Answer: flatworms such as Planaria.
- A flatworms such as Planaria
- B human beings like us
- C birds and their kin
- D various common insects
Correct answer: A. flatworms such as Planaria
Explanation: Flame cells (protonephridia) carry out excretion in flatworms.
Filtrate flows through four functionally distinct stages of the nephron: Bowman's capsule filters blood, the PCT reabsorbs most useful substances unconditionally, the Loop of Henle builds a concentration gradient via counter-current exchange, the DCT secretes selected substances, and the collecting duct performs the final ADH-controlled water reabsorption.
Concept context
Nitrogenous waste, kidney structure, urine formation in the nephron, and hormonal regulation of excretion.
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