas chromatograph/mass spectrometer (GC/MS) - an instrument that identifies the molecular composition and concentrations of various chemicals in water and soil samples

gas chromatography - a method of separating chemical components of a mixture, which involves the passage of a gaseous sample through a column having a fixed adsorbent phase

gas laws - laws that predict how gases will behave with changes in temperature, pressure, and volume

gastric - pertaining to the stomach

gastric filaments - in scyphozoan medusae, a fringe of short, threadlike filaments whose secretory cells secrete digestive enzymes. They are located on the floor of each gastric pouch

Image of gastric mill of tanner crab

Gastric mill and teeth within the stomach of a grooved tanner crab (Chionoecetes tanneri). (Photo: NOAA)


gastric mill - the grinding apparatus in the cardiac stomach of crustaceans. It is formed by three chitinous teeth that project into the stomach; the thick-walled muscular pouch below the crop in many birds and reptiles, used for grinding food

Image of gastric pouch of jellyfish

Gastric pouch region of the jellyfish, Aurelia. The horseshoe-shaped structure is a gonad. (Photo: John Houseman, BIODIDAC)


gastric pouch - in scyphozoans (jellyfish), one of four sacs is which food in digested. Each pouch contains a conspicuous horseshoe-shaped gonad on its floor

gastrodermis - the epithelial lining of the gastrovascular (digestive) cavity of cnidarians and ctenophores (comb jellies)

gastrolith - A deposit of calcium salts made in the stomach of many crustaceans during the period between molts. It may be used to store calcium needed in the new exoskeleton

Image of a sea slug (Gastropoda)

A sea slug of the Class Gastropoda, Phylum Mollusca.


Gastropoda - a class of the phylum Mollusca that includes snails, sea slugs, nudibranchs, limpets, and cone shells. There are approximately 30,000 living species described. Many species are inhabitants of coral reefs and nearby seagrass beds

gastrovascular canal - a series of tubes that connect the gastrovascular cavities of colonial coral polyps

gastrovascular cavity - the internal digestive cavity of cnidarians and ctenophores that is lined with the gastrodermis

gastrozooid - a polyp in hydrozoans and other colonial cnidarians which is specialized for feeding

Image of a gastrula

An echinoderm gastrula. It was formed by the invagination of blastomeres at the vegetal pole area of the blastula to produce the archenteron, which will become the digestive system.The opening into the archenteron is the blastopore, which will become the anus of the adult. The cavity of the archenteron is the gastrocoel. The roof of the archenteron, which forms the mesoderm, will expand and pinch off mesodermal vessicles with an internal cavity that will become the coelom (see: mesoderm). A - ectoderm; B - blastocoel; C - archenteron; D - endoderm; E - blastopore. (Photo: Dr. Anna E. Ross, Christian Brothers University, TN)


gastrula - the embryonic stage of an animal that has cells differentiated into germ layers. Sequentially, It follows the blastula stage

Image of early gastrula

An early gastrula. The cells at the vegetal hemisphere have begun to invaginate into the blastocoel, forming the archenteron. (Photo: Dr. Anna E. Ross, Christian Brothers University, TN)


gastrulation - during embryonic development of most animals, a complex and coordinated series of cellular movements occurs at the end of cleavage. The details of these movements vary among species, but usually result in the formation of of an embryonic stage termed the gastrula. The gastrula has two primary germ layers, the ectoderm and endoderm in diploblastic animals, and three primary germ layers with the development of the mesoderm in triploblastic animals

Gause's principle - the principle that "no two species can coexist indefinitely on the same limiting resource." Also called Gause's Law, or the 'competitive exclusion principle'

gb (gigabase pairs) - one billion (109) pairs of nucleotide bases in DNA

gel - a jelly-like substance formed by the coagulation of a colloidal liquid; a cytoplasmic phase

gel electrophoresis - a process for separating molecules by forcing them to migrate through a gel under the influence of an electric field

geminate species - a little differentiated species evolved from a close common ancestor; a "twin" species. For example, pairs on either side of the Isthmus of Panama who are each other's closest relative and were probably one species before the sea level dropped

