Question

scientists discover five new species of shrimp. the table shows the nucleotide differences among the five species.

	species 1	species 2	species 3	species 4	species 5
species 2	4	–	21	13	25
species 3	21	21	–	2	26
species 4	13	13	2	–	26
species 5	26	25	26	26	–

which cladogram represents how the species should be arranged, based on the information in the table?

(a) cladogram with branches: 2, 5, 1, 3, 4 (with 1 and 3 closer, 1/3 and 5, then 4, then 2)
(b) cladogram with branches: 3, 4, 2, 1, 5 (with 3, then 4/2, then 4/2/1, then 5)
(c) cladogram with branches: 4, 3, 5, 1, 2 (with 4, then 3, then 5, then 1, then 2)
(d) cladogram with branches: 4, 3, 5, 1, 2 (with 4, then 3/5, then 3/5/1, then 2)

Explanation:

Step1: Identify closest species pairs

Look for the smallest nucleotide difference values:

• Species 1 & 2: 4 differences
• Species 3 & 4: 2 differences
• Species 1 & 3: 21, 1 & 4:13, 5 has 26 differences with 1,3,4, 25 with 2

Step2: Group closely related species

Pair 1-2 (closest, 4 differences) and pair 3-4 (closest, 2 differences). Species 5 is the most distantly related (highest differences with all others).

Step3: Match to cladogram structure

Check which cladogram has 1+2 as a subgroup, 3+4 as a subgroup, and 5 as an outgroup relative to 1/2, with 4 as the most distant from the 1/2/5 cluster. This matches option D.

Answer:

D. The cladogram with species 4 as the outermost branch, followed by a subgroup of 3, then a subgroup of 5, then a subgroup of 1 and 2.