Glossary Database

Select a Letter to view the associated terms.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

 Glossary Term: 

Definition:
 Habitat  the place where an organism normally lives (Morris 1992).
 Hair  One of the structures typically found on a caterpillar. It can come in a variety of forms, such as feathery, branched, or forked. The more correct term for this kind of hair is seta (pl. setae).
 Hair pencil  A hair-like structure on the legs or abdomens of some butterflies and moths that is believed to aid in the distribution of pheromones during courtship.
 Half-life  The time required for half of a given sample of a radioactive isotope to decay to its daughter isotope.
 Halide  A mineral compound characterized by a halogen such as fluorine, chlorine, iodine, or bromine as the anion. Halite, NaCl is an example of a halide.
 Halite  An evaporate mineral composed of sodium chloride (NaCI).
 Hand specimen  A small specimen that fits into the hand and can be easily carried.
 Hanging valley  A tributary valley with the floor lying (hanging) above the valley floor of the mainstream or shore to which it flows. Hanging valleys commonly are created by deepening of the main valley by glaciation, but they can also be produced by faulting or rapid retreat of a sea cliff.
 Hanging wall  The surface or block of rock that lies above an inclined fault plane.
 Hardness  1. mineralogy. The measure of the resistance of a mineral to scratching or abrasion. 2. water. A property of water resulting from the presence of calcium carbonate and magnesium carbonate in solution.
 Harem  the mating and association of several adult females with one male (Morris 1992).
 hatchery  Man-made and operated facility where wild fish are trapped; their eggs harvested, fertilized and hatched; young are reared and then released back in to the wild. Hatchery programs largely attempt to compensate for wild population losses resulting from anthropogenic impacts.
 Head  One of the three main regions comprising an insect. It is the region at the front and bears most of the sensory organs, such as the antennae.
 Headland  An extension of land seaward from the general trend of the coast; a promontory, cape, or peninsula.
 Headwall  A steep slope at the head of a valley like the rock cliff at the back of a cirque.
 Headward erosion  Extension of a stream headward, up the regional slope of erosion.
 Headwaters  The small streams that are the sources of a river.
 Heat  The energy that flows into or out of system because of a difference in temperature.
 Heat flow  The flow of heat from the interior of Earth.
 Hemipenes  The paired copulatory organs lying laterally in a cavity in the base of the tail in snakes and lizards (Peters 1964).
 Hemiptera  the true bugs, a large order of insects including bedbugs, cicadas, and aphids, with mouth parts adapted for piercing and sucking and with mandibles in the form of long stylets lying in a trough-like labium (Morris 1992).
 Hemisphere  Half of a sphere or a globe, or any celestial body.
 Hemoglobin  the oxygen-carrying pigment of the erythrocytes, formed by the developing erythrocyte in the bone marrow. It is a complex protein composed of four heme groups and four globin polypeptide chains (Morris 1992).
 Herbaceous  1. of or relating to an herb. 2. soft and green, rather than woody (Morris 1992).
 Herbivorous  Feeding exclusively or mainly on plants (Morris 1992).
 heterocercal  The caudal fin is heterocercal if the vertebral column extends up into the dorsal lobe. The fin is often asymmetrical. When the base of caudal fin is not at right angles to the body it usually heterocercal.
 Heterogeneity  the fact or state of being dissimilar, as in composition, source, quantity, dimensions, and so on (Morris 1992).
 Hibernacula  The places in which an animal hibernates or overwinters; winter quarters (Morris 1992).
 Hibernaculum  A structure made by some caterpillars in which they overwinter. Often it consists of a leaf rolled and tied with silk.
 Hibernate  To pass the winter in a condition of hibernation (Morris 1992).
 Hibernation  1.) A state of dormancy or reduced activity typically entered at the onset of winter. Hibernating saves the animal a great deal of energy at a time where food is not readily available. Also referred to as 'overwintering.'2.) A dormant, sleeplike state, with a lower body temperature and slower heart and breathing rate, that is characteristic of various animals during the winter months in cold climates, such as bears, bats, certain birds, snakes, frogs, and turtles; this state tends to protect against cold weather and to reduce the need for food (Morris 1992). Ground squirrels are good examples of hibernating mammals as some hibernate for about 9 months. Hibernators do arouse from hibernation periodically, but usually stay in their hibernation chamber or nest.
 Hierarchy  A group of people, or things arranged in order of rank or grade.
