[Campbell Biology P.764] The 'WHAT IF?' section in the text asks why Drosophila melanogaster... | Practice Question

The 'WHAT IF?' section in the text asks why Drosophila melanogaster and Caenorhabditis elegans might be less appropriate model organisms for making inferences about humans and other vertebrates. Based on the entire provided text and general biological knowledge, which of the following is the most likely reason?

  • A: *Drosophila* and *C. elegans* are more complex than vertebrates, making comparisons difficult.
  • B: Humans and other vertebrates evolved directly from *Drosophila* and *C. elegans*, making them too closely related for broad inferences.
  • C: *Drosophila* and *C. elegans* are protostomes, while echinoderms (like sea urchins) and chordates (including humans) are deuterostomes, sharing a more recent common ancestor and similar developmental patterns, making echinoderms potentially more appropriate for certain comparative inferences.
  • D: *Drosophila* and *C. elegans* lack a coelom, which is a fundamental feature of vertebrates.

Explanation

The text states that 'The close relationship between echinoderms and chordates does not mean that one phylum evolved from the other. In fact, echinoderms and chordates have evolved independently of one another for over 500 million years.' This implies a shared ancestry distinct from other invertebrate groups. Biologically, echinoderms and chordates are both deuterostomes, meaning they share a common embryonic developmental pattern e.g., anus forms from blastopore, radial cleavage . In contrast, Drosophila an arthropod and C. elegans a nematode are protostomes. Differences in early embryonic development and phylogenetic distance make protostomes less appropriate for directly inferring about deuterostome-specific features, including those in vertebrates.