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Glossary of Terminology: I

The glossary is organized alphabetically by page -- A through Z. Literature sources are listed on the References Page.

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Number of records found : 163


ichnotaxon - a taxon based on the fossilized work of an animal, including fossilized trails, burrows, and tubes

ichthyo- - pertaining to fishes

ichthyoallyeinotoxic fish - an algal-grazing fish species which is effected by ichthyoallyeinotoxism. Ingesting affected fishes may lead to hallucinogenic fish poisoning

Ichthyoallyeinotoxism - hallucinogenic fish poisoning caused by ingesting the heads or flesh of certain types of reef fishes (e.g., mullets, goatfishes, surgeonfishes, damselfishes, and rabbitfishes) in the tropical Pacific and Indian Oceans. The toxin affects primarily the central nervous system. Symptoms consist of dizziness, loss of equilibrium and motor coordination, hallucinations, and mental depression. Incidences have also been reported in the Mediterranean Sea, caused by ingesting a species of bream (Sarpa salpa). The effects have been compared to LSD-induced hallucinations; also called " hallucinogenic fish poisoning"

ichthyochory - the dispersal of plant seeds or spores by fishes

Image of reef fish

The diver is studying the behavior and ecology of squirrelfishes on a Caribbean coral reef. (Photo: Dr. Anthony R. Picciolo, NOAA)


ichthyology - the scientific study of fishes

Ichthyosarcotoxism - food poisoning caused by the toxic substance, ichthyosarcotoxin, in the flesh or organs of fishes

icon - a small picture displayed on a computer monitor that identifies a command or file.

iconotype - in taxonomy, a drawing or photograph of a type specimen

idiopathic - denotes a disease of unknown cause or origin

igneous rock - a rock formed by the cooling and crystallization of molten magma

Image of Buck Island from IKONOS satellite

Four-meter true color IKONOS image of Buck Island Reef National Monument shows an extensive underwater coral reef ecosystem.


IKONOS satellite - high-resolution (1-2 meter resolution) imaging satellite; the world's first commercial satellite for imagery of this type

illecium - a "fishing rod-like" appendage on the head of some fishes, usually a modified dorsal fin spine

image resolution - the area represented by each pixel of a satellite image. The smaller the area represented by a pixel, the more accurate and detailed the image

imagery - visible representation of objects and (or) phenomena as sensed or detected by cameras, infrared and multispectral scanners, radar, and photometers

imbricate - with overlapping parts, such as scales

imitation - a behavior that occurs when an animal immediately mimics the actions of another animal while they are in each other's presence

immature - describes an animal that has not reached sexual maturity, regardless of size or age

immersed corallite - a corallite that forms a depression in the surface of the colony

immersed corallite - a corallite that is embedded in the surrounding coenosteum, i.e., one that forms a depression on the colony surface

immune system - a system that provides the organism with a defense against infection. In higher organisms it is afforded by the presence of circulating antibodies and white blood cells. Antibodies are manufactured specifically to deal with the antigens associated with different diseases as they are encountered. White blood cells attack and destroy foreign particles in the blood and other tissues

immunogen - any substance that can elicit an immune response

impact - a change, caused by external sources, in the chemical, physical (including habitat) or biological quality or condition of a habitat or environment

imperforate coral - corals with solid skeletons with no inter-polyp connections

impermeable - having the property of restricting the passage of substances across a membrane

imposex - the imposition of male characteristics on female organisms, as caused by some pollutants. For example, a pseudo-hermaphroditic condition in female gastropods (development of a false penis) caused by tributylin (TBT), a biocide used in anti-fouling paints

imprimis - in the first place

in adnot. - in an annotation (in adnotatio)

in hospite - within the host

in litt. - in correspondence or communicated in writing; used for an unpublished source of information (in litteris)

in situ - in the natural or original position

in situ data - measurements made at the actual location of the object or material measured, in contrast to remote sensing

in situ hybridization - a method of detecting the presence of specific nucleic acid sequences within a cytological preparation. A DNA or RNA probe is labeled, radioactively or chemically, and hybridized to a cytological preparation to detect RNA, or to a denatured cytological preparation to detect complementary DNA. The hybridization is detected by autoradiography (for radioactive probes) or by chromogenic reactions or fluorescence (for chemically-labeled probes)

in syn. - in synonymy (in synonymis)

in vitro - a laboratory experiment or study performed outside the body of a living organism in a test tube, petri dish, or other vessel

