2. Aim: How do scientists explain the development of life on earth?

3. What were the conditions on earth 4.5 billion years ago? Harsh Early Earth 1)Hot 2)Little Oxygen 3)Abundant Lightning 4) Volcanic Activity

4. Primitive Earth’s Energy Source As earth cooled, thunderstorms drenched the earth with water and the oceans formed. Lightning provided an energy source for life to begin.

5. Inorganic compounds formed organic compounds. Experiment by Stanley Miller & Harold Urey Amino Acids, Nitrogenous Bases, Monsaccharides, Fatty Acids How did life begin on earth? Formation of Organic Compounds

6. Formation of Organic Polymers: Scientists have proven that polymers of organic compounds like polysaccharides, polypeptides, lipids and nucleic acids could have formed during the conditions of early earth. “RNA World” Scientists hypothesize that the first genes were RNA. RNA served as the both the molecule that stored the genetic info. & the molecule that directed protein synthesis.

7. Formation of Pre-Cells: Experiments show that membranes can form around organic polymers in a solution if certain kinds of lipids are present. **The simplest living organisms are far more complex than these “pre-cells”

8. Where did life begin? Today’s deep sea vents are populated with simple unicellular organisms that may resemble some of the earliest living cells.

9. First organism on Earth Anaerobic prokaryote cellsheterotrophs The first organisms on earth were simple unicellular organisms.

10. Where did the oxygen come from? Some of these early forms of life developed into unicellular Autotrophs (they got their energy from the sun and produced oxygen)

11. Aerobic Organisms Now, that the new atmosphere had OXYGEN, organisms that could use oxygen to do cell respiration slowly developed.

12. How do scientists explain this change from simple to more complex organisms? Theory of Evolution 1)The process by which species change over time (simple to complex). 2)Present day species are related to ancient species.

13. What is a theory? Is an explanation, supported by observations and/or experiments, that can be used to explain related occurrences. Theory of Evolution

14. What is the evidence that supports the Theory of Evolution? 1)Fossil Record- collection of fossils that provides clues to the history of Earth’s organisms. The fossil record spans much of geologic time (billions of years of Earth’s history). 2)Similarities in Structure 3)Similarities in Development (Embryology) 4)Molecular Biology (DNA & Proteins)

15. How do we know that we have evolved from ancestors distinctly different from us? Hint: How do we know dinosaurs existed? The fossil record (remains of dead organisms) have given scientists the clues they needed to determine an organisms ancestry by comparing them to present day species. FOSSILS

16. The fossil record shows… Life has evolved from simple to more complex Older Organisms: more simplistic Newer Organisms: more complex

17. What do we learn from fossils? http://www.ucmp.berkeley.edu/education/explorations/tours/stories/middle/C7a.html How did behaviors evolve? How long did individuals live? How do features evolve over time? http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

18. Speciation Evolution has lead to the formation of new species from different ancient organisms Species- a group of organisms that share certain characteristics & can mate with one another, producing fertile offspring.

19. Descendents Common Ancestor Similar to a family tree Descendents

20. Evolutionary Tree Ancestral common species (bottom) Species living at present time (top)

21. Our Common Ancestor Unicellular Common Ancestor 100’s of Millions of year ago

22. How closely related are they? Which organisms are closely related? Those who have a recent common ancestor (a close point of intersection in a tree diagram) Which are distant relatives? Those who have a distant common ancestor (a far point of intersection in a tree diagram)

23. What organisms are our closest relatives? Why?

24. Summary of early evolution Present day