[Campbell Biology P.1033] Which of the following statements about protonephridia, as describe... | Practice Question

Which of the following statements about protonephridia, as described and illustrated, is correct?

  • A: Protonephridia are characteristic of vertebrates and use blood pressure for filtration.
  • B: A flame bulb consists solely of a tubule cell with cilia.
  • C: The beating of cilia in flame bulbs draws interstitial fluid into the tubule network to form filtrate.
  • D: The urine produced by freshwater flatworms through protonephridia is highly concentrated to conserve water.

Explanation

The text states that 'During filtration, the beating of the cilia draws water and solutes from the interstitial fluid through the flame bulb, releasing filtrate into the tubule network.' This directly supports option C. Options A and B contain factual inaccuracies regarding the animal group and flame bulb components, respectively. Option D is incorrect because the urine is dilute to counteract osmotic water uptake in freshwater environments.