Notesale: Turn your study into money

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Energy flow

Topic 4
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2

Biology SL

➢ This happens because
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Not all of an organism is swallowed as a food source

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Not all of the food swallowed can be absorbed and used in the body

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Some organisms die without having being eaten by an organism from the
next trophic level

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There’s considerable heat loss due to cell respiration at all trophic levels

Pyramid of energy
➢ A pyramid of energy is used to show how much and how fast energy flows from one
trophic level to the next in a community
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They take into account the rate of energy production, not just the quantity

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Unit: kilojoules per square meter per year (kJ/m /yr)

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➢ Energy is lost so each trophic level becomes smaller
➢ Pyramids of numbers show the population size of each trophic level, not the energy
Food webs
➢ The number of organisms in the chain and the quantity of light available will
determine how long the chain is
➢ The biomass of a trophic level is an estimate of the mass of all the organisms within
that level
➢ Some molecules along the food chain can’t participate in the accumulating
biomass, because they’re lost in various forms
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carbon dioxide, water, urea, feaces

➢ Sometimes it’s necessary to describe a food web rather than a food chain, because
many animals have complex dietary preferences

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