Tuesday, September 18, 2007

Evidence of Evolution by Natural Selection

Hi everyone. Today we started off by talking about fossil records and made way into the links between species. One of Mrs. Foglia's key points was that changes in the climate and environment can lead to extinction. Some creatures have adaptations acquired through many generations that allow them to survive, others that are not suited for the change would start to die off. We also talked about an interesting piece of information, knowing that all life started in the ocean, some creatures had to be links from sea to land animals.

The tetrapod is a missing link, and it was only discovered last year! But also, if mammals evolved on land, some had to return to the ocean for animals such as whales and dolphins to be sea mammals. Also, Mrs. Foglia showed us homologous structures and analogous structures, and we talked about convergent evolution and parallel evolution. Homologous structures are structured and developed similarly, but serve different functions and look differently externally. They have a common ancestor. Analogous structures are just the reverse, they have similar functions and external form, but the internal structure and development is not the same. There is no common ancestor in this evolutionary relationship. Analogous structures are part of convergent evolution. The idea of convergent evolution is that different creatures evolved in a similar way externally, though internally they are very different. Parallel evolution is when creatures, though separated and not closely related, served same job in their environment. Then, we finished off by talking about vestigial organs. These are structures that basically have no function, such as the appendix in humans, and a pelvis in a whale.

The sherpa for tomorrow will be KellyP.

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