
Concept explainers
To say that species A is more closely related to species B than to species C is to say that A and B
a. have a more ancient common ancestor than do A and C.
b. have a more recent common ancestor than do A and C.
c. are more similar in appearance than are A and C.
d. live in the same area, but C does not live there.

Introduction:
The evolutionary tree is constructed based on the anatomical and molecular similarities among different organisms. When two species A and B diverged from a common ancestor the similarities of traits found in the two species can be present in the more recent common ancestor. When species C does not share traits or the genetic differences are high compared to species A and B than species C is not descendant of an ancestor of A and B.
Answer to Problem 1MC
Correct answer:
The species A is more closely related to species B, it means that species A and B have a more recent common ancestor than do A and C.
Explanation of Solution
Explanation for the correct answer:
Option (b) is given that species B and A are more closely related as they have a more recent common ancestor as compared to A and C. The species B and A diverged from a more recent common ancestor due to mutations. Thus, the genetic differences between A and B are less than those between A and C when three species are compared. This implies that A and B are closely related. Hence, option (b) is correct.
Explanation for incorrect answers:
Option (a) is given that species B and A are more closely related as species B and A have a more ancient common ancestor than do A and C. The descendants of the most recent ancestor are said to be more closely related, whereas the descendants of more ancient common ancestors are less closely related. So, it is an incorrect option.
Option (c) is given that species B and A are more closely related as they are more similar in appearance than are A and C. The similarities in appearance are not used to compare closely related species. It is the molecular similarity determined by analyzing the genetic level, which is the key to find the divergence from a common ancestor. So, it is an incorrect option.
Option (d) is given that species B and A are more closely related as they both live in the same area but C does not live there. The place of living is not considered to find the close relationship between the species, as it is the genetic similarities, which determine whether the species are closely related or not. So, it is an incorrect option.
Hence, options, (a), (c), and (d) are incorrect.
Thus, it can be concluded that the species B and A are more closely related as they are descendants of a more recent common ancestor. The close relation is determined using molecular analysis.
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Chapter 19 Solutions
Biology: Life on Earth (11th Edition)
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