You experiment with a live earthworm and notice the following results: - With an intact earthworm,when you "poke" a segment,it contracts.
- When you cut off the first segments containing the brain,the remaining worm still crawls.
- When you cut the nerve in each septal wall,contractions continue.
- If you cut the body wall,leaving the nerve cord intact,crawling still continues.
- When you cut both the body wall nerve and the nerve cord,there are no longer any coordinated contractions.
What is a reasonable conclusion?
A) An earthworm's brain controls crawling.
B) The ventral nerve cord controls all contractions.
C) Mechanical stimulation of each segment triggers contractions.
D) Earthworms use ventral nerve cord to coordinate contractions along the length of the worm and mechanical stimulation of each segment to triggers segmental responses during crawling.
E) None of the choices are correct.

Question

Quizplus · Accepted Answer

The experiments show that the brain is not necessary for crawling and that cutting the nerve in each septal wall or the body wall nerve does not stop contractions completely. This suggests that the ventral nerve cord is the main controller of contractions along the length of the worm and that mechanical stimulation of each segment triggers segmental responses during crawling. Therefore, D is the most reasonable conclusion.

You Experiment with a Live Earthworm and Notice the Following