1. The Origin of Life Notes:
Chapter 14

2. Origin of Life outline A. Background Age of earth
Life began when/where
Fossil
Relative dating
Radioactive dating
B. Spontaneous generation
1. Redi:
2. Pasteur
C. Biogenesis
D. First cells
E. Endosymbiont theory

3. The Beginning: Earth is about 4.4 billion years old
Life began on Earth about 3.5 billion years ago in the ocean

4. Evidence of Life:
Fossils: Evidence of an organism that lived long ago, can include remains or imprints of organism in sedimentary rock (clay, mud)

5. A Protoceratops drinking at a river falls into the water and drowns
Sediments from upstream rapidly cover the body, slowing its decomposition. Minerals from the sediments seep into the body.
Over time, additional layers of sediment compress the sediments around the body, forming rock. Minerals eventually replace all the body’s bone material.
Earth movements or erosion may expose the fossil millions of years after it formed.

6. 2 Methods for Determining a Fossil’s Age:
Relative Dating: lower rocks are older than higher ones

7. Relative Dating:

9. 2 Methods for Determining a Fossil’s Age
Radiometric Dating--Used to find specific age of a fossil
As fossils age, elements in fossil decay
Scientists measure the amount of decay with radioactive isotopes to determine age.

10. Radiometric Dating:

11. How does life arise?
Experimental group
Spontaneous generation (abiogenesis): life from nonliving things
Francesco Redi: disproved theory by showing that flies must come from other flies
Control group

12. How does life Arise? Spontaneous generation:
Louis Pasteur: concluded that microorganisms must come from other microorganisms
used S-shaped flasks that let in only air = no organisms

13. Biogenesis: life only from other living things
Miller & Urey: showed that organic molecules could have formed the beginning of life

14. Early Cells
Protocell-- Large complex structure that carries out some life functions
Anaerobic prokaryotes– no oxygen in original atmosphere; autotrophs released oxygen as they performed photosynthesis to make food
Aerobic organisms—(heterotrophs)respiration with O2 in atmosphere
Complex eukaryotic cells--evolved from prokaryotic cells as conditions for life improved

15. The origin of cells:
Prokaryotes: cells without a nucleus or organelles
Eukaryotes: cells with a nucleus and organelles
cells grew in complexity once conditions for life improved

16. Early Cells
Endosymbiont theory--Present day eukaryotic cells evolved from symbiotic relationships between early prokaryotes