Question

scientists compile many pieces of evidence to infer evolutionary relationships. here is one such piece of evidence.

the gene bdnf encodes a protein, brain - derived neurotrophic factor, that is involved in the growth and maintenance of nerve cells in the brain and spinal cord. this table shows the number of nucleotides in bdnf that are identical between three different aquatic vertebrates: blue whales, coelacanths (a type of lobe - finned fish), and asian bonytongue fish.

the number of identical nucleotides in bdnf between pairs of aquatic vertebrates

coelacanths and asian bonytongue fish	445
blue whales and coelacanths	626
asian bonytongue fish and blue whales	468

which claim is best supported by this evidence?

• of the three species, blue whales and coelacanths are most closely related.
• of the three species, asian bonytongue fish and blue whales are most closely related.
• of the three species, coelacanths and asian bonytongue fish are most closely related.

Explanation:

To determine evolutionary relationships from nucleotide similarity, more identical nucleotides between two species suggest a closer evolutionary relationship (as they share more genetic material). We compare the number of identical nucleotides in BDNF:

• Coelacanths & Asian bonytongue fish: 445
• Blue whales & coelacanths: 626
• Asian bonytongue fish & blue whales: 468

The highest value is 626 (blue whales and coelacanths), so they are most closely related.

Answer:

Of the three species, blue whales and coelacanths are most closely related.