Image of sponge gemmule

A sponge gemmule. Calcareous spicules projecting from the covering of the gemmule provide additional protection. (Photo credit: Rick Gillis, Ph.D., Biology Dept., University of Wisconsin-La Crosse)


gemmule - an asexual, spore-like reproductive unit in sponges, capable of overwintering and developing into an adult sponge the following summer

gen. et sp. nov. - in taxonomy, the abbreviation for genus et species nova, meaning new genus and species

Genbank - a database of nucleotide sequences

gene - the functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein

gene array - a regular pattern of DNA fragments, or oligonucleotides, spotted onto a solid support and used as a diagnostic tool to measure many individual gene expression levels simultaneously

gene expression - the conversion of information from gene to protein via transcription and translation

gene flow - the movement of genes through or between populations as the result of out-crossing and natural selection

gene frequency - the relative occurrence of a gene in a given population, usually expressed as a percentage

gene index - a listing of the number, type, label and sequence of all the genes identified within the genome of a given organism

gene locus - the specific place on a chromosome where a gene is located

gene mapping - determination of the relative locations of genes on a chromosome

gene pool - the sum total of genes, with all their variations, possessed by a particular species at a particular time

gene product - the product, either RNA or protein, that results from expression of a gene. The amount of gene product reflects the activity of the gene

gene silencing - the interruption or suppression of the expression of a gene at the levels of transcription or translation

gene splicing - a cell process by which a gene is cut into different parts, exons and introns. The exons are the coding region and are put back together to make the gene that is transcribed and translated into a protein

gene therapy - an approach to preventing and/or treating disease by replacing, removing or introducing genes or otherwise manipulating genetic material. In some cases, the material can be injected with a genetic vaccination. In other cases the material is introduced through harmless bioengineered viruses that carry the therapeutic gene to the cell. Globules known as liposomes can also be used to carry therapeutic genes to specific cells

gene-based medicine - instead of solely replacing defective genes, gene-based medicine is the application of nucleic acids (DNA, RNA) containing genetic information as therapeutic reagents in general. Nucleic acids are used to add a therapeutically beneficial function to cells, delete pathological functions from cells, or utilize cells for the production of therapeutic proteins. This can be either a transient or a permanent effect

genecology - the study of the genetic basis of ecological differentiation; the study of the genetic composition of populations in relation to their habitats

generalist - an organism which can survive under a wide variety of environmental conditions, and does not specialize to exist under any particular set of circumstances

generation - offspring from the same parental group going through their life cycle together

generation time - the average amount of time between the appearances of two successive generations (parent and offspring)

genet - In corals, the genetic individual that results from a single planula. For clonal corals, e.g., Acropora, a genet often includes numerous asexually-produced individuals (ramets)

genetic code - the chemical code by which genetic information in DNA is translated into biological function. A set of three nucleotides (codons), the building blocks of DNA, signifies one amino acid. Amino acids are the the building blocks of proteins

genetic disease - a disease that has its origin in changes to the genetic material. Genetic diseases usually refer to diseases that are inherited in a Mendelian fashion, although non-inherited forms may also result from genic (DNA) mutation

genetic distance - a measure of the genetic similarity between any pair of populations. Such distance may be based on phenotypic traits, allele frequencies or DNA sequences

genetic diversity - the variety of different types of genes or alleles in a species or population

genetic drift - random changes in the frequency of alleles in a population. In small populations, it can lead to the elimination of a particular allele by chance alone. It is thought to be one cause of speciation when a group of organisms is separated from its parent population

genetic engineering - the technique of selectively removing, modifying, or adding genes to a DNA molecule by use of recombinant DNA or other specific molecular gene transfer or exchange techniques. These techniques produce endogenous proteins with properties different from those of the normal, or to produce entirely different proteins altogether. Organisms modified by genetic engineering are sometimes referred to as transgenic, bioengineered, or genetically modified

