Glossary

ABIOTIC Physical rather than biological; not derived from living organisms.

ACCRETIONARY WEDGE Sediments and oceanic lithosphere scraped off the top of a subducting oceanic crustal plate and onto the less dense, nonsubducting plate at a convergent plate boundary.

ACID PRECIPITATION Rain or any other form of precipitation that is unusually acidic, mostly caused by human emissions of sulfur and nitrogen compounds which react in the atmosphere to produce acids.

ADAPTATION The process whereby an organism becomes better suited to its habitat, or a characteristic which is especially important for an organism’s survival.

ALCOHOL A colorless, volatile, flammable liquid synthesized or obtained by fermentation of sugars and starches and widely used, either pure or denatured.

ALLUVIAL Describing sediment which is or has been carried by water. See also colluvial.

ALLUVIAL FAN A geological feature created when a fast-moving confined stream with a high suspended load suddenly widens out, slows down, and drops a portion of its sediment, creating a broad fan of alluvial deposit.

ALLUVIAL VALLEY A valley along a stream or former stream where most of the upper layers of the soil have been deposited by alluvial processes.

ALTERNATE LEAVES An arrangement of leaves (or buds) on a stem in which one leaf arises from a node, creating the appearance of leaves alternating on the stem. See also opposite and whorled leaves.

AMNIOTIC EGG A water-tight, fluid-filled egg in which the developing embryo is protected by a series of membranes and often a hard or leathery shell which resists desiccation.

AMPHIBIANS Ectothermic animals that metamorphose from a juvenile water-breathing form to an adult air-breathing form.

ANADROMOUS Describing fish that spend most of their lives in ocean habitats but migrate to freshwater for breeding.

ANIMAL UNIT MONTHS (AUM) Common measure of livestock stocking rates, calculated from the amount of forage required for one mature cow to maintain its weight for one month.

ANNUAL A plant that lives for only one growing season. See also perennial.

ANOXIC Having dangerously low levels of oxygen.

ANTENNA One of the jointed, movable sensory appendages occurring in pairs on the heads of insects and most other arthropods.

ANTHROPOGENIC Relating to or resulting from the influence of human beings on nature.

AQUATIC Living predominantly in water.

AQUIFER A layer of rock, gravel, or soil with high permeability allowing it to hold an underground body of water.

ARTHROPOD An invertebrate animal with bilateral (left-right) symmetry, a hard exoskeleton, jointed legs, a segmented body, and many pairs of limbs. Arthropods include insects, spiders, centipedes, shrimp, and crayfish.

ASPECT The direction that a hill or mountain slope faces.

ATMOSPHERE The gaseous envelope surrounding the Earth; the air.

ATOM The smallest component of an element having the chemical properties of the element.

AUTOCHTHONOUS Describing anything that originates in or is native to the area in which it is found.

AUTOTROPH An organism capable of generating its own food source; generally plants that produce food through photosynthesis.

BEDLOAD Larger, macroscopic particles of rock and mineral carried by a stream or other body of water. See also suspended load.

BEDROCK Solid rock underneath loose material such as soil, sand, clay, or gravel.

BEHAVIOR The actions or reactions of organisms in response to external or internal stimuli.

BILATERAL SYMMETRY A basic body plan in which the left and right sides of the organism are approximate mirror images of each other when the body is divided along the midline.

BINOMIAL NOMENCLATURE The system of two-part Latin names used to give each species a unique name consisting of a combination of a genus and a species name.

BIODIVERSITY The number and variety of organisms within a given ecosystem.

BIOFUEL Fuel produced from renewable resources, especially plant biomass, vegetable oils, and treated municipal and industrial wastes.

BIOGEOCHEMICAL CYCLES The movement of matter through Earth’s systems in which a chemical or molecule moves through both biotic and abiotic stages, such as the water cycle, the carbon cycle, and the nitrogen cycle.

BIOGEOGRAPHY The study of the distribution of biodiversity over space and time. It aims to reveal where organisms live, and at what abundance.

BIOMASS The mass of living biological organisms in a given area or ecosystem at a given time.

BIOREGION A region defined by characteristics of its natural environment, such as flora, fauna, climate, habitat type, and topography.

BIOSPHERE The total portion of the Earth in which life exists, taken as the combination of all global ecoregions.

BIOTA The total of all organisms within a given ecosystem at a given time.

BIOTIC Biological; derived from living organisms.

BODY PLAN The blueprint for the way the body of an organism is laid out.

BRACT A leaf in a flower cluster or a leaf base of a flower, usually differing somewhat from an ordinary leaf in size, form, or texture. It is often much reduced but occasionally large and showy, sometimes petallike, highly colored, and very conspicuous.

BROADLEAF HARDWOOD A tree with wide, flat leaves, as contrasted to needles, that is usually deciduous, with examples including oak, cottonwood, and alder. The wood is denser and hence harder than the wood of most conifers.

BRUSH Shrubs; an area composed of woody plants less than 15 feet tall. See also chaparral.

BUD A growing point enclosed by closely overlaid rudimentary leaves.

BULB An underground vertical shoot that has modified leaves (or thickened leaf bases) that are used as food storage organs by a dormant plant.

BUOYANCY The upward force that a fluid exerts on an object that is less dense than the liquid itself.

CAMOUFLAGE Protective coloring or another feature that conceals an animal and enables it to blend into its surroundings.

CARBON EMISSIONS The release of carbon into the atmosphere over a specified area and period of time.

CARBON SEQUESTRATION The process of removing carbon from the atmosphere and depositing it in a reservoir. Carbon sequestration naturally occurs during photosynthesis.

CARNIVORE An animal that feeds primarily on the meat of other animals rather than plant sources.

CARTILAGINOUS Having a skeleton consisting mainly of cartilage, a type of dense connective tissue composed of specialized cells called chondrocytes.

