ch20 (energy flow)

sun, external source of energy

light E. → chem E. by PHS

then pass down food chain

energy lost…

lost as:

• heat (RSP)

• uneaten parts

• excretory products, feaces

• dead bodies

1000 → 100 → 10

autotroph

make its own food

heterotrophs / consumer

feed on other for energy

decomposer (saprophytes)

feed on dead bodies, get nutrients

1st trophic level

producer

eg. grass

2nd trophic level

primary consumer

eg. rabbit

3rd trophic level

secondary consumer

eg. fox

4th trophic level

tertiary consumer

eg. wolf

ecological pyramids limitations

• it can belong to > 1 trophic level

• energy flow to decomposers is not shown

explain pyramid of number

• energy lost in each level, less & less E. available

• size of predator > prey, eat many prey to have energy

pyramid of biomass???

total mass of organisms at each trophic level

explain pyramid of biomass

• biomass less & less when go up the levels

explain pyramid of biomass - special case

• high reproduction rate