The small blood vessels that deliver blood to and pick blood up from tissues are

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Agene pool: a) is the collection of all the alleles found in a single species b) is the collection of all the alleles found in a single population c) is the collection of all the chromosomes found in a single population d) is the collection of genes in a species that allow the individuals to swim

Explain how paleontologists use trilobite fossils as index fossils for various geologic time periods.