CASCADE RANGE Mountain range in the Sierra-Cascade system running north-south from British Columbia, Canada, all the way through Washington and Oregon and into California.

CELLULOSE A stringy, fibrous substance that forms the main material in the cell walls of plants.

CENTIPEDE Any of numerous predacious, chiefly nocturnal arthropods constituting the class Chilopoda, having an elongated, flattened body composed of 15 to 173 segments, each with a pair of legs, the first pair being modified into poison fangs.

CENTRAL VALLEY The extremely wide and long valley in the center of California bordered by the Coast Ranges to the west and the Sierra Nevada to the east. Sometimes called the Great Valley.

CEPHALOTHORAX The anterior section of arachnids and many crustaceans, consisting of the fused head and thorax.

CHANNELIZATION Any activity that moves, straightens, shortens, cuts off, diverts, or fills a stream channel, whether natural or previously altered.

CHAPARRAL A plant community common to California and other Mediterranean climate regions characterized by very dense growths of evergreen, drought-resistant shrubs and small trees such as scrub oak, chamise, and ceanothus.

CHELICERAE The first pair of usually pincerlike appendages of spiders and other arachnids.

CHEMICAL ENERGY Energy liberated by a chemical reaction or absorbed in the formation of a chemical compound.

CHEMOSYNTHESIS The synthesis of organic compounds by energy derived from chemical reactions, typically in the absence of sunlight.

CHITIN A tough, protective, semitransparent substance, primarily a nitrogen-containing polysaccharide, forming the principal component of arthropod exoskeletons and the cell walls of certain fungi.

CHLOROFLUOROCARBONS Compounds consisting of chlorine, fluorine, and carbon atoms that are degraded by the sun’s radiation in the stratosphere and destroy stratospheric ozone.

CHRYSALIS The pupa of certain kinds of insects, especially of moths and butterflies, that is inactive and enclosed in a firm case or cocoon from which the adult eventually emerges.

CIRQUE A shallow horizontal depression formed by glacial action, often holding a small lake.

CISMONTANE CALIFORNIA Land to the west of the Sierra-Cascade mountains.

CLEAR-CUTTING The felling and removal of all trees from a given tract of forest.

CLIMATE The combination of all weather factors, such as temperature, humidity, and precipitation, over a long period of time.

CLOACA The common cavity into which the intestinal, urinary, and generative canals open in birds, reptiles, amphibians, many fishes, and certain mammals.

CLOACAL SCENT GLAND A secretory organ of the cloaca that has been implicated in the scent-marking behavior of some reptiles, amphibians, and monotremes.

CLONE A plant or other organism that has been reproduced asexually to produce a genetically identical offspring.

CO₂ (CARBON DIOXIDE) A chemical compound composed of two oxygen atoms bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth’s atmosphere in this state.

COAL-FIRED POWER Energy produced by the heat from burning coal which is used to generate electricity.

COAST RANGES The group of mostly contiguous mountain ranges more or less directly inland from the Pacific Coast, running north-south from extreme Northern California to Ventura County in the south and making up the western border of the Central Valley.

COCOON The silky envelope spun by the larvae of many insects, such as silkworms, serving as a covering while they are in the pupal stage.

COLLABORATIVE CONSERVATION A deliberate and inclusive process of two or more people, groups, or entities coming together to work out issues related to sustaining and improving natural resources and human communities.

COLLUVIAL Describing sediment which was moved by gravitational processes rather than water. See also alluvial.

COMMUNITY Populations of different plant and animal species occupying the same geographical area.

COMPLETE METAMORPHOSIS Insect development in which egg, larval, pupal, and adult stages occur, each differing greatly in morphology.

COMPOST A mixture of various decaying organic substances, such as dead leaves or manure, used for fertilizing soil.

COMPOUND LEAF A leaf that has a fully subdivided blade, each leaflet of the blade separated along a main or secondary vein.

CONFINED STREAM A stream with steep canyon walls or other obstructions marking its banks and preventing lateral changes to its morphology.

CONIFER A plant bearing cones, including pine, fir, and spruce.

CONNECTIVITY A measure of the extent to which plants and animals can move among habitat patches. Landscape features such as corridors, greenbelts, and ecological networks provide potential means for achieving habitat connectivity.

CONSERVATION The protection, preservation, management, or restoration of natural environments and the ecological communities that inhabit them. Conservation is generally held to include the management of human use of natural resources for current public benefit and sustainable social and economic utilization.

CONSERVATION EASEMENT OR COVENANT A deeded transfer of partial interest in real property to a private or public institution to conserve land or its resources for future generations. Conservation easements can result in tax benefits for landowners and are binding on all future owners of the property.

CONSUMER A heterotrophic organism that derives energy from other organisms or organic matter.

CONVERGENT PLATE BOUNDARY A tectonic boundary where two plates are moving toward each other.

CORE The dense innermost portion of the Earth composed mostly of iron, nickel, and other metals.

CORE HABITAT Habitat that is far enough away from other habitat types to avoid their influences. See also edge habitat.

CREPUSCULAR Describing animals that are primarily active during twilight, that is, at dawn and at dusk.

CROPLAND Land which is managed by humans for intensive agriculture.

CRUST The outermost portion of the Earth comprising the continental surfaces as well as ocean floors and varying in depth from 5 to 70 kilometers (3 to 40 miles).

CRUSTACEAN Any of various predominantly aquatic arthropods of the class Crustacea, including lobsters, crabs, shrimps, and barnacles, characteristically having a segmented body, a chitinous exoskeleton, and paired, jointed limbs.

CUMULATIVE EFFECT The combined toxic effects of pollution or other environmental impacts that build in organisms or an ecosystem over time.

DAM An artificial blockage along a stream created with the purpose of impounding water.

DEAD ZONE A low-oxygen area in the ocean due to an excess of nutrients, typically from chemical fertilizer runoff, and resulting in a large reduction in aquatic life. (The vast middle portions of the oceans which naturally have little life are not considered dead zones.) The term can also be applied to the identical phenomenon in large lakes.

