Starter
Can you sort the cards in front of
you into the correct definitions?
When you think you have them in the
correct order, add these definitions to the
glossaries in the back of you books.
A few key words…
Producer
The plant in the food chain - they make food
by photosynthesis.
Consumer
Animals that eat the producer. For example
rabbits, caterpillars, cows and sheep.
Secondary consumers
Usually eat animal material - they are
carnivores. For example cats, dogs and lions.
Herbivore
Eats plants only.
Carnivore
Eats meat only.
Omnivore
Eats both plants and meat.
Trophic Level
Predators
Prey
Position occupied by a group of organisms in a
food chain.
Kill for food. They are either secondary or
tertiary consumers
The animals that predators feed on.
Pyramids of Biomass
Learning Objectives
1. Construct and interpret pyramids of biomass
2. Describe how energy and mass is transferred along a food
chain
3. Explain why energy and biomass is reduced at successive
stages in a food chain
Every living organism needs
energy to survive – but where
does it come from?
Radiation from the Sun
(solar or light energy)
is the main source of energy for all
living things. The Sun’s light energy
is captured and used by green
plants and algae during
photosynthesis, to make new
biomass.
Biomass is the dry mass of living
material in an animal or plant.
Biomass is the mass of material in living
organisms. Ultimately all biomass is built up using
energy from the sun. Biomass is often measured
as the dry mass of biological material in grams.
The biomass made by plants is passed on through
food chains or food webs. It goes into the animals
that eat the plants. It then passes into the
animals that eat other animals.
In a food chain there are usually more producers
than primary consumers, and more primary
consumers than secondary consumers.
How many do they need to eat?
We can draw this as
a Pyramid of Numbers.
However the number of
organisms at each level
does not accurately
reflect what is
happening to the
Biomass.
A pyramid of biomass is a chart,
drawn to scale, showing the biomass
at each stage in a food chain. The
bars become narrower as you reach
the top. This pyramid of biomass is
for the food chain:
oak tree → caterpillar → blue tit →
sparrowhawk
Note that you do not need to draw
the organisms. But you must draw
your pyramid of biomass to scale.
Each bar should be labelled with the
name of the organism.
Construct your own Pyramid of Biomass:
Count up the number of leaves. Each leaf weighs 5g.
Construct your own Pyramid of Biomass:
Now count the number of
aphids that can eat that
amount of leaves
in one day.
Each Aphid weighs 1g
Now count the number of lady birds that can
eat that amount of aphids in one day.
Each Ladybird weighs 10g
Construct your own pyramid of biomass
Organism
Numbers
Biomass
Leaves
25
5 x 25 = 125g
Aphids
20
1 x 20 = 20g
Ladybirds
1
10 x 1 = 10g
1. Plot a bar chart on graph paper that shows the biomass of each organism.
2. Cut out each coloured bar and stick it into your book to create a scaled
pyramid of biomass – starting with leaves at the bottom, then aphids, then
lady birds at the top
Answer these questions that interpret your pyramid:
a) What percentage of the biomass of the leaves is passed on to the aphids?
b) What percentage of the aphids is passed on to the ladybirds?
Count up the number of bushes. Each bush weighs 500g.
Count up the number
of caterpillars. Each
caterpillar weighs 10g.
Count up the number of birds. Each bird weighs 50g.
Findings from our pyramids of biomass
Q1. What is happening to the biomass as we go
up the food chain?
Q2. What is happening to the energy as we go
up the food chain?
Findings from our pyramids of biomass
The amount of material and energy contained in
the biomass at each stage is less than it was at a
previous stage.
This is because some material and energy taken in
is passed out as waste by the organism.
A lot of the biomass eaten is used in respiration by
the animal cells to release energy, and used for
growth and movement.
Plenary
The amounts of ______ and _______ contained in
living things always gets less at each stage of a
food _______ from ________ onwards. Biomass
is lost as ________ products and used to release
energy in _______. This is used for _______ and
to control body __________. Only a small amount
is used for _________.
biomass temperature
energy
chain
growth
movement producers
respiration waste
Plenary
The amounts of biomass and energy contained in
living things always gets less at each stage of a
food chain, from producers onwards. Biomass is
lost as waste products and used to release energy
in respiration. This is used for movement and to
control body temperature. Only a small amount is
used for growth.
Pyramids of Biomass
Learning Objectives
1. Construct and interpret pyramids of biomass
2. Describe how energy and mass is transferred along a food
chain
3. Explain why energy and biomass is reduced at successive
stages in a food chain