Lecture One

Question 1

When and what caused the universe to begin?

Answer 1

13.7 BYA, the Big Bang.

Question 2

What were the original elements in the universe and what happened to them?

Answer 2

The original elements were Hydrogen and Helium. These condensed into stars, which eventually created the heavier elements which were scattered via supernovas.

Question 3

How old is our solar system and earth?

Answer 3

Our solar system is about 4.6 BYA, the Earth is approximately 4.55 BYA (an accumulation of comets and asteroids).

Question 4

What is “Primitive Earth”?

Answer 4

The first half billion years after the Earth was created where the Earth was too hot to allow water to accumulate on the surface. No life.

Question 5

What started happening 4 BYA on Earth?

Answer 5

The Earth cooled enough for outer layers to solidify and oceans to form. Volcanoes and other vents in the crust released gases that formed a new atmosphere. There was no free oxygen, the new atmosphere consisted of Carbon Dioxide, Nitrogen gas, Hydrogen Sulfide, Water Vapour, Methane, and possibly Ammonia.

Question 6

Was there free oxygen present in the atmosphere 4 BYA