DECIDUOUS Describing a plant that sheds foliage at the end of the growing season.

DECOMPOSER An organism, often a bacterium or fungus, that feeds on and breaks down dead plant or animal matter, thus making organic nutrients available to the ecosystem.

DECOMPOSITION The breakdown of a formerly living entity into simpler materials, minerals, and nutrients that provide sustenance to other organisms.

DELTA The end of a stream where it flows into an ocean or other large standing body of water allowing the stream to deposit its suspended sediment over a widening area.

DENTICLE A toothlike or platelike scale on the outside of a cartilaginous fish, such as a shark or ray.

DEPOSITION ZONE A portion of a stream where large amounts of suspended load sediments are deposited on the banks and/or bed.

DESERT A climate region that receives less than 10 inches of rainfall annually.

DESICCATION The drying out of a living organism through exposure beyond the point where it can survive.

DETRITIVORE An organism that feeds on and breaks down dead plant or animal matter, returning essential nutrients to the ecosystem.

DIAPAUSE A physiological state of dormancy especially in immature insects, with very specific triggering and releasing conditions. It is used as a means to survive predictable, unfavorable environmental conditions, such as temperature extremes, drought, or reduced food availability.

DIURNAL Describing an animal whose behavior is characterized by being active during the day and sleeping at night.

DIVERGENT PLATE BOUNDARY A tectonic boundary where plates split apart or separate from one another and allow molten mantle material to rise up.

DIVERSION Removal of water from a natural stream for human use.

DIVERSION CHANNEL A man-made canal that separates water from a stream and delivers it elsewhere, often for agricultural use.

DOMESTICATED Describing animals that are tamed, especially by generations of breeding, to live in close association with human beings as pets or work animals and that usually have been made dependent so that they lose their ability to live in the wild.

DOMINANCE HIERARCHY A system or set of relationships in animal groups that is based on a hierarchical ranking, usually established and maintained by behavior in aggressive encounters one or a few members hold the highest rank, and the others are submissive to those ranking higher and dominant to those ranking lower.

DORMANT In a state of rest or inactivity; quiescent.

DRAINAGE BASIN The topographic region drained by a river and its tributaries; also called a catchment basin or a watershed.

DYNAMIC EQUILIBRIUM A system in a steady state. In this case it refers to a plant community that is relatively stable.

ECOSYSTEM The combination of all living organisms and natural features of a given geographic area, with emphasis given to their interdependence.

ECOSYSTEM MANAGEMENT The inclusion of biodiversity and ecosystem health into the goals for land and water management at a landscape scale.

ECTOTHERMIC Refers to organisms that control body temperature through external means.

EDGE HABITAT Habitat on or near the boundary between two different habitat types. See also core habitat.

ELECTRICAL ENERGY Energy made available by the flow of electric charge through a conductor.

ELECTROMAGNETIC ENERGY A form of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space.

ELECTROMAGNETIC WAVE A wave of energy having a frequency within the electromagnetic spectrum and propagated as a periodic disturbance of the electromagnetic field when an electric charge oscillates or accelerates.

ELIASOME A fleshy, protein-rich “food patch” on some seeds or fruits.

EMBODIED ENERGY The energy that was used to make a product and to get it from its source to the consumer.

ENDEMIC Describing a species (or other well-defined group) that is native only to a single geographical range. See also paleoendemic.

ENDOTHERMIC Describing organisms with the ability to control their body temperatures through internal means such as muscle shivering or fat burning; that is, they keep their body temperatures at roughly constant levels, regardless of the ambient temperature.

EPICORMIC SPROUTING Growth that emerges from dormant buds along the trunk and branches of a tree.

EPIPHYTE A plant that grows above the ground, supported nonparasitically by another plant or object and deriving its nutrients and water from rain, the air, dust, etc.

EROSION The movement of soil and rocks from the surface of one area and their eventual deposition elsewhere by processes such as gravity, water flow, wind, or glacial action.

ESTIVATE To pass the summer in a state of torpor; to be dormant in the hot, dry season.

ESTIVATION Also known as “summer sleep,” a state of animal dormancy somewhat similar to hibernation. Animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation.

ESTUARY An aquatic coastal habitat created by a mix of freshwater and marine influences.

ETHANOL A volatile, flammable, colorless liquid best known as the type of alcohol found in alcoholic beverages and in modern thermometers.

EUKARYOTE Any organism having as its fundamental structural unit a cell type that contains specialized organelles in the cytoplasm, a membrane-bound nucleus enclosing genetic material organized into chromosomes, and an elaborate system of division by mitosis or meiosis, characteristic of all life-forms except bacteria, blue-green algae, and other microorganisms.

EUTROPHIC Having an abundance of mineral nutrients, particularly nitrogen and phosphorous, usually due to chemical fertilizer pollution.

EUTROPHICATION A process where water bodies receive excess nutrients that stimulate excessive plant growth, especially of algae.

EVERGREEN Having leaves all year-round. This contrasts with deciduous plants, which completely lose their foliage for part of the year.

EVOLUTION Change in the genetic composition of a population during successive generations, as a result of natural selection acting on the genetic variation among individuals, and resulting in the development of new species.

EXOSKELETON A hard, protective outer body covering of an animal, such as an insect, crustacean, or mollusk. The exoskeletons of insects and crustaceans are largely made of chitin.

EXOTHERMIC Describing an animal whose body temperature is regulated by external factors.

EXOTIC SPECIES Species of organisms introduced into habitats where they are not native.

EXTINCT No longer in existence. It is used to describe species that have ended or died out.

EXTINCTION The state or process of causing a population, species, or taxa to cease to exist.

EXTIRPATED Locally extinct. It is used to describe species (or other taxa) no longer existing in the chosen area of study but still existing elsewhere.

EXTRUSIVE Describing igneous rock that cools and forms aboveground.

