Read photosynthesis inputs and products

Supplied materials

• All measurements and observations below are supplied classroom examples. They are not data from actual learners or a claim about a particular real site.
• Paper or a browser document for a labeled drawing, table or explanation.
• Worked problem inputs: A plant adds dry biomass while taking up carbon dioxide and water. Explain why soil mass alone cannot account for the gain.
• Assessment case 1: A plant model gains dry carbon-containing biomass while taking up CO₂. What source contributes that carbon? Which inference or prediction is best supported?
• Assessment case 2: Which scientific label fits the specifically described step or feature? Supplied case: Liquid reactant supplies hydrogen.
• Assessment case 3: Which scientific label fits the specifically described step or feature? Supplied case: Six-carbon sugar forms.
• Assessment case 4: Which scientific label fits the specifically described step or feature? Supplied case: Gas is released by photosynthesis.
• Assessment case 5: Which scientific label fits the specifically described step or feature? Supplied case: Air carbon becomes part of sugar.
• Assessment case 6: A supplied sugar stores chemical energy captured during photosynthesis. What happens when it later supports respiration? Which inference or prediction is best supported?

Learn the idea

Photosynthesis transforms light energy into chemical energy and uses carbon dioxide and water to form sugars in a simplified overall model. Oxygen is released. Real pathways include many reactions.

Carbon dioxide means carbon input in the overall model. Water means hydrogen-containing input in the overall model. Glucose means sugar product storing chemical energy. Oxygen means gas product released in the model.

For the supplied mechanism problem, A plant adds dry biomass while taking up carbon dioxide and water. Explain why soil mass alone cannot account for the gain. Photosynthesis incorporates carbon from atmospheric carbon dioxide into sugars. Water and other inputs contribute too. Plants need minerals, but they do not obtain all added biomass by eating soil.

1. Read the supplied problem and mark the structures, processes or quantities named: A plant adds dry biomass while taking up carbon dioxide and water. Explain why soil mass alone cannot account for the gain.
2. Draw the relevant boundary, pathway or comparison and label it using the scientific ideas above.
3. Write a causal explanation or calculation, showing how each observation supports the result.
4. Compare your reasoning with the worked solution; name a condition that would change or limit the inference.

Check your reasoning

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Take it further

New task: trace one carbon atom from atmospheric CO₂ into a plant-made sugar. Expected: carbon enters via photosynthesis; do not assign all added plant carbon to soil minerals.

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