ecology 4 - pyramid of numbers and biomass
DESCRIPTION
Ecology 4 - Pyramid of Numbers and BiomassTRANSCRIPT
Topic Outline
• Ecology
• Population,
community and
ecosystem
• Biotic and abiotic
environment
• Relationships
• Food chain and web
• Energy transfer
between trophic
levels
• Carbon cycle
• Pyramid of numbers
and biomass
• Water pollution
• Conservation and
biodiversity
ECOLOGY
Pyramids of
energy, numbers
and biomass
Lesson Outline
• Pyramid of energy
• Pyramid of numbers
• Pyramid of biomass
Ecological Pyramids
• Pyramid of energy – shows energy flow through the trophic levels of a
food chain.
• Pyramid of numbers – shows the number of organisms at each trophic
level at a particular time.
• Pyramid of biomass – shows the mass of organisms at each trophic level
at a particular time.
Pyramid of energy
• shows energy flow through the trophic
levels of a food chain.
Pyramid of numbers
• shows the number of organisms at each
trophic level at a particular time.
Pyramid of numbers
• Consider the following food chain:
• If there is 1 lion in an area and it feeds on 7
giraffes in a month.
• Each giraffe feeds on 2 trees in a month.
• What would a pyramid of numbers look
like?
tree giraffe lion
Pyramid of numbers
• This pyramid is broad
at the bottom and
narrow towards the
top.
Pyramid of biomass
• Consider the following food chain:
• Biomass of 1 lion = 20kg
• Biomass of 1 giraffe = 20kg
• Biomass of 1 tree = 30kg
• What would a pyramid of biomass look like?
tree giraffe lion
Pyramid of biomass
• For this food chain,
the pyramid of
biomass has a similar
shape to the pyramid
of numbers.
Worksheet time
• Let’s try constructing our own pyramids!
• Pyramids need not always be broad at the
bottom and narrow at the top!
– Use rectangles.
– Producers are always at the bottom,
consumers at the top.
Grass rabbit snake hawk
Pyramid of numbers Pyramid of biomass
Tree aphid protozoa
Pyramid of numbers Pyramid of biomass
Tree aphid ladybird small bird
Pyramid of numbers Pyramid of biomass
grass zebra tsetse fly
Pyramid of numbers Pyramid of biomass
Comparison – which pyramid to use?
• If the producer is a large plant, then the second layer of the pyramid will be much larger than the base.
• It would make more sense to draw a pyramid of biomass
A pyramid of
numbers
A pyramid of
biomass
Conclusion
• Pyramids of biomass are a more accurate
representation of the food chain.
• Pyramids of biomass (almost) always have
a broader base and narrower tip.
– What is the exception?
References
• http://www.globalchange.umich.edu/gctext/I
nquiries/Inquiries_by_Unit/Unit_4.htm