in vivo - studies conducted in intact living organisms or cells

inc. sed. - of uncertain taxonomic position or affinities (incertae sedis)

incidental parasite - an accidental parasite

incipient population - a small population that is just beginning to reproduce and become established in an area or community

incisiform tooth - a chisel-shaped tooth used for cutting. Typically, it wider than it is thick

inclined corallite - a corallite that grows at an angle up from the colony surface

incomplete dominance - in genetics, an interaction between alleles in which both alleles are expressed more or less equally. The expression for a phenotype for a given trait exhibits a blending of the genetic messages from the allele partners controlling that trait. An example may be a cross between a homozygous red trait (AA) and a homozygous white trait (aa), where neither the red (A) nor white (a) trait is dominant. The phenotypic expression of the offspring is pink (Aa), the intermediate phenotype

incomplete protein - a protein which does not supply all the essential amino acids

incurrent canal - in sponges, an inpocket of the epidermis (pinacoderm) which opens into a choanocyte chamber via a small opening, the prosopyle

independent assortment - the random alignment of homologous chromosomes during meiosis. Each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random

independent variable - a variable controlled by the experimenter

indeterminate cleavage - cleavage where the fate of the resulting daughter cells is not determined after the initial divisionof a fertilized egg. If the cells separate, each has the potential to develop into an entire organism and the resulting individuals are genetically identical (identical twins). Inderterminate cleavage is characteristic of deuterostomes

indeterminate species - a category used in grading the severity of threat to an endangered species. When graded 'indeterminate', the species is thought to be under severe threat but adequate data is unavailable

indicator species - any organism that by its presence or absence, its frequency, or its vigor, indicates a particular property of its surrounding environment; a species whose presence is a sign that certain environmental conditions exist

indigenous - native to a particular country or area

Indo-Pacific - a vast region encompassing the tropical Indian and Pacific Oceans from Africa in the west to Hawaii and French Polynesia in the east. This area represents the largest marine biogeographic region in the world

inductive reasoning - the process of observing data, recognizing patterns, and making generalizations from the observations; reasoning from particular facts to a general conclusion

inert - refers to unmoving or unchanging. In chemistry, a substance which does not or rarely combines with other substances. In medicine, it means a substance that has little or no effect on the human body

infauna - animals that inhabit the sandy or muddy surface layers of the ocean bottom, i.e., those that live buried or dig into the substrate

infection - a pathological state resulting from the invasion and multiplication of pathogenic microorganisms in the body of an organism

infectious - capable of spreading disease

infectious agent - an organism capable of spreading disease

inferior - anatomically beneath, lower, or toward the bottom (e.g., the mouth is inferior to the nose)

inflamation - a protective response of vascular tissues to injuries to the body caused by pathogens or other harmful agents. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process

inflated - swollen or expanded

informatics - the management and analysis of data using advanced computing techniques

information management - the integration of a variety of activities designed to manage information and information resources throughout their life cycle. Activities include planning, budgeting, organizing, directing, training, promoting, and controlling the information and information resources throughout the process of collecting, processing, transmitting, disseminating, and disposing of information; the manipulation, reorganization, analysis, graphing, charting, and presentation of data for specific management and decision-making purposes

Information Technology (IT) - a very general term referring to the entire field of Information Technology - anything from computer hardware to programming to network management

infra- - a prefix meaning "below"

infrared radiation (IR) - earth-emitted radiation over thermal wavelengths: 3-15 micrometers. Used for satellite remote sensing because it can be used to monitor weather and oceanographic conditions 24 hours a day

infrared scanner - an instrument that detects infrared radiation and converts the detected energy to an electrical signal for recording on another medium

infrasonic - sound waves that have a frequency that is lower than what humans can hear (i.e. below about 20 hertz). Some baleen whales and elephants produce infrasounds to communicate over long distances

infraspecific name - in taxonomy, a general term for any name below the rank of species. The term includes subspecific and infrasubspecific names

infrasubspecific - in taxonomy, a category below the subspecies level

infundibuliform - funnel-shaped

ingestion - the intake of water or food substances by "swallowing" them, taking them into the body cavity or into a cell vacuole

inhalant system - in sponges, part of the aquiferous system between the ostia and prosopyle

