Checkpoint Week 3 Sci275

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Date Submitted: 09/24/2011 04:47 PM

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Checkpoint: Succession and Natural Selection

Primary succession is defined as the change in species composition over time in the environment that was in the area without having topsoil. This means the environment was previously uninhabited or not having any soil and animals. Secondary succession is defined as changes in species composition that takes place with disturbance of an existing habitat. That would mean there is soil already in place.

The animation would be secondary succession. The animation consisted of a creek within a forest. Beaver’s thought it would be fun to make a dam at the top of the stream, so that caused the stream to expand and create a large pond. The stream got bigger and deeper so it flooded where the original trees grew. The trees got to water logged and caused them to die, and then sedge grass began to grow. Now the ecosystem in the pond now becomes a bog ecosystem. With the bog system maturing, the soil starts to fertilize. With time passing it starts to get different species of trees to grow and form in the large pond. Then with many years going by the bog starts to diminish and it becomes a bog forest. It seems that there is more secondary succession is more common than the primary succession.

Propose a hypothesis to explain how limbless salamanders evolved according to Darwin’s theory of natural selection?

I would have to say that in this case with the salamander. The salamander doesn’t support its own weight in the water so having extra limb’s it would slow it down. So in this case it can swim faster and is able to move faster to get away from other animals. I think over time this kind of salamander will be to pass along traits and then some day all salamanders will have no or smaller limbs.