Concept explainers
To estimate: The date when the most recent common ancestor of all three species lived using the given genetic data.
Introduction: A common ancestor of different species is an evolutionary link between the different species. Different organisms have evolved by differentiation and divergence from the common ancestor, which is their origin. The degree of differentiation or the time that it takes for an organism to evolve from a common ancestor is measured by the genetic distance.
Explanation of Solution
Pictorial representation: Fig.1 represents the phylogenetic tree of the common ancestry.
Fig.1: Phylogenetic tree
A species and B species are closely related, but species C is more distant to A and B. The phylogenetic tree shows that the common ancestor of A and B were seen 1.2 million years ago. As species C is even more distant, the common ancestor of all three was seen much before 1.2 million years ago. Since it took 1.2 million years to lead to a difference of 18 base pairs, time when the common ancestor on A, B, and C was seen, can be estimated to be 1.2 to 2 million years before the common ancestor of A and B.
To describe: The assumptions made to get the estimated date.
Introduction: A common ancestor of different species is an evolutionary link between the different species. Different organisms have evolved by differentiation and divergence from the common ancestor, which is their origin. The degree of differentiation or the time that it takes for an organism to evolve from a common ancestor is measured by the genetic distance.
Explanation of Solution
Species C is more distant to species A and B, hence their common ancestor is expected to present much earlier than the common ancestor of A and B. Species C is estimated to have lived 1.2 to 2 million years before the common ancestor of A and B.
To derive this, several assumptions are made such as follows:
- It is assumed that
speciation is a long and gradual process which occurs over a period of time. - Phylogenetic trees can be used to study diversification.
- It is assumed that the three species A, B, and C have some similarities and hence have a common ancestor, which serves as a point of origin for diversification of species.
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Chapter 7 Solutions
Evolution
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