[Campbell Biology P.1182] Based on Figure 50.36 and the accompanying text, which statement ac... | Practice Question
Based on Figure 50.36 and the accompanying text, which statement accurately describes the mechanism of earthworm locomotion through peristalsis?
A: Longitudinal muscles contract to extend segments, while circular muscles relax to thicken them, enabling forward movement.
B: Circular muscles contract to constrict segments, and bristles anchor these segments, allowing the longitudinal muscles to pull the worm forward.
C: During forward movement, head segments become thick and anchored by bristles due to longitudinal muscle contraction, while segments behind the head are thin and elongated due to circular muscle contraction.
D: Peristalsis involves rhythmic waves of muscle contractions where alternating segments shorten (longitudinal muscles contract) and lengthen (circular muscles contract), with bristles providing anchor points.
Explanation
Peristalsis in earthworms involves the coordinated action of circular and longitudinal muscles. Circular muscle contraction constricts segments, making them long and thin, while longitudinal muscle contraction shortens and thickens segments. These alternating contractions, coupled with anchoring by bristles, create a wave-like motion that propels the worm forward.