FERTILIZER Any of a large number of natural or synthetic materials, including manure and nitrogen, phosphorus, and potassium compounds, spread on or worked into soil to increase its capacity to support plant growth.

FISHERY Harvesting of fish, shellfish, and sea mammals as a commercial enterprise; also the location or season of commercial fishing.

FLOODPLAIN The portion of land surrounding a stream that receives periodic seasonal flooding.

FLOWER The part of a seed plant comprising the reproductive organs and their envelopes if any, especially when such envelopes are more or less conspicuous in form and color.

FOOD WEB A series of organisms related by predator-prey and consumer-resource interactions; the entirety of interrelated food chains in an ecological community.

FORAGE To wander in search of food or provisions; also the food or provisions found by this method.

FORAGING FLOCK Animals that join each other and move together while searching for food.

FORB An herb (a nonwoody plant, annual or perennial) that is not a grass.

FOREST CERTIFICATION Certification verifying that forests are well managed as defined by a particular standard and ensuring that certain wood and paper products come from responsibly managed forests.

FORESTRY The art and science of managing forests, tree plantations, and related natural resources and generally concerned with assisting forests to provide timber as raw material for wood products; wildlife habitat; natural water quality management; recreation; landscape and community protection; employment; aesthetically appealing landscapes; biodiversity management; watershed management; erosion control; and using forests as “sinks” for atmospheric carbon dioxide.

FOSSIL FUEL A hydrocarbon deposit, such as petroleum, coal, or natural gas, derived from living matter of a previous geologic time and used for fuel.

FRUIT The ripened ovary or ovaries of a seed-bearing plant, together with accessory parts, containing the seeds and occurring in a wide variety of forms.

FRY A recently hatched fish which has fully absorbed its yolk sac and can now hunt and consume live food. The fry of live-bearers do not have a yolk sac and therefore need to begin feeding immediately after birth.

GASEOUS Existing in the state of a gas; not solid or liquid.

EOGRAPHICAL RANGE The overall area within which a given species can be expected to be found.

GEOTHERMAL ENERGY Power extracted from heat stored in the earth. Geothermal energy originates from the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface.

GILL The respiratory organ of aquatic animals, such as fish, that breathe oxygen dissolved in water.

GLACIAL ACTION The impacts that the presence and movement of a glacier have on the surrounding geology, including the shaping of the landscape through erosion and deposition of soil, minerals, rocks, and boulders and the compaction of the Earth’s crust and mantle under the glacier’s weight.

GLACIAL CYCLE Periods characterized by cooler and drier climates over most of the Earth and large land and sea ice masses extending outward from the poles.

GLACIER A large sheet of ice formed in an alpine or other cool area.

GREENHOUSE EFFECT The heating of the surface of a planet or moon due to the presence of an atmosphere containing gases that absorb and emit infrared radiation.

GREENHOUSE GAS Any of the atmospheric gases that contribute to the greenhouse effect by absorbing infrared radiation produced by solar warming of the Earth’s surface. They include carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and water vapor.

GROUNDWATER Any water found beneath the ground surface, including aquifers, permafrost, and general soil moisture.

GRUB A soft, thick wormlike larva of an insect.

HABITAT The plants, animals, climate, topography, and other natural factors that comprise the place where an organism or population lives.

HABITAT FRAGMENTATION A landscape-scale process involving the breaking up of large expanses of continuous habitat into smaller patches of discontinuous habitat.

HEADWATERS The tributary stream farthest upstream from a river’s eventual drainage basin.

HEAVY METALS A broad group of metallic elements that are known to have toxic effects under high concentrations, such as mercury, iron, copper, and lead.

HEMIMETABOLOUS Describing an organism that undergoes incomplete metamorphosis.

HERBACEOUS Describing a plant with little or no woody tissue and which dies down at the end of the growing season to the soil level.

HERBIVORE An animal that eats mostly plants.

HETEROTROPH An organism that must consume other organisms in order to survive.

HIBERNATION A state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate.

HOLOMETABOLOUS Describing an organism that undergoes complete metamorphosis.

HORTICULTURE The industry and science of plant cultivation.

HYBRIDIZATION Crossbreeding of individuals from genetically different populations or species.

HYDRAULIC MINING A form of mining that employs water to dislodge rock material or move sediment.

HYDROELECTRIC ENERGY Electricity generated by the production of power through use of the gravitational force of falling or flowing water.

HYDROGEN BOND A special type of bond exhibited by molecules showing polarity and containing hydrogen, notably water.

HYDROLOGY The field of study relating to the Earth’s water resources, including their movement, changes, and quality.

HYPHAE The strands of long cells that comprise the living bodies of multicellular fungi.

IGNEOUS ROCK A rock type formed by the cooling and solidifying of molten magma. Igneous rocks can be either intrusive or extrusive.

INCOMPLETE METAMORPHOSIS Insect development, as in the grasshopper and cricket, in which the change is gradual and characterized by the absence of a pupal stage. See also complete metamorphosis.

INDIGENOUS Originating in and characteristic of a particular region or country; native.

INSECT An arthropod of the class Insecta that has three pairs of legs, a segmented body divided into three regions (head, thorax, and abdomen), one pair of antennae, and usually wings.

INTERGLACIAL A geological interval of warmer global average temperature that separates glacial periods within an ice age.

INTERNODES The sections of a plant stem between nodes.

INTERTIDAL ZONE The region between the high-tide mark and the low-tide mark.

INTRUSIVE Describing igneous rock that forms and cools underground.

INVASIVE Describing any nonnative (exotic) species whose introduction does or is likely to cause economic or environmental harm or harm to human health.

INVERTEBRATE An animal, such as an insect or mollusk, that lacks a backbone or spinal column.

JET STREAM Narrow, powerful bands of fast-moving wind in upper portions of the Earth’s atmosphere on the boundaries between large air masses of differing temperatures.