 High-grade metamorphism  Metamorphism that occurs under high temperature and high pressure, usually caused by deep burial.
 Hill topping  A behavior commonly exhibited by Swallowtail (Papilio spp.) butterflies where males and females will congregate at a high point in the landscape, such as at the top of a ridge. By doing so, each individual butterfly's chance of finding a mate is increased.
 Hinge  The line where folded beds show maximum curvature. The line formed by the intersection of the hinge plane with the bedding surface.
 Hogback  A narrow, sharp ridge formed on steeply inclined, resistant rock.
 Holarctic  Occurring in the temperate regions of the entire Northern Hemisphere.
 Holocene  The present epoch of geologic time from approximately 10,000 years ago to the present. View timeline of geologic events.
 homocercal  A caudal fin in which the vertebral column ends in a plate at its base and does not extend into the dorsal lobe. The base is at right angles to the long axis of the body.
 Homogeneous  The same in structure, quality, size, etc. Such as a formation that is homogeneous throughout means that it is uniform throughout, with similar grains size, texture, sediment type, etc.
 Honey gland  See Dorsal nectary organ.
 Honeydew  A sugary solution secreted by aphids, some caterpillars, and other insects, which is agreeable to some insects, and is consumed.
 Horizon  1. geologic. A plane of stratification assumed to have been originally horizontal. 2. soil. A layer of soil distinguished by characteristic physical properties. Soil horizons generally are designated by letters (for example, A horizon, B horizon, C horizon).
 Horn  1.) A sharp peak formed at the intersection of the headwalls of three or more cirques. 2.)A hardened structure that extends from the head of some caterpillars.
 Hornblende  A variety of the amphibole mineral group.
 Hornfels  A nonfoliated metamorphic rock of uniform grain size, formed by high-temperature metamorphism, typically formed by contact metamorphism around igneous intrusions.
 Horns  consist of an inner, boney core covered by an outer sheath that is much like our fingernails. Horns are not shed annually as are antlers. They are found in the Bovidae family (bighorn sheep and mountain goats), and in pronghorns.
 Horst  An elongate fault block that has been uplifted in relation to the adjacent rocks.
 Host plant  The plant used for food by a specific species. Butterflies typically lay their eggs on the host plant used by the caterpillar. A single species of butterfly may use one or several species of plants as host plants.
 Hot spot  The expression at Earth's surface of a mantle plume, or column of hot, buoyant rock rising in the mantle beneath a lithospheric plate.
 Hummock  A small, rounded or cone-shaped, low hill or a surface of other small, irregular shapes. A surface that is not equidimensional or ridgelike.
 hybrid  A cross between two different genera or species.
 Hybridize  To breed with a member of a different species. Often the offspring of such a union, called a hybrid, is infertile.
 Hydration  Chemical combination of water with other substances.
 Hydraulic  Pertaining to a fluid in motion.
 Hydraulic head  The pressure exerted by a fluid at a given depth beneath a surface. It is proportional to the height of the fluid's surface above the area where the pressure is measured.
 Hydrocarbon  Any organic compound, gaseous, liquid, or solid, consisting solely of carbon and hydrogen. Crude oil is basically a complex mixture of hydrocarbons.
 Hydrologic  Having to do with water, or the study of it on the earth.
 Hydrologic system  The system of moving water at Earth's surface.
 Hydrologic Unit Code (HUC)  An area designated by the United States Geological Survey as belonging to a certain watershed.
 Hydrology  The study of surface and subsurface water.
 Hydrolysis  Chemical reaction with water.
 Hydrosphere  The waters of Earth, as distinguished from the rocks (lithosphere), the air (atmosphere), and living things (biosphere).
 Hydrostatic pressure  The pressure within a fluid (such as water) at rest, exerted on a given point within the body of the fluid.
 Hydrothermal deposit  A mineral deposit formed by hot water. The high temperature commonly is associated with emplacement of a magma.
 Hydrous  Said of a mineral compound containing water. Containing water, especially in chemical combinations.
 Hydroxide  A compound consisting of an element or radical combined with the radical OH-hypersthene.
 Hypersthene  A common rock-forming mineral in igneous rocks of the orthopyroxene group.
 Hypocenter  The point in the earth where an earthquake originates; also known as the focus.
 Hypothesis  A provisional explanation for observations subject to continual testing and modification. If well supported by evidence, hypotheses are then generally called theories.