Topic 1 Evolution: Origin of Life Timeline

Question 1

• The universe is 12-15 billion years old, the solar system is 4.6 billion years old, the earth is ~4.5 billion years old, the microfossils of prokaryotes are 3.6 billion years old, photosynthetic bacteria are 2.3 billion years old, and eukaryotes are ~1.8 billion years old.

Answer 1

Note

Question 2

• Earth and the atmosphere formed through volcanoes - the atmosphere had CH4, NH3, CO, CO2, H2, N2, H2O, S, HCl, and HCN gases. There was little to no O2!

Answer 2

1. Part 1

Question 3

• Primordial seas formed - as the earth cooled, gases condensed and formed a sea filled with water and minerals

Answer 3

2. Part 2

Question 4

• Complex molecules were synthesized - the organic soup formed from inorganic compounds driven by energy from UV rays, lightning, heat, and radiation. The resulting organic compounds included acetic acid, formaldehyde, and amino acids

Answer 4

3. Part 3

Question 5

a. Oparin & Haldane

b. Stanley Miller

Answer 5

Parts of Part 3

Question 6

• These scientists proposed the organic soup theory. They said that if there was O2 in the primordial atmosphere, no organic molecules would have formed because oxygen is very reactive. Oparin’s hypothesis was that the early Earth’s environment was reducing, which provides the chemical requirements to produce complex molecules from simple building blocks. An oxidizing environment would have broken the complex molecules apart

Answer 6

a. Oparin & Haldane

Question 7

• He tested Oparin’s theory and produced organic molecules. Miller & Urey sealed ammonia, methane, water, and hydrogen in a flask and simulated lightning; they created a simulated environment of the primordial Earth. The experiment produced several organic molecules, amino acids, and starting materials. However, no nucleic acids were made!

Answer 7

b. Stanley Miller

Question 8

• Polymers formed and self-replicated - simple monomers became polymers through dehydration condensation reactions. Proteinoids are abiotically produced polypeptides. If we heat amino acids in the lab, they will dehydrate and form proteinoids, confirming the validity of this step

Answer 8

4. Part 4

Question 9

• Organic molecules became protobionts - protobionts were precursors of cells. They are metabolically active but unable to reproduce. Microspheres/liposomes and coacervates (spontaneously formed lipid or protein bilayer bubbles) are experimentally (abiotically) produced protobionts that have some selectively permeable qualities.

Answer 9

5. Part 5

Question 10

• Primitive heterotrophic prokaryotes formed - they obtained energy by consuming other organic substances

Answer 10

6. Part 6

Question 11

• Primitive autotrophic prokaryotes formed - heterotrophic prokaryotes mutated and gained the ability to produce their own food. An example of autotrophic prokaryotes is cyanobacteria

Answer 11

7. Part 7

Question 12

• Ozone layer formed which ended abiotic chemical evolution - photosynthetic activity of autotrophs produced large amounts of oxygen. UV light and oxygen formed the ozone layer. The ozone layer absorbed UV light, thus blocking the energy needed for abiotic synthesis of organic materials. This causes the termination of primitive cells and abiotic evolution

Answer 12

8. Part 8

Question 13

• Eukaryotes formed - the endosymbiotic theory explains that eukaryotic cells originated mutually among prokaryotes. The theory states that certain organelles like mitochondria and chloroplasts were once free-living prokaryotes. Other prokaryotes then phagocyted the mitochondria and chloroplast, and thus they lived in symbiosis. Evidence for this theory is seen with thylakoid membranes of chloroplasts that resemble photosynthetic membranes of cyanobacteria. Mitochondria and chloroplasts have double membranes and also have their own circular DNA that is not wrapped with histones, a trait of prokaryotes. The ribosomes of these organelles resemble those of bacteria, and they reproduce independently via a process similar to binary fission.

Answer 13

9. Part 9

Question 14

• The modern atmosphere is roughly 78% nitrogen (N2), 21% oxygen, 1% argon, and some less important gases. Earth’s crust is 47% oxygen and 28% silicon.

Answer 14

Note