Bio

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hydrosphere:

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The earth's (1) liquid water (oceans, lakes, other bodies of surface water, and underground water), (2) frozen water (polar ice caps, floating ice caps, and ice in soil, known as permafrost), and (3) small amounts of water vapor in the atmosphere.

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stratosphere:

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Second layer of the atmosphere, extending about 17Ð48 kilometers (11Ð30 miles) above the earthÕs surface. It contains small amounts of gaseous ozone (O3), which filters out about 95% of the incoming harmful ultraviolet (UV) radiation emitted by the sun. Compare troposphere

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food web:

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Complex network of many interconnected food chains and feeding relationships. Compare food chain.

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range of tolerance:

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Range of chemical and physical conditions that must be maintained for populations of a particular species to stay alive and grow, develop, and function normally. See law of tolerance

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photosynthesis

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Complex process that takes place in cells of green plants. Radiant energy from the sun is used to combine carbon dioxide (CO2) and water (H2O) to produce oxygen (O2) and carbohydrates (such as glucose, C6H12O6) and other nutrient molecules. Compare aerobic respiration, chemosynthesis.

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tertiary (higher-level) consumers:

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Animals that feed on animal-eating animals. They feed at high trophic levels in food chains and webs. Examples are hawks, lions, bass, and sharks. Compare detritivore, primary consumer, secondary consumer.

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population:

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Group of individual organisms of the same species living in a particular area.

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scavenger:

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Organism that feeds on dead organisms that were killed by other organisms or died naturally. Examples are vultures, flies, and crows. Compare detritivore

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aquatic life zone:

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Marine and freshwater portions of the biosphere. Examples include freshwater life zones (such as lakes and streams) and ocean or marine life zones (such as estuaries, coastlines, coral reefs, and the deep ocean).

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prokaryotic cell:

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Cell that doesn't have a distinct nucleus. Other internal parts are also not enclosed by membranes. Compare eukaryotic cell

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detritivore:

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Consumer organism that feeds on detritus, parts of dead organisms, and cast-off fragments and wastes of living organisms. The two principal types are detritus feeders and decomposers.

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salinity:

Back 12

Amount of various salts dissolved in a given volume of water

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dissolved oxygen (DO) content:

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Amount of oxygen gas (O2) dissolved in a given volume of water at a particular temperature and pressure, often expressed as a concentration in parts of oxygen per million parts of water.

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pyramid of energy flow:

Back 14

Diagram representing the flow of energy through each trophic level in a food chain or food web. With each energy transfer, only a small part (typically 10%) of the usable energy entering one trophic level is transferred to the organisms at the next trophic level. Compare pyramid of biomass, pyramid of numbers.

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law of tolerance:

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The existence, abundance, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by the species.

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trophic level:

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All organisms that are the same number of energy transfers away from the original source of energy (for example, sunlight) that enters an ecosystem. For example, all producers belong to the first trophic level, and all herbivores belong to the second trophic level in a food chain or a food web.

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food chain:

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Series of organisms in which each eats or decomposes the preceding one. Compare food web

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sexual reproduction: .

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Reproduction in organisms that produce offspring by combining sex cells or gametes (such as ovum and sperm) from both parents. This produces offspring that have combinations of traits from their parents. Compare asexual reproduction.

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chemosynthesis:

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Process in which certain organisms (mostly specialized bacteria) extract inorganic compounds from their environment and convert them into organic nutrient compounds without the presence of sunlight

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troposphere:

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Innermost layer of the atmosphere. It contains about 75% of the mass of earthÕs air and extends about 17 kilometers (11 miles) above sea level. Compare stratosphere

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dew point:

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Temperature at which condensation occurs for a given amount of water vapor.

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tolerance limits:

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Minimum and maximum limits for physical conditions (such as temperature) and concentrations of chemical substances beyond which no members of a particular species can survive. See law of tolerance

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functional diversity:

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Biological and chemical processes or functions such as energy flow and matter cycling needed for the survival of species and biological communities. See biodiversity, ecological diversity, genetic diversity, species diversity

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pyramid of numbers:

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Diagram representing the number of organisms of a particular type that can be supported at each trophic level from a given input of solar energy at the producer trophic level in a food chain or food web. Compare pyramid of biomass, pyramid of energy flow.

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limiting factor principle

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Too much or too little of any abiotic factor can limit or prevent growth of a population of a species in an ecosystem, even if all other factors are at or near the optimum range of tolerance for the species.

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secondary consumer:

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Organism that feeds only on primary consumers. Compare detritivore, omnivore, primary consumer.

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aerobic respiration:

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Complex process that occurs in the cells of most living organisms, in which nutrient organic molecules such as glucose (C6H12O6) combine with oxygen (O2) and produce carbon dioxide (CO2), water (H2O), and energy

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pyramid of biomass:

Back 28

Diagram representing the biomass, or total dry weight of all living organisms, that can be supported at each trophic level in a food chain or food web. See pyramid of energy flow, pyramid of numbers.

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natural greenhouse effect:

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Heat buildup in the troposphere because of the presence of certain gases, called greenhouse gases. Without this effect, the earth would be nearly as cold as Mars, and life as we know it could not exist. Compare global warming.

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species diversity:

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Number of different species and their relative abundances in a given area. See biodiversity. Compare ecological diversity, genetic diversity

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ecological efficiency:

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Percentage of energy transferred from one trophic level to another in a food chain or web.

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biodiversity:

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Variety of different species (species diversity), genetic variability among individuals within each species (genetic diversity), variety of ecosystems (ecological diversity), and functions such as energy flow and matter cycling needed for the survival of species and biological communities (functional diversity).

