Question

Which trait is shared by all vertebrates except cyclostomes at some point in development?

Answer 1

The trait shared by all vertebrates except cyclostomes at some point in development is the presence of a vertebral column.

So, the correct answer is option 2.

Step-by-step explanation:

Cyclostomes, which include jawless fishes like lampreys and hagfish, lack a true vertebral column during any stage of their development. However, in other vertebrates, the vertebrae form around the embryonic notochord, which is another characteristic of chordates, and eventually replace it in adults to form the backbone.

The notochord typically becomes the nucleus pulposus of the intervertebral discs in more derived vertebrates. This distinguishes vertebrates from invertebrate chordates, which may retain a notochord into adulthood, as seen in cephalochordates and urochordates.

So, the correct answer is option 2.

Complete question:

Which trait is shared by all vertebrates except cyclostomes at some point in development?

1. notochord.
2. vertebrae.
3. cartilaginous skeleton.
4. cranium.
5. mouth with jaws.