genetic map position - the location of a gene on a genetic map, deduced from recombination frequencies

genetic marker - a DNA sequence used to "mark" or track a particular location (locus) on a particular chromosome

genetic modification - human-designed changes in an organism, whether done through traditional breeding or genetic engineering. The terms "genetically modified" and "genetically engineered" are sometimes used interchangeably

genetic mutation - a permanent structural alteration in DNA. In most cases, DNA changes either have no effect or cause harm, but occasionally a mutation can improve an organism's chance of surviving and passing the beneficial change on to its descendants

genetic pollution - the accidental tranfer of genetic material from a genetically engineered organism to one that is not genetically engineered

genetic stability - a measure of the resistance to change, with time, of the sequence of genes within a DNA molecule or of the nucleotide sequence within a gene

genetically modified organism - an organism that has been modified by the application of recombinant DNA technology

genital bursa - an invagination at the base of an arm of a brittle star. Each bursa is a pouch lined with ciliated epidermis and is the primary respiratory surface for the organs of the perivisceral coelom. The epidermal cilia generate a ventilating current. The bursae have the gonads on the coelomic side of their wall

genome - all the DNA contained in an organism or a cell, which includes both the chromosomes within the nucleus and the DNA in mitochondria

genome size - the size of a genome (all the genetic material in the chromosomes of a particular organism) is generally given as its total number of base pairs

genomic library - a collection of clones made from a set of randomly generated overlapping DNA fragments that represent the entire genome of an organism

genomics - the comprehensive analysis of all the genes of an organism; molecular characterization of all the genes and gene products of a species, including the study of gene sequences, gene mapping, and gene function; genomics usually involves high speed sequencing of the DNA and computer searches for sequences that code for genes. Genomics allow researchers to identify specific genes responsible for specific proteins with specific functions in an organism

genotype - the genetic constitution of an individual or group. In taxonomy, the genotype is the type species of a genus

genus - a taxonomic group containing one or more species

geo-referenced data - refers to data with geographic location information included, such as latitude and longitude

geochemistry - the study of the chemical elements, their isotopes, and related processes with respect to the abundance and distribution of materials within the Earth's waters, crust, and atmosphere

geoecotype - a regional ecotype (a population adapted to a restricted habitat as a result of natural selection within a local environment)

Geographic Information System (GIS) - a system that allows automatic location of information suitable for mapping. Usually involves a software system that takes geographic position data and other data (e.g., type of bottom sediment) in order to create a map. Data on processes (e.g., current speed) can be incorporated to make a geographic model of flow

geographical isolation - a form of reproductive isolation in which members of a population become separated from another population by geographical barriers that prevent the interchange of genes between the separated populations

geographical speciation - speciation occurring during a period of geographical isolation

geoid - a surface of constant gravitational potential at zero elevation; an imaginary elliptical surface around the earth with constant gravitational potential. The surface of the sea, measured over time and without waves, would be a geoid; the hypothetical surface of the Earth that coincides everywhere with the mean sea level

geologic time scale - a relative time scale based upon fossil content. Geological time is divided into eons, eras, periods, and epochs

geoportal - a web portal used to locate and access geospatial information and associated geographical services via the internet

Image of GOES I/M satellite

Artist+s rendition of GOES I/M, geostationary satellites whose mission includes data collection and broadcasting, and environmental sensing. (Image: NASA/Goddard Space Flight Center)


geostationary satellite - satellite whose orbit around the equator equals that of the Earth's rotation, making it possible for them to view the same disc of Earth's surface below continuously

geostrophic current - a flow that sustains a balance between Coriolis deflection and a pressure gradient

