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How Can I Survive Without You?

Birds have hollow bones

Over time organisms have developed structures that help them survive in their environments. Organisms with these traits are the ones that will live long enough to reproduce and pass these favorable traits to their offspring.

Look closely at a feature of bird’s bones that enable them to fly. Unlike a mammal’s bones, bird bones are hollow. As a result, their bodies are much lighter which makes flight easier. Because this enables them to fly so well, they gain a great advantage in finding food, escaping predators, and finding mates.
As you look at the bird bones at the right, you should notice that you can actually see the holes in each of the bones. Notice that there is still enough bone material inside to maintain strength. Explore other bird adaptations.
Remember that most birds need to fly to survive. Having less dense bones is an advantage, as this trait makes the bird much lighter. To understand why being lighter is an advantage, imagine running a race wearing a 50 pound backpack verses running the race without all the extra weight. Flying, for birds, is like running the race for humans; having less dense bones is like removing the backpack.

Fish have fins

Fish fins allow them to move easily through water so fins are an advantage to fish. It’s kind of like putting on flippers when you swim. The flippers help you move faster through the water. Observe fish fins in action in a Quicktime movie.



  1. How would the hair on a bear help it to survive?
  2. What characteristics does a lizard have which help it survive in a desert?
  3. What specific traits do mule deer have which allow them to survive in Utah?

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Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 7th grade science core.

Updated October 24, 2008 by: Glen Westbroek

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