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Exploratour - Life on Earth

Short-eared owl
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This tour is a detailed look at life on Earth, and what we know about how it came to be. To proceed with the tour, just click on the forward indicator in the button at the top right portion of this page.

If you had to explain to someone what "life" is, what would you tell them? Do all living things move? Do they eat and breathe? Even though we all seem to know what is meant by saying something is "alive", it's not very easy to describe what "life" is.

After many years of studying living things, biologists have determined that all living things, do share some things in common. Therefore, in order for something to be considered to "have life" as we know it, it must possess these characteristics:

1) Living things need energy
2) Living things grow and develop
3) Living things respond to their surroundings
4) Living things reproduce
5) Living things reproduce and pass their traits onto their offspring
6) Over time, living things evolve (change slowly) in response to their environment

We will discuss some of these things in the pages that follow.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF