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Horseshoe Crab |
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| Sometimes natural selection operates to prevent change in a population. This type of natural selection, called stabilizing selection, may explain why some organisms have remained virtually the same for hundreds of millions of years. For example, the horseshoe crab, often referred to as a living fossil, has remained essentially unchanged for approximately 500 million years. | ||||||
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| David Cayless/Oxford Scientific Films | ||||||
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| Appears in these articles: | ||||||
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| Evolution; Horseshoe Crab | ||||||
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