6.2 Variation and evolution

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Question 4
Medium

Scientists think that the bear species shown below all evolved from a common ancestor that lived about 20 million years ago.

The diagram shows how these species may have evolved:

An evolutionary tree showing the relationships between six bear species. At the far left, the timeline starts at "20 million years ago" with a common "Ancestor". Moving to the right, Node A (dated 15 million years ago) splits into: 1) a top branch leading directly to the Giant panda, and 2) a bottom branch. The bottom branch continues to Node B (dated 10 million years ago), which splits into: 1) a branch leading directly to the Spectacled bear, and 2) another branch continuing to the right. This branch then reaches Node C (dated 5 million years ago) which splits into: 1) a branch leading to the Sloth bear, and 2) a branch continuing to the right. This branch hits Node D (dated 2 million years ago) which splits into: 1) a branch leading to the American black bear, and 2) a branch continuing to Node E. Node E (dated 400 thousand years ago) splits into the Polar bear and the Brown bear. The horizontal axis represents Time, running from the left to the right ("Present day"). Key: Node A = 15 million years ago, Node B = 10 million years ago, Node C = 5 million years ago, Node D = 2 million years ago, Node E = 400 thousand years ago.

Use the diagram to answer the following questions:

a.

What was the most recent time that the American black bear and the Polar bear shared a common ancestor?

  • 400 thousand years ago
  • 2 million years ago
  • 5 million years ago
  • 15 million years ago
[2]
b.

Which present-day bear in the diagram is the most distant relative of the Polar bear?

[2]

6.2 Variation and evolution Questions

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  3. /6.2 Variation and evolution