13-3 Fossil Record

Where are most fossils found?

Most fossils are found in sedimentary rock.

How do animals get trapped in sedimentary rocks?

Some dead animals fall to the bottom of the sea and the become embedded in the sediment layers. Soon, the sediments pile up and the pressure turns the layers into a rock, preserving the dead organism. Some are preserved petrified and turn to rock, while other are soft pieces of the organism.

_______ is used for dating recent fossils, while _________ is better used for older fossils.

Carbon-14; Potassium-40

What are some ways that fossil be formed?

Fossils were sometimes formed when animals fell into ice or became trapped in snow. Insect fossils were created when insects were trapped in sticky sap that solidify into amber. Last, they might form when animals became mired in peat bogs, quicksand, or tar pits.

What is one thing the fossil record shows about the ancient world?

It shows the change in climate and geography. For example, if you find the fossil of a species who lives in water in what is dry land, you know that land used to be a different terrain.

Who are paleontologists?

Paleontologists are scientists who study fossils.

How do scientists place an absolute date on a fossil?

Scientists find a sample of rock in the same layer of the fossil, and test it's age using radioactive dating.

How are sedimentary rocks formed?

Sedimentary rocks are formed when extreme weather condition break down rocks into sand, silt and clay. These particles are carried by flowing bodies of water into large bodies of water. The particles are heavier than water and build up at the bottom of the large body of water.

What is the fossil record?

The fossil record is a collection of millions of fossils that represent the preserved collective history of the Earth's organisms.

Overall, what does the fossil record show?

The fossil record shows that change followed change on Earth.

What helps scientists find fossils embedded in in sedimentary rocks?

The natural forces that form sedimentary rocks also help reveal the fossils. For example, the extreme weather conditions will break down the younger layers of rock and expose the fossils. Occasionally, scientists have the luck of coming across these exposed fossils in the rock.

How are fossils preserved?

The preservation of fossils vary. Some may be perfectly preserved and the small structures of the bone or feather can be observed. Other times, the fossils are not preserved well and it is ambiguous what organism they came from.

How big are fossils?

There are many types of fossils and they can range in size. They could be large and complete, or small and incomplete.

How do biologists learn about extinct plants and animals?

They learn by examining preserved traces of those organisms, or fossils.

Why is the fossil record not complete?

This is because many species that die or go extinct do not become fossilized so we can not get a full idea of what organisms used to walk the earth. Because sedimentary rocks only form in bodies of water, animals in the desert and other regions may not ever become fossils after death.