An average normal range is between 4,500 and 10,000 white blood cells per microliter
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At the base of the food chain
<span>More individuals are produced each generation that can survive.
Phenotypic variation exists among individuals and the variation is heritable.
Those individuals with heritable traits better suited to the environment will survive.
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When reproductive isolation occurs new species will form.</span></span>
When a meteoroid passes through earth's atmosphere, it heats up due to air resistance. The heat causes gases around the meteoroid to glow. most meteoroids that enter earths atmosphere disintegrate before they hit the ground.