b18.8, b18.9 - trophic levels and biomass transfers

what is biodiversity

the variety of all of the different species of organisms on earth or within an ecosystem or within a species

what are the trophic levels

• producer

• primary

• secondary

• tertiary

what is biomass

the mass of material in living organisms often measured in dry mass

why do we measure biomass more in dry mass

less bias as water content of a plant fluctuates throughout the day

pyramids of numbers or pyramids of biomass for accuracy

pyramids of biomass

in a pyramid of biomass why do we lose mass as we go up the pyramid

• not all organisms are eaten

• some biomass is excreted

• lots of energy taken for respiration instead of building new biomass

what % of all energy from the sun is used for photosynthesis

1%

why is such little energy used for building new biomass

• cannot all be digested

• some energy used for respiration and homeostasis

why is it rare to have more than 4 trophic levels

as you lose energy with every passing trophic level so the more layers to the top, the less energy and nutrients the apex predator gets

what are apex predators

carnivores with no predators

how do decomposers work

they secrete enzymes and the broken down molecules diffuse back into them

what % of energy is passed between trophic levels

10%

why do losses of biomass occur

not all the ingested material is absorbed

where does the energy not used for building biomass go

• egested as faeces

• lost as waste products like co2 and water in respiration or water and urea in urine

• large amounts of glucose needed for respiration