Productivity in ecosystems Flashcards
What do plants do in an ecosystem?
Synthesise organic compounds from atmospheric or aquatic carbon dioxide.
- Most of the sugars synthesised by plants are used by the plants in respiration
- The rest are used to make other groups of biological molecules. These form the biomass of the plants
Which processs are not 100% efficient
- photosynthesis and respiration are not 100% efficient
- transfer of biomass and its stored chemical energy is also not 100% efficient
What is gross primary production (GPP)?
The chemical energy store in plant biomass in a given area or volume
What is net primary production (NPP)
The chemical energy store in plant biomass in after respiratory losses to the environment have been taken into account
What is the equation for net primary production (NPP)?
NPP = GPP + R
R= energy used in respiration
Why is gross primary production so low?
Only 1% of the light falling on a plant is used in photosynthesis to produce glucose
99% of the light either passes through the leaf without hitting chloroplasts, is reflected off of the leaf, or is transferred to heat energy
What is a community?
all living organisms of all species
What is an ecosystem?
living and non living organisms and components
What are the units for NPP and GPP
kJ m-2 yr-1
What is the equation for net production of consumers (N)
N = I - (F+R)
What does R represent in the equation, N = I - (F+R)
respiratory losses to the environment as heat
How is biomass measured
in terms of mass of carbon or dry mass of tissue per given area per given time
What are the units for biomass
kgm^-2 yr^-1 / gm^-2 yr^-1
What does N represent in the equation, N = I - (F+R)
net production of consumers (kJ m^-2 yr^-1)
What does I represent in the equation, N = I - (F+R)
chemical energy stored in ingested food
What does F represent in the equation, N = I - (F+R)
chemical energy lost to the environment in faeces and urine
Define trophic
feeding
What is a food chain
a straightforward feeding (trophic) relationship from producers through consumers
Why are trophic levels in food chains limited to below 5
energy is lost at every trophic level
What is the first trophic level
producer (plant)
What is the 2nd trophic level
primary consumers
What is the 3rd trophic level
secondary consumers
What is the 4th trophic level
tertiary comsumers
What units is energy flow through an ecosystem measured
in units of energy per area per unit of time
kJ m^-2 yr^-1
What is the ultimate energy source in an ecosystem
sunlight
Why is the utilisation and conversion of sunlight into chemical energy not efficient
- light may miss chloroplasts
- some light may be reflected
- some light is the wrong wavelength
How efficient is energy transfers between trophic levels
5-10% efficient this is why food chains tend to only have 4/5 trophic levels
Why are energy transfers between trophic levels not 100% efficient
- most energy is transferred to the environment as heat, which is lost during respiration
- some parts of an organism are not consumed or digested
- loss occurs via excretory products
Outline the methos of measuring biomass of plant material
- Heat plant material at 100C for 15 minsand then weigh and record mass.
- A lower temperature for a longer time-period can be used. Higher temperatures can cause organic compounds to burn. - Reheat at same temperature for the same period and reweigh.
- Repeat until a constant mass is obtained
- this indicates all the water has been removed. - Divide the dry mass by the area from which the plant material was removed.
What is the purpose of c a lorimetry
estimates the chemical energy store in biomass
What is the basic procedure of calorimetry
- Known mass biomass is completely burnt so all the energy released is used to heat a known volume of water.
- The increase in the temperature of the water is then used to calculate the chemical energy of the biomass.
How much energy is required to raise the temperature of 1cm^3 of water
4.2 joules of energy is required to raise the temperature of 1cm^3 of water 1°C.
What is the function of the stirrer in a calorimeter
so water temperature is even throughout
What is the function of the ignition wires in a calorimeter
they make the sample hot
What is the function of the insulation in a calorimeter
so heat energy isnt transferred to surroundings
What is the function of the reaction chameber in a calorimeter
made of metal so heat is easier to be conducted into the water
What is the function of the oxygen atmosphere in the reaction chamber of a calorimeter
allows complete combustion to occur
What is the equation for the efficiency of energy transfer between two trophic levels
(energy available after transfer ÷ energy available before transfer) x 100
Why is growing crops more efficient than cattle farming?
Growing crops involves only one trophic level whereas cattle farming uses two with a larger % of energy trapped in photosynthesis being lost as heat energy from respiration
What is the purpose of intensive rearing?
designed to maximise yield from animals by reducing energy loss
- attempt to convert the smallest amount of food into maximum yield of meat/animal products
Why does keeping animals confined increase the efficiency of energy conversion
- Movement restriction means less energy use in muscle contraction
- Environment is warmer so animals lose less heat and therefore respire less in order to maintain body temperature
- Food is highly controlled so optimum nutrition is provided with little wastage.
Food has a high energy content and high digestibility so more of the food is used to increase biomass.
What are other ways of improving yield in domestic livestock
selective breeding - to produce high-yield varieties
growth hormones - to increase growth rates and biomass
What is a factory farming environment like?
- control feeding
- restrict movement
- warm environment
- exclude preadarotes
What is selective breeding?
- more efficient at converting food to body mass
- high yield
- hormones to increase growth rate and produce more milk
- unethical
What ethical issues are involved with factory farming and selective breeding
- increased stress injury and aggressiveness
- rapid spread of disease
- increased use of drugs (antibiotics)
- reduced genetic diversity
