Which external structures aid earthworms in movement by gripping the soil?

Which external structures aid earthworms in movement by gripping the soil?

• A. Intestine
• B. Setae
• C. Crop
• D. Aortic arches

Answer: (B)

Earthworms move by muscular waves, and they need something to grip the surrounding soil as they inch forward. The external structures that do this are setae, tiny bristles on each body segment. When the worm contracts its muscles, the setae protrude into the soil and serve as anchors, preventing backward slipping. This anchoring lets the rest of the body be pulled forward with each contraction, producing forward movement. The other options are internal organs (digestive parts like the intestine and crop, or the circulatory aortic arches), which don’t grip soil to aid locomotion.

Earthworms move by muscular waves, and they need something to grip the surrounding soil as they inch forward. The external structures that do this are setae, tiny bristles on each body segment. When the worm contracts its muscles, the setae protrude into the soil and serve as anchors, preventing backward slipping. This anchoring lets the rest of the body be pulled forward with each contraction, producing forward movement. The other options are internal organs (digestive parts like the intestine and crop, or the circulatory aortic arches), which don’t grip soil to aid locomotion.