kairomone - a class of pheromone which is an interspecific chemical secretion that benefits the receiver but not the emitter; also defined as a pheromone produced by organisms to attract a mate, though in some cases can also undesirably attract the attention of a predator

Karst - a limestone terrain characterized by sinks, caverns, abrupt ridges, protuberant rocks and drainage characteristics due to greater solubility of limestone in natural waters than is common. The term is derived from the geographical name of part of Slovenia

Karst cave - a cave caused by dissolution of limestone by water

karyogamy - a process of fusion of the nuclei of two sex cells or gametes; the second step in syngamy

karyology - the study of the nucleus of a cell

karyolysis - the disintegration and dissolution of a cell nucleus upon death of the cell

karyorrhexis - the rupture of a cell nucleus, releasing disintegrated chromatin

karyotype - the entire chromosome complement of an individual cell, as seen during the mitotic phase

Kelvin scale - an absolute scale of temperature in which each degree equals one kelvin. Water freezes at 273.15 K and boils at 373.15 K

kenozooid - a small bryozoan heterozooid that strengthens and supports the colony, as well as fill spaces; long, branching, tubular, transparent stolons which extend above the substratum and to which the feeding individuals (autozooids) are attached

A number of small keys (cays) in Jobos Bay, Puerto Rico.

key - a small, low coastal island or emergent reef of sand or coral; flat mound of sand and admixed coral fragments built upon a reef flat or just above high tide level. A synonym of cay

key character - in taxonomy, a diagnostic character used in a taxonomic key

key stimulus - in ethology or animal behavior, the stimulus which releases a fixed action pattern

keystone predator - the dominant predator or the top predator that has a major influence on community structure

keystone species - a species that is disproportionately important in the maintenance and balance of its community integrity

kilobase (kb) - a length unit equal to 1000 base pairs of a double-stranded nucleic acid molecule; 1000 pairs of nucleotide bases in DNA

kindling fluorescent protein - a photoactivatable marker that turns itself off after a selectable period

kinetic energy - energy associated with motion

kinetics - the study of acceleration, motion, or rate of change

kinetochore - a structure forming at the centromere during mitosis for binding microtubules; a platelike structure necessary for chromosomal movement during mitosis; it develops on the centromere and links the chromosomes to the mitotic spindle

kingdom - in taxonomy, the highest ranked category in the taxonomic hierarchy. All organisms are classified into one of five kingdoms: Monera (the prokarytic Kingdom. Includes archaebacteria, eubacteria and cyanobacteria); Protista (unicellular eukaryotes); Fungi (yeasts and mushrooms); Plantae (plants); and Animalia (animals). Some scientists recognize slightly different classification schemes

kinocilium - a minute short cellular hair-like process (microvillus) responsible for locomotion in motile unicellular organisms, or in higher forms, generates a current of fluid

knee root - an aerial root of a mangrove that emerges from the ground then loops back in. It is also called a peg root. It is not clear whether knee roots have a role in respiration

knob - a projecting structure on the reef margin or reef front wherein the upper surface flares outward, giving the surface a greater diameter then the basal section

knoll - a small reef within the lagoon or on shallow shelves

knot - The unit of speed used in navigation that is equal to 1 nautical mile (6,076.115 ft or 1,852 m) per hour

Koch's Postulates - a set of criteria for judging whether a given bacterium is the cause of a given disease; a useful benchmark in judging whether there is a cause-and-effect relationship between a bacteria (or any other type of microorganism) and a clinical disease. The postulates are as follow: The bacteria must be present in every case of the disease; The bacteria must be isolated from the host with the disease and grown in pure culture; The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host; The bacteria must be recoverable from the experimentally infected host

Krebs cycle - a series of enzymatic reactions in mitochondria involving oxidative metabolism of acetyl compounds to produce high-energy phosphate compounds that are the source of cellular energy ; also known as the tricarboxylic acid (TCA) cycle and as the citric acid cycle

Photos: (Left) The Kure Atoll Reserve Preservation Area includes approximately 17 square nautical miles (57 square kilometers) of submerged coral reef habitats; (Right) An endangered Hawaiian monk seal and her pup. (Photos: NOAA)

Kure Atoll - the most remote of the Northwestern Hawaiian Islands, and the northern-most coral atoll in the world, located at the extreme northwest end of the Hawaiian archipelago. The atoll has almost 80,000 acres of coral reef habitat with 28 species of stony corals so far documented. Kure Atoll is an important pupping and resting area for Hawaiian Monk seals. The island is also a nesting area for smany species of sea birds, and a wintering area for a variety of migratory bird species from North America and Asia