Video Transcript
The diagram shows a partially
completed evolutionary tree for the classification of families belonging to the
order Carnivora. Based on the information given in
the diagram, which of the following statements is true? (A) Members of the Canidae and
Ursidae families are more closely related than members of the Canidae and Hyaenidae
families. (B) Members of the Canidae and
Felidae families are more closely related than members of the Felidae and Hyaenidae
families. (C) Members of the Viverridae and
Herpestidae families have evolved from the most recent common ancestor. Or (D) there are six unique species
shown in this evolutionary tree.
Our question asks about a diagram
resembling a phylogenetic tree. A phylogenetic tree can show
evolutionary relatedness between species. Let’s start with a closer look at
the diagram. It is referring to order, suborder,
and family classifications of organisms. This means that it refers to
broader groupings than individual species. This means that we can already
exclude answer option (D), as there are no individual species shown in this
evolutionary tree.
Let’s work through the phylogenetic
tree to see which families are most related. Firstly, we know that all of these
organisms belong to order Carnivora. This order splits into two
suborders: Feliformia and Caniformia. The last common ancestor of these
two suborders is designated by a yellow circle. The two different suborders, and
families belonging to these suborders, are characterized by the blue and red
lines.
Now let us review the answers to
our question to arrive at the correct one.
Answer choice (A) states that
members of the Canidae and Ursidae families are more closely related than members of
the Canidae and Hyaenidae families. This answer choice is true because
Canidae and Ursidae share the same suborder classification, whereas Hyaenidae
belongs to suborder Feliformia. Members of the Canidae and Ursidae
families have evolved from a common ancestor in the suborder Caniformia, represented
here by a red dot. In comparison, the most common
ancestor of Canidae and Hyaenidae is the ancestor of the suborders Feliformia and
Caniformia, which split into different branches much earlier than the most common
ancestor of the Canidae and Ursidae families. Therefore, Canidae and Ursidae
families are more closely related.
Answer (B) is incorrect because
members of the Canidae and Felidae families are not more closely related than
members of the Felidae and Hyaenidae families, as these families are not classified
into the same suborder. Two families of the same suborder
will always be more closely related to each other than two families from different
suborders.
Answer choice (C) is also incorrect
because members of the Viverridae and Herpestidae families did not evolve from the
most recent common ancestor. The last common ancestor for
Viverridae is represented by a pink circle, while the last universal common ancestor
for the Herpestidae family is represented by a green circle.
So we can now see that the only
true statement provided is answer choice (A). Members of the Canidae and Ursidae
families are more closely related than members of the Canidae and Hyaenidae
families.
