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Visualizing life on Earth: data interpretation in evolution

by the Understanding Evolution team

The living world offers many bizarre and beautiful details: flowers that mimic insects, beetles that shimmer like jewelry, the dance of DNA as a cell divides. With all this detail, it's easy to get lost in biology's details and miss its big picture. To see that big picture, we'll leave behind magnifying lenses and microscopes and zoom out on planet Earth.

Imagine that you are an alien, exploring Earth in your spacecraft. As you zip from pole to pole, what would you notice about life on Earth? Perhaps first, that Earth is home to millions of different species. Second, that those species aren't just randomly scattered over the planet. In fact, most of them live close to the equator (in the tropics), and as you head to the poles, there are fewer and fewer species to be found.

arctic, tropic, and antarctic zones

This pattern might seem obvious. "Of course, the tropics are rich and the poles are barren. What do you expect? It's cold up there!" But it doesn't have to be that way. On an alien world, the poles might be packed with life and the equator a wasteland. Or life could be spread out evenly over the whole planet. Why is life on Earth distributed the way it is and not some other way?

In this module, you will examine the same data that scientists have used to try to answer this question and can compare your own ideas to those that scientists have come up with. You'll dive into the past to try to understand why species live where they do today and figure out how evolution has shaped these patterns. Click the Next button to get started.

In this interactive investigation we'll explore these key questions:
  • What evolutionary processes have affected the distribution of Earth's species today and in the past?

  • How do scientists study past evolutionary processes on Earth?

  • How do graphs and charts help scientists test their hypotheses?

Jump ahead to:

Intro | Investigation Phase 1 | Investigation Phase 2 | Investigation Phase 3 | Investigation Phase 4 | Conclusion

Freshwater shrimp photo provided by Micrographica; tiger photo provided by Gerald and Buff Corsi © California Academy of Sciences; mushroom photo © Br. Alfred Brousseau, Saint Mary's College; tundra photo by Dr. Robert T. and Margaret Orr © 2004 California Academy of Sciences

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