Geotiff - a file format that embeds image registration information directly into a raster file; an industry-neutral raster file format widely used and recognized by all of the major GIS software vendors. ESRI began support for Geotiff at version 7.0 of ARC/INFO and version 3.0 of ArcView. Geotiff represents an effort by over 160 different remote sensing, GIS, cartographic, and surveying related companies and organizations to establish a TIFF-based interchange format for georeferenced raster imagery

germ cell - a reproductive cell; a sperm cell or ovum; a gamete; an oocyte or spermatocyte

germ layers - distinct layers of cells, produced during the early embryonic developmental process of gastrulation, which gives rise to all cells, tissues, organs, and organ systems of the organism's body. The three types of germ layers are the ectoderm, endoderm, and mesoderm. Diploblastic organisms (e.g. cnidarians) have two layers, ectoderm and endoderm; triploblastic organisms (all higher animal groups) have mesoderm between these two layers

germ line - a term used to refer to the cell lineage that contributes to the formation of gametes

germinal epithelium - the tissues of the primary reproductive organs that produce eggs and sperm cells

gestation period - the period of development of the young in viviparous animals, from the time of zygote formation (fertilization) until birth

ghost crab - any of several light-colored burrowing crabs of the genus Ocypoda frequenting the tide line along sandy shores from the northeast United States to Brazil. Ghost Crabs have a relatively thin, light exoskeleton and two large black eyes that stand up like periscopes. They are called ghosts because of their ability to instantly disappear from sight, moving at speeds at speeds up to 10 miles per hour, while making sharp directional change and disappearing into their burrows

ghost net - a lost or abandoned fishing net that drifts through the oceans posing a danger to fishes and other marine life

gibbosity - swelling or protuberance; a convex hump; something that bulges out or is protuberant or projects from a form

giemsa stain - a stain that contains both acidic and basic dyes, used in staining histological sections for identifying acidic and basic cell components, including protozoan parasites

gigabyte (gb) - a measurement of storage space equal to a thousand megabytes

Image of a fish

The gill cover (operculum) of this fish is lifted to expose the gills, which are the respiratory organs of fishes and many other aquatic animals.


gill - a highly vascularized respiratory organ with a large surface area in aquatic animals. Gills are in direct contact with the surrounding water for gas exchange

gill arch - one of several curved bony or cartilaginous structures located on either side of the pharynx that support the gills of fishes and amphibians. Each gill arch is made up of an upper and a lower limb that are joined posteriorly. The gill filaments and gill rakers are attached to the gill arches

gill chamber - in fishes, the cavity containing the gills on each side of the rear of the head, enclosed by the operculum and the branchiostegal membrane

gill filament - a fingerlike projection from a gill arch through which respiratory gases enter and leave the blood

Image of gill net

A fisherman setting out a gill net. (Photo: NOAA)


gill net - a net primarily designed to catch fish by entanglement in a mesh that consists of a single sheet of webbing which hangs between cork line and lead line, and which is fished from the surface of the water

Image of gill arch with gill rakers and filaments

Gill arch of an almaco jack (Seriola rivoliana) showing the gill rakers and gill filaments. (Photo: NOAA)


gill raker - one of a series of knob- or comb-like projections on the front edge of the gill arch. Gill rakers aid in the fish's feeding. Their shape and number are a good indication of the diet of the fish. Fishes which eat large prey, such as other fishes, have short, widely spaced gill rakers that prevent the prey item from escaping between the gills. Fishes which eat smaller prey have longer, thinner and more numerous gill rakers. Species which feed on plankton have the longest, thinnest and most numerous gill rakers. Gill rakers also protect and clean the gill fillaments. Counts of gill rakers are used as taxonomic characters

gill tuft - a fluffy cluster of gill filaments

gladiate - sword-shaped

gland - a group of cells or a single cell in animals or plants that is specialized to secrete a specific substance

glider - a type of autonomous underwater vehicle (AUV) that uses small changes in its buoyancy in conjunction with wings to convert vertical motion to horizontal, and thereby propel itself forward with very low power consumption

