1.1 Fossils

What is a trace fossil? What are some examples?

A fossilized structure that formed in sedimentary rock by animal activity. Examples include; tracks, burrows and dung.

How are fossils that are in amber created?

Insects or other small organisms that were trapped in tree sap thousands of years ago can remain unchanged, even after the sap turns into a hard material

What is a mummified fossil?

When organisms' bodies dry out very quickly before they decay, their bodies will be shriveled, but much of the original material will remain.

How does gentle burial effect fossil preservation potential?

A gentle burial also increases an organism's chances of becoming a fossil. Gentle burial helps preserve the delicate parts and details of the organism. Organisms that are not buried gently can be crushed.

What is a mold?

An impression left by an organism's body or trace, like a footprint or burrow.

Describe fossils created by Casts and Molds.

Are fossils that form when the body of an organism leaves an imprint in the sediment. This imprint remains even after the original body material has completely decayed and disappeared. Casts and molds are often found together.

How does being a burrowing animal effect fossil preservation potential?

Burrowing animals have high preservation potential because they gently "bury" themselves before they die. Burrowing provides the most rapid burial possible.

What happened during the Cenozoic period?

Current period. Many of the plants and animals we know today came to being during this period. Mammals dominate the Cenozoic era. Fossils show that a great variety of plants and animals are abundant during this era. Humans first appear in the fossil record about 200,000 years ago.

What happened during the Mesozoic period?

Fossil records show that reptiles were dominant. This gives rise to the dinosaurs. Often known as the age of the dinosaurs. Birds and mammals come into being. Pangaea starts to break up and shift to the continents that we see today. The end of this period is marked by the asteroid that hit the Earth and caused another mass extinction.

Describe what can fossils tell us about Earth's past.

Fossils help scientists to discover previously unknown chapters in Earth's history. Scientists can reconstruct ancient ecosystems and habitats using fossil records. By studying fossils in a particular rock layer, a scientist can describe what the animal and plant communities in that area were. They can compare these fossil communities with communities found today. This helps them build a picture of the environment the fossils came from and how it changed over time.From fossil information, they can even determine the ecological relationships between now-extinct organisms. If they found evidence of mass extinction, it would be possible to pinpoint a significant moment in Earth's environmental history.

How does having hard parts effect fossil preservation potential?

Hard parts of organisms are preserved as fossils much more often than soft parts. Shells, bones, and teeth are easily preserved as fossils. This is because hard parts are less likely to be crushed during burial. Hard parts are also more difficult to decompose. Soft parts like skin and internal organs decompose easily and are preserved only under the very best conditions. Organisms that have hard parts in their bodies—such as fossilized clam shells, dinosaur skeletons, and tree trunks—are discovered much more often than fossilized jellyfish or fungi.

What is a cast?

If sediment fills in these molds and hardens into rock, a cast can form. A cast is a fossil copy of the original organism or trace.

Are organisms with high preservation potential guaranteed to become fossils? Why or Why not?

No. All the conditions have to be just right. It is very unlikely that any individual organism will become fossilized. Fossils that do form are often destroyed by weathering, erosion, plate tectonics, or other rock cycle processes.

Describe fossils created by Petrification.

Occurs when an organism's body tissues are replaced by minerals. This process is similar to permineralization. However, unlike permineralization, petrification does not usually preserve the original body material. Petrification does preserve the shape of the organism's body. While some petrified wood is formed by permineralization, much of it is formed by petrification.

Describe fossils created by Permineralization.

Occurs when the small holes in an organism's body are filled with minerals. This happens when water containing dissolved minerals is absorbed by an organism's body. When the water evaporates, the minerals are left behind. Permineralization only replaces some of the original body material with minerals. Some petrified wood is formed by permineralization. Permineralization can preserve very delicate details. Sometimes even individual cells are preserved.

Why did dinosaurs go extinct?

Only theories. Possibly due to volcanic activity and tectonic plates shifting climate changed and caused extinction. It is also possible a asteroid hit the Earth and caused a huge cloud of dust that cooled the planet and caused an extinction event.

How does little exposure to oxygen effect fossil preservation potential?

Organisms buried in very deep water where there is little to no oxygen do not decay much. This is because many of the bacteria and chemical reactions that drive decomposition need oxygen.

Describe fossils created by Carbonization.

Organisms contain carbon. Sometimes, when an organism dies, the carbon in its body starts to break down. Some of the original material is decayed; however, the carbon also forms a dark coating on top of the dead organism. This preserves the organism's body as a carbonized fossil. Carbonized organisms can be so well preserved, even details like the patterns or colors of skin or leaves can remain.

How does burial in organic matter effect fossil preservation potential?

Organisms that are buried in environments like swamps that are full of organic matter and low in oxygen have higher preservation potential. These conditions prevent the buried organisms from decaying.

How does rapid burial effect fossil preservation potential?

Organisms that are buried quickly after death (or are buried alive) are more likely to become fossils. This is because they are less likely to be eaten and do not get a chance to decompose.

Name the 4 major time periods in order.

Precambrian, Paleozoic, Mesozoic, Cenozoic.

What are the different types of Fossilization?

Preservation of original material, carbonization, permineralization, petrification, casts and molds,

What determines the preservation potential of a fossil?

Rapid burial, gentle burial, is it a burrowing animal, little exposure to oxygen, if buried in organic matter, if the organism has hard parts.

What is relative dating?

Scientists use the geologic time scale to compare fossil records from different time periods. This is called relative dating. For example, perhaps one type of fossil is known to appear during the Early Jurassic Period and another during the Late Jurassic Period. Scientists can infer that anything found in the layer between these fossils will come from the Middle Jurassic. Relative dating is how the majority of fossils are dated.

Describe fossils formed by the preservation of original material.

Sometimes part or all of the original organism remains, even after thousands or millions of years. Fossils formed by preservation of original material include mummified fossils and remains preserved in amber, tar pits, or ice.

What is absolute dating?

The age given in years, of a fossil, a rock, a feature, or an event; usually determined through radiometric dating. Scientists can use radiometric dating or other means (such as tree rings) to determine the approximate age, in years, of a specimen. The term "absolute" (when understood to mean "exact or complete") is slightly misleading, as scientists can determine only the approximate age of a specimen or an event in geologic time.

How have scientists used the fossil record to create a geologic time scale?

The most widely used geologic time scale is split into a series of time periods within longer time periods. The longest time period is usually an eon. Eons are split into eras. Eras are split into periods, which in turn are split into epochs, and then ages. Each eon, era, and so on, has its own name. Each boundary between divisions is marked by the appearance, disappearance, or change in dominance of particular fossil groups.

What is a fossil?

The preserved remains or traces of an organism that lived in the past

What happened during the Paleozoic period?

This is marked by an explosion of organisms. It is often called the Cambrian Explosion. The most abundant organisms were invertebrates (without backbones) like sponges, corals and snails. Later the first vertebrates (with backbone) were fish. Later plants and amphibians. Reptiles were the first to live on land. A series of volcanic eruptions occur and a mass extinction happens wiping out 90% of animals.

What happened during the Precambrian period?

This is the longest amount of time. Relatively few fossils and most of them are microscopic one-celled organisms like bacteria.

Explain what fossils can tell us about the environment.

When scientists find tropical plant fossils in today's Arctic, it means these regions were once much warmer. Clues such as this help scientists to understand the positions of ancient continents and how Earth's climate has changed in the past. Fossils also provide evidence of how sea levels have changed or how the composition of the atmosphere has changed.

What is a body fossil?

actual parts of an organism, unaltered or altered bones, shells, leaf imprints