5.3 Energy and ecosystems Flashcards
Are plants producers or consumers?
producers
Why are plants producers?
because they can produce their own carbohydrates (glucose) via photosynthesis
What is lost between each trophic level?
energy
How is energy lost between each trophic level?
via respiration and excretion
What is biomass?
The mass of carbon or dry mass of tissue per given area.
How can you measure biomass?
by removing all the water
What does the productivity of an ecosystem depend on?
the biotic + abiotic factors
What will maximise the productivity of an ecosystem, and why is this good?
lots of water, light, warmth + green plants will maximise the rates of photosynthesis, therefore resulting in more carbohydrates being produced
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, taking into account the energy lost due to respiration (R)
NPP = ?
GPP - R
What is NPP in simple terms?
the energy left over that is available to the plant to create new biomass + therefore available to the next trophic level in a food web.
What is the equation for the net production of consumers?
N = I - F + R
In the equation N = I - F + R, what does N stand for?
net production of consumers
In the equation N = I - F + R, what does I stand for?
the chemical energy store in ingested food
In the equation N = I - F + R, what does F stand for?
the chemical energy lost to the environment in faeces + urine
In the equation N = I - F + R, what does R stand for?
respiratory losses
What is the units for the net production of consumers?
KJ ha-1 year-1
Why is it recorded as per unit area?
to standardize the results to enable environments to be compared
Why is it recorded as per year?
- to take into account the impact that seasons will have on rain, light + heat.
- it provides annual average to allow for comparisons between environments.
Succession occurs in natural ecosystems. Describe and explain how succession occurs. (4)
- (Colonisation by) pioneer species;
- pioneer species change the environment (e.g. by forming soil)
- environment becomes less hostile for new species
- there is an increase in biodiversity
- to climax community
Biofuels are fuels which can be produced from plants. Scientists have developed a standard method called net life-cycle carbon dioxide production (NLP) to find the overall effect of producing and using particular biofuels on carbon dioxide production.
(a) Petroleum is used as a comparison when evaluating NLPs of biofuels. Suggest two reasons why (2)
- Is widely / commonly used;
- Produces large amount of carbon dioxide;
Producing and using biofuels from corn ethanol results in a negative percentage change in carbon dioxide production. Explain why. (2)
- CO2 taken up in photosynthesis;
- More taken up than produced (when it is used) with less CO2 produced than petrol;
Large areas of land have to be used to grow the plants to make biofuels. Ecologists have suggested that changes in land use could lead to a decrease in biodiversity.
Suggest how changes in land use could lead to a decrease in biodiversity. (2)
- fewer species
- fewer habitats
Residual food intake (RFI) is the difference between the amount of food an animal actually eats and its expected food intake based on its size and growth rate. Scientists have selectively bred cattle for low RFI.
(a) (i) Explain the advantage to farmers of having cattle with a low RFI. (2)
- Reduced cost;
- Less feed
When RFI is calculated, low values are negative. Explain why they are negative. (1)
Amount of food taken in less than expected.
Methane is produced by anaerobic microorganisms in the soil. The scientists found that rice fields that are not flooded do not produce large amounts of methane. Suggest why. (2)
- flooding produces anaerobic conditions
- more active aerobic microorganisms
In the previous year, field A had been used for grazing cattle. Field B had been used to grow the same crop as this year. When no fertiliser was added, the mass of crop from field A was higher than from field B. Explain this difference. (2)
- because cattle excreted / produced faeces
- in field B crop used elements / minerals
how can the chemical energy store in dry biomass by estimated
using calorimtery
energy released = specifc heat capicity of water x volume of water (cm3) x temp increase of water
populations of different species form a
community
give 3 reason for the low effency of energy transfer from secondary consumers to tertiary consumers in an ecosystem (3)
heat loss from respiration
food not digested
not all eaten
excretion
suggest 2 reasons for conserving rainforests
protect species
for biodoversty
protect habitats
reduce climate change
source of medicine
reduces erosion/ eutrophication
farming cattle for humans to eat is less effective than farming crops because of energy transfer explain why (2)
energy lost between trophic levels
energy lost via respiration/ excretion
the chemical energy store in dry biomass can be estimated using….
calorimetry
use your knowledge of NPP to explain why freshwater marshes have a high CUE (carbon use effecentcy) and the advantage of this.
low respiration
less energy lost via respiration
more growth/ biomass
The student used the equation however she subsfrusted height for biomass. This was because she didn’t want to destroy the plants to measure their biomass. State the assumptions the student has made and suggest why this might not be valid (2)
assumed that height is directly proportional to biomass
height doesn’t include the roots
some increase in height because of water gain
loss of nutrients into lake Malawi has resulted in a decrease in some fish populations explain why
algae bloom block light
no photosyntjsis so plants die
sarpobitic aerbocally respire
less oxygen for fish to respire
