A2 OCR Biology Key Terms and Definitions Ecosystems

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Biotic Factor
A living component of the environment that affects the distribution and abundance of a species. E.g. feeding, predation, parasitism, mutalism, competition, etc.
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Abiotic Factor
A non-living component of the environment that affects the distribution and abundance of a species. E.g. temperature, light intensity, oxygen concentration, carbon dioxide concentration, water supply, pH, wind speed, inorganic substances, etc.
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Producer
An organism that transfers energy from light or an inorganic compound to organic compounds; plants are producers, using light energy to produce carbohydrates and other organic substances.
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Consumer
An organism that obtains its energy from organic compounds such as carbohydrates, fats and proteins.
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Primary Consumer
The first consumer in a food chain; a herbivore.
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Secondary Consumer
A carnivore that feeds on herbivores.
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Tertiary Consumer
A carnivore that feeds on a secondary consumer.
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Trophic Level
The stage of a food chain at which an organism feeds.
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Food Web
Many interconnecting food chains.
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Food Chain
A diagram showing a sequence of organisms in which chemical energy passes from one organism to the next.
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Decomposer
An organism that breaks down organic remains of other organisms, returning matter from them to the soil and air,
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Detritus
Remains of plants and animals, such as dead leaves, used as a nutrient source by decomposers and detritivores.
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Detritivore
An organism that feeds on detritus.
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Efficiency
The total energy put into a system divided by the useful energy obtained; it is often multiplied by 100 and stated as a percentage.
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Productivity, or Primary Productivity
The energy transferred from sunlight to chemical potential energy by plants, usually measured in kJm ¯² year ¯¹.
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Gross Primary Productivity (GPP)
The total quantity of energy transferred by plants from sunlight into plant tissues.
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Net Primary Productivity (NPP)
The energy left as chemical energy after plants have supplied their own needs by respiration.
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Energy Content Calculation
Energy content = number of organisms X mean dry mass of one organism X energy content of 1g of dry mass
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Photosynthetic Efficiency Calculation
Photosynthetic efficiency (2-5%) = amount of light energy falling onto a crop DIVIDED BY amount of light energy converted to carbohydrate.
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Monoculture
An area covered by a single variety of a single plant species.
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Moraine
The jumble of rocks left behind by a retreating glacier.
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Pioneer Plants
A plant that is adapted to grow on newly exposed ground, and therefore often found in the very early stages of primary succession.
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Succession
A directional change in a community over time.
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Community
Number of different species that live together in the same area.
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Habitat
A place where a population of organisms live.
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Species
Organisms that look similar and can interbreed to produce fertile offspring.
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Population
Number of organisms of the same species.
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Niche
The role of an organism in an ecosystem; the effects that it has on other components of the ecosystem, and the effects that they have on it.
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Ecosystem
A self contained system including all the living organisms and the environment interacting with each other. Combined physical and biological components of an environment.
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Primary Succession
Sucession that occurs on a piece of ground that began with no soil.
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Secondary Succession
Succession that occurs following the clearance of land that already had soil.
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Seral Stages
One of the communities that exists during a succession.
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Climax Community
The final stage at the end of the process of succession.
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Line Transect
Taking samples along a line running across the area to be surveyed.
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Belt Transect
Taking samples from quadrats placed along a line running across the area to be surveyed.
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Continuous Transect
A line along which the organisms at every point on the line are recorded.
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Interrupted Transect
Taking samples at intervals along the length of a line.
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Nitrogen Fixation
The conversion of nitrogen from unreactive gas to a more reactive form such as ammonium or nitrate ions.
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Nitrogenase
An enzyme that catalyses the conversion of nitrogen gas to ammonium ions.
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Mutualism
A close relationship between two organisms in which both benefit.
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Ammonification
The production of ammonia from nitrogen-containing compounds such as proteins, amino acids or urea.
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Nitrifying Bacteria
Bacteria that oxidise ammonium ions to nitrite or nitrate; they include Nitrobacter and Nitrosomonas.
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Nitrification
The production of nitrite and nitrite ions by the oxidation of ammonium ions.
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Denitrifying Bacteria
Bacteria that convert nitrite or nitrite ions to nitrogen gas.
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Denitrification
The production of nitrogen gas from nitrite or nitrite ions.
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Other cards in this set

Card 2

Front

A non-living component of the environment that affects the distribution and abundance of a species. E.g. temperature, light intensity, oxygen concentration, carbon dioxide concentration, water supply, pH, wind speed, inorganic substances, etc.

Back

Abiotic Factor

Card 3

Front

An organism that transfers energy from light or an inorganic compound to organic compounds; plants are producers, using light energy to produce carbohydrates and other organic substances.

Back

Preview of the back of card 3

Card 4

Front

An organism that obtains its energy from organic compounds such as carbohydrates, fats and proteins.

Back

Preview of the back of card 4

Card 5

Front

The first consumer in a food chain; a herbivore.

Back

Preview of the back of card 5
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