Biology Dictionary – I-K

Meanings of biological terminology

EUGENE M. MCCARTHY, PHD GENETICS

Definitions:

I Symbol for: (1) iodine; (2) isolucine.

Iapetus Ocean /ī-AP-ə-təs/ An ocean that once existed (Late Precambrian to Devonian) between the former continents of Avalonia, Baltica, and Laurentia.

iatric /ī-AT-rick/ adj. Medical.

iatrology /ī-ə-TRAWL-ə-jee/ n. Medical science.

ice age (1) any prolonged period of extensive glaciation; (2) capitalized: the Pleistocene.

ichnite /IK-nīt/ (also ichnolite /IK-nə-līt/) n. A fossil footprint or track.

ichnology /ik-NAWL-ə-jee/ n. The scientific study of the fossilized traces of past animal activity, such as footprints, burrows, trails, and borings — ichnologist /ik-NAWL-ə-jəst, -jist/

ichthyic /ik-THEE-ick/ adj. Of or pertaining to fish.

ichthyology /IK-thee-AWL-lə-jee/ The scientific study of fish — ichthyologist /IK-thee-AWL-lə-jəst, -jist/

icteritious /IK-ter-RISH-us/ adj. Yellowed with jaundice.

icterohematuria /IK-ter-ō-heem-ə-TER-ee-ə/ A disease of sheep caused by the protozoan blood parasite Babesia ovis; a jaundiced condition results from the destruction of erythrocytes.

identical twins Genetically identical individuals that develop from a single zygote. See also: fraternal twins.

idiopathic /id-ee-ə-PATH-ick/ adj. Pertaining to disease without known cause.

IDL abbr. Intermediate-density lipoprotein.

IF abbr. Initiation factor.

Ig abbr. Immunoglobulin.

igneous rock /IG-nee-əs/ n. Rock formed from the cooling and solidification of magma. Because igneous deposits can be accurately dated, they are useful for determining the age of fossils (the approximate age of a fossiliferous deposit can often be determined by evaluating the age of beds of igneous rock that over- or underlie it).

IHP abbr. Inositol hexaphosphate.

ile abbr. Isolucine.

ileal /ILL-ee-əl/ adj. Of or pertaining to the ileum.

ileocecal valve /ill-ee-ō-SEE-cəl/ A one-way valve between the ileum and the cecum, which prevents the contents of the large intestine from returning to the ileum.

ileum (pl ilea) /ILL-ee-əm/ n. The lower, third portion of the small intestine, lying between the jejunum and the cecum. It is about 4 meters in length.

ilium (pl ilia) /ILL-ee-əm/ n. The wide upper portion of the innominate bone ("hip bone") — iliac /ILL-ee-ack/ adj.

immune /im-MYOON/ adj. Resistant to, or protected against a disease.

immune system The system that defends an organism against infection. The cellular components of this system are all derived from the same cells (hematopoietic stem cells), residing in the bone marrow, that can alternatively mature into erythrocytes. MORE INFORMATION

immunity /im-MYOON-ə-tee/ n. The condition of being immune.

immunogenic /im-MYOON-ə-JEN-ick/ adj. Producing immunity.

immunodeficiency /im-MYOON-ō-də-FISH-en-see/ n. The condition of being immunodeficient.

immunodeficient /im-MYOON-ō-də-FISH-ənt/ adj. Unable to produce a normal complement of antibodies.

immunoglobulins (Ig) /im-MYOON-ə-GLAWB-yə-lins/ See antibodies.

immunology /IM-yə-NAWL-ə-jee/ n. The study of the structure and function of the immune system, innate and acquired immunity, the bodily distinction of self from nonself, and laboratory techniques involving the interaction of antigens with specific antibodies — immunologist /IM-yə-NAWL-ə-jist/

immunotherapy /im-MYOON-ə-THAIR-ə-pee/ n. (1) use of the immune system to treat or prevent disease (e.g. vaccines); (2) therapy of diseases caused by the immune system.

