3.5.3 - ENERGY + ECOSYSTEMS Flashcards
(15 cards)
freshwater marshes have one of the highest rates of gross primary production (GPP) and net primary production (NPP) of all ecosystems.
carbon use efficiency (CUE) is the ratio of NPP:GPP. freshwater marshes have a high CUE.
use your knowledge of NPP to explain why freshwater marshes have high CUE and the advantage of this (2)
- low respiration (less energy lost in respiration)
- more growth/biomass
explain why a increase in shoot biomass can be taken as a measurement of net primary productivity (2)
- represents dry mass/mass of carbon
- represents GPP - R
farming cattle for humans to eat is less efficient than farming crops because of energy transfer.
explain why (2)
- energy lost between trophic levels
- energy lost via respiration/excretion/faeces
give three reasons for the low efficiency of energy transfer from secondary consumers to tertiary consumers in an ecosystem (3)
- not all eaten OR food not digested
- heat loss from respiration
- excretion
what is biomass? (2)
- the mass of carbon or dry mass of tissue
- per a given area
describe the process of calorimetry (4)
- dry the sample, and burn it
- use this to heat a known volume of water
- measure the temperature change
- use this to calculate the chemical energy store in the biomass
define gross primary production (GPP) (2)
the chemical energy store in plant biomass, in a given area or volume
define net primary production (NPP) (2)
the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
what is the equation for NPP (1)
GPP - R = NPP
what is net primary production available for? (3)
- for plant growth and reproduction
- available to other trophic levels in the ecosystem
- such as herbivores and decomposers
what is the equation for net production of consumers? (1)
I - (F + R) = N
how is are primary and secondary productivity measured? give an example (2)
- measured as biomass in a given area in a given time
- for example, kJ ha^-1 year^-1
why is the efficiency of energy transfer considered low? explain why energy is lost at each trophic level (4)
- some light energy is reflected by plants
- some light energy is not absorbed by plants as it may be the wrong wavelength
- energy is lost to surrounds as heat from respiration
- energy is lost in faeces and urine
- not all parts of an organism are consumed/ingested
describe one way in which farmers may increase efficiency in a non-human food chain (2)
- simplifying food webs
- with the use of pesticides
describe one way in which farmers may increase efficiency in a human food chain (2)
ANY PAIR
- restricting movement
- so less energy is lost as heat from respiration
OR
1. keep them warm
2. so less energy used to generate heat