Image of dissected squid

Ventral view of a dissected squid revealing the ink sac. (Photo: Biology Dept., Fairfield University, Fairfield, CT)


ink sac - a diverticulum of the rectum of most cephalopods, where an 'inky" melanin solution is stored. The ink is ejected from a duct opening at the base of the siphon. It serves to cloud the water, and enable these animals to escape from predators

innate - not established by conditioning or learning; "an unconditioned reflex"; a genetic behavior pattern

innate releasing mechanism - in ethology or animal behavior, an innate system within an animal that responds to a stimulus in the environment to produce a genetic stereotyped behavior; a stimulus-response mechanism

inner cell mass - the cluster of cells inside the mammalian blastocyst. These cells give rise to the embryonic disk of the later embryo and, ultimately, to the fetus

inorganic matter - chemical substances of mineral origin which contain no organically produced carbon

inquilinism - a symbiotic association in which one symbiont lives in close association with another, generally in its shell, tube or burrow, or actually within a body cavity of the host

inquilinism - a symbiotic association in which one symbiont lives in close association with another, generally in the tube or burrow or actually within a body chamber of the host

inserted gene - a gene introduced into the DNA of a recombinant organism which is not present at the same position in the DNA of the organism before genetic modification

insolation - the amount of solar radiation received on a given body or in a given area

instar - a discreet, in-between molt stage, during the metamorphosis of an arthropod from larva to adult

instinct - an unlearned, genetically coded behavior pattern that is internally motivated and characteristic of the species; the innate capacity of an animal to respond to a given stimulus in a relatively fixed way

insular - relating to, or characteristic of, or situated on an island

integer - a number without a decimal (0, 1, 25, 173, 1032, etc.). Integer values can be less than, equal to, or greater than zero

integrated coastal zone management - the process of combining all aspects of the human, physical and biological aspects of the coastal zone within a single management framework

Integrated Coral Observing Network (ICON) - As of October 2005, the coral research program at NOAA's Atlantic Oceanographic and Meteorological Laboratory (AOML) was titled the "Integrated Coral Observing Network" (ICON), rather than the Coral Reef Early Warning System (CREWS). ICON is focusing up

Integrated Ocean Observing System (IOOS) - a “user-driven” integrated system of observations, data management and communications, and data analysis and modeling that provides data and information required to achieve seven societal goals: 1) Improve predictions of climate change and variability (weather) and their effects on coastal communities and the nation; 2) Improve the safety and efficiency of marine operations; 3) More effectively mitigate the effects of natural hazards; 4) Improve national and homeland security; 5) Reduce public health risks; 6) More effectively protect and restore healthy coastal marine ecosystems; and 7) Enable the sustained use of marine resources

Integrated Taxonomic Information System (ITIS) - a partnership of U.S., Canadian, and Mexican agencies, other organizations, and taxonomic specialists cooperating on the development of an online, scientifically credible, list of biological names. ITIS is also a participating member of Species 2000, an international project indexing the world's known species

intensity - pertaining to sound, the average amount of sound power (sound energy per unit time) which is transmitted through a unit area in a specified direction. The magnitude of the intensity is often referred to as the intensity, without specifying the direction from which the sound is travelling

intention movement - an incomplete behavior pattern that provides information about the activity a particular animal is about to perform, and acts as a signal to others

Interactive Data Language (IDL) - a commercial array-oriented language with numerical analysis and display features, first released in 1977. It supports interactive reduction, analysis, and visualisation of scientific data

interannual - refers to a climatic process that re-occurs every three to ten years. El Niño is an example of a climatic process that re-occurs every 4-6 years

interface - the common boundary between two substances such as a water and a solid, water and a gas, or two liquids, such as water and oil

interferon - a family of small proteins that stimulate viral resistance in cells

Graphic of bivalve

Some experts believe that the "living fossil" genus Neopilina, an internally segmented mollusk in the class Monoplacophora, is an an evolutionary link between mollusks and other more obviously segmented invertebrates, such as annelid worms. (Graphic: BIODIDAC)


intermediate form - a fossil or modern species that possesses characters definitive of two or more different taxa, or that displays characters morphologically intermediate between two different taxa

intermediate host - in a parasite's life cycle, it is a host organism in which a parasite undergoes a stage of asexual development

intermittent spawning - spawning at intervals

International Code of Zoological Nomenclature (the Code) - in taxonomy, an authoritative document containing a system of rules and recommendations to be followed in giving a scientific name to an animal or animal group. It has been adopted by the International Congresses of Zoology (more recently the International Union of Biological Sciences) and is administered by the International Commission on Zoological Nomenclature. The most recent version of the Code is the Fourth Edition published in September 1999 and took effect on January 1, 2000; usually referred to as the "Code"

