Aniamals, Adaptation, and the Galapagos Islands Discover with Darwin
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Make the Match

Imagine you're aboard the Beagle. You've carefully collected five tortoise subspecies from five different islands for observation. But a flash rainstorm has mixed up the field journal pages that show which tortoise lives on which island.

Consider the evidence and return each tortoise to its home island.

Before you start on your mission, it’s helpful for you to know that giant tortoises have three different kinds of upper shells, usually called carapaces. Darwin was intrigued by these different shaped shells. But it took many years to determine that the different shaped shells were adaptations to the particular environments of each island.

Saddleback tortoiseSaddleback tortoises – have longer necks and legs than their domed buddies, and have a shell shape that lets them extend their heads up higher. These tortoises live on drier islands with scattered plant life that's often hard to reach from the ground. Over many generations the tortoises with “saddleback” shaped shells were more successful at getting food from higher bushes and trees than dome-shaped tortoises. The tortoises that ate better were also better able to survive and reproduce.

Domed tortoiseDomed tortoises – live on wetter islands with plenty of vegetation available close to the ground. Domed tortoises have the advantage of being better protected against attacks from predators because they can draw their neck and head into their domed shells and block off their shell entrance with their front legs.

Intermediate tortoiseIntermediate tortoises – tortoises that live on islands with climates that are in between moist and dry. Intermediate tortoises have shells that give them more protection than saddlebacks, but less than domed tortoises. They can reach higher than domed tortoises, but not as high as saddlebacks.

Click each of the five tortoises to learn more about it. As you examine the tortoise, figure out what kind of shell it has: saddleback, dome, or intermediate.

Then take a look at each of the five islands. When you think you have a match drag one of the tortoises to one of the islands.


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