5,4,3,2,1 go

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5,4,3,2,1 go can you talk about food chains and
food webs for 60 seconds mentioning as many as
the key words as possible?
Food web
Producer
Consumer
Decomposer
Food chain
Primary consumer
Omnivore
Detritivore
Energy loss
Quarternary
Secondary consumer
Trophic level
Tertiary consumer
Habitat
Heat
Respiration
Carnivore
Herbivore
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Ecological pyramids
WAL
About how energy moves and is lost between
trophic levels

• What percentage of energy is transferred from one
  level to the next?

• What are the relative merits and disadvantages
  of each?

• What are the different types of ecological
  pyramid?

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Today we are covering from the specification
Pages 70-72 of your textbook
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Pyramids of numbers

• Food chains and food webs are a useful means of
  showing what different organisms eat and
  therefore energy flow. They do not provide
  quantitative information ecological pyramids
• Usually they look like this

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Pyramids of Numbers
What can be the problem? They can look odd
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Pyramids of Numbers

• No account is taken of size one tree is given
  the same value as 1 aphid therefore they can look
  inverted.
• The number of individuals s so great that it is
  impossible to represent them accurately on the
  same scale as other species in the food chain
  one tree and 1 million aphids
• They can look odd

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Pyramids of Numbers
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Pyramids of biomass

• More reliable, quantitative description of a food
  chain is provided when their biomass is measured.
• Biomass is the total mass of the plants and/or
  animals in a particular place.

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Pyramids of Biomass
Biomass dry mass of organisms Given as gm-2
for an area Or gm-3 for a volume
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Measuring biomass

• Problem
• finding the biomass of worms
• Why is this so hard?
• How would you do it?

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• To eliminate the problem of variability due to
  moisture content, you can dry your earthworms at
  60C for 24-48 hours to get dry earthworm
  biomass.
• Problem the variability due to gut contents
• Answer?
• Keep the live earthworms in containers until they
  empty their guts (24-48 hours, if they dont die
  in the process)
• Dissect the preserved earthworm and flush their
  opened gut
• ash dry worms leaving only mineral gut contents.

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The answer? A statistical relationship between
length dry biomass
Dry worm weigh ash dry _at_ 500 oC Remove
ash Weigh gut contents Subtract gut contents
weight from dry weight
Q. Why is the graph so useful?
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Pyramids of biomass

• Fresh mass is quite easy to access but varying
  amounts of water makes it unreliable.
• Use dry mass but the organisms must be killed,
  therefore only small sample, which may not be
  representative.

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Pyramids of Biomass
Anomaly from pyramid of biomass with aquatic food
chain Q. Why is there less biomass in producers
than primary consumers?
A. Sample is made at a single point in time and
plant biomass may vary with season. Phytoplankton
may also be reproducing quickly and so large
turnover of biomass.
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Pyramids of energy

• Most accurate representation of energy flow
  through an ecosystem.
• Collecting data can be difficult and complex.
• Data are collected in a given area (e.g one
  square metre) and in a set time (e.g. a year).
• Results are more reliable than those for biomass
  as 2 organisms of the same biomass may store
  different amounts of energy.
• 1g of fat stores 2x amount of energy of 1g
  carbohydrate.

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Pyramid of Energy
Energy stored in each trophic level of a Florida
ecosystem Q. Why might deriving energy content
be difficult?
A. Two organisms of the same dry mass may have
different energy contents e.g. more or less fat
which is high in energy.
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Task

• Do application questions and summary questions

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Ecological pyramids
WAL
About how energy moves and is lost between
trophic levels

• What percentage of energy is transferred from one
  level to the next?

• What are the relative merits and disadvantages
  of each?

• What are the different types of ecological
  pyramid?

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