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Ecology
Definitions
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Habitat – The natural home or
environment of an animal, plant, or other
organism. Eg. Marine habitat
Niche – the relational position of
species in an ecosystem to each other and
how an organism or population responds
to the distribution of resources and
competitors
Population – all the organisms of one
particular species within a specified
area at a particular time, sharing the
same gene pool and more or less
isolated from other populations of the
same species.
 Community – all of the populations of
all of the different species within a
specified area at a particular time.
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Ecosystem - all the organisms living in a
particular area, as well as all the
nonliving (abiotic), physical components
of the environment with which the
organisms interact, such as air, soil, water
and sunlight.
Linked together by energy flow and
cycling of nutrients.
Vary in size but always form a functional
entity.
Producer – an organism that makes its own
organic nutrients, using energy from the sun,
by photosynthesis.
Consumer – an organism that gets its
energy by feeding off another organism
Food Chains and Food webs
Food chain – chart
showing the flow
of energy from
one organism to
the next beginning
with the producer.
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Food web – network
of interconnected
food chains showing
the energy flow
through part of an
ecosystem
Trophic Level – position of an organism in a
food chain, food web or pyramid of biomass,
numbers or energy.
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Energy is lost from each trophic level as it is
used by the organism for:
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Respiration while the animal is alive
Excretion of waste products
The only energy passed on is what is in the
biomass. About 10% of what it ate.
The higher one goes in the food chain the less
energy available so most chains only have 5
trophic levels.
Nitrogen cycle
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Nitrogen in several forms.
78% of atmosphere is nitrogen gas.
But most not usable by life on Earth.
nitrogen is transformed into a form usable
by plants.
In two ways:
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Nitrogen fixation
Rhizobium are bacteria established
inside root nodules of legumes (peas,
beans, clover, and soy),
N2 + 8 H+ + 8 e− → 2 NH3 + H2
NH3 + H+ → NH4+, using enzyme
nitrogenase
In return, the plant supplies the bacteria
with carbohydrates, proteins, and oxygen
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Nitrosomonas oxidizes ammonia into nitrite
Nitrobacter oxidizing nitrite to nitrate
Nitrates then absorbed by plants
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decomposing bacteria start ammonification,
to convert plants and animals back into
ammonia
anaerobic bacteria will convert them back into
nitrogen gas, denitrification.
In watery soils, bacteria use nitrates and
nitrogen gas is formed.
Nitrobacter
Rhizobium
Nitrosomonas
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Lightning, ultraviolet radiation and electrical
equipment can fixate nitrogen.
Algae and other more complex plants use nitrates and
ammonia created by nitrogen fixation.
Animals eat these plants and use the nitrates in their
bodies.
The remains of dead plants and animals are
decomposed, creating ammonia.
This ammonia is a turned back into nitrate by bacteria
through a process called nitrification.