Science Chapter 8, Section 2
Log in Sign up. How can we help? What is your email? Upgrade to remove ads. Remains of organisms that are actually changed to rock. Most fossils form when. Organisms that die become buried in sediments. Particles of soil and rock. A hollow space in sediment in the shape of an organism or part of an organism. Is a copy of the shape of the organism that made the mold.
Scientists can determine a fossils age in two ways. Relative dating and radioactive dating. Allows scientists to determine the actural age of fossils. Are unstable elements that decay or break down into different elements. The half-life of a radioactive element. Is the time it takes for half the in a sample to decay. No members of a species are still alive. Most of what scientists know about extinct species is based on.
The millions of fossils that scientists have collected are called the. Proposes that evolution occurs slowly but steadily. A theory that accounts for the gaps in the fossil record. Scientists use the age of fossils to learn how organisms changed. Almost all of the species found as fossils. The calendar of Earth history is called the. By studying the fossil record, scientists have created a calendar of. Scientists have divided the history of Earth into units of time called.
If no members of a species are still alive. Then the species is extinct. Two unanswered questions about evolution involve. The causes of mass extinctions and the rate at which evolution occurs. Most living things died without leaving fossils behind. So the fossil record is not complete. An incomplete how do scientists use radioactive dating to determine the age of a rock record leaves. A mass extinction is when many types of living things become.
Extinct at the same time. Scientists are not sure what causes. Many scientists think major changes in Earth's dating for over 40s in london. Most scientists think that evolution can occur at. Sometimes evolution is slow and steady. At other times evolution happens very rapidly.
Effect Questions about Earth's history. Cause Sometimes slow, sometimes fast. Effect Speed of evolution. In layers of sedimentary rock the older fossil layer is usually at. In layer of sedimentary rock the layer at the top is usually. Scientists use unstable elements that decay called radioactive elements. To determine the actual age of a fossil. Potassium breaks down into. How do scientists use radioactive dating to determine the age of a fossil. Scientists compare the amount of a radioactive element in a sample to the amount of the element into which it breaks down.
The largest span of time in the Geologic Time Scale is. The three eras of the Geologic Time Scale.