Evidence for Evolution

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by wspenc33
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Evidence for Evolution

Homologous structures are parts of an organism that are similar to comparable parts of other species. Organisms with homologous structures give evidence toward an ancient common ancestor from which many might have evolved. Analogous structures, however, are similar structures that don’t come from a common ancestor. They develop due to the similar environments or needs of a species. Last but not least, are vestigial structures. Vestigial structures are features that no longer serve a purpose to the current organism. Whales, for example, have hip and leg bones. At some point in the past, these may have been important, but as natural selection took place they slowly disappeared.The field of science surrounding the genetic relationships between species and how they change over time is called Phylogeny. Many scientists like to think of it like a tree, animals slowly splitting out and dividing. Shown by the passing of genes through the branches of the tree. By looking at the genes of these organisms, we can see patterns in the genetic structure that may point towards a common ancestor.When looking at the embryos of fish, birds, pigs, cows, and humans, it’s hard to tell the difference in the early stages. They develop in much the same way, and only in the later stages do they develop the specific structures that allows them to survive in their environment. What do these similarities in the early embryos show? That’s right, a common ancestor.

Fossil records provide us with a complete history of the change and evolution of the earth. Using the fossil record, we can determine when, and where animals lived and even how they looked and evolved. Using two techniques in dating these fossils, we can find and compare approximately when these fossils formed. One technique, called relative dating compares the timing of two different fossils and simply finds which is older. Using relative dating, we can determine the relative order of past event. Using numerical dating, we can determine x amount of years since the fossil was formed, giving us an actual time period which it may be from rather than an older or not older. Using all this information we can determine how species changed over time.

Natural selection is the process by the which traits in organisms become more or less common as organisms interact with the environment. Selection happens through survival of the fittest, where the creatures with the adaptations best suited to their environment survive and pass their genes to their offspring. These slight and random variations in creatures that allow them to survive better occur steadily over time. Artificial selection, however, is the process by which humans breed for particular traits. This is often done to create the perfect crop or even domesticated animal.

A long time ago all the continents of the world were combined in one super continent called Pangea. Due to plate tectonics (the idea that Earth has an outer shell that is divided into many different moving pieces) Pangea split apart and slowly moved to form the continents where they are today. Animals that at one time may have been part of a larger species on Pangea may have been split up when the land masses split. These animals changed as the continents drifted apart and the climates on these lands changed. Biogeography looks at the past and present distribution of plants and animals on these land masses

Natural selection and Artificial Selection

Chemical and Anatomical Similarities of Related Life Forms

Fossil Record of Change in Earlier Species


Geographic Distribution of Related Species


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