KINETIC ENERGY The energy which an object possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity.

LADDER FUELS Fuels which provide vertical continuity between strata, thereby allowing fire to carry from surface fuels into the crowns of trees or shrubs with relative ease.

LANDFILL A burial site for the disposal of waste materials, usually lined to prevent leakage of fluids.

LARGE WOODY DEBRIS Fallen trees, logs and stumps, root wads, and piles of branches along the edges of streams, lakes, and bays, often defined as material that is greater than 4 inches in diameter.

LARVA The immature, wingless, feeding stage of an insect that undergoes complete metamorphosis.

LEAF An aboveground plant organ specialized for photosynthesis.

LEAF LITTER Dead plant material, such as leaves, bark, needles, and twigs, that has fallen to the ground.

LEVEE A man-made wall or embankment intended to contain the flow of a river or other body of water and prevent flooding of the surrounding land.

LIANA Any of various long-stemmed, usually woody vines that are rooted in the soil at ground level and use trees, as well as other means of vertical support, to climb up to the canopy in order to get access to well-lit areas of the forest.

LICHEN An organism that is the result of a symbiotic relationship between a fungus and algae and grows in leaflike, crustlike, or branching forms on rocks and trees.

LIFE CYCLE The series of changes in the growth and development of an organism from its beginning as an independent life-form to its mature state in which offspring are produced.

LILIACEOUS Of, relating to, or denoting plants of the lily family (Liliaceae).

LIMITING FACTOR A factor that controls a process, such as organism growth or species population, size, or distribution. The availability of food, predation pressure, and availability of shelter are examples of factors that could be limiting for an organism.

LITHIFICATION The process in which loosely deposited sediments compact under pressure to become hard rock.

LITHOSPHERE The outer solid part of the Earth, including the crust and uppermost mantle.

LITTORAL ZONE The part of a lake, stream, or the ocean that is closest to the shore.

MACROINVERTEBRATE An invertebrate large enough to be seen with the unaided eye.

MAGMA Molten rock beneath the Earth’s surface which is usually associated with tectonic faults or other specific hot spot areas. When extruding to the surface, molten rock is known as lava.

MAMMAL Any vertebrate of the class Mammalia, having the body more or less covered with hair, nourishing the young with milk from the mammary glands, and with the exception of the egg-laying monotremes, giving birth to live young.

MANDIBLE One of the pincerlike mouthparts of insects and other arthropods.

MANTLE The portion of the Earth’s interior between the core and the crust.

MARSUPIAL Any of various mammals of the order Marsupialia, whose young are undeveloped when born and continue developing outside their mother’s body attached to one of her nipples. Most marsupials have longer hind legs than forelimbs, and the females usually have pouches in which they carry their young.

MARSUPIUM The pouch or fold of skin on the abdomen of a female marsupial.

MECHANICAL ENERGY The sum of potential energy and kinetic energy present in the components of a mechanical system.

MEDITERRANEAN CLIMATE The climate of regions found, roughly speaking, between 30 and 40 degrees latitude north and south of the equator, on the western side of continents; a climate having sunny, hot, dry summers and mild, rainy winters.

METAMORPHIC ROCK ROCK formed when existing rock is subjected to high heat and pressure transforming it into a new rock type.

METHANE An odorless, colorless, flammable gas that is the major constituent of natural gas and is used as a fuel and as an important source of hydrogen.

MICROBE An organism that is microscopic (usually too small to be seen by the naked human eye).

MICROCLIMATE A small climate zone where climatic factors differ from the surrounding area due to localized influences such as slope, aspect, and elevation.

MICROORGANISM Catchall term for any microscopic life-form, including plankton, algae, bacteria, fungi, protists, and many others.

MIGRATORY Traveling from one place to another at regular times of the year, often over long distances.

MILLIPEDE Any terrestrial arthropod of the class Diplopoda, having a cylindrical body composed of 20 to more than 100 segments, each with two pairs of legs.

MOLECULE A group of two or more atoms linked together by sharing electrons in a chemical bond. Molecules are the fundamental components of chemical compounds and are the smallest parts of compounds that can participate in chemical reactions.

MOLT To periodically shed part or all of a coat or an outer covering, such as feathers, cuticle, or skin, which is then replaced by a new growth.

MONOTREMES The most primitive order of mammals, characterized by certain birdlike and reptilian features, such as hatching young from eggs, and having a single opening for the digestive, urinary, and genital organs, comprising only the platypus and the echidnas of Australia and New Guinea.

MORPHOLOGY The shape of a thing. Plant or animal morphology is the study of common forms and features that can identify a species. Geomorphology and river morphology involve the description of important land or stream features.

MOSS A flowerless plant belonging to the Bryophyta phylum which grows in tufts, sods, or mats in moist areas such as tree trunks, the ground, and rocks.

MUSHROOM The reproductive structure of some fungi, often called a fruiting body and viewed as analogous to the fruit of a plant.

MYCELIUM The mass of hyphae that makes up the growing body of most fungi.

MYCORRHIZAL FUNGI A type of fungi that lives in a mutually beneficial symbiotic relationship with a plant’s root system, supporting as well as receiving support from its host.

NATIVE Describing a plant or animal that occurs naturally in a given environment without having been introduced by human activity.

NATURAL GAS A gas consisting primarily of methane that occurs naturally beneath the Earth’s surface, often with or near petroleum deposits.

NATURALIST A scientist who studies the natural world and environment in all its forms and relations, with an emphasis on observational rather than experimental methods.

NATURALIZED Describing any nonnative species that has adapted and grows or multiplies as if native.

NECTAR A sugar-rich liquid produced by plants.

NICHE A particular relationship to the various species and climate that allows an individual or species to live within an ecosystem.

NITROGEN OXIDES Binary compounds of oxygen and nitrogen. They are commonly found in vehicle exhaust, cigarette smoke, and smog. When dissolved in the atmosphere, they can lead to acid rain which damages ecosystems.