International Commission on Zoological Nomenclature (ICZN) - the judicial body empowered to enforce and interpret the International Code of Zoological Nomenclature

International Coral Reef Initiative (ICRI) - an environmental partnership and network that brings all the stakeholders together with the objective of sustainable use and conservation of coral reefs for future generations. ICRI is an informal mechanism that allows representatives of over 80 developing countries with coral reefs to sit in equal partnership with major donor countries and development banks, international environmental and development agencies, scientific associations, the private sector and non-governmental organizations (NGOs) to decide on the best strategies to conserve the world's coral reef resources

International Zoological Congresses - the legislative bodies responsible for the rules of the International Code of Zoological Nomenclature and for authorization of the activities of the International Commission on Zoological Nomenclature

Internet Service Provider (ISP) - a company or organization that provides access to the Internet

interorbital - the space between the eyes

interoreceptor - a neurological receptor that is located within the organism's body and detects physiological changes, e.g. pH, temperature, chemicals in blood

interpolated name - in taxonomy, a name placed within parentheses (after a generic name to denote a subgenus; after a genus-group name to denote an aggregate of species, or after a specific name to denote an aggregate of subspecies. Names used in this way are not counted as one of the names in a binomen or trinomen

interradial - in fishes, between the rays (or spines), e.g. interradial pigment is pigment on the membrane between the rays.

interradial canal - one of four branched ciliated canals in scyphozoan medusae that originates from the gastric pouches and move materials from the ring canal back toward the stomach and gastric pouches

interradial membrane - in fishes, the tissue between the fin rays or spines

interradial pigment - in fishes, interradial pigment is pigment on the membrane between the fin rays

intersex - an organism which possesses a mixture of male and female characteristics

intersexual - involving both sexes, male and female

interspecific - between members of different species

interspecific competition - competition between individuals of different species

interspinous membrane - in fishes, the membrane between fin spines

interstices - the openings or pore spaces in a rock, soil, and other such material

interstitial - refers to the interstices or pore spaces in rock, soil, or other material subject to filling by water; fluid-filled spaces between cells in tissues

interstitial fauna - animals that live in the spaces within sediment particles (interstitial spaces)

interstitial water - water in the pore spaces of soil or rock

Image of rocky intertidal zone

Sea anemones crowd a rocky intertidal zone (Photo: Nancy Sefton)


intertidal zone - the region between the highest water line and the mean low tide level

Intertropical Convergence Zone (ITCZ) - the region near the equator where the trade winds of the Northern and Southern Hemispheres converge

intolerant organism - an organism (or species) that is not adaptable to human alterations to its environment and thus declines in number where alterations occur

intranet - a private network inside an organization that uses the same kinds of software found on the public internet, but which is only for internal use

intrasexual - involving only one of the sexes, male or female

intraspecific - among members of the same species

intraspecific competition - competition between individuals of the same species

intratentacular budding - a type of asexual reproduction where daughter corallites grow from the inside wall of parent corallites, usually by division of the parent corallite

intrinsic - belonging to a thing by its very nature; the essential nature or constitution of a thing; inherent; in and of itself

introgression - the movement or incorporation of genes from one population into another through hybridization followed by backcrossing. Usually refers to movement of genes from one species to another or among sub-species that have been geographically isolated then brought back together by changes in the species ranges or planting of exotic populations

introgressive hybridization - the spread of genes of one species to another species through hybridization. The hybrids are able to breed back into one of the parental populations. This allows the reintroduction of alleles that may have been lost during the speciation process

intromittent organ - a copulatory structure employed by the males of species that practice internal fertilization to transfer sperm cells into the reproductive tube of the female, e.g., the clasper of a shark, skate or ray; penis; modified anal fin (gonopodium) of live-bearer fishes

intron - DNA sequences that interrupt the protein-coding sequence of a gene; introns are transcribed into mRNA but the sequences are eliminated from the RNA before it is used to make protein; junk DNA; in eukaryotic cells, a sequence of DNA that is contained in the gene but does not encode for protein. The presence of introns "splits" the coding region of the gene into segments called exons

