IB Biology SL C4.2 Transfers of energy and matter questions

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Type
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Question 1

Multiple choiceEasy1 mark

The diagram shows the inputs used by four organisms that synthesize carbon compounds. Which organism is an autotroph?

The carbon source shown is the sole carbon-containing input.external light energyglucoseOrganism Acarbon compoundsexternal light energyamino acidsOrganism Bcarbon compoundsexternal light energycarbon dioxide (CO2)Organism Ccarbon compoundsexternal light energystarchOrganism Dcarbon compounds
Show answer and explanation

Answer: C. An autotroph uses an external energy source to synthesize carbon compounds from simple inorganic substances. Organism C receives external light energy and its sole carbon-containing input is CO₂, a simple inorganic substance.

A: treats glucose, an organic carbon source, as a simple inorganic substance.
B: treats amino acids, which are organic, as a simple inorganic carbon source.
D: treats starch, an organic carbon source, as a simple inorganic substance.
Remember: autotrophy depends on the source of carbon, not only on the energy source.

Question 2

Paper 2Medium3 marks

A bacterial culture was grown in darkness in a medium in which carbon dioxide was the only source of carbon. The same amount of iron was supplied in each culture, but in different forms. All other conditions were identical.

Form of iron suppliedChange in bacterial biomass after 48 hours
Iron(II) compoundsIncrease
Iron(III) compoundsNo increase
(a)

Classify these bacteria as photoautotrophs or chemoautotrophs.

[1]
(b)

Explain how the bacteria can produce carbon compounds in the condition where biomass increased. Refer to both the carbon source and the energy source.

[2]

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