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| | "Species, Speciation, and the Environment" by Niles Eldredge, Ph.D. |
 | | Species also remain stable because of the very nature of their internal structural organization; all species are broken up into local populations that are integrated into local ecosystems. |
 | | A population of the American robin, Turdus migratorius, faces a very different existence in, say, the wet woodlands of the Adirondack Mountains in the Northeastern United States, compared to what the local populations of the same species experience in Santa Fe, New Mexico. |
 | | Such disjunct populations encounter very different food, water availability, ambient temperatures, potential predators, and possibly even disease vectors. |
| www.actionbioscience.org /evolution/eldredge.html (3161 words) |
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