Scientists measured carbon dioxide levels in a sealed container containing pond water, algae, and aquatic invertebrates over 24 hours. The graph showed CO₂ levels decreased during daylight hours and increased at night. Which of the following best explains this pattern?

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Question

Scientists measured carbon dioxide levels in a sealed container containing pond water, algae, and aquatic invertebrates over 24 hours. The graph showed CO₂ levels decreased during daylight hours and increased at night. Which of the following best explains this pattern?

Accepted Answer

Photosynthesis by algae removes CO₂ during the day; respiration by all organisms releases CO₂ continuously — Award 1 mark for recognising that photosynthesis (which removes CO₂) occurs during daylight and exceeds respiration, while at night only respiration occurs, releasing CO₂. B is incorrect — algae respire continuously, not only at night. C is incorrect — invertebrates cannot photosynthesize. D is incorrect — decomposers are active continuously, though the question focuses on algae and invertebrates.

Answer

Photosynthesis by algae removes CO₂ during the day; respiration by all organisms releases CO₂ continuously

Answer

Decomposers are only active during nighttime hours

Answer

Invertebrates photosynthesize during the day and respire at night

Answer

Algae only respire at night, releasing large amounts of CO₂

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