1. CHAPTER 14 Goals: Discover what information fossils records can give us, including the ages of extinct animals and links between different species.
SKIM READ CH 14 on pages

2. CHAPTER 14 Goal: Discover what information fossils records can give us, including the ages of extinct animals and links between different species.
Fossils: Any preserved evidence of an organism.
Without fossils, we would lose much of our understandings about Earth’s history.

3. EARTH IS AN EVERY CHANGING AND EVOLVING PLACE

4. CH What is this??

5. BIG BANG
The Earth formed 4.6 billion years ago.
As Earth was struck by large objects it heated and melted the elements that Earth was made of causing the elements to arrange themselves from most dense (at Earth’s core) to the least dense that are on the surface of the Earth.
About 500 million years after Earth was formed it cooled enough for liquid water to form our oceans. This is when the first life appeared.

6. Section 14.1: Earth’s Early History
The first atmosphere had little to no oxygen.
It was made of water vapor, carbon dioxide, sulfur dioxide, carbon monoxide, hydrogen cyanide, hydrogen sulfide, nitrogen and hydrogen.

8. FOSSILS ARE ONLY CREATED in certain conditions.
About 99 % of the species that have ever lived are now extinct and only a tiny percentage of those organisms are fossilized.
FOSSILS ARE ONLY CREATED in certain conditions.
* Fossils are most commonly found in sedimentary rocks.
 *Sedimentary rocks: are formed when silt, sand, or clay builds up in the bottom of a river, lake or ocean.

9. Fossil Formation

10. Fossil Creation:
As they layer over each other the pressure becomes greater on the bottom layer and it turns this layer into rock such as sandstone and limestone.
Each of these layers can be identified with a time period in history.
This is called Relative Dating.

11. Clues in Rocks (con’t)
Relative dating – a method used to determine the age of rocks by comparing them with other layers.
Fossils cannot be formed in igneous or metamorphic rocks.
Law of superposition – younger layers of rocks are deposited on top of older layers.

12. Clues in Rocks (con’t) Law of Superposition:
Which layer is the youngest?
Which layer is the oldest?
Is layer E older or younger than layer C?

13. Clues in Rocks (con’t)
Radioactive dating – the decay of radioactive isotopes to measure the age of a rock.
Half-life – the amount of time it takes for half of the original isotope to decay.
Because half-lives are often known, the current amount of a radioactive element and the original amount are compared to date the rock.
However, fossilized rocks do not often contain radioactive isotopes, so they cannot be aged this way.

14. Dating Mummies…..
Carbon-14 can be used to date substances like bones and tissues.
But must be less than 60,000 years old because carbon has a relatively short half- life.

15. How can fossils be used to link animals together?

16. The Geological Time Scale
Geological time scale – a model that expresses major geological and biological events.
Eon  Era  Periods
Image on page 397

17. The Geological Time Scale
The Precambrian eon is actually longer than the Phanerozoic eon.
We are currently in the Quaternary period.

18. Plate Tectonics
Evolution in the Cenozoic era was shaped by massive geological changes.
All continents used to fit together, like puzzle pieces, to form one massive continent, called Pangea.
Continents drifted apart because of plate tectonics.
Plate tectonics – Movement of several large plates that make up the surface of the Earth.

19. Plate Tectonics

20. Section 14.2: Origins: Early Ideas
Theory of Biogenesis – living organisms can only produce other living organisms.
This theory replaced the idea of spontaneous generation in the mid-1800’s, which states that life arises out of nonlife.
Discovered by Louis Pasteur in an experiment involving nutrient broth.

21. Origins: Early Ideas

22. Origins: Modern Ideas
If life can arise only from pre-existing life, then how did the first life form appear?
There are many hypotheses, but scientists agree that there are critical steps that have had to occur for life to be created:
Organic materials appeared.
Proteins must have been created.
DNA and RNA sequences appeared for protein production.
Membranes were created to allow molecules to turn into cells.

23. Cellular Evolution
Scientists’ current hypothesis is that the first cells on Earth were prokaryotic.
Once oxygen began
forming in the
atmosphere, when
prokaryotes evolved
the ablity to go
through
photosynthesis.
These are called
cyanobacteria, and appeared 2.5 billion years ago.

24. Cellular Evolution (con’t)
Eukaryotic cells (have a nucleus) appeared in the fossil record 1.8 billion years ago.
Endosymbiotic Theory – the ancestors of eukaryotic cells lived with prokaryotic cells.
Discovered by Lynn Margulis in 1966.

25. Cellular Evolution (con’t)
Prokaryotes often lived inside the eukaryotes and undigested prey, or as internal parasites.

26. Cellular Evolution (con’t)
Evidence for the endosymbiotic theory:
Mitochondria and chloroplasts contain their own DNA, which are arranged in a circular pattern, as in prokaryotic cells.
Ribosomes in mitochondria and chloroplasts more resemble those in
prokaryotes than in
eukaryotes.

27. Dinosaurs were already on the decline?