Energy Transfer Flashcards
Why are green plants referred to as photoautotrophs
They use energy from the sun in photosynthesis to synthesise organic molecules such as glucose
What is a basic food chain?
Producer –> Primary Consumer –> Secondary Consumer –> Tertiary Consumer –> Predator
State ways in which energy is lost at each tropic level
- Heat
- Excretion (urine)
- Egestion (faeces)
- Movement
- Respiratory losses
How is energy transferred throughout a food chain?
It is transferred through trophic levels and passes through in the form of food through one level to the next
What is biomass?
Mass of living material measured over a particular area
How do you work out dry mass for plants?
Use an oven to remove all the water form plant material before weighing to determine biomass
- Find mass before putting in oven
- Turn oven on at 95-100*C
- Heat + reweigh
- Repeat and reweigh until mass is constant for 3 consecutive readings
Why is dry mass calculated as dry mass of tissue?
Percentage of water varies from species to species
Why is biomass recorded per unit area?
To compare biomass in different locations
Units for biomass?
- g/m2
- kg/hectare
- lb/ft2
How do you convert biomass into mass of carbon?
Multiply biomass by 0.5
Why can’t all the energy at the leaf surface be absorbed?
- Reflected at the leaf surface
- Incorrect wavelength
- Transmitted through leaf without coming into contact with a chloroplast
What is Gross Primary Production (GPP)?
Chemical energy store in plant biomass in a given area or volume
What is Net Primary production (NPP)?
Chemical energy store in plant biomass after respiratory losses (R) to the environment have been taken into account
How do you calculate Net Primary Production (NPP)?
NPP = GPP – R
What can NPP be used for?
- Plant growth + reproduction
* Other trophic levels (herbivores + decomposers)
Why doesn’t energy consumed equate to NPP between producer and primary consumer?
This is because some of the plant may not have been eaten i.e roots
What is the typical energy transfer % from producer to primary consumer?
5 – 10%
Of the food consumed, not all energy is used for biomass, state 4 ways energy is lost
- Lost in urine during excretion
- Lost as heat during respiration
- Used for metabolic processes
- Most of plant is indigestible so mostly lost as faeces
Why is energy transfer for secondary consumer more efficient?
This is because animal tissue is more digestible
What is the energy transfer % between consumers?
20%
How do you calculate net production for consumers?
N = I – (F + R) I = Chemical energy store in ingested food F = Chemical energy lost in faeces + urine R = Respiratory losses to the environment
What are endotherms?
Animals that maintain a constant body temp for e.g birds have high rates of respiration which generate heat as less of the food is converted into biomass
Why do herbivores convert less food into biomass?
This is because there is lots of cellulose in plant food which is indigestible so its lost in faeces
State a few practices used by farmers to minimise energy losses from animals?
- Keep animals in confined spaces to reduce energy lost in movement (Intensive Rearing of livestock)
- Environment kept warm so less energy used to maintain constant body temp
- Controlled feeding so little is lost through faeces
- Slaughtered young, when growing, as most energy is being used to produce biomass
What is the monoculture of crop plants?
When one crop is grown on a large scale to achieve the greatest yield. This can involve simplifying food webs so energy is not lost to non-human food chains
Why are insecticides used?
They will stop insects eating the crops as they reduce yields
Why are herbicides used (weedkillers)?
They will kill other plants and will reduce competition for nitrates, water etc.
Why are hedges removed?
Makes it easier to remove combine harvesters and hedges will compete for nitrates and water and they could contain insects that eat crops lower yields
