1. Do Now 5.2
Objectives:
Identify and describe the four geological eons of Earth’s history.
Identify 12 major events in the history of Earth, and their approximate time.
Task (Answer, don’t copy):
What structures in kidneys are responsible for excretion?
What is the path of blood flow through the mammalian heart chambers?

2. A Brief History of Earth
1. If you were to make a timeline showing the major events in the history of Earth, what are the top 3 things you would include?
A Brief History of Earth

4. The History of Earth in 12 steps
Required knowledge:
Order (not dates) of 12 events (except below)
What happened for each event
Relative orders of time
BYA vs MYA
Eons of Geological Time
Precambrian (formation of Earth 4.5 BYA to Cambrian Explosion 543 MYA)
Paleozoic (Cambrian Explosion to Permian Extinction 250 MYA)
Mesozoic (Permian Extinction to K-T Extinction 65 MYA)
Cenozoic (65 MYA to present)

5. The Big Bang 13.7 BYA
The beginning of matter, energy, and time. box 1.

6. Best Evidence For BBT Expanding Universe (comological redshifting)
Cosmic Microwave Background Radiation
New Discovery 2014:
Gravity Waves

7. Formation of Sol, our Sun: 4.6 BYA
The light and heat it produces are a result of nuclear fusion. This occurs because of the massive gravity of such a large object. Box 2

8. Formation of Earth And Moon: 4.5 BYA
Rocks, dust, and meteorites were pulled together by gravity to form Earth. The moon was formed by a massive collision during this period also. Box 3

9. The oldest rocks scientists have ever found are about 4
The oldest rocks scientists have ever found are about 4.0 billion years old, but we think Earth was around even before that. Why aren’t there any rocks left from 4.5 to 4.0 billion years ago?

10. Here’s the Plan

11. Tenacious DNA
An epic look at the history of the DNA in each of your cells…

12. Pre-Cambrian Earth
The Precambrian Eon begins with the formation of the solar system about 4,500 MYA (= 4.5 BYA).
The Pre-Cambrian is incomprehensibly long: it is 86% of Earth’s history.
Rocks form: 4,000 MYA
Abiogenesis (life “evolves”): 3,800 MYA
Eukaryotes evolve (endosymbiosis): 2,700 MYA
The Precambrian Eon lasts until 543 MYA, with an event commonly called the Cambrian Explosion

13. 4.The Origin of Life on Earth: Abiogenesis

14. Evidence for a Common Origin
DNA and RNA are the 'universal' basis for all life on Earth: all cells use RNA to make proteins.
Only 20 amino acids are used in all living things on Earth. L-amino acids exclusively are used in all living things on Earth.
ATP is the 'universal' energy used in all living cells.
Fermentation (glycolysis) is the first step in ALL metabolism.
The genetic code is almost identical in organisms as different as bacteria and humans

15. The First Cells 3.8 BYA = Box 4
The very first cells were heterotrophs, and soon used up all of the organic chemicals around them.
The only way life could continue is if cells started to make their own chemical “food.”

16. Most Similar to The First Life: Archaea, a group of prokaryotes

17. Endosymbiosis: origin of Eukaryotes 2.7 BYA Box 5

18. Later Pre-Cambrian Life
Prokaryotes are the only life on Earth for over a billion years.
By the end of the Precambrian Eon, some simple animals (sponges, flatworms, roundworms, cnidarians) had evolved.
A mass extinction occurs (Vendian) 543 MYA, officially ending the Precambrian Eon

19. Cambrian Explosion (6th box) 540 MYA
The Cambrian Explosion (or Cambrian diversification; 540 MYA) was a brief period in history where many new types of organisms evolve:
Arthropods
Chordates
Hard-Shelled animals
No major animal phyla have evolved since the Cambrian Explosion… why?

20. Later in the Paleozoic Land Plants and Fishes Evolve: 480 MYA
Reptiles Evolve: 350 MYA
These are boxes 7 and 8…

21. End of the Paleozoic: the Permian Extinction (Box 9)
“The mother of all extinctions.”
Somewhere between 70 and 95% of all organisms become extinct 250 MYA.
Worst mass extinction ever recorded on Earth. Competing hypotheses over cause.
End of the Paleozoic: the Permian Extinction (Box 9)

22. Mesozoic Eon = “Age of the Dinosaurs” 248 – 65 MYA
Dinosaurs and Mammals Evolve: 220 MYA ( add after box 9)
Cretaceous
Jurassic
Triassic

23. Birds – Branch of the Dino Family Tree
Birds evolve 150 MYA (Box 10)

24. Cenozoic Eon: 64 MYA to Today
You are living in the Cenozoic Eon, the “Age of Mammals.”
Begins with the K-T (aka K-Pg) extinction 65 million years ago (meteorite that wiped out the dinosaurs) Box 10
Box 11: Humans diverge from ape populations 6 MYA.

25. Homo sapiens Box 12
About 200,000 years ago, the first members of our species evolve, from other archaic Homo species (H. erectus)
By 50,000 years ago, humans are culturally and intellectually modern (i.e. cave paintings

26. Top 13 1. Big Bang 13.7 BYA 2. Solar System 4.6 BYA
Formation of Earth & Moon 4.5 BYA
4. First Cells 3.8 BYA
5. Endosymbiosis 2.7 BYA
6. Cambrian Explosion 543 MYA
7. Land Plants & Fishes 480 MYA
8. Reptiles 350 MYA
9. Permian Extinction 250 MYA Largest mass extinction in Earth’s history (9B: Dinos & Mammals 220 MYA)
10. Birds 150 MYA
11. K-T Extinction 65 MYA (asteroid kills dinos)
12. Hominids diverge from apes 6 MYA
13. Homo sapiens evolve 0.2 MYA