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Energy flow - Biology SL Topic 4.2 role of photosynthesis, food chains, heat, food webs

Biology SL Topic 4.2 role of photosynthesis, food chains, heat, food webs
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Biology SL

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IB

Academic year: 2016/2017
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Energy flow Topic 4 Biology SL

The role of photosynthesis ➢ Photosynthetic organisms take simple inorganic carbon dioxide and convert it into energy-rich glucose ○ The addition of minerals allows the producers to synthesize complex molecules ➢ Chemical energyrefers to the fact that organic compounds are rich in energy, thanks to the chemical bonds that exist between carbon and other atoms ○ Two ways to release the energy from organic compounds ■ Digest the food ■ Burn it

Food chains ➢ The flow of energy through a food chainis the process of passing energy from one organism to another through feeding ➢ Afood chainis a sequence showing the feeding relationships and energy flow between species ➢ Trophic levelsare used to indicate how many organisms the energy has flown through ○ 1st trophic level => producers/autotrophs ○ 2nd trophic level => primary consumers ○ 3rd trophic level => secondary consumers ➢ Energy is lost in every trophic level so we can’t have more than 4-5 trophic levels

Heat ➢ Any heat produced by cellular respiration is lost to the environment ➢ If something is eaten, some of the chemical energy is passed onto the next organism ➢ If something dies, detritivores and decomposers will use its available energy ➢ During cell respiration not all energy is convertedinto ATP ○ Some of it is converted into heat energy ■ Once the heat energy leaves the body, it can’t be used as a biological energy resource ⇒ heat is lost from the ecosystem ➢ Unlike nutrients, energy can’t be recycled ○ Only chemical energy can be used from the next trophic level ■ Typically only 10-20% of the energy available is used from the previous step in a food chain

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Energy flow Topic 4 Biology SL

➢ This happens because ○ Not all of an organism is swallowed as a food source ○ Not all of the food swallowed can be absorbed and used in the body ○ Some organisms die without having being eaten by anorganism from the next trophic level ○ There’s considerable heat loss due to cell respiration at all trophic levels

Pyramid of energy ➢ Apyramid of energyis used to show how much and how fast energy flows from one trophic level to the next in a community ○ They take into account the rate of energy production, not just the quantity ○ Unit: kilojoules per square meter per year (kJ/m 2 /yr) ➢ 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 ○ 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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Energy flow - Biology SL Topic 4.2 role of photosynthesis, food chains, heat, food webs

Subject: Biology SL

707 Documents
Students shared 707 documents in this course
Level:

IB

Was this document helpful?
Energy flow Topic 4.2 Biology SL
The role of photosynthesis
➢Photosynthetic organisms take simple inorganic carbon dioxide and convert it into
energy-rich glucose
○The addition of minerals allows the producers to synthesize complex
molecules
➢Chemical energy
refers to the fact that organic compounds are rich in energy,
thanks to the chemical bonds that exist between carbon and other atoms
○Two ways to release the energy from organic compounds
■Digest the food
■Burn it
Food chains
➢The flow of energy through a food chain
is the process of passing energy from one
organism to another through feeding
➢A
food chain
is a sequence showing the feeding relationships and energy flow
between species
➢Trophic levels
are used to indicate how many organisms the energy has flown
through
○1st trophic level => producers/autotrophs
○2nd trophic level => primary consumers
○3rd trophic level => secondary consumers
➢Energy is lost in every trophic level so we can’t have more than 4-5 trophic levels
Heat
➢Any heat produced by cellular respiration is lost to the environment
➢If something is eaten, some of the chemical energy is passed onto the next
organism
➢If something dies, detritivores and decomposers will use its available energy
➢During cell respiration not all energy is converted into ATP
○Some of it is converted into heat energy
■Once the heat energy leaves the body, it can’t be used as a biological
energy resource ⇒ heat is lost from the ecosystem
➢Unlike nutrients, energy can’t be recycled
○Only chemical energy can be used from the next trophic level
■Typically only 10-20% of the energy available is used from the
previous step in a food chain
1

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