Which of the following pairs of structures in living organisms do not perform similar functions?

Step 1: Analyze the question We need the pair of structures whose functions are not similar. Three pairs should be functionally alike, and one pair should be different.

Step 2: Check each option

• A. Lungs and spiracles: Both are gaseous exchange structures. Lungs serve mammals, and spiracles serve insects. The functions are similar.
• B. Root hairs and mammalian hairs: Root hairs absorb water and mineral salts from the soil. Mammalian hairs provide insulation, protection and sensation. The functions are completely different.
• C. Feathers and scales: Both cover and protect the body. Feathers also insulate birds, and scales protect fish and reptiles. The functions are similar.
• D. Contractile vacuole and kidneys: Both are involved in osmoregulation and excretion. The contractile vacuole removes excess water from protozoans like Amoeba, and kidneys regulate water and remove waste in mammals. The functions are similar.

Step 3: Answer Only root hairs and mammalian hairs do not perform similar functions.

Exam tip: In "which pair is NOT similar" questions, find the function of each structure first. Then eliminate the pairs that match. Remember that root hairs are for absorption, while hairs on animals are for protection or insulation.