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Slide 1

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Population & Pyramids
Food Chains, Pyramids of
Biomass & Competition…read more

Slide 2

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Food Chain ~ a sequence (usually shown as a diagram)
of feeding relationships between organisms, showing
who eats what and the movement of energy through
trophic levels.
Biomass ~ any organic, non fossil material ­ e.g
vegetable matter or animal waste which can be used as
fuel. An example would be generation of gas from
decomposing organic waste.
Habitats ~ places inhabited by communities of living
Photosynthesis ~ is the process where green plants
use water and carbon dioxide and sunlight to produce
carbohydrates (stored energy) and release oxygen (as a
by product).…read more

Slide 3

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Ecosystem ~ a community of animals, plants
and micro-organisms together with the habitat
they live in.
Predator ~ an animal that hunts, kills and eats
other animals for food.
Prey ~ organisms that predators kill for food.
Species ~ used in the classification of living
organisms, referring to related organisms
capable of interbreeding.
Population ~ a group of members of a single
species living in a habitat.…read more

Slide 4

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Populations & Pyramids
Food chains show the feeding relationship in a
habitat. Pyramids of biomass are charts that
show the mass of living organisms at each step
in a food chain. Energy is lost moving up in a
food chain, and this limits the length of the chain
­ so its more efficient to feed people with plants
than with meat.
Organisms usually compete with each other for
resources. The populations of predators and
prey are interrelated.…read more

Slide 5

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Food Chains
A food chain shows who eats what in a particular habitat.
For example, grass seed is eaten by a Vole, which is
eaten by a Barn Owl. The arrows between each item in
the food chain always points from the food to the feeder.
This is the direction in which the energy flows in the food
chain.…read more

Slide 6

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Food Chains
Food chains always start with producers, which
are almost always green plants. The other
organism in the food chain are consumers ­ they
get all their energy and biomass by consuming
(eating) other organisms.
Most food chains are quite short, and they rarely
consist of more than four steps. This is because
a lot of energy is lost at each step. After about
three steps, very little energy is still available for
use by living organisms. This also explains why
there are few organisms at the top of food
chains, compared with those lower down.…read more

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