23.2 biomass transfer through an ecosystem Flashcards Preview

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Flashcards in 23.2 biomass transfer through an ecosystem Deck (19):

what is a trophic level

each stage in a food chain


what is the first trophic level

producers - organism which converts light energy into chemical energy by photosynthesis


what are the subsequent trophic levels

consumers - organism that obtains energy by feeding on other organisms


define biomass

mass of the living material present in a particular place or in particular organisms


how do you calculate biomass at each trophic level

biomass present in each organism X total number of organisms present


what is biomass measured in

grams per square meter (g/m²)
grams per cubic meter (g/m³)


how do you measure biomass

- measure the mass of fresh material present
- water content has to be discounted
- dry mass has to be calculated


how do you calculate dry mass

1. organisms are killed and dried
2. placed in an oven at 80C until all water is evaporated
3. to minimise destruction, only a small sample is taken BUT it may not be representative


define ecological effieciency

the efficiency with which biomass or energy is transferred from one trophic level to the next


define gross production

- total solar energy that plant converts into organic matter
- around 20-50% of energy is used in respiration


how do you calculate net production

gross production - respiratory losses


efficiency at producer level

producers only convert 1-3% of light into biomass because:
- not all solar energy is available for photosynthesis (90%=reflected and some is transmitted)
- other factors list photosynthesis
- proportion of 'energy' is lost as it is used in photosynthesis rezctions


efficiency at consumer levels

consumers covert 10% of biomass into their own organic tissue because:
- not all biomass of an organism is eaten
- energy is transferred to the environment as metabolic heat due to movement/respiration
- some parts of organisms are indigestible and are egested
- energy is lost in excretory materials such as urine


how much of energy from sunlight is embodied as biomass in a tertiary consumer



how do you calculate ecological efficiency

biomass available after transfer/biomass available before transfer


what do humans depend on which manipulates the environment

- agriculture manipulates environment to favour crops and rear animals for food/produce
- provided with necessary abiotic conditions
- competition from other species and predators are removed


how does agriculture affect food chains

simplifies food chains as fewer trophic levels are present so as much energy as possible is transferred into biomass


farming animals for food - TROPHIC LEVELS

producers - animal feed
primary consumers - livestock
secondary consumers - humans


cultivating plants for human consumption - TROPHIC LEVELS

producers - crops
primary consumers - humans