Ichthyosaur: An extinct group of
marine fish-like or porpoise-like reptiles abundant in Mesozoic seas. Idiomorph: This term is used to describe the fungal mating types which are extremely dissimilar from each other and do not show homology between strains of the opposite sex (as opposed to the allelic relationship in most polymorphic systems). Also used as ideomorph. Immigration:A movement of individual into a new population or region. Imprinting: See genomic imprinting. In vitro: Literally, 'in glass' meaning in the laboratory. In vivo: Literally, 'in the living organism'. Inbreeding depression: Reduction in offspring fitness resulting from mating between blood relatives. Inbreeding: Production of offspring by (blood) related parents. Its most extreme form is self-fertilization in hermaphrodites (most invertebrates and plants). Incest: Sexual relationships between parents and children, or between brothers and sisters. Inncidental catch: Catch of a species that was not the focus of a fishery, but taken along with the species being sought. Incomplete dominance: One allele is not expressed, but the other allele expresses itself normally so that the phenotype gets half the dose of the effect. Infauna: Animals that live buried in the sediment Ingroup: In a cladistic analysis, the set of taxa which are hypothesized to be more closely related to each other than any are to the outgroup. Initiation complex: A multi-protein complex that forms at the site of transcription initiation and is composed of RNA polymerase II, ubiquitous or general transcription or initiation factors (TFII or IF/eIF) and gene-specific enhancers/silencers. Innate immunity: Pre-existing and non-specific defense immunity with a very low memory component if any. As the primitive immune response against bacteria, it is present in invertebrates and vertebrates. Inner shelf: The continental shelf extending from the mean low tide line to a depth of 20 m. Inorganic: Part of or derived from non-biological material. A chemical compound that does not include a carbon chain. Compare organic. Instantaneous Rate Of Fishing Mortality: When fishing and natural mortality act concurrently, F is equal to the instantaneous total mortality rate, multiplied by the ratio of fishing deaths to all deaths. Also called: rate of fishing; instantaneous rate of fishing; *force of fishing mortality . Instantaneous Rate Of Growth: The natural logarithm of the ratio of final weigl1t to initial weight of a fish in a unit of time, usually a year. When applied collectively to all fish of a given age in a stock, the possibility of selective mortality must be considered . Instantaneous Rate of Mortality: The natural logarithm (with sign changed) of the survival rate. The ratio of number of deaths per unit of time to population abundance during that time, if all deceased fish were to be immediately replaced so that population does not change. Also called: *coefficient of decrease. Instantaneous Rate Of Natural Mortality: When natural and fishing mortality operate concurrently it is equal to the instantaneous total mortality rate, multiplied by the ratio of natural deaths to all deaths. Also called: *force of natural mortality . Instantaneous Rate of Recruitment: Number of fish that grow to catchable size per short interval of time, divided by the number of catchable fish already present at that time. Usually given on a yearly basis: that is, the figure just described is divided by the fraction of a year represented by the "short interval" in question. This concept is used principally when the size of the vulnerable stock is not changing or is changing only slowly, since among fishes recruitment is not usually associated with stock size in the direct way in which mortality and growth are. Instantaneous Rate Of Surplus Production: Equal to rate of growth plus rate of recruitment less rate of natural mortality--all in terms of weight and on an instantaneous basis. In a "balanced" or equilibrium fishery, this increment replaces what is removed by fishing, and rate of surplus production is numerically equal to rate of fishing. Also called: *instantaneous rate of natural increase. Instar: The intermolt stage of a young arthropod. Insular: Of or pertaining to an island or its characteristics (i.e., isolated). Integrase: An enzyme that catalyzes a site-specific recombination (integration or excision) involving a prophage and a bacterial chromosome. Intercalary band: Marginal growth zones between thecal plates; usually straited horizontally or transversely. Intertidal: The ocean of estuarine shore zone exposed between high and low tides. intestine -- The portion of the digestive tract between the stomach and anus; it is the region where most of the nutrients and absorbed. Introduced Species: An organism that has been brought into an area, usually by humans, where it does not normally occur. Introduced species often compete with and cause problems for native species. Introduced species are also called exotic, nonnative, and alien species. See also invasive species, native species. Intron: A non-coding section of DNA within a gene that is not translated to a peptide. Intervening sequences between exons. Introns are featured in the primary transcript (pre-mRNA) but removed by splicing during nuclear RNA processing/editing. Invasive Species: An introduced species that out-competes native species for space and resources. Scotch Broom is an invasive species that out-competes local vegetation and results in a monoculture, and hence a decrease in local diversity. See also introduced species, native species. Invertebrate: All animals other than those in the phylum Chordata; lower metazoans. They do not possess a notochord or vertebral column. Examples are worms, corals, sponges, etc. The protochordates are sometimes called higher invertebrates. Isobath: A contour mapping line that indicates a specified constant depth. isogamous - Sexual reproduction in which the fusing gametes differ morphologically from the vegetative cells, but are morphologically identical to each other (Taylor 1987); e.g. Alexandrium monilatum. Isopoda: An order of about 4,000 species of dorsoventrally compressed crustaceans that have abdominal gills and similar abdominal and thoracic segments. Terrestrial pillbugs and thousands of benthic marine species are included. Most species are scavengers and/or omnivores; a few are parasitic. Isotherm: A contour line connecting points of equal mean temperature for a given sampling period. Iterative evolution: Repeated origination of lineages with generally similar morphology at different times in the history of a clade. Iteroparous: Refers to an organism that reproduces several times during its lifespan (i.e., does not die after spawning). |