IMP abbr. Inosine monophosphate.

imping /IMP-ing/ n. Grafting of intact feathers onto broken ones (a measure used in avian conservation).

imprinting /IM-print-ing/ n. (1) a genetic phenomenon in which phenotype is dependent on the parent that passed on the gene; (2) sexual preferences determined by exposure to stimuli at an early stage of development (for example, if a duckling is spends the time of its early development with chickens, it will later prefer to mate with chickens instead of other ducks.

incision /in-SISH-ən, -SIZH-/ n. A cut made with a knife.

incisor /in-SIZE-er/ n. One of the slicing teeth at the front of the mouth.

incubator /in-kyə-BAIT-er, -kyoo-/ n. (1) an apparatus for maintaining eggs at a constant temperature; (2) an apparatus, for rearing premature babies, in which such factors as temperature and oxygen levels can be closely controlled; (3) a device for culturing bacteria.

incubation /in-kyə-BAY-shən, kyoo/ n. (1) in reptiles and birds: the maintenance of a constant egg temperature; (2) in premature human infants: the time spent in an incubator; (3) in disease: the time between first infection and emergence of symptoms; (4) in bacteriology: the period of culture development.

independent assortment n. The random distribution into gametes, during meiosis, of genes on different chromosomes. See also: linkage.

indeterminate growth /in-də-TERM-ə-nət/ Growth that continues throughout life. Compare: determinate growth.

infection /in-FECK-shən/ n. A condition in which an organism, or a portion of an organism, is invaded by a virus, microorganism, fungus, or animal parasite. When pathogenic, the invader causes damage to its host.

inflammasome /in-FLAM-ə-zome/ n. A multi-protein oligomer responsible for activation of inflammatory processes.

inflammation /in-flam-MAY-shən, -fləm-/ n. The response of an organism to the injurious stimuli (pathogens, toxins, trauma, chemical irritatants, etc.) which initiates the healing process.

inflammatory /in-FLAM-mə-tor-ee/ n. Causing or involving inflammation.

inflorescence /in-flə-RESS-ehns/ n. A cluster of flowers.

infraclass /IN-frə-CLASS/ See: subphylum.

infraorder /IN-frə-OR-der/ See: subclass.

infraorbital /IN-frə-ORB-ə-təl/ adj. Beneath the orbit.

ingestion /in-JEST-shən/ n. Swallowing (in order to introduce something into the digestive tract). The term ingestion can also refer a cell engulfing or surrounding food or some other material. Compare: absorption.

Inia geoffrensis n. Scientific name of the Amazon River Dolphin.

inoculate /in-KNOCK-yə-late/ v. To inject or introduce a pathogenic (usually weakened) microorganism into the body in order to stimulate the production of antibodies — inoculation /in-KNOCK-yə-LAY-shən/

inorganic adj. (1) in chemistry, refers to compounds lacking carbon; (2) not from living things.

insectivore /in-SEK-tə-vore/ n. An organism that feeds on insects.

insectivorous /in-sek-TIV-ə-rəs/ adj. Feeding on insects.

insemination /in-SEM-ə-NAY-shən/ n. The introduction of semen into the reproductive tract of a female.

in situ hybridization n. Use of a DNA or RNA probe to detect complementary DNA sequences cultured eukaryotic cells or bacterial clones.

insertion n. (1) the attachment point of a muscle, ligament or tendon to a bone; (2) a chromosome abnormality in which a piece of DNA is incorporated into a gene and thereby disrupts the gene's normal function. See also: chromosome, DNA, gene, mutation.

InsP₃ abbr. Inositol 1,4,5-trisphosphate.

inspire /in-SPIRE/ v. To breath in, to inhale (draw air into the lungs) — inspiration /IN-spə-RAY-shən/ — inspiratory /IN-spə-rə-tore-ee, in-SPIRE-rə-tore-ee/

instinct /IN-stinct/ n. Unlearned, genetically inherited urges and patterns of behavior — n. instinctive /in-STINK-təv, -tiv/

instill /in-STILL/ v. To introduce a liquid drop by drop — instillation /IN-still-LAY-shən/

instillator /IN-still-LAY-ter/ n. An apparatus that carries out a process of instillation.

insulin /IN-sə-lən, -lin/ n. A hormone that causes blood sugar levels to fall. Individuals with diabetes melitus have a deficiency of this hormone. Normally, it is secreted by the islets of Langerhans in the pancreas.

