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Level 2

Chapter 2


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biodegradation
the breaking down of dead organic matter by living organisms such as bacteria (2.1)
biomass
the total mass of living plants, animals, fungi, and bacteria in a given area (2.1)
carnivores
secondary consumers that eat primary consumers and often other secondary consumers. They are often at the tertiary level of a food chain; also known as top carnivores (2.1)
consumer
an organism that eats other organisms (2.1)
decomposers
organisms (e.g., bacteria and fungi) that break down wastes and dead organisms and change them into usable nutrients available to other organisms (2.1)
ecological pyramid
a food pyramid. There are three types of ecological pyramids: pyramid of biomass, pyramid of numbers, and pyramid of energy. (2.1)
energy flow
the flow of energy from an ecosystem to an organism and from one organism to another (2.1)
food chain
a model that shows the flow of energy from plant to animal and from animal to animal (2.1)
food pyramid
a model that shows the loss of energy from one trophic level to another; often called an ecological pyramid (2.1)
food web
a model of the feeding relationships within an ecosystem; formed from interconnected food chains (2.1)
herbivores
primary consumers that eat plants (2.1)
nutrients
important components of nutrient cycles in the biosphere (2.1)
omnivores
consumers that eat both plants and animals (2.1)
primary consumers
organisms in the second trophic level (e.g., grasshoppers and zooplankton), which obtain their energy by eating primary producers (2.1)
primary producers
organisms in the first trophic level, such as plants and algae (2.1)
producers
organisms that produce food in the form of carbohydrates during photosynthesis (2.1)
pyramid of biomass
an ecological pyramid that shows the number of organisms at each trophic level multiplied by their mass (2.1)
pyramid of energy
an ecological pyramid that shows the amount of energy available at each trophic level (2.1)
pyramid of numbers
an ecological pyramid that shows the number of organisms at each trophic level (2.1)
secondary consumers
organisms in the third trophic level (e.g., frogs and crabs), which obtain their energy by eating primary consumers (2.1)
tertiary consumers
organisms in the fourth trophic level (e.g., hawks and sea otters), which obtain their energy by eating secondary consumers (2.1)
trophic levels
steps in a food chain that show feeding and niche relationships among organisms (2.1)
carbon cycle
the nutrient cycle in which carbon is moved through the biosphere; maintains the balance of CO2 in the atmosphere (2.2, 11.1)
carbonate
a combination of carbon and oxygen (CO3􏰆2) that is dissolved in ocean water (2.2)
cellular respiration
the process in which both plants and animals release carbon dioxide back into the atmosphere by converting carbohydrates and oxygen into carbon dioxide and water (2.2)
denitrification
[DEE-nih-tri-fi-KAY- shuhn] the process in which nitrogen is returned to the atmosphere (2.2)
denitrifying bacteria
bacteria that convert nitrate (NO3–) back into nitrogen gas (N2) (2.2)
detrivores
consumers that feed at every trophic level, obtaining their energy and nutrients by eating dead organic matter (2.2)
geologic uplift
the process of mountain building in which Earth’s crust folds and deeply buried rock layers rise and are exposed (2.2)
leaching
removal by water of substances that have dissolved in moist soil (2.2)
nitrification
the process in which ammonium (NH4􏰆) is converted into nitrate (NO3􏰇) (2.2)
nitrifying bacteria
soil bacteria involved in two stages of nitrification. In the first stage, certain species convert ammonium (NH4􏰇) into nitrite (NO2􏰆); in the second stage, different species convert nitrite (NO2􏰆) into nitrate (NO3􏰆). (2.2)
nitrogen cycle
the nutrient cycle in which nitrogen is moved through the biosphere (2.2)
nitrogen fixation
the process in which nitrogen gas (N2) is converted into compounds that contain nitrate (NO3􏰆) or ammonium (NH4􏰇) (2.2)
nitrogen-fixing bacteria
bacteria that convert nitrogen gas (N2) into ammonium (NH4􏰇) during decomposition, playing a significant role in nitrogen fixation (2.2)
nutrient cycles
the way nutrients are cycled in the biosphere; the continuous flows (exchanges) of nutrients in and out of stores (2.2)
phosphorus cycle
the nutrient cycle in which phosphorus is moved through the biosphere (2.2)
photosynthesis
a process in which carbon dioxide enters the leaves of plants and reacts with water in the presence of sunlight to produce carbohydrates and oxygen; photosynthesis also occurs in some micro-organisms (1.2, 2.2)
sedimentation
the process in which soil particles and decaying organic matter accumulate in layers on the ground or at the bottom of large bodies of water, contributing to the formation of sedimentary rock (2.2)
stores
nutrients that are accumulated for short or long periods of time in Earth’s atmosphere, oceans, and land masses (2.2)
weathering
the process in which rock is broken down into smaller fragments (2.2, 11.1)
bioaccumulation
the gradual build-up of synthetic and organic chemicals in living organisms (2.3)
biomagnification
the process in which chemicals not only accumulate but become more concentrated at each trophic level in a food pyramid (2.3)
bioremediation
the use of organisms— usually micro-organisms or plants— to break down chemical pollutants in water or soil to reverse or lessen environmental damage (2.3)
DDT
an insecticide and well-known persistent organic pollutant, now banned in many countries (2.3)
half-life
in biology, the time it takes for a living tissue, organ, organism, or ecosystem to eliminate one half of a substance that has been introduced into it (2.3)
heavy metals
metallic elements with a high density that are toxic to organisms at low concentrations (2.3)
keystone species
species (e.g., salmon) that can greatly affect population numbers and the health of an ecosystem (2.3)
parts per million
a measurement of chemical accumulation; 1 ppm means one particle mixed with 999 999 other particles (2.3)
PCBs
synthetic chemicals containing chlorine that are used in the manufacture of plastics and other industrial products, become stored in the tissue of animals, and also persist in the environment (2.3)
persistent organic pollutants
carbon-containing compounds that remain in water and soil for many years (2.3)
pesticides
a general term for chemicals that are used to eliminate pests, such as insecticides that kill insects and herbicides that kill weeds (2.3)
adaptive radiation
the development of a number of new species from a common ancestor; the new species are adapted to inhabit different niches (3.1)