Food Pyramids

Food Pyramids - Transcript

Food Pyramids
2nd Year Biology
Energy loss in a food chain
• Only 10% of energy is passed along to the
next level in a food chain. The rest of the
energy is lost through:
• -waste
• -heat
• -movement
• -respiration
A Pyramid of Numbers
• Food chains and webs show the flow of
materials and energy in habitats, but
they do not give you any idea of how
many organisms there are in the habitat.
• A pyramid of numbers is a diagram
showing the numbers of organisms
present in each level of a food chain
• Let's go back to the
grass vole barn owl food chain.
• Suppose the numbers found in a particular
habitat are as follows:
2000 grass plants
25 voles
1 barn owl
The pyramid of numbers would be
as shown below.
Sometimes you do not get a pyramid because
one organism in the chain is unusually large,
e.g. one large oak tree providing food for many
caterpillars.
Pyramids of Biomass
• Biomass is a word used to describe the
mass of living material in an area.
• If you could collect all of the plants and
animals in an area and weigh them, this
would be the biomass of that area.
A pyramid of biomass is a diagram showing the total
weight (mass) of organisms at each level of a food
chain.
Biomass always gives a pyramid since producers must
have the most biomass and consumers must have less
Pyramids of biomass are
always pyramid-shaped.