NOCTURNAL Describing an animal whose behavior is characterized by being active during the night and sleeping during the day.

NODE The place on a plant stem where buds, leaves, and branches originate.

NODULE A swelling such as a root nodule that is formed on plants in the pea family (Fabaceae) housing symbiotic bacteria that fix atmospheric nitrogen for the plant.

NONAMNIOTIC EGG An egg that lacks a covering and must be fertilized externally.

NONNATIVE Describing organisms that are not indigenous to the ecosystem to which they were introduced and that are capable of surviving and reproducing without human intervention.

NONPOINT SOURCE (NPS) POLLUTION Pollution that comes from many disparate sources.

NONRENEWABLE RESOURCE A natural resource that cannot be produced, regrown, regenerated, or reused on a scale which can sustain its consumption rate.

NOXIOUS WEED A plant species that has been designated by state or national agricultural authorities as a plant that is injurious to agricultural and/or horticultural crops and/or humans and livestock.

NUCLEUS The central region of the cell, in which DNA is stored.

NUTRIENT CYCLING The process by which mineral and gas nutrients are moved from the soil, water, or atmosphere to plants and then to animals and microorganisms and eventually back into the soil, water, and atmosphere.

NUTRIENT LOADING The contribution of large amounts nutrients to an ecosystem, usually due to fertilizer or other chemical pollution runoff.

OLD-GROWTH FOREST A forest significantly past the age of maturity of its dominant species. Usually characterized by well-developed structure, many snags, and dead wood on the ground; a late-successional forest type for the area. It sometimes refers to undisturbed or never-harvested areas.

OLIGOTROPHIC Having a marked deficiency of nutrients or other materials needed to sustain life.

OMNIVORE An animal that eats both plant and animal material.

OPPOSITE LEAVES Leaves that arise from a single node in opposing pairs on either side of a stem. See also alternate and whorled leaves.

ORGANELLE A specialized part of a cell having some specific function; a cell organ.

OUTCROSSING The practice of introducing unrelated genetic material into a breeding line to increase genetic diversity.

OUTLET The terminal end of a stream where it flows into the ocean or other large body of water.

OVARY (PLANT) The ovule-bearing lower part of a pistil that ripens into a fruit.

OXBOW LAKE A crescent-shaped lake formed when a meander of a stream is cut off from the main channel.

OXYGEN An element constituting 21 percent of the atmosphere by volume that occurs as a diatomic gas, O2, combines with most elements, is essential for plant and animal respiration, and is required for nearly all combustion.

OZONE An unstable, poisonous allotrope of oxygen, O3, that is formed naturally in the ozone layer from atmospheric oxygen by electric discharge or exposure to ultraviolet radiation. It is also produced in the lower atmosphere by the photochemical reaction of certain pollutants.

OZONE LAYER The layer of the upper atmosphere where most atmospheric ozone is concentrated, from about 8 to 30 miles above the Earth’s surface.

PALEOENDEMIC An endemic species with a long geological record and which once had a more extensive geological range than currently found.

PARASITE An organism that lives in a symbiotic relationship with another, deriving benefit from its host at some cost to the host.

PARASITIC FUNGI A type of fungi that lives in or on another organism, often weakening or eventually killing its host.

PARENT MATERIAL The underlying material that soil develops from, generally bedrock that has decomposed in place, or material that has been deposited by wind, water, or ice.

PAROTID GLAND An external skin gland on the back, neck, and shoulder of toads and some frogs and salamanders.

PARTICULATE MATTER Material suspended in the air in the form of minute solid particles or liquid droplets, especially when considered as an atmospheric pollutant.

PECTORAL FIN Either of the anterior pair of fins just behind the head of a fish, attached to the pectoral girdle, corresponding to the forelimbs of higher vertebrates.

PENINSULAR RANGES Mountain ranges of the Sierra-Cascade system with a north-south axis and running from Riverside County in Southern California all the way through Baja California, Mexico.

PERENNIAL A plant that lives for more than two years. See also annual.

PERIPHYTON The mixture of algae, bacteria, other microorganisms, and organic detritus that coats underwater surfaces in a stream, lake, or other body of water.

PERMEABILITY The ease with which water moves through a particular soil or rock.

PETAL One of the often brightly colored parts of a flower surrounding the reproductive organs. Petals are attached to the receptacle underneath the carpels and stamens and may be separate or joined at their bases.

PHEROMONE Any chemical substance released by an animal that serves to influence the physiology or behavior of other members of the same species.

PHOTOSYNTHESIS A process by which plants convert carbon dioxide into organic compounds, especially sugars, using the energy from sunlight.

PHYLOGENY The evolutionary development and history of a species or higher taxonomic grouping of organisms.

PHYTOPLANKTON Chlorophyll-containing microorganisms which form the base of the food web in many aquatic ecosystems.

PISTIL The female, ovule-bearing organ of a flower, including the stigma, style, and ovary.

PLACENTAL Describing mammals having a placenta; all mammals except monotremes and marsupials.

PLANT COMMUNITY The plant populations existing in a shared habitat or environment.

PLANT MORPHOLOGY The general term for the study of the morphology (physical form and external structure) of plants.

PLATE A section of the Earth’s crust that moves about as a discrete whole, relative to other plates.

PLEISTOCENE The geologic epoch covering the most recent periods of glaciation, from about 2.6 mya to 10,000 years ago when the Holocene epoch is marked as beginning.

POIKILOTHERMIC Describing an animal whose internal temperature varies along with that of the ambient environmental temperature. Most, but not all, ectotherms are poikilothermic.

POLLEN The male sex cells in plants. In flowering plants, pollen is produced in thin filaments in the flower, called stamens.

POLLINATION The fertilization of a seed due to the movement of pollen from male flower parts to female flower parts, often requiring wind or pollinators such as bees or other insects.