integrin /in-TAY-grən/ n. An adhesive extracellular matrix protein found in animals.

integument /in-TEG-yə-ment/ n. The outer, protective coating of an organism.

interbedded adj. Refers to layers (beds) of rock alternating with layers of a different type of rock.

interclass /IN-ter-CLASS/ adj. Between different classes of the same phylum (said of hybrid crosses).

interfamilial /IN-ter-fam-MIL-ee-əl/ adj. Between different families of the same order (said of hybrid crosses).

interference See: negative interference, positive interference.

intergeneric /IN-ter-jə-NAIR-ik/ adj. Between different genera of the same family (said of hybrid crosses).

interglacial /IN-ter-nōd/ n. A lengthy period of warmer global climate separating consecutive cold (glacial) periods within an ice age.

internode /IN-ter-nōd/ n. The region of a plant stem between two nodes.

interordinal /IN-ter-ORD-in-əl/ adj. Between different orders of the same class (said of hybrid crosses).

interphase /IN-ter-faze/ n. The period in the eukaryotic cell cycle when cell growth occurs and DNA is replicated in the nucleus; alternates with mitosis. MORE INFORMATION

interspecific hybridization /IN-ter-spə-SIFF-ick/ Hybridization between organisms treated as distinct species. MORE INFORMATION

interstitial /IN-ter-STISH-əl/ adj. Occurring in or being the space between.

intertidal zone /IN-ter-TIDE-əl/ The zone between the high and low tide marks, which is subject to alternating flooding and drying.

intestine (also intestines) /in-TEST-in/ n. The portion of the digestive tract lying between the pylorus and the anus.

intestine, large /in-TEST-in/ n. The large intestine, or colon, is the portion of the digestive tract leading from the ileum to the anus. It functions primarily in extracting moisture from digested matter so as to convert it to solid feces. The large intestine begins with the cecum, which is attached to the vermiform appendix (see picture). To see the various other regions of the large intestine, click on the figure at right. The colon is usually from 1.5 to 2.0 meters in length.

intestine, small /in-TEST-in/ n. The portion of the digestive tract lying between the stomach and large intestine. It functions in the extraction of nutrients from digested matter. The small intestine is composed of the duodenum, jejunum, and ileum.

intramuscular /IN-trə-MUSK-yə-ler/ adj. Into or within a muscle.

introgression /IN-trə-GRESH-ən/ n. The natural introduction of a genetic trait via hybridization from a donor population into some other, otherwise genetically stable, population (however, there are conceptual problems with this term).

intron /IN-trawn/ n. A portion of a gene that is transcribed into mRNA but cut out of the mRNA before it is translated into protein. See also: exon.

intrusion /in-TROO-shən/ n. Rock formed from cooled magma that forced its way into preexisting rock.

inversion /in-VER-shən/ n. A chromosome segment that has been reversed with respect to the remainder of the chromosome.

invertebrate /in-VERT-ə-brət/ (1) n. Any animal lacking a backbone. Invertebrates do not develop a notochord during embryogenesis; (2) adj. Of, pertaining to, or being such an animal.

in vitro /in VEET-troh/ Performed or occurring outside a living organism, such as in a laboratory.

in vivo /in VEEV-vō/ Carried out or occurring in a living organism.

ion /Ī-awn/ n. An atom or small molecule with a negative or positive charge — ionic /ī-AWN-ick/

ion channels /Ī-awn, -ən/ n. Proteins, present in all cell membranes, governing the passage of specific ions between the interior and exterior of the cell.

ionize /Ī-ə-nīz/ (British: ionise) v. To change into ions.

IP₁ abbr. Inositol-1-phosphate.

IP₃ abbr. Inositol 1,4,5-triphosphate.

IPTG abbr. Isopropyl β-D-1-thiogalactopyranoside.

irideremia /ear-id-er-EEM-ee-yə/ n. Congenital absence of the iris, whether partial or complete.

iridescence /ear-ə-DESS-əns, ear-id-/ n. The quality of changing color depending on the angle of observation.

