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Summary A* Energy and ecosystems notes
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A* Energy and ecosystems notes
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Energy & EcosystemsHow is sunlight used as energy?
sunlight in the ultimate energy source, it is converted into chemical energy during photosynthesis, it
is passed on as food between other organisms, it flows through an ecosystem as nutrients are
recycled.
What is a producer?
A producer is a photosynthesising organism which manufactures organic substances using light
energy, water, CO2 and mineral ions.
What is a consumer?
A consumer is an organism which gains its energy by feeding on other organisms.
Describe primary, secondary and tertiary consumers.
a primary consumer eats producers, a secondary consumer eats primary consumers, a tertiary
consumer eats secondary consumers (secondary and tertiary include predators, scavengers and
parasites).
What is a decomposer?
A decomposer is an organism which uses the energy contained in producers and consumers when
they die to break down complex materials into valuable minerals and elements which can then be
absorbed by plants (recycled), e.g., bacteria, fungi and detritivores (earthworms and maggots).
What is biomass?
Biomass is the total mass of living material in a specific area at a given time.
What is fresh mass & dry mass?
Fresh mass= complicated by water content. Dry mass= dehydrated (process kills the organisms)- per
area in a given time, grams per square metre gm-2.
What is the main source of energy?
The sun.
How much of total light energy captured is made available to the food chain?
1-3%.
Therefore…
Each organism in turn only passes on a small amount of energy.
Why is most of the suns energy not converted to organic matter by photosynthesis?
Over 90% of the suns energy is reflected back into the atmosphere or absorbed by the atmosphere,
not all wavelengths can be used by plants, light may not fall on chlorophyll molecule and limiting
factors may limit the rate of photosynthesis.
, What is gross production?
The total chemical energy converted into organic matter (biomass) by photosynthesis.
What do plants use 20-50% of this energy for?
Respiration.
What is net production?
The total energy converted into food available for other organisms.
How to calculate net production?
Gross production- respiratory losses.
How much do producers transfer?
2% of solar energy into chemical energy.
How much do primary consumers transfer?
10% of food energy stored in plants to animal tissue.
Secondary & tertiary consumers?
Slightly more efficient as they transfer about 15-20% of energy into animal tissue.
What is the percentage of energy transferred at each stage due to?
Some of the organism is not eaten, some parts are indigestible so passed out in faeces, some energy
is lost in excretory materials such as urine and some energy losses occur as heat from respiration as
it is transferred to the environment (maintaining body temp).
What is net productivity?
N=I-(F+R)
N= net production I= chemical energy stored of ingested food F= energy loss in faeces or urine R=
energy lost in respiration.
Why do food chains have a limited number of trophic levels?
As insufficient energy is available to support more organisms.
What happens at higher trophic levels?
Total biomass decreases.
What happens further up the food chain?
The total amount of energy stored at each trophic level decreases.
How to calculate percentage efficiency?
=energy available after transfer/ energy available before transfer x100
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