Unlocking Earth's History: Fossils, Rocks, and the Story of Life
Classified in Geology
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Evidence from Rocks About Life
Rocks are an important source of information about many forms of life that existed on this planet.
Why Can't Scientists Be Sure How Earth Was Created?
Because no rocks date to the formation of the Earth.
How Fossil Teeth Reveal an Animal's Diet
Size and shape indicate diet.
Explaining Relative Dating of Fossils
Sedimentary rocks form layers, with newer layers added on top of older layers. This does not tell scientists the exact age of the fossil; however, it does tell the scientist the fossil's age in relation to other fossils above or below it.
Common Radioactive Isotopes
Potassium-40 and Carbon-14 are two common radioactive isotopes.
What Is a Mass Extinction?
A mass extinction is when many organisms disappear from the fossil record at the same time.
What Does the Cambrian Explosion Refer To?
It refers to the huge quantity of new life that appeared during the Cambrian period.
Fossils and the Geological Time Scale
| Fossils | May be bone, tooth, or imprint; provide info about the variety of life in the past; can provide info about ancient climates. |
| Geological Time Scale | Divided into eras; eras are further divided into periods; divisions based on the kind of organisms that lived then. |
Key Concepts
- Humans are large mammals that appeared in the Cenozoic Era.
- The theory of plate tectonics explains how continents move.
- Most fossils are found in sedimentary rocks.
- Scientists use radiometric dating.
Francesco Redi's Experiment
What Did Francesco Redi's Experiment Prove?
That maggots do not come from spontaneous generation; they come from flies.
Pasteur and Biogenesis
How Did Pasteur Develop the Concept of Biogenesis?
Pasteur used a specially designed glass bottle that allowed air to enter the bottle but kept microorganisms out. There was a broth with nutrients in the bottle.
Origin of Life
What Two Things Had to Happen Before Life Could Appear on Earth?
Organic molecules had to be present, and they had to form into more complex molecules.
What Happens When Amino Acids Are Heated?
They become proteins.
Results of Oxygen in the Atmosphere
Organisms that use oxygen evolved, and an ozone layer was created.
Mini Glossary: Key Events in the Origin of Life
- Oceans contain organic molecules.
- Protocells develop.
- Prokaryotes appear.
- Organisms use chemosynthesis.
- Organisms use photosynthesis.
- Ozone layer develops.
- Complex organic molecules form.