Glossary of Marine Biology

 

G, H, I, J, K

Go Home

 

Gametophyte. Haploid stage in the life cycle of a plant

 

Generation time. The time period from birth to average age of reproduction

 

Genetic drift. Changes in allele frequencies that can be ascribed to random effects

 

Genetic locus. A location on a chromosome (possibly of a diploid organism with variants that segregate according to the rules of Mendelian heredity)

 

Genetic polymorphism. Presence of several genetically controlled variants in a population

 

Genotype. The genetic makeup of an organism, with respect to a given genetic locus, the alleles it carries

 

Genus. (plural: genera) The level of the taxonomic hierarchy above the species but below the family level

 

Geostrophic flow. Movement of water in the oceans as a combined response to the Coriolis effect and gravitational forces created by an uneven sea surface

 

Geotactic. Moving in response to the earth's gravitational field

 

GIS. Geographic Information System. 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.

 

Global warming. Predicted increase in the earth's oceanic and atmospheric temperature, owing to additions of carbon dioxide to the atmosphere, as a result of human activities

 

GPS. Global Positioning System. An electronic device that uses positioning signals from satellites in order to locate precisely latitutude and longitude. Now used nearly exclusively for locating ship sampling stations at sea, but also useful for locations near and on shore.

 

Grab. Benthic sampling device with two or more curved metal plates designed to converge when the sampler hits bottom and grab a specified volume of bottom sediment

 

Grazer. A predator that consumes organisms far smaller than itself (e.g., copepods graze on diatoms)

 

Greenhouse effect. Carbon dioxide traps solar-derived heat in the atmosphere near the earth.

Gregarious settling. Settlement of larvae that have been attracted to members of their own species

 

Gross primary productivity. The total primary production, not counting the loss in respiration

 

Guild. A group of species, possibly unrelated taxonomically, that exploit overlapping resources

 

Gyre. Major cyclonic surface current systems in the oceans

 

Halocline. Depth zone within which salinity changes maximally

 

Hardy-Weinberg law. Law that states that the frequencies of genotypes in a population at a locus are determined by random mating and allele frequency

 

Herbivore. An organism that consumes plants

 

Harmful algal bloom. A bloom of (usually) planktonic microalgae belonging to a strain of a species that has a toxic harmful to marine organisms or humans consuming marine organisms.

 

Heritable character. A morphological character whose given state can be explained partially in terms of the genotype of the individual

 

Hermaphrodite. An individual capable of producing both eggs and sperm during its lifetime

 

Hermatypic. Reef-building

 

Heterotrophic algae. Algae that take up organic molecules as a primary source of nutrition

 

Heterozygote. With respect to a given genetic locus, a diploid individual carrying two different alleles

 

Highly stratified estuary. An estuary having a distinct surface layer of fresh or very-low-salinity water, capping a deeper layer of higher salinity, more oceanic water

 

Histogram. A multiple-bar diagram representing the frequency distribution of a group as a function of some variable. The frequency of each class is proportional to the length of its associated bar

 

Holoplankton. Organisms spending all their life in the water column and not on or in the sea bed

 

Homeotherm. An organism that regulates its body temperature despite changes in the external environmental temperature

 

Homozygote. With respect to a given genetic locus, a diploid individual carrying two identical alleles

 

Hydrographic. Referring to the arrangement and movement of bodies of water, such as currents and water masses

 

Hydrothermal vents. Sites in the deep ocean floor where hot, sulfur-rich water is released from geothermally heated rock

 

Hypothesis. A refutable statement about one or a series of phenomena

 

Infaunal. Living within a soft sediment and being large enough to displace sedimentary grains

 

Interspecific competition. Condition in which one species' exploitation of a limiting resource negatively affects another species

 

Interstitial. Living in the pore spaces among sedimentary grains in a soft sediment

 

Isotonic. Having the same overall concentration of dissolved substances as a given reference solution

 

Keystone species. A predator at the top of a food web, or discrete subweb, capable of consuming organisms of more than one trophic level beneath it