1. History of the Earth
Mr. Hamilton
Biology

2. First life on Earth
Took 1 billion years for the earth to cool and support life.
Bacteria: The only thing that could survive in conditions of early earth.
Proteins are believed to have come from energy produced from lightening and storms.

3. Fossil: Any trace of a once living organism.
Track, imprint, shell or the organism itself
Must buried and under water for a fossil to form.
The drier the climate the more likely you will find remains.

4. Age of Earth Believed to be 4.6 billion years old.
Determined by relative dating and radiometric dating.
Relative dating is when scientists estimate the age using the law of superposition—younger fossils are closer to the surface.
Radiometric dating: (Radioactive) Process of using radioactive isotopes to determine the age of fossils.
Radioactive isotopes decay into stable elements with the same number of neutrons.

6. Age of Earth (cont.)
Half-life: Time it takes for half of a radioactive isotope to change into a stable element. Each isotope has a different half-life.
EXAMPLE: C14 half life is 5730 years.
23 g starting and 5.75 g when it is discovered.
Cut 23 g in half until you reach 5.75 g.

7. Age of Earth (cont.) 23/2=11.5/2=5.75 This is 2 half lives.
5730 x 2 = years old

8. If a sample had 68 grams to start with and 4
If a sample had 68 grams to start with and 4.25 grams when discovered, how old is the fossil?
5730 years
11460 years
17190 years
22920 years 20

9. If a sample had 35 grams originally, how much would it have after 17000 years?20

10. Natural Selection
Nature influences traits organisms will have as they adapt in response to the environment.
Proposed by Charles Darwin—mid 1800’s
Foundation for theory of evolution
Survival of the fittest—Those that are able to adapt will survive—if not, they will die out.

11. Process of Natural Selection
Variation among members of same species
Struggle for survival
Only some survive and reproduce
Causes genetic change
Adaptation to the environment.

12. Natural Selection
Peppered moth study performed by Kettlewell shows this.
Experiments done that replicated what happened in England during Industrial Revolution.
As the trees changed color, the population of moths changed due to camouflage.

13. Natural Selection (cont.)
Sexual selection: Enhancing traits that ensure reproduction:
EX: Bright colors in birds, antlers/horns in sheep, deer, elk, etc., size/strength in animals.

14. Age of Earth (cont.)
22920/5730 = 4
Now you must cut 35 in half four times.
35/2=17.5/2=8.75/2=4.375/2=2.1875
2.19 g

15. First life Models
Primordial soup: Idea that the oceans contained organic compounds and these formed proteins from energy produced from storms on earth’s surface.
Bubble model: Gases were expelled from volcanoes in bubbles from the ocean. Reactions took place in these bubbles and contents were released into atmosphere as they floated to the surface.

16. Timeline First life was in the sea—Jawless fish 1st vertebrates.
First life on land—Amphibians—transition between water and land. Reproduce in water but live on land.
Reptiles and mammals followed.

17. Primates Grasping hands and feet
Binocular vision—Two slightly different views from each eye. The brain combines both images.
The first primates were prosimians
Color vision

18. Humans and other primates:
Opposable thumb—Stands out at an angle from other fingers and can be brought together with other fingers to grasp objects.
Diurnal—Active during day.

19. Hominids Primates that are bipedal—can walk upright on two legs.
Australopithecines
Homo habilis
Homo erectus
Homo sapien: Neanderthal & Cro-magnon