[Campbell Biology P.770] Describe the path of water and the primary feeding mechanism in an ... | Practice Question

Describe the path of water and the primary feeding mechanism in an adult tunicate and a lancelet Branchiostoma .

  • A: Adult tunicate: Incurrent siphon → pharyngeal slits → atrium → excurrent siphon; uses mucous net. Lancelet: Mouth → pharyngeal slits → atrium → atriopore; uses cirri to block particles.
  • B: Adult tunicate: Excurrent siphon → pharyngeal slits → atrium → incurrent siphon; uses cilia. Lancelet: Mouth → gills → anus; uses suction.
  • C: Adult tunicate: Water enters directly into the stomach; filter feeds with tentacles. Lancelet: Water enters through cirri; uses muscular contractions for feeding.
  • D: Both adult tunicates and lancelets use an incurrent siphon and filter food using a notochord.

Explanation

For the adult tunicate, the text states it 'draws in water through an incurrent siphon; the water then passes through the pharyngeal slits into a chamber called the atrium and exits through an excurrent siphon. Food particles are filtered from the water by a mucous net.' For the lancelet, it states 'Water enters the mouth and passes through the pharyngeal slits into the atrium, a chamber that vents to the outside via the atriopore; large particles are blocked from entering the mouth by tentacle-like cirri.' This information perfectly matches option A.