Global Biodiversity Information Facility (GBIF) - an international non-profit organization that provides free and universal access to data regarding the world's biodiversity. A wide range of countries and organizations participate in GBIF and have made their data available through the GBIF web site (http://www.gbif.org)

global change - a transformation which occurs on a worldwide scale (for example, an increase in CO2 in the atmosphere) or exhibits sufficient cumulative effects to have worldwide impact (for example, local species extinction resulting in global loss of biodiversity)

Global Coral Reef Monitoring Network (GCRMN) - a global network whose aim is to improve management and sustainable conservation of coral reefs for people by assessing the status and trends in the reefs and how people use and value the resources. It does this by providing many people with the capacity to assess their own resources, within a global network, and to spread the word on reef status and trends

global warming - an increase in temperature that occurs globally

Image of porcupine fish

The porcupine fish, when threatened, swallows water and takes on a globular shape. (Photo: Copyright Corel Corporation)


globular - globe-shaped; having the form of a sphere, or nearly so

glucose - a monosaccharide,C6H12O6, that is the end product of carbohydrate metabolism and is the chief source of energy for living organisms

glutinous - sticky

gnathic - pertaining to the jaw

Gnathostomata - the group of vertebrates that possess jaws; includes fishes, amphibians, reptiles, birds, and mammals

goatfish - any species of bony fishes in the family Mullidae. Goatfishes, also called surmullets, are elongate, moderately sized fishes which are characterized by a pair of long, tactile barbels under the chin. Some species are brilliantly colored and some are noted

goby - any species of bony spiny-rayed fishes in the family gobiidae. Gobies are small fishes with large heads and elongated tapering bodies. They comprise the largest family of marine fishes, with over 2000 species. Gobies range in size from the mudskipper (about 15-30 cm) to the tiny pygmy goby, Eviota sigillata, a 1-2 cm long coral reef-dwelling goby which has the shortest lifespan for any known vertebrate

Image of Hurrican Floyd developed from GOES data

Image developed by NASA from GOES data-Hurricane Floyd at the U.S. coast on September 15, 1999 (Hal Pierce, NASA Goddard Space Flight Center)


GOES (Geostationary Operational Environmental Satellite) - a class of satellite operated by NOAA, positioned in a nearly stationary orbit over the equator at an altitude of about 22,500 miles. GOES-8 is currently the operational "east" spacecraft at 75 degrees West longitude, while GOES-10 is the "west" spacecraft located at 135 degrees West. GOES-11 is in standby at 110 degrees West

gonads - the primary sex organs of an animal. In males they are the testes, and in females, the ovaries

Image of hydrozoan gonangium

A gonangium of the hydrozoan Obelia. 1= medusa bud; 2= perisarc; 3=gonotheca; 4= coenosarc. (Photo: Rick Gillis, Ph.D., Biology Dept., University of Wisconsin-La Crosse)


gonangium - a reproductive polyp of a colonial hydrozoan. It consists of a stalk containing medusa buds surrounded by a thin membrane, the gonotheca

gonochoric - having separate sexes. Individuals within the species contain only one or the other of male and female reproductive systems

gonoduct - any duct that generally transfers eggs or sperm cells

gonophore - a sexual zooid produced as a medusa bud upon a hydroid, sometimes becoming a free hydromedusa and sometimes remaining attached

gonopodium - a term given to the anal fin (or the anterior portion of it) of a male fish when it is modified to function as a copulatory organ, e.g., in guppies

gonopore - an opening between the reproductive system and the outside environment; the genital pore of many invertebrates

gonotheca - a thin membrane covering the body of a gonangium, the reproductive polyp of a colonial hydrozoan

gonozooid - a reproductive polyp of a colonial hydrozoan

Image of sea fan (Gorgonia)

A sea fan, Gorgonia ventalina, in the Florida Keys.


gorgonian - an anthozoan of the subclass Octocorallia, commonly called sea fans and sea whips

gorgonin - a fibrous protein in the mesoglea which provides skeletal support for sea fans and other members of the Order Gorgonacea

Image of portable GPS unit

Portable GPS unit utilized in surveying.