POLLINATOR The biotic agent (vector) that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization.

POTENTIAL ENERGY Energy stored within a physical system. It is called potential energy because it has the potential to be converted into other forms of energy, such as kinetic energy, and to do work in the process.

PRECIPITATION Condensed water vapor in the atmosphere that falls to Earth’s surface, including rain, snow, and hail.

PREDATOR An organism that feeds on other organisms (prey).

PRE-IMAGO An insect in the stage preceding its sexually mature adult stage.

PRESERVATION Keeping in perfect or unaltered condition.

PRIMARY CONSUMER An animal that feeds on plants; an herbivore.

PROKARYOTE Any cellular organism that has no nuclear membrane and no organelles in the cytoplasm except ribosomes and that has its genetic material in the form of single continuous strands forming coils or loops, characteristic of all organisms in the kingdom Monera, such as the bacteria and blue-green algae.

PROTISTS A diverse group of eukaryotic microorganisms that are either unicellular or multicellular without specialized tissues.

PUPA The nonfeeding stage between the larva and adult in the metamorphosis of some insects during which the larva typically undergoes complete transformation within a protective cocoon or hardened case.

PUPATE Among insects, to go into a pupal stage, often wrapped in a cocoon or chrysalis, from which the insect will emerge as a fully formed adult.

RADIOACTIVE DECAY The process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation.

RAIN SHADOW The area of dry land that lies on the leeward (or downwind) side of a mountain range, thereby receiving much less rainfall.

RAINFOREST A forested area where the annual rainfall is very high (often but not always defined as greater than 160 inches a year), usually characterized by high levels of biodiversity.

REACH A segment of a stream, usually marked by geographic boundaries at the up- and downstream ends.

REPRODUCTION The sexual or asexual process by which organisms generate new individuals of the same kind.

RESERVOIR (WATER) A natural or artificial pond or lake used for the storage and regulation of water.

RESTORATION The process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed.

RIPARIAN ZONE The habitat area directly on either side of a stream’s banks.

ROCK CYCLE The cycle in which the three classes of rocks — igneous, sedimentary, and metamorphic — transform into one another by geological processes.

RUNOFF The flow of rain or snowmelt over land, typically when the land has become saturated or is impervious.

SALINITY The amount of salt present, especially dissolved salt in a body of water.

SALMONID The family of fish containing salmon, trout, whitefish, and others.

SAN ANDREAS FAULT Significant California earthquake fault running more than 800 miles from the Salton Sea to Cape Mendocino, formed by the relative horizontal movement of the Pacific and North American tectonic plates.

SAPROPHYTIC FUNGI A type of fungi that thrives on dead trees, plants, or other organic matter, thereby contributing to the decomposition process.

SCALE (PLANT PART) A small, thin, usually dry, often appressed plant structure, such as any of the protective leaves that cover a tree bud or the bract that subtends a flower in a sedge spikelet.

SCAT Excrement, especially of an animal.

SCAVENGER A carnivore that feeds on already dead animal tissues, which aids the decomposition process.

SCLEROPHYLLOUS Describing leaves of trees and shrubs that are evergreen, hard, thick, leathery, and usually small.

SEDIMENT Material that is carried in a suspended state by water or glacial action, ranging in size from microscopic particles of silt or clay up to rocks and boulders.

SEDIMENTARY ROCK Rock formed by the deposition of sediment out of its suspension in water or air, followed by a gradual solidification and hardening under pressure.

SEDIMENTATION The deposition of a stream’s suspended load sediment over a given area.

SELECTION PRESSURE The effect of selection on the relative frequency of one or more genes within a population.

SEPAL One of the usually separate, green parts that surround and protect the flower bud and extend from the base of a flower after it has opened.

SERPENTINE SOIL A soil type characterized by a high magnesium-calcium ratio and generally low nutrient levels.

SHEETFLOW Water that flows over a large and irregular area, usually with a shallow depth, rather than in a restricted stream bed.

SHRUB Category of woody plant, distinguished from a tree by its multiple stems and lower height, usually less than 5 to 6 meters (15 to 20 feet) tall.

SIERRA NEVADA The significant mountain range of Eastern California running north-south from Plumas County to the area east of Bakersfield and comprising the eastern border of the Central Valley.

SILK Also known as gossamer, a protein fiber spun by spiders. It is often used to make webs or other structures, which function as nets to catch other creatures or as nests or cocoons for protection for their offspring.

SILT A sedimentary material consisting of very fine particles intermediate in size between sand and clay.

SILVICULTURE The art and science of controlling the establishment, growth, composition, health, and quality of forests to meet diverse needs and values of the many landowners, societies, and cultures.

SIMPLE LEAF A leaf that has an undivided blade. See also compound leaf.

SLOPE The steepness or angle of a hillside, usually in degrees.

SLOUGH A type of swamp or shallow lake system, typically formed as or by the backwater of a larger waterway.

SMOG Air pollution containing ozone and other reactive chemical compounds formed by the action of sunlight on nitrogen oxides and hydrocarbons, especially those in automobile exhaust.

SOLAR POWER The result of converting sunlight into electricity.

SNAG A standing, partly or completely dead tree, often missing a top or most of the smaller branches.

SOCIOBIOLOGY The study of the biological bases for animal social behavior.

SOIL A mixture of fine-particle mineral constituents, such as clay, silt, sand, and many trace minerals, along with decomposed organic matter, air, and water.

SOIL DEPOSITION The geological process by which material is added to a landform or landmass.

SPAWN The mass of eggs deposited by fishes, amphibians, mollusks, crustaceans, etc.

SPECIALIST A species that requires a very specific habitat, food source, or other limiting factor in order to survive.

SPECIES A group of related organisms having common characteristics and capable of interbreeding.

SPINNERET Any of various tubular structures from which spiders and certain insect larvae, such as silkworms, secrete the silk threads from which they form webs or cocoons.

