TOPIC 5 - energy and ecosystems Flashcards
how do plants use sugars from photosynthesis?
- as respiratory substrates
- to synthesise other biological molecules eg cellulose
what is biomass?
total dry mass of tissue or mass of carbon measured over a given time in a specific area
suggest units for biomass?
area - gm^-2
volume - gm^-3
how can the chemical energy stored in dry mass be estimated?
- using calorimetry
- energy released = SHC of water x vol of water x temperature change
what are some limitations in measuring biomass?
- takes a long time to fully dehydrate a plant sample = because need to be heated at low temp to prevent burning
- precise equipment is needed
- the more simple and basic the calorimeter the less accurate
how can a student ensure that all water has been removed from a sample before weighing?
- heat the sample and reweigh until the mass reading is constant
define gross primary production (GPP)
total chemical energy in plant biomass within a given volume or area
define net primary productivity (NPP)
total chemical energy available for plant growth, reproduction and energy transfer to other trophic levels AFTER respiratory losses (R)
give the mathematical relationship between GPP and NPP
NPP =. GPP- R
R = respiratory losses
why is most of the suns energy not converted to organic matter?
- solar energy is absorbed by atmosphere or reflected by the clouds
- some photosynthetic pigments cannot absorb some wavelengths of light
- not all light falls directly on chlorophyll molecule
- energy is lost as heat during respiration
how can the net production of consumers be calculated?
N = I - (F+R)
I = chemical energy from ingested food
F = energy lost as faeces and urine
R = respiratory losses
why does biomass decrease along a food chain?
- energy lost in nitrogenous waste eg faeces and urine
- some of the organism isnt consumed
- energy lost to surroundings as heat
define primary and secondary productivity?
rate of primary and secondary production
biomass in a specific area over a given time
outline some common farming practices used to increase the efficiency of energy transfers?
- controlled diet so that most of the food is digested
- artificial heating: to reduce energy loss to maintain body temperature
- exclusion of predators: no energy lost to other organisms in the food web
- herbicides pesticides insecticides
- restriction of movement
give a general equation for % efficiency?
energy converted to a useful form/ total energy supplied x 100