GPS (Global Positioning System) - a network of satellites and receiving devices used to compute accurate geographical positions on the Earth. A GPS is used in navigation, and its precision supports cadastral surveying

gradient analysis - an intuitive method to portray variation along a single or multiple environmental gradients. The plots display species or community abundance in response to a known environmental gradient, i.e., the analysis of species composition along a gradient of environmental conditions

gradualism - a model of evolution that assumes slow, steady rates of change, as contrasted with punctuated equilibrium, an evolutionary model in which change occurs in relatively rapid bursts

Gram's stain - a method for differential staining of bacteria; Gram-positive cells stain purple-black and Gram-negative cells stain pink; useful in bacterial taxonomy and identification

granular gland cell - an epithelial cell that contains lysosomes that are secreted into the gastrovascular cavity of cnidarian polyps for extracellular digestion of food materials

Graphics Interchange Format (GIF) - a bit-mapped digital image graphics file format suitable for efficiently importing image data into computer files or for transmitting or displaying the formatted image on a computer monitor or printing it out. GIF supports color and various resolutions. It also includes data compression, making it especially effective for scanned photos

Image of gravid crab

Gravid green crab with egg mass on the abdomen. (Photo: Gary Weber)


gravid - pregnant; heavy with young; full of ripe eggs or distended by such fullness

Image of Gray

A reef scene showing biodiversity at Gray's Reef. (Photo: NOAA)


Gray's Reef National Marine Sanctuary - Gray's Reef comprises one of the largest nearshore sandstone reefs in the southeastern United States.It is located 32 kilometers (17.5 nautical miles) off Sapelo Island, Georgia. Designated in 1981, the Gray's Reef National Marine Sanctuary boundaries protect 17 square miles of open ocean. Sandstone outcroppings and ledges up to ten feet in height separate the sandy, flat-bottomed troughs in a reef that combines temperate and tropical flora and fauna. The rocky platform, some 60 to 70 feet below the surface, is covered by a carpet of attached organisms and is known locally as a "live bottom habitat." Gray's reef is not a coral reef. It is a consolidation of marine and terrestrial sediments (sand, shell, and mud) which was laid down as loose aggregate between 6 and 2 million years ago

Image of sea urchin

Sea urchins are important grazers on coral reefs. Their diet, however, is not totally restricted to plants and algae.


grazer - an animal which feeds on plants

Great Barrier Reef - the largest complex barrier coral reef in the world, approximately 2,000 km (1,250 mi) long, in the Coral Sea, forming a natural breakwater for the northeastern coast of Australia. It is separated from the mainland by a shallow lagoon from 16–161 km (10 to 100 mi) wide. It is It is composed of more than 2,800 individual reefs and in some places it is more than 122 m (400 ft) thick. The Great Barrier Reef Marine Park, more than 340,000 km2 (130,000 mi2), encompasses most of the reefs and interreef areas as well as the neighboring lagoon and a large section of the continental shelf. It is the largest UNESCO World Heritage Area

Image of green algae

The green alga Caulerpa taxifolia with feather-like branches. The leaf is 5-65 cm in length. (Photo: NOAA)


green algae - green algae belong to the Division Chlorophycota. These algae contain photosynthetic pigments similar to those in higher plants (chlorophylls a and b, as well as secondary pigments: carotenes, lutein, and zeaxanthin) and have a green color. Green algae include unicellular forms, filamentous forms, and leaf-like thalluses.

green carbon - carbon stored in the Earth's forests and their soils

greenhouse effect - the heating that occurs when gases such as carbon dioxide trap heat escaping from the Earth and radiate it back to the surface

greenhouse gases - atmospheric gases, primarily carbon dioxide, methane, and nitrous oxide restricting some heat-energy from escaping directly back into space

gregarious - living or moving in a group with others of its kind, as in a flock of birds or school of fish