SPIRACLE An aperture or orifice through which air or water passes in the act of respiration, such as the blowhole of a whale.

STAMEN The pollen-bearing organ of a flower, consisting of the filament and the anther.

STEM The supporting structure of a plant, serving also to conduct and to store food materials.

STOMATE A pore, found in the leaf and stem epidermis, that is used for gas exchange.

STRATOSPHERE The region of the Earth’s atmosphere extending from the tropopause to about 50 kilometers (31 miles) above the Earth’s surface. The stratosphere is characterized by the presence of ozone gas (in the ozone layer) and by temperatures which rise slightly with altitude because of the absorption of ultraviolet radiation.

STREAM ORDER Classification system for streams. First-order streams are source streams, and order ranking increases only when two tributaries of the same order join.

SUBDUCTION ZONE A zone in which one crustal plate goes beneath another.

SUBSTRATE (ORGANISMS) The surface on or in which plants, algae, or certain animals, such as barnacles or clams, live or grow. A substrate may serve as a source of food for an organism or simply provide support.

SUBSTRATE (STREAMS) The material that rests at the bottom of a stream.

SUSPENDED LOAD Sediment which is carried in a suspended state in a stream or other body of water.

SYMBIONT One member of a symbiotic relationship.

SYMBIOTIC Describing any relationship in which an organism lives together with another of a different species. Symbiotic relationships can be mutualistic, in which both organisms benefit; parasitic, in which one benefits and the other is harmed; or commensal, in which one benefits and the other is unaffected.

SYRINX The vocal organ of a bird, consisting of thin vibrating muscles at or close to the division of the trachea into the bronchi.

TACTILE Of, pertaining to, endowed with, or affecting the sense of touch.

TAXA Units used in biological classification or taxonomy, such as kingdom, phylum, class, order, family, genus, or species; plural of taxon.

TECTONICS The motions of the Earth’s plates and upper mantle.

TEMPERATE Describing the two geographical zones on the Earth’s surface between the tropical zone and the Arctic or Antarctic Circle, where seasons are generally pronounced and variable.

TERRESTRIAL Living predominantly or entirely on land.

TETRAPOD Vertebrate animal having four feet, legs, or leglike appendages or descended from four-limbed ancestors.

THERMAL ENERGY A form of energy that manifests itself as an increase in temperature.

THORAX The middle division of the body of an insect, to which the wings and legs are attached. The thorax lies between the head and the abdomen.

THREATENED (SPECIES OR COMMUNITY) Describing any species or community (including animals, plants, fungi, etc.) which are vulnerable to extinction in the near future.

TIDAL FLUX The difference in the water level at high tide and low tide; high-tide level minus low-tide level, typically measured in feet.

TIDAL POWER A form of hydropower that converts the energy of tides into electricity or other useful forms of power.

TOPOGRAPHY The terrain in a given area, including a description of the changes in elevation, aspect, prominent features such as rocks, and in some cases characteristic vegetation and soil types.

TORPOR A (usually short-term) state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism.

TRANSFORM PLATE BOUNDARY A tectonic boundary where two plates slide horizontally past one another in opposite directions.

TRANSLOCATE Move or transfer from one place to another; cause to change location.

TRANSMONTANE CALIFORNIA Land to the east of the Sierra-Cascade mountains.

TRANSVERSE RANGES The mostly east-west mountain ranges north of the Los Angeles area, sometimes called the Los Angeles Mountains.

TRIBUTARY A stream that flows into a larger stream.

TROPHIC LEVEL Any class of organisms that occupy the same position in a food chain, such as primary consumers, secondary consumers, and tertiary consumers.

TROPICAL Pertaining to, characteristic of, occurring in, or inhabiting the tropics, which are characterized by uniformly warm and wet weather or sometimes alternating wet and dry seasons.

TROPICS The geographical zone of the Earth’s surface between the Tropic of Cancer and Tropic of Capricorn, which experiences uniformly warm and wet weather or sometimes alternating wet and dry seasons.

UNDERSTORY An underlying layer of vegetation, especially the plants that grow beneath a forest’s canopy.

VERNAL POOL A seasonal body of standing water that typically forms in the spring from melting snow and other runoff, dries out completely in the hotter months of summer, and often refills in the autumn. Vernal pools range from broad, heavily vegetated lowland bodies to smaller, isolated upland bodies with little permanent vegetation. They are free of fish and provide important breeding habitat for many terrestrial or semiaquatic species such as frogs, salamanders, and turtles.

VERTEBRATE An animal that has a spinal column.

VOLATILE ORGANIC COMPOUNDS Compounds that have a high vapor pressure and low water solubility. Many are human-made chemicals from the manufacture of paints, adhesives, petroleum products, fuels, solvents, pharmaceuticals, and refrigerants. They are a common source of contamination because many are toxic and are known or suspected human carcinogens.

VOMERONASAL ORGAN Also called Jacobson’s organ, an organ inside the mouth on the palate. It can be found in all vertebrates, but it is enhanced in only a few. It is used to detect pheromones and is responsible for snakes’ sense of smell.

WATER CYCLE The continuous process in which the Earth’s water changes form from gas to liquid and sometimes solid and is thus moved around the surface and atmosphere of the planet. It is also known as the hydrologic cycle.

WATERSHED The topographic region drained by a river and its tributaries. Also called a drainage basin.

WAVE POWER The transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example, for electricity generation, water desalination, or the pumping of water into reservoirs.

WETLANDS Transitional zones between land and water that are inundated with water periodically.

WHORLED LEAVES A series of leaves arranged in a ring arising from a single node. See also alternate and opposite leaves.

WOODY PLANT A plant having hard lignified tissues or woody parts, especially stems.

The definitions in the glossary were derived from a variety of sources, including government documents (from the US Geological Survey, US Department of Agriculture, Natural Resource Conservation Service, and others), academic course sites, and online dictionaries, such as Wikipedia.