Image of starfish blastula

The cells at the vegetal hemisphere of this starfish blastula have begun to push into the blastocoel (invaginaton), forming a diploblastc embryo with a new cavity, the primitive gut, or archenteron. The cells lining the archenteron are endodermal cells. (Photo: Dr. Anna E. Ross, Christian Brothers University, TN)


invagination - an inward folding of a layer of cells forming an interior pocket

invalid name - in taxonomy, any name for a given taxon other than the valid name

inversion - a chromosomal re-arrangement that reverses the order of a linear array of genes on the chromosome

Image of invertebrate feather worms

Feathery invertebrate tube worms in the Caribbean Sea (Photo: Dr. Anthony Picciolo).


invertebrate - an animal that lacks a vertebral column (backbone)

involute - rolled inwards fom the edges

ion - a positively or negatively charged atom produced through loss or gain of one or more electrons

ion channel - a pore in a cell membrane, formed by an integral protein, that selectively regulates the diffusion of ions into and out of the cell. An ion channel switches between open and closed when the protein undergoes a conformational change. Ion channels are usually selective for a specific ion type (e.g., Na, or K, or Cl, or Ca)

ionic bond - a chemical bond in which one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion

ionizing radiation - high-energy radiation capable of producing ionization in substances through which it passes, i.e., radiation that has enough energy to eject electrons from electrically neutral atoms, leaving behind charged atoms or ions; examples are alpha particles (helium nuclei), beta particles (electrons), neutrons, and gamma rays (high frequency electromagnetic waves, x-rays)

ionocyte - a type of cell commonly found in the gills of fishes and some crustaceans. They play a role in regulating the salt concentration of cells in relation to the external environment, and differ greatly between freshwater and saltwater organisms; also called "chloride secretory cell"

Image of deep sea "greeneye" fish

This deep-sea fish called a "green eye" (Chlorophthalmidae) exhibits a beautiful iridescent pattern around its large eyes and head. (Photo: NOAA Ocean Exploration)


iridescent - exhibiting rainbow colors

iridiophore - a colorless chromatophore which contains purines, mostly guanine in the form of large, nonmotile crystals

irruption - a sudden sharp increase in the relative numbers of a population which may cause the mass movement of a population from one place to another

irruptive growth - a growth pattern defined by population explosions and subsequent sharp population crashes; sometimes called Malthusian growth

ischemia - a condition in which a tissue or organ does not receive a sufficient supply of blood

isobath - a line on a map or chart that connects all points having the same depth below a water surface

isoenzyme - one of a group of enzymes that are very similar in catalytic properties, but may be differentiated by variations in physical properties, such as isoelectric point or electrophoretic mobility; also called 'isozyme'

isogamous - having haploid gametes that are similar in size, structure and motility. An isogamete can unite with another to form a zygote

isogenic chromosome - in a diploid organism, a chromosome in which both alleles at every locus are identical on both copies

isohyetal line - a line drawn on a map or chart joining points that receive the same amount of precipitation

isolecithal - an egg cell in which the total amount of yolk is small and the yolk granules are fairly uniformly distibuted throughout the cytoplasm, and cleavage completely bisects the cell, e.g., the egg of a starfish. A synonym is "homolecithal"

Graphic depicting SST utilizing isobars

Isobars are utilized to depict NOAA-11 AVHRR SST climatology in this diagram.


isoline - a line on a surface connecting points of equal value

isometric contraction - a muscular contraction in which tension increases while the length of the muscle remains constant

isometric growth - growth that occurs at the same rate for all parts of an organism so that its shape is consistent throughout development

isomorphic - having the same or similar form

isotonic contraction - a muscular contraction in which tension is constant while the length of the muscle changes

isotope - one of two or more species of atoms of the same chemical element that have the same atomic number and occupy the same position in the periodic table. They are nearly identical in chemical behavior, but they differ in atomic mass or mass number. Therefore, they behave differently in the mass spectrograph, in radioactive transformations, and in physical properties, and may be separated or detected by means of these differences

isthmus - a narrow strip of land connecting two larger land masses, such as the isthmus of Panama

iterative process - a process for calculating a desired result by means of a repeated cycle of operations. An iterative process should come closer to the desired result as the number of iterations increases. Each repetition of the process is also called an "iteration", and the results of one iteration are used as the starting point for the next iteration

iteroparity - the reproductive condition in which individuals reproduce several times during their lifetime

iteroparous - a life history in which individuals reproduce more than once in a lifetime

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