IS abbr. Insertion sequence.

ischium /ĪS-kee-əm/ n. The lower portion of the hip bone.

ischiopubic /ĪS-kee-ō-PYOO-bick/ adj. Pertaining to the ischium and pubes.

ischochymia /ĪS-kō-KĪM-ee-yə/ Retention of food due to dilation of the stomach.

isoenzyme /Ī-sō-EN-zīm/ n. An isozyme.

isogeneic graft /ī-sə-jə-NAY-ik/ n. A graft involving a genetically identical donor and host.

isoleucine /Ī-sō-LOO-seen/ (I or ile) n. An essential-amino acid. CODONS | MOLECULAR STRUCTURE | BIOSYNTHESIS PATHWAY

isomer /Ī-sə-mer/ n. Any of two or more chemical compounds with the same molecular formula, but differing in structure.

isometry /ī-SAWM-mə-tree/ (or isometric growth /ī-sə-MEHT-rick/) n. Growth of a part at the same the rate as that of some other part. Compare: allometry.

isoprene unit n. A branched chain of five carbon atoms present in all terpenoids. MOLECULAR STRUCTURE

isoprenoids n. See: terpenoids.

isopropyl β-D-1-thiogalactopyranoside (IPTG) also known as isopropylthiogalactoside n. A compound that triggers transcription of the lac operon. Unlike the lactose metabolite allolactose, which has the same effect, IPTG cannot be metabolized by E. coli. Thus, in E. coli, unlike allolactose, it triggers transcription constitutively. In a laboratory setting, IPTG is commonly used in identifying E. coli colonies that have been transformed with recombinant plasmids. MOLECULAR STRUCTURE

isotonic solution /ī-sə-TAWN-ick/ See: hypertonic solution — isotonicity /ī-sə-taw-NIS-sit-ee/

isotopes /Ī-sə-tōpes/ n. Variants of the same chemical element, differing with respect to the number of neutrons present but having nearly identical chemical properties (different isotopes always have the same number of protons).

isozymes /Ī-sə-zīmz/ n. An enzyme performing the same function as another enzyme but having a different amino acid sequence. They catalyze the same reactions, but differ in molecular structure and with respect to other characteristics such as isoelectric point and molecular weight.

isthmoplegia /ĪS-mō-plee-jee-yə/ n. Paralysis of the fauces.

isthmus /ĪS-məs/ n. A narrow connecting structure or passage — isthmian /ĪS-mee-ən/

isthmitis /is-MĪT-is/ n. Inflammation of the throat, particularly the fauces.

ITP abbr. Inosine triphosphate.

iteroparity /it-er-ə-PAIR-ə-tee/ n. The condition of producing offspring repeatedly during the lifetime of an individual. Compare: semelparity

J (1) abbr. joule; (2) symbol for: Jurassic Period.

jaglion /JAG-lī-ən/ (also jaguon /JAG-wawn/) n. Hybrid produced by the mating of a lioness and a jaguar. MORE INFORMATION

jarovization /jar-ə-vī-ZAY-sən/ n. Vernalization.

jaundice /JAWN-dəs/ n. A condition resulting from excess bilirubin in the blood. It is characterized by yellowness of the skin, mucous membranes, and the whites of the eyes. Often a sign of liver malfunction, although it can also result from obstruction of the bile duct, or from excessive destruction of erythrocytes.

Java man n. A name used for a representative of the hominid Homo erectus discovered on the island of Java; formerly Pithecanthropus erectus.

Jebel-Qatrani Formation A geological formation in northeastern Egypt. It is composed primarily of Oligocene strata. MORE INFORMATION

jejunum /jə-JOON-əm/ n. The second portion of the small intestine; lying between the duodenum and the ileum. It is a little over 2 meters in length.

JH abbr. Juvenile hormone.

joule n. 10⁷ ergs.

jugum n. A connecting bar or ridge.

jumart /JOO-mart/ n. An equid-bovid hybrid, that is, a cross between either a cow or a bull and either a horse or a donkey MORE INFORMATION.

jumping genes n. An informal name for transposons.

junk DNA (also non-coding DNA) n. Regions of the genome not coding for genes, especially those composed of repetitive sequences; in most organisms a majority of the genome consists of so-called junk DNA which may have regulatory and other functions.

juvenile hormones (JHs) also allatum hormones n. Hormones regulating many aspects of insect physiology; particularly important in controlling the metamorphosis of holometabolous insects; secreted by the corpora allata.

