Question

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 worm segment left 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. Segments are independently controlled by local nerves.
b. The nerve cord is essential for locomotion.
c. The brain coordinates segmental movements.
d. Local reflexes control segmental contractions.

Answer 1

The conclusion that 'local reflexes control segmental contractions' is supported by the evidence from the earthworm experiment, which showed continued movement even after the brain was removed and demonstrated the importance of the ventral nerve cord for coordinated contractions.

Step-by-step explanation:

When examining the experimental results observed with the earthworm, you can conclude that local reflexes control segmental contractions. The contraction of segments when poked indicates a local response to stimulation. Even after the anterior segments containing the brain were removed, the remaining segments still crawled, showing that control is not exclusively brain-dependent.

When you cut the nerve in each septal wall, and contractions continued, it suggests that segments can be independently controlled by local nerves. The ability to crawl when the body wall is cut, leaving the ventral nerve cord intact, supports the importance of the nerve cord for coordination.