1. Chapter 14
The History of Life

2. History in Rocks
It is believed that the earth is about 4.6 billion years old.
The oldest rocks that have been found on Earth formed about 3.9 billion years ago.
Fossils (evidence of an organisms that lived long ago) tell us information about the earth.

3. How Fossils Form
1. Trace fossils – a marking left by an animal and may include a footprint, a trail, or a burrow.

4. 2. Casts – when minerals in rocks fill a decayed organism, they make a replica, or cast, of the organism.

5. 3. Petrified fossils – minerals sometimes penetrate and replace the hard parts of an organism, producing copies of them.

6. 4. Imprints – a thin object that falls into sediment can leave an imprint when the sediment hardens into rock.

7. 5. Amber-preserved and frozen fossils – an entire organism was quickly trapped in ice or tree sap that hardened into amber.

8. 6. Molds – when an organism is buried in sediment and then decays, leaving an empty space.

9. The Age of a Fossil
Relative dating – If the rock layers have not been disturbed, the layers at the surface must be younger than the deep layers.
Scientists can determine the order of appearance and extinction of the species that formed fossils in the layers.

11. Radiometric dating
Scientists use radiometric dating techniques utilizing the radioactive isotopes in rocks or fossils.

12. Radioactive parent isotopes and their stable daughter products
Radioactive Parent Stable Daughter
Potassium 40 Argon 40
Uranium 235 Lead 207
Uranium 238 Lead 206
Carbon 14 Nitrogen 14
Rubidium 87 Strontium 87
Thorium 232 Lead 208

13. Write three facts about each era and the years they took place
1. Precambrian era
2. Paleozoic era
3. Mesozoic era
4. Cenozoic era

14. The Origin of Life Early Ideas
Spontaneous generation – the idea that nonliving material can produce life.
Meat left out decaying, “produced” maggots.
Francsco Redi’s experiment disproved this idea.

15. Many scientists still believed that microorganisms (bacteria) could spontaneously be produced.
Louis Pasteur’s experiment disproved this idea.

17. The Origin of Life Modern Ideas
Biogenesis – living organisms come only from other living organisms.
In 1953, Miller and Urey performed an experiment to see if the conditions of early earth could produce organic (carbon containing) molecules.
After a week of performing their experiment, several kinds of amino acids and sugars appeared.

19. The Origin of Life
Sidney Fox performed experiments to see if these complex organic molecules could combine to produce cells.
He was able to produce protocells after heating the organic molecules.
Protocells – a large, ordered structure, enclosed by a membrane, that carriers out some life activities, such as growth and division.

20. Protocell
RNA
Phospolipid bilayer

21. The First True Cells
The first cells are thought to have been heterotrophic prokaryotes. They used the organic molecules for food that were abundant on earth.
However, when the organic molecules were gone, autotrophic prokaryotes became abundant and used chemosynthesis to make glucose.

22. Next probably came the photosynthetic prokaryotes that used sunlight to make glucose.
These organisms produced oxygen and affected life on earth.

23. Endosymbiont theory
Complex eukaryotes probably evolved from prokaryotes that incorporated mitochondria and chloroplasts for their energy making ability.
Mitochondria and chloroplasts have DNA similar to prokaryotes.