The Fossil Record

When the environment changes in ways that affect a location’s characteristics, temperature, or availability of resources, some organisms survive and reproduce, and others die.

Most will decompose, while some are buried and compressed in sedimentary rock, forming fossils over long periods of time.

Some kinds of plants and animals that once lived on Earth don’t exist anymore. Examples of these are dinosaurs and other extinct species.

Fossils tell scientists what an organism looked like and about the environment that existed when the animal lived.

Evidence of animal activity like footprints, burrows, and coprolites.

Molds, casts, replacement (like petrified wood), trapped in amber, and mummified.

Earth processes like erosion and earthquakes can move sediment from one location to another, often uncovering and exposing fossils. Scientists also concentrate their search efforts in areas that are known to have lots of fossils, like Utah.

Trace fossils provide information about how an organism lived, including but not limited to how it moved, what it ate, and where it lived.

Over time, sediment forms layers beneath the Earth’s surface. The deeper fossils are found in the Earth’s crust, the older they are. The closer to the surface fossils are found, the younger they are.

The fossil record provides evidence that organisms that are extinct today once existed. It also gives a chronological history for how organisms have evolved in water and on land.

Organisms have become progressively more complex over time. Early in Earth’s history, organisms were very simple, many made of a single cell. As millions of years have passed, organisms have evolved to be more complex, with human beings the most complex of all!

Organisms living in the water all possessed characteristics that allowed them to breathe underwater, such as gills. Over time, these organisms adapted to live successfully on land with structures like lungs and legs.