A series of chemical reactions carried out by photoautotrophes. These organisms are the producers in ecosystems. The process transfers energy from sunlight and carbon from inorganic compounds such as carbon dioxide into food chains. The process results

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A series of chemical reactions carried out by
photoautotrophes. These organisms are the
producers in ecosystems. The process transfers
energy from sunlight and carbon from inorganic
compounds such as carbon dioxide into food
chains. The process results in biomass. The
energy stored is termed the gross primary
production and net primary production if
respiration losses are taken into account.
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Photosynthesis
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An ecological unit including the community of
living things and the abiotic factors that affect
them.
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ecosystem
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A process carried out by bacteria which convert
nitrogen gas into ammonium compounds. The
bacteria can be found free living in the soil and
associated with legume plants in their roots.
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Nitrogen fixation
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The mass of organisms at a particular trophic
level in a food chain or web. It is also used to
describe the growth (production) of organisms.
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Biomass
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Heterotrophic microorganism that secretes enzymes
into its environment and absorbs the products of
digestion.
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Saprophyte
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The removal of the amino group from amino acids
to release ammonia and organic acids which can be
used in respiration. The process is carried out
by putrefying bacteria on excess amino acids.
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Deamination
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One of the steps in a food chain. It describes
organisms that feed in a similar way such as
producers or primary consumers.
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Tropic level
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The loss of nitrate from waterlogged soils due to
anaerobic bacteria using the ion as an
alternative electron final electron acceptor to
oxygen in respiration.
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Denitrification
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The form of nutrition involving the digestion and
absorption of complex organic molecules e.g.
herbivore, carnivore and detritivore.
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Heterotrophism
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The total amount of energy stored in biomass by
photosynthesis or other autotrophic nutrition.
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Gross primary production
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A method of nutrition where simple inorganic
molecules are used to produce complex organic
molecules e.g. photosynthesis in green plants and
protoctistans.
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Autotrophism
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A type of heterotrophic nutrition where the
organism takes organic molecules from another
organism which causes it harm e.g. human tapeworm.
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Parasitism
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A series of processes converting ammonium ions
first to nitrite ions and then nitrate ions,
making nitrogen available to plants. The steps
are carried out by bacteria releasing sufficient
energy for them to fix carbon dioxide and produce
organic molecules.
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Nitrification
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A relationship between two different species
where both benefit in some way e.g. the alga in a
lichen is protected from desiccation by a fungus
which in turn uses some of the photosynthetic
products made by the alga.
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Mutualism
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A relationship between two organisms in which one
organism benefits while the other neither
benefits nor is harmed.
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Commensalism
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The production of ammonia by putrefying
microorganisms as they use excess proteins from
decaying protein.
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Ammonification
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A sampling area of fixed size used to quickly and
easily provide information about communities and
populations. It is generally used together with a
suitable randomising system to avoid bias but can
therefore provide unreliable data when an
organisms distribution isnt itself random.
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quadrat
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A systematic sampling method where samples
(usually quadrats) are placed in a line. It is
used to identify changes in space e.g. the
frequency of weeds in relationship to the
distance from a hedge.
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transect
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A factor caused by the physical environment such
as temperature or pH.
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abiotic
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A diagram that describes the feeding
relationships of organisms. The diagram shows the
way that energy is passed between them.
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Food chain
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A factor caused by the biological environment
such as competition and predation.
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biotic
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The number of an organism in a given area at a
given time. It is affected by the impact of
biotic and abiotic factors on birth rate, death
rate and migration.
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population
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The loss of substrate such as soil from an
ecosystem. This is one of the effects of loss of
soil structure by poorly managed agriculture and
the loss of protective vegetation such as hedges.
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erosion
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The place where an organism lives. The particular
set of biotic and abiotic factors in that place
will be matched with adaptations in the organism.
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habitat
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Competition for a resource between two organisms
of the same species.
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intra-specific competition
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A chemical assessment of organic pollution in
waterways. A sample is fully oxygenated and then
incubated for a set time. The greater the loss of
oxygen due to respiration of microorganisms, the
higher the degree of organic pollution.
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BOD
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The amount of energy stored by autotrophs after
respiration losses have been subtracted.
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Net primary production
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Changes to a community with time. The changes are
due to changes to the abiotic environment by the
organisms in the community which leads to
competition between those organisms and invading
organisms.
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succession
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The collection of living things present in an
ecosystem. The living things provide the biotic
factors of the ecosystem and are linked by
nutrient cycling and food webs. Measurements of
the number of different organisms is called
diversity.
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community
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Plants with non-woody stems e.g. grasses. These
plants form an early link in most successions,
out competing pioneer species but are themselves
out competed by woody species.
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herbaceous
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Where organisms of different species compete for
the same resource e.g. light, food and nesting
sites.
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inter-specific competition
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A chemical that is toxic to organisms that
compete with humans for food. Some forms create a
problem in ecosystems because they are
non-biodegradable and are accumulate and magnify
along food chains to concentrations that are
toxic to non-pest species.
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pesticide
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A stable community resulting from a primary or
secondary succession. The form of the community
depends on the ecosystems climate e.g. in the UK
it would be broad-leaved woodland but in the
Arctic circle it would be tundra.
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climatic climax
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A measurement of the number of species present in
an ecosystem. The value may change with time e.g.
during a succession. It can be used as an
indicator of the level of damage to an ecosystem
by pollution.
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diversity
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A measurement of the number of a particular
species in an ecosystem. The value can be given
quantitatively e.g. as a population or
qualitatively e.g. using terms such as rare or
frequent giving a relative indication of number.
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abundance
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The number of samples in which an organism is
found.
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frequency
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The increase in nutrient level in aquatic
ecosystems. Such increases may be associated with
a reduction in oxygen level and damage to
communities as a result of organic or fertiliser
pollution.
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eutrophication
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The build up of non-biodegradable chemicals in
the environment. Such substances are often
fat-soluble and their concentrations may increase
along food chains until they reach toxic levels.
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bioaccumulation
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The collection of biotic and abiotic factors that
affect a community of organisms in an ecosystem.
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environment
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When a substance can be broken down in the
environment. This generally means that organisms
possess enzymes capable of the breakdown.
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biodegradable
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Where an animal kills and feeds on another
animal. The relationship between the animal and
its prey often leads to a cyclical change in both
populations.
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predation
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The utilisation of a resource can continue
indefinitely without damage to the ecosystem that
provides it.
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sustainability
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This describes the complete way of life of an
organism. Two different organisms that share any
aspect of their way of life will be in
competition. If the overlap is significant, one
organism will lose and its way of life will
change by natural selection or it will become
extinct.
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niche