Grenada Bank - an archipelago of over 30 islands and cays extending from Grenada to St. Vincent. The Grenada Bank supports the most extensive coral reefs and related habitats in the southeastern Caribbean

grid - a network of uniformly spaced parallel lines intersecting at right angles. When superimposed on a map, it usually carries the name of the projection used for the map. For example: Lambert grid, transverse Mercator grid, and universal transverse Mercator grid

griseous - blue-grey color

groin - a solid structure built at an angle from a shore prevent erosion from currents, tides and waves, or to trap sand

gross photosynthetic rate - the total rate of CO2 fixation with no allowance for the CO2 simultaneously lost during respiration

gross primary production - the total amount or weight of organic matter created by photosynthesis over a defined time period (total product of photosynthesis)

ground truthing - measurements conducted on the ground or at sea to calibrate, compare or verify observations made from satellites or aircraft

ground water - underground water that is generally found in the pore space of rocks or sediments and that can be collected with wells, tunnels, or drainage galleries, or that flows naturally to the earth's surface via seeps or springs. The term is not applied to water that is percolating or held in the top layers of the soil, but to that water in the zone of saturation below the water table

groundfish - fishes, usually of commercial value, that live on or near the bottom; also called "bottom fish"

grounding - a ship's striking a shoal or reef

grouper - any species of bony fishes in the subfamily Epinephelinae of the sea bass family, Serranidae. Groupers have a typical seabass appearance with robust bodies, large mouths and sharp teeth. Some get to be enormous in size, many feet long and reaching weights

Grouper Moon Project - a collaborative conservation program between REEF and the Cayman Islands Department of the Environment studying the Nassau grouper (Epinephelus striatus)

growth band - a band formed yearly on coral by the secretion of CaCO3; one yearly growth band contains two smaller bands representing winter growth and summer growth

growth factor - any of various chemicals, particularly polypeptides, that have a variety of important roles in the stimulation of new cell growth and cell maintenance. They bind to the cell surface on receptors. Specific growth factors can cause new cell proliferation

growth rate - the increase in mass per unit of time

growth  - an increase in cell size or cell number, or both

grunt - any species of bony spiny-rayed fishes in the family Haemulidae. Grunts are medium-sized tropical fishes that are capable of making a grunting sounds by the grinding of pharyngeal teeth.They inhabit coral reef or hard bottom areas. Many forage at night over nearby sand and grass flats

Diagram of guanine

Diagram of the chemical structure of guanine, one of the four nitrogenous bases in DNA.


guanine - one of the four nitogenous bases in DNA and RNA that make up the letters ATGC, guanine is the "G". The others are adenine, cytosine, and thymine. Guanine always pairs with cytosine

guano - the manure of birds and bats that is often used as fertilizer

guild - a group of species that use the same resources in a similar way; an ecological association based on similar roles in a community rather than evolutionary descent, as for example, filter feeders or browsers

gular - of, relating to, or located on the throat

gulf - a portion of an ocean or sea that extends into the land; a partially land-locked sea, e.g., the Gulf of Oman

Image of Gulf Stream SST

Sea surface temperature image of the Gulf Stream, derived from infrared measurements of the Moderate-resolution Imaging Spectroradiometer (MODIS), May 8, 2000. (Image produced from 11- and 12-micron bands by Bob Evans, Peter Minnett, and co-workers, University of Miami)


Gulf Stream - the warm ocean current of the North Atlantic. It originates in the westward equatorial current and is deflected northward by the coast of South America into the Gulf of Mexico and then follows the coast of North America to Nantucket, where it is deflected eastward toward northern Europe

gunwale - the upper edge of the side of a ship

gustation - pertains to the sense of taste

gut - the digestive tube formed between the mouth and anus in which food is digested and nutrients absorbed; it consists of the mouth, pharynx, esophagus, stomach, intestine, and anus, though some animals do not have all these regions

guyot - a flat-topped submarine mountain

gynetype - a female type specimen

gynogenetic - containing genetic material derived from the female parent only

gyre - a large water-circulation system of geostrophic currents rotating clockwise in the Northern Hemisphere or counterclockwise in the Southern Hemisphere

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