Fossils
by Alecia Strohl
Fossils offer a glimpse into the past by preserving remains of organisms. Fossils can vary from location to location, based on climate, landforms, and occurrence of natural disasters. Fossils come in many forms, and each help scientists learn about the past in different ways. A mold fossil is a fossilized impression made in a substance, like rock, and is a negative, or opposite, image of the organism. Shells and bones often form mold fossils. Cast fossils are formed when a mold is filled in with minerals over time. As these minerals harden, they form a 3-d model of the organism. Trace fossils, or ichnofossils are another type of fossil. They are not physical remains of organisms, but evidence of life from the past. Examples of trace fossils include surface tracks, tunnels, burrows, nests, and footprints. One other type of fossil are true form fossils, which are actual fossilized remains of organisms. The tissues of these organisms are preserved in tar, ice, or amber. Form fossils provide scientists with the best evidence of past life because organisms’ features like color and shape are preserved.
Question 1
Form fossils provide scientists with the best evidence of past life.
What reason does the author provide to support this information from the text?
Responses
APreserved evidence, like tracks, show where organisms have been.
Preserved evidence, like tracks, show where organisms have been.
BThe organisms' actual remains are preserved in tar, amber, or ice.
The organisms' actual remains are preserved in tar, amber, or ice.
CThe organisms' shapes are preserved as a negative, or opposite, images.
The organisms' shapes are preserved as a negative, or opposite, images.
D3-D images of organisms are formed as molds are filled in with minerals.