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primary consumer:

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Organism that feeds on all or part of plants (herbivore) or on other producers. Compare detritivore, omnivore, secondary consumer.

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detritus:

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Parts of dead organisms and cast-off fragments and wastes of living organisms

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biotic:

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Living organisms.

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ecological diversity:

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The variety of forests, deserts, grasslands, oceans, streams, lakes, and other biological communities interacting with one another and with their nonliving environment. See biodiversity. Compare functional diversity genetic diversity, species diversity.

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atmosphere:

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The whole mass of air surrounding the earth

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ecosystem:

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Community of different species interacting with one another and with the chemical and physical factors making up its nonliving environment

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herbivore:

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Plant-eating organism. Examples are deer, sheep, grasshoppers, and zooplankton

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metabolism:

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Ability of a living cell or organism to capture and transform matter and energy from its environment to supply its needs for survival, growth, and reproduction.

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decomposer:

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Organism that digests parts of dead organisms and cast-off fragments and wastes of living organisms by breaking down the complex organic molecules in those materials into simpler inorganic compounds and then absorbing the soluble nutrients. Producers return most of these chemicals to the soil and water for reuse. Decomposers consist of various bacteria and fungi. Compare consumer, detritivore, producer.

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carnivore:

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Animal that feeds on other animals.

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limiting factor

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Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem.

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net primary productivity (NPP):

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Rate at which all the plants in an ecosystem produce net useful chemical energy; equal to the difference between the rate at which the plants in an ecosystem produce useful chemical energy (gross primary productivity) and the rate at which they use some of that energy through cellular respiration. Compare gross primary productivity

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lithosphere

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Outer shell of the earth, composed of the crust and the rigid, outermost part of the mantle outside the asthenosphere; material found in earthÕs plates. See crust, mantle

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biosphere:

Back 46

Zone of earth where life is found. It consists of parts of the atmosphere (the tropo-sphere), hydrosphere (mostly surface water and groundwater), and lithosphere (mostly soil and surface rocks and sediments on the bottoms of oceans and other bodies of water) where life is found. Sometimes called the ecosphere.

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consumer:

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Organism that cannot synthesize the organic nutrients it needs and gets its organic nutrients by feeding on the tissues of producers or of other consumers; generally divided into primary consumers (herbivores), secondary consumers (carnivores), tertiary (higher-level) consumers, omnivores, and detritivores (decomposers and detritus feeders). In economics, one who uses economic goods

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habitat:

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Place or type of place where an organism or population of organisms lives. Compare ecological niche.

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climate:

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Physical properties of the troposphere of an area based on analysis of its weather records over a long period (at least 30 years). The two main factors determining an areaÕs climate are temperature, with its seasonal variations, and the amount and distribution of precipitation

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carbon cycle:

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Cyclic movement of carbon in different chemical forms from the environment to organisms and then back to the environment

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biomass:

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Organic matter produced by plants and other photosynthetic producers; total dry weight of all living organisms that can be supported at each trophic level in a food chain or web; dry weight of all organic matter in plants and animals in an ecosystem; plant materials and animal wastes used as fuel.

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genetic diversity:

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Variability in the genetic makeup among individuals within a single species. See biodiversity.

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eukaryotic cell:

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Cell containing a nucleus, a region of genetic material surrounded by a membrane. Membranes also enclose several of the other internal parts found in a eukaryotic cell. Compare prokaryotic cell.

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detritus feeder:

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Organism that extracts nutrients from fragments of dead organisms and their cast-off parts and organic wastes. Examples are earthworms, termites, and crabs. Compare decomposer.

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condensation nuclei:

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Tiny particles on which droplets of water vapor can collect

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hydrologic cycle:

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Biogeochemical cycle that collects, purifies, and distributes the earthÕs fixed supply of water from the environment to living organisms and then back to the environment.

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gross primary productivity (GPP):

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The rate at which an ecosystem's producers capture and store a given amount of chemical energy as biomass in a given length of time. Compare net primary productivity

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asexual reproduction:

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Reproduction in which a mother cell divides to produce two identical daughter cells that are clones of the mother cell. This type of reproduction is common in single-celled organisms.

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cell:

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Smallest living unit of an organism. Each cell is encased in an outer membrane or wall and contains genetic material (DNA) and other parts to perform its life function. Organisms such as bacteria consist of only one cell, but most of the organisms we are familiar with contain many cells. See eukaryotic cell, prokaryotic cell.

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biome:

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Terrestrial regions inhabited by certain types of life, especially vegetation. Examples are various types of deserts, grasslands, and forests.

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anaerobic respiration:

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Form of cellular respiration in which some decomposers get the energy they need through the breakdown of glucose (or other nutrients) in the absence of oxygen. Compare aerobic respiration.

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biogeochemical cycle:

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Natural processes that recycle nutrients in various chemical forms from the nonliving environment to living organisms and then back to the nonliving environment. Examples are the carbon, oxygen, nitrogen, phosphorus, sulfur, and hydrologic cycles.

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eukaryotic cell:

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Cell containing a nucleus, a region of genetic material surrounded by a membrane. Membranes also enclose several of the other internal parts found in a eukaryotic cell. Compare prokaryotic cell.

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producer: .

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Organism that uses solar energy (green plant) or chemical energy (some bacteria) to manufacture the organic compounds it needs as nutrients from simple inorganic compounds obtained from its environment. Compare consumer, decomposer.

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community:

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Populations of all species living and interacting in an area at a particular time

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nitrogen cycle:

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Cyclic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment

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omnivore:

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Animal that can use both plants and other animals as food sources. Examples are pigs, rats, cockroaches, and people. Compare carnivore, herbivore

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nutrient:

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Any food or element an organism must take in to live, grow, or reproduce

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organism: .

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Any form of life.