Fossils

Fossils are the ______, imprints, or traces of once-living organisms preserved in rock.

Remains

Compare and contrast mold and cast fossils.

A mold is a hollow rock left by an organism, A cast is when the rock is filled with sediment. They both are usually found in creeks, rivers, and streams. A mold is a negative imprint, While a cast preserves the external form of the organism.

The calico scallop is an index fossil. It is well documented to have lived 1.8 million years ago. Therefore, the approximate age of the rock in which this fossil is found is A. 0.9 million years. B. 1.8 million years. C. 3.6 million years. D. 5.4 million years.

B. 1.8 million years.

How might scientists be able to use fossils to infer that the climate of the central United States was a lush subtropical forest millions of years ago?

Scientists can use fossils to learn about past environments. By studying to the fossilized remains of ancient organisms, scientists can infer what type of climate they lived in by comparing them to similar organisms alive today.

What can trace fossils tell you about ancient organisms?

Trace fossils are not the preserved remains of ancient organisms. Instead, they provide information about the activities of the organisms. Examples are fossilized footprints and burrows.

Carbon films are formed when a thin film of carbon is left, forming a silhouette of the original organism.

True

Fossils most often form when a dead organism is buried in sediments.

True

Index fossils are the remains of species that existed on Earth for relatively short periods of time.

True

Any trace of an ancient organism that has been preserved in rock is called a a. landform. b. continent. c. fossil. d. landmass.

C

All of the following conditions help preserve organisms as fossils EXCEPT ____. a. quick burial by sediments b. hard parts c. protection from scavengers d. activities of microorganisms

D

To be a useful index fossil, a species must have been rare.

False

How can fossil correlation be used to determine the ages of rock layers?

Fossil correlation uses the principle that rock strata containing fossils of the same age must be the same age as the fossils. Geologists can compare the known lifespan of the fossilized plant or animal to postulate the age of the rock layers.

Describe how a fossil would form through mineral replacement.

Fossils form through the process of mineral replacement beginning when an organism dies and is buried. Groundwater seeps around the organism, and the minerals in the water gradually replace the minerals in the hard parts of the organism.

How does a carbon film fossil form?

Fossils usually form when sediment buries a dead organism. As sediment piles up, the organism's remains are subjected to pressure and heat. These conditions force gases and liquids from the body. A thin film of carbon residue is left, forming a silhouette of the original organism called a carbon film.

Why aren't there many fossil jellyfish?

Jellyfish are invertebrates, so they do not have the hard body parts that favor fossilization.

How does coal form?

Millions of years ago, swamps covered much of Earth. Layers of dead, decaying swamp plants formed a soft material called peat. Over time, layers of rock formed over the peat. Slowly, the peat changed into coal.

Do all rocks contain fossils? Describe the conditions necessary for fossils to form.

Not all rocks contain fossils. Whether or not a dead organism becomes a fossil depends upon how well it's protected from scavengers and agents of physical destruction. however, quick burial isn't always enough to make a fossil. organisms have a better chance of becoming fossils. If they have hard parts such as bones, shells, or teeth. hard parts decay more slowly.

fossil formed when an outline of the original organism is formed from left-over carbon

carbonaceous film

made when sediments fill in a cavity made when an object decayed and the sediments harden into rock

casts

A ______ may tell a geologist when, where, and how an organism lived.

fossil

The ______ parts of organisms are most likely to become fossils.

hard

A ______ is the cavity left behind in the rock after an organism's hard part has dissolved.

mold

hollow place in rock made when an organism died and was buried and holes in the rock let air or water reach it and dissolve the organism

molds

Preserved animal tracks are called ______ fossils.

trace

Index fossils are the remains of species that were once abundant and

widespread geographically