Evidence for Evolution

    Cards (5)

    • Fossils are remains of organisms from millions of years ago, preserved in the rocks.
    • A replacement fossil is a gradual replacement by minerals. Things that don't decay easily can last a long time. Eventually, they are replaced by minerals as they decay. The fossils stay distinct inside the rock.
    • Cast and impression fossils happen when an organism is buried in a soft material like clay. It later hardens against the organism, leaving a cast of itself. An animal's burrow or plant's rootless traces can be preserved as casts.
    • Preservation happens in places where no decay occurs.
    • To decay, decomposers need oxygen, enough moisture, optimum temperature and pH, so decay won't take place.
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