1. How Life Began
Wake County
Biology Curriculum

3. Early Earth The Earth formed about 4.6 billion years ago.
It formed by debris coming together due to gravity.

6. Early Earth
The melted Earth formed layers with the most dense material at the center and the lighter materials forming the crust.
The lightest materials formed the atmosphere.

8. Early Earth
As the Earth cooled, water condensed and formed oceans.

10. Early Earth
Storms dominated the atmosphere because the Earth was still hot. Therefore there was much lightning.

12. Early Earth
The atmosphere was a mixture of hydrogen cyanide, methane, carbon dioxide and monoxide, nitrogen, hydrogen sulfide, ammonia, water, and other chemicals.

14. Early Earth There was NO oxygen on Earth.
The oceans were brown due to large amounts of dissolved iron.

16. Early Earth The Moon was closer so it appeared larger than today.
Debris was still bombarding the Earth from the new solar system.

18. Under these conditions, could life evolve?
Early Earth
Under these conditions, could life evolve?

19. encarta.msn.com

20. How did life begin?

21. "Primordial soup" is a term introduced by the Soviet biologist Alexander Oparin. In 1924, he proposed a theory of the origin of life on Earth through the transformation or “evolution” of carbon molecules created by Earth’s ancient environment.

22. JUST KIDDING!

24. First Organic Molecules Stanley Miller and Harold Urey
In the 1950’s, these two scientists wanted to find out if organic molecules could form under the conditions of the new planet Earth.
Urey and Miller filled a container with hydrogen, methane, ammonia, and water to represent the atmosphere.
They heated it to represent volcanic activity.

25. First Organic Molecules

27. First Organic Molecules
They sealed it to keep out other living things such as bacteria.
They sent sparks through it to simulate the lightning.

28. First Organic Molecules

29. First Organic Molecules
They waited to see what would happen. They thought they would have to wait months.
However, after just a few days, they checked it and found 13 out of 20 amino acids, and nucleic acids.

30. First Organic Molecules

31. Biochemistry is the study of the structure and function of cellular components such as proteins, carbohydrates, lipids, nucleic acids and other biomolecules.
These are the chemicals of life we studied earlier in the year.

32. Microspheres
Under certain hot conditions, amino acids form proteinoid microspheres.
Similar to cell membranes, they
are selectively permeable.

34. Cell Membranes
Simple fatty acids clumped together then formed naturally occurring phospholipids.

35. Simple carbohydrates give the newly forming cells energy.

36. Finally, the most accepted theory states that RNA was the first nucleic acid that allowed the first protocells to replicate.

37. After time, the RNA evolved into simple DNA.

38. The First Prokaryotes
The latest and most accepted hypothesis of where the first prokaryotes evolved is at deep ocean thermal vents.

39. ocean-ridge.ldeo.columbia.edu

40. The First Prokaryotes
These volcanic vents would have the heat energy, the chemicals, and the water needed for simple life forms to evolve.

42. Quick Geologic Activity
You and a partner will have 5 events/organisms
On post-it notes, guess when they first appeared on earth