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Chapter 3

Terms

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Cells
minute biological compartments within which the processes of life are carried out
Base
substances that bond readily with hydrogen ions
Cellular respiration
the process in which a cell breaks down sugar or other organic compounds to release energy used for cellular work; may be anaerobic or aerobic, depending on the availability of oxygen
Matter
anything that takes up space and has mass
Enzymes
molecules, usually proteins or nucleic acids, that act as catalysts in biochemical reactions
Population
a group of individuals of the same species occupying a given area
Kinetic energy
energy contained in moving objects such as a rock rolling down a hill, the wind blowing through the trees, or water flowing over a dam
Species
a population of morphologically similar organisms that can reproduce sexually among themselves but that cannot produce fertile offspring when mated with other organisms
Consumers
an organism that obtains energy and nutrients by feeding on other organisms or their remains
Hydrologic cycle
the natural process by which water is purified and made fresh through evaporation and precipitation. This cycle provides all the freshwater available for biological life
Sulfur cycle
the chemical and physical reactions by which sulfur moves into or out of storage and through the environment
Metabolism
all the energy and matter exchanges that occur within a living cell or organism; collectively, the life processes
Energy
the capacity to do work (that is, to change the physical state or motion of an object)
Molecule
a combination of two or more atoms
Ecology
the scientific study of relationships between organisms and their environment. It is concerned with the life histories, distribution, and behavior of individual species as well as the structure and function of natural systems as well as the level of populations, communities, and ecosystems
Second law of thermodynamics
states that, with each successive energy transfer or transformation in a system, less energy is available to do work
Isotopes
forms of a single element that differ in atomic mass due to a different number of neutrons in the nucleus
Decomposers
fungi and bacteria that break complex organic material into smaller molecules
Food web
a complex, interlocking series of individual food chains in an ecosystem
Carbon sink
places of carbon accumulation, such as in large forests (organic compounds) or ocean sediments (calcium carbonate); carbon is thus removed from the carbon cycle for moderately long to very long periods of time
Food chain
a linked feeding series; in an ecosystem, the sequence of organisms through which energy and materials are transferred, in the form of food, from one trophic level to another
Acid
substances that release hydrogen ions (protons) in water
Carbon cycle
the circulation and reutilization of carbon atoms, especially via the processes of photosynthesis and respiration
pH
a value that indicates the acidity or alkalinity of a solution on a scale of 0 to 14, based on the proportion of H+ ions present
Biomass
the total mass or weight of all the living organisms in a given population or area
Nitrogen cycle
the circulation and reutilization of nitrogen in both inorganic and organic phases
Atoms
the smallest unit of matter that has the characteristics of an element; consists of three main types of subatomic particles: protons, neutrons, and electrons
Productivity
the synthesis of new organic material. That done by green plants using solar energy is called primary productivity.
First law of thermodynamics
states that energy is conserved; that is, it is neither created nor destroyed under normal conditions
Herbivores
an organism that eats only plants
Photosynthesis
the biochemical process by which green plants and some bacteria capture light energy and use it to produce chemical bonds. Carbon dioxide and water are consumed while oxygen and simple sugars are produced
Chemical energy
potential energy stored in chemical bonds of molecules
Ions
electrically charged atoms that have gained or lost electrons
Trophic level
step in the movement of energy through an ecosystem; an organisms's feeding status in an ecosystem
Potential energy
stored energy that is latent but available for use. A rock poised at the top of a hill or water stored behind a dam are examples of potential energy
Elements
a molecule composed of one kind of atom; cannot be broken into simpler units by chemical reactions
Conservation of matter
in any chemical reaction, matter changes form; it is neither created nor destroyed
Omnivores
an organism that eats both plants and animals
Ecosystem
a specific biological community and its physical environment interacting in an exchange of matter and energy
Carnivores
organisms that mainly prey upon animals
Heat
a form of energy transferred from one body to another because of a difference in temperatures
Organic compounds
complex molecules organized around skeletons of carbon atoms arranged in rings or chains; includes biomolecules, molecules synthesized by living organisms
Phosphorus cycle
the movement of phosphorus atoms from rocks through the biosphere and hydrosphere and back to rocks
Entropy
disorder
Scavengers
an organism that feeds on the dead bodies of other organisms
Producer
an organism that synthesizes food molecules from inorganic compounds by using an external energy source; most producers are photosynthetic
Compound
a molecule made up of two or more kinds of atoms held together by chemical bonds
Biological community
the population of plants, animals, and microorganisms living and interacting in a certain area at a given time
Detritivores
organisms that consume organic litter, debris, and dung
Atomic number
the characteristic number of protons per atom of an element. Used as an identifying attribute.

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