Question

scientists compile many pieces of evidence to infer evolutionary relationships. here is one such piece of evidence.
elongation factor 2 is a protein involved in translating mrna into proteins. it is found in all organisms and contains between 600 and 800 amino acids. this table shows the number of amino acids in elongation factor 2 that are identical between three different organisms: cows, escherichia coli bacteria, and pyrobaculum islandicum archaea.
which claim is best supported by this evidence?
of the three organisms, p. islandicum archaea and e. coli bacteria are most closely related.
of the three organisms, cows and e. coli bacteria are most closely related.
of the three organisms, p. islandicum archaea and cows are most closely related.

Explanation:

In evolutionary biology, the more identical amino - acids in a conserved protein (like elongation factor 2) between two organisms, the more closely related they are. We compare the number of identical amino - acids for each pair.
For cows and E. coli bacteria: 102 identical amino - acids.
For P. islandicum archaea and E. coli bacteria: 177 identical amino - acids.
For P. islandicum archaea and cows: 193 identical amino - acids.
Since 193 (the number of identical amino - acids between P. islandicum archaea and cows) is the highest among the three values, this pair has the most genetic similarity (at least in terms of this protein) which implies a closer evolutionary relationship.

Answer:

Of the three organisms, P. islandicum archaea and cows are most closely related.