AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Producers are mostly plants and algae which transfer about 1 % of the…
Full specification wording
Transfer of biomass: Producers are mostly plants and algae which transfer about 1 % of the incident energy from light for photosynthesis.
Producers occupy the first trophic level and are mainly green plants on land and algae in water.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 2 of 7
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Producers occupy the first trophic level and are mainly green plants on land and algae in water. They absorb light energy using chlorophyll and convert carbon dioxide and water into glucose and oxygen during photosynthesis, storing the glucose as starch, cellulose, lipids and other biomass. Only about 1 % of the incident light energy falling on a producer is transferred into biomass; the rest is reflected, transmitted through leaves, or absorbed by non-photosynthetic parts, or has wavelengths not used by chlorophyll. Some absorbed energy is also lost as heat during respiration. This low efficiency explains why producers need a large surface area of leaves or algal cells, and why the total biomass of producers in an ecosystem is much greater than that of consumers.
What earns the marks
- Identifies producers as mostly plants and algae that carry out photosynthesis.
- States that producers transfer approximately 1 % of the incident light energy into biomass.
- Names the inputs of photosynthesis as carbon dioxide and water and the products as glucose and oxygen.
- Explains that most incident light is reflected, transmitted or absorbed by non-photosynthetic material, or is of unsuitable wavelength.
- Links the stored products of photosynthesis to the biomass available to primary consumers.
- Recognises that energy absorbed by producers may also be lost as heat during respiration.
Common mistakes and how to put them right
Stating that producers absorb all the light that falls on them.
Put it right: Only about 1 % of incident energy is transferred into biomass.
Writing that plants take in energy from the soil.
Put it right: Plants obtain light energy from the Sun and mineral ions, not energy, from the soil.
Confusing the 1 % figure with the 10 % transfer between trophic levels.
Put it right: 1 % refers to light energy captured by producers, while 10 % refers to biomass passed between consumer levels.
Exam tips
- Quote the 1 % value only when the question asks about light energy captured by producers.
- Use the word incident when describing light falling on a leaf, and distinguish it from light absorbed by chlorophyll.
- Link the low percentage to named fates of light such as reflection, transmission and absorption by non-photosynthetic tissue.
Try the lesson
The start of the Transfer of biomass: Producers are mostly plants and algae which transfer about 1 % of the incident energy from light for photosynthesis. lesson, made from checked teaching notes for this specification point.
Have a go first
Which organisms are described as the producers at the start of most food chains?
Listen
Producers occupy the first trophic level and are mainly green plants on land and algae in water. They absorb light energy using chlorophyll and convert carbon dioxide and water into glucose and oxygen during photosynthesis, storing the glucose as starch, cellulose, lipids and other biomass. Only about 1 % of the incident light energy falling on a producer is transferred into biomass; the rest is reflected, transmitted through leaves, or absorbed by non-photosynthetic parts, or has wavelengths not used by chlorophyll. Some absorbed energy is also lost as heat during respiration. This low efficiency explains why producers need a large surface area of leaves or algal cells, and why the total biomass of producers in an ecosystem is much greater than that of consumers. A strong answer earns marks for these points. Identifies producers as mostly plants and algae that carry out photosynthesis. States that producers transfer approximately 1 % of the incident light energy into biomass. Names the inputs of photosynthesis as carbon dioxide and water and the products as glucose and oxygen. Explains that most incident light is reflected, transmitted or absorbed by non-photosynthetic material, or is of unsuitable wavelength. A common slip: Stating that producers absorb all the light that falls on them. Instead, only about 1 % of incident energy is transferred into biomass. Exam tip: Quote the 1 % value only when the question asks about light energy captured by producers.
Key words
Say what each word means before you turn the card.
Producers
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Incident light
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Fate of incident light
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See every definition
- Producers
- Mostly plants and algae, which transfer about 1 % of the incident energy from light for photosynthesis.
- Incident light
- Light falling on a producer; only about 1 % of its energy is transferred into biomass.
- Fate of incident light
- The rest is reflected, transmitted through leaves, absorbed by non-photosynthetic parts, or has wavelengths not used by chlorophyll.
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