1. History of Life on Earth

2. How long would it take to count to 1 billion if it took a second to count to each number?
31 years, 251 days, 7 hours, 46 minutes, and 39 seconds to count to 1 billion.

3. Outline Early History of Earth Evidence of Early Life
How Old is Something
Fossil Record
History of Life on Earth
Where Did Life Come From

4. Early History of Earth How old is the Earth?
4.6 billion years old (4,600,000,000)
How do scientists explain how the earth formed?
Big Bang Theory
Large explosion billion years ago
Created the universe

5. Early History of Earth What was Earth like at first?
Very hot and constant volcanic eruptions
Atmosphere consisting of Ammonia, Methane, Water Vapor, Carbon Dioxide, and Nitrogen
What is missing?
Oxygen

6. Evidence of Early Life
Fossil: remains or imprints of long dead organisms preserved in the Earth’s surface
most are found in sedimentary rock (mud from dried up waters)
2 basic types of fossils
1. Imprint: footprints or plant impressions
2. Remains: bones or teeth

7. Evidence of Early Life

8. How Old is Something How do scientists determine the age of a fossil?
Relative Dating: examine how deep the fossil is buried
the deeper it is buried, the older it is
Radiometric Dating: study radioactive elements found in the fossil and rocks around it
Half-life -> amount of time it takes for ½ of an element to break down
Each element breaks down at a specific rate
Measure the amount of an element present in a fossil to determine when it actually died

9. How Old is Something

10. Fossil Record
Collection of all types of fossilized organisms that have been discovered
About 300,000 species of fossilized organisms have been discovered
Estimated to be about 2% of all species that have lived on Earth
New species are still being found
2 patterns can be observed
Fossils appear in order
Not random, not mixed together
Example – don’t find human remains with dinosaur remains
As we progress through time, fossils look more and more like modern day creatures

11. Fossil Record

12. Fossil Record

13. Fossil Record

14. History of Life on Earth
Time frames are divided into periods
Jurassic is one example
Each period has certain characteristics specific to it
What it looks like
What lives there
Factors that determine what life could be found on Earth
Amount of oxygen
Continental shift
Meteors
Volcanoes
Climate

15. History of Life on Earth
4.6 Billion Years Ago – Earth Forms
3.5 BYA – First single-celled life
550 Million Years Ago – First animals appear (lived in oceans)
500 MYA – Mass extinction caused by an ice age (85% of all species die)
440 MYA – First bony fish, plants and animals appear on land
345 MYA – First insects, amphibians, and reptiles
250 MYA – Mass extinction caused by meteorite hit and mega volcanoes (96% of all species die)

16. History of Life on Earth
245 MYA – Age of dinosaurs begins
65 MYA – Age of dinosaurs ends, Mass extinction caused by massive meteorite impact (76% of all species die)
7.5 mile wide meteorite struck in Mexico
Impact was 1 billion times more powerful that the Hiroshima atomic bomb
55 MYA – Spread of birds, mammals, flowering plants, and insects
5 MYA – First hominids (humanlike primates)
8,000 Years Ago – Modern Humans

17. Meteorite Craters
¾ of a mile in diameter
111 miles in diameter

18. Where Did Life Come From
Spontaneous Generation vs. Biogenesis
Spontaneous generation: idea that life can come from non-living things
No longer accepted by scientists
Biogenesis: theory that live can only come from other living things