Year 10 Science · Unit 1 · Lesson 14
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Learning Goals
Read the graph
DNA similarity to humans (%)
Data: Estimated from comparative genomics studies; approximate values for educational purposes.
(a) Describe the overall trend shown in the graph.
(b) How much more similar is chimp DNA to human DNA compared with mouse DNA? Calculate the difference.
(c) Use the graph data to explain what DNA similarity tells us about when these species diverged from humans.
Real-world context
Australia separated from the supercontinent Gondwana approximately 50 million years ago, drifting northward in complete isolation. During this time, marsupials diversified to fill every ecological niche. Today, Australia has a sugar glider (a marsupial) that looks and behaves almost identically to the North American flying squirrel (a placental mammal). DNA analysis confirms they are not closely related, the sugar glider is more closely related to kangaroos than to any squirrel.
(a) Explain what convergent evolution is, and use the sugar glider and flying squirrel as your example.
(b) What does the independent evolution of similar forms in Australia and elsewhere tell us about the power of natural selection?
1. What is a molecular clock and what assumption does it rely on?
2. Why do some students find it surprising that humans share 50% of their DNA with bananas? Explain what this DNA similarity actually means.
Wrap Up
In one sentence, what was the main idea of this lesson?