Question

What can be inferred about the evolution of the cranium and vertebral column from examining hagfishes and lampreys?

a) Both developed a cartilaginous cranium first, followed by the vertebral column.
b) Hagfishes developed a cranium earlier than lampreys.
c) Lampreys developed a bony cranium, while hagfishes have a cartilaginous one.
d) Both species lack a cranium and vertebral column.

Answer 1

Examining hagfishes and lampreys indicates that the cranium developed first, followed by the evolution of a partial vertebral column in lampreys, signaling separate development stages of these structures in vertebrate history.

Step-by-step explanation:

From examining hagfishes and lampreys, it can be inferred that the development of the cranium and vertebral column evolved at separate times in the history of vertebrates. Hagfishes, which appeared more than 500 million years ago, possess a cranium but lack a vertebral column. Instead, they retain the notochord throughout their life, which provides basic structural support. On the other hand, lampreys showcase the evolution of a partial vertebral column, an advancement that hagfishes do not have. Therefore, the correct inference from examining both these jawless fishes would be that both developed a cartilaginous cranium first, followed by the vertebral column (answer a). Lampreys represent an intermediate step towards the vertebrates that have a complete vertebral column and a more evolved cranium.