Jurassic Period (J) /jure-ASS-ik/ (~199.6–145.5 mya) n. The second geologic period of the Mesozoic Era. First recognized by Alexander von Humboldt, who realized that strata in Europe's Jura mountain range had not yet been included in the stratigraphic system. The first birds and salamanders arose in the Jurassic, and it was the great heyday of the dinosaurs. Angiosperms had not yet arisen and ferns, cycads, and conifers dominated the landscape.

k abbr. Kilo- (a prefix meaning one thousand).

K (1) abbr. lysine; (2) symbol for: potassium; (2) symbol for: Cretaceous Period.

Human karyotype colored to show pairing (Enlarge)

karyotype /KARE-ee-ə-type/ n. (1) the set of chromosomes present in a particular type of organism, viewed in terms of their characteristic size and structure; (2) a photomicrograph of the chromosomes present in an individual's somatic cells, often arranged in a standard format showing the number, size, and shape of each type of chromosome. See also: spectral karyotype. MORE INFORMATION

karyotypic /kare-ee-ə-TIP-ick/ n. Of or pertaining to a karyotype or karyotypes.

Kcat abbr. The maximum number of moles of substrate that an enzyme can convert to product per catalytic site per unit time.

kDa abbr. Kilodalton.

keratin /KARE-ə-tin/ n. A structural protein found in hair, nails, and the tough outer layer of skin (stratum corneum). Keratin is used as a coating on pills that should pass through the stomach intact.

keratinized /KARE-ə-tin-īzd/ adj. Characterized by a having a high content of keratin.

keratoconjunctivitis n. Inflammation of the cornea and conjunctiva of the eye.

Ketone

ketone /KEE-tone/ n. A molecule, containing the carbonyl group (CO), with general structure as shown in the figure at left.

kg abbr. kilogram.

KHCO₃ abbr. Potassium carbonate.

human kidney (Enlarge)

KHSO₄ abbr. Potassium bisulfate.

KI abbr. Potassium iodide.

kidneys /KID-neez/ n. Organs present in vertebrates, usually near the spine, that function in cleansing the blood of uric acid, urea, and other metabolic wastes. In humans, they are bean shaped. The interior surface of the kidney is lined with the pelvis renalis or renal pelvis, which is continuous with the lining of the ureter. LOCATION OF KIDNEYS

kilobase (kb) /KILL-ə-base/ n. Unit of length for DNA fragments equal to 1000 nucleotides.

kilodalton (kDa) /KILL-ə-DAWL-tən/ n. 1000 dalton units.

kinesialgia /kin-ee-see-AL-zhə/ n. Pain resulting from movement of the muscles.

kinesiology /kə-neez-ee-AWL-ə-jee/ n. The study of the movement of muscles.

kinetochore n. The region on centromere to which the microtubules of the spindle apparatus attach during mitosis and meiosis. MORE INFORMATION

kingdom /KING-dəm/ n. In taxonomy, a division of a domain that itself contains one or more phyla. CHART OF RELATIVE TAXONOMIC RANKS

kinocilium n. The motile cilium of one of the hair cells of the inner ear.

km abbr. Kilometer.

kM abbr. Michaelis constant.

KMnO₄ abbr. Potassium permanganate.

knapping n. The shaping of stone tools by a process of chipping off flakes.

kolypeptic abbr. Interfering with digestion.

koniology /kone-ee-AWL-ə-jee/ (also coniology n. The study of dust in relation to its effects on health.

koniometer /kone-ee-AWM-ə-ter/ n. A measurement device for estimation of atmospheric dust loads.

krypton (Kr) /KRIP-tawn/ n. Rare gaseous element; Atomic weight 83.80, atomic number 36. PERIODIC TABLE

KT Cretaceous-Tertiary.

KT extinction /KAY-tee/ n. See: Cretaceous-Tertiary mass extinction.

kyogenic /kī-ə-JEHN-ik/ adj. Causing pregnancy.

kyphosis /kī-FŌ-səs/ n. A curvature of the upper spine; commonly known as hunchback or hump back.

kysthitis /kiss-THĪ-təs/ n. Vaginal inflammation.

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