Board Pop Quiz: Fossil Record (04/18/24)

Fossil Record and Evolution

• A fossil is the preserved remains or evidence of an organism, used to document changes in organisms over time and identify extinct species.

Fossil Formation

• When an organism dies, its remains fall to the bottom of an ocean or lake, and layers of sediment cover it.
• Over time, the organism's remains are replaced with minerals, eventually becoming rock, forming a type of fossil called a cast fossil.
• Other types of fossils include mold fossils, where the hard parts of an organism dissolve, leaving an empty space, and trace fossils, which show the activity of ancient organisms.

Determining the Age of a Fossil

• Scientists use radioactive elements to determine the age of a fossil, measuring the amount of radioactive element and stable element in a rock.
• Different elements are used for absolute dating, including carbon, potassium, uranium, and lead, each with its own range of years.

The Fossil Record and Geologic Time Scale

• The fossil record provides information on the history of life on Earth, showing how organisms have changed over time.
• By knowing the age and location of a fossil, scientists can show which organisms lived during the same time period and which have a common ancestor.

Fossil Evidence for Evolution

• The fossil record shows evidence of how reptiles have changed over time, with fossils showing different numbers of holes behind the eye.
• Fossils of sponges, fish, amphibians, reptiles, and mammals provide evidence of a long history of changing life forms.

Key Concepts

• Radioactive elements release energy as they break down into stable elements.
• Absolute dating determines the actual age of an event or fossil in years.
• Relative dating puts events or fossils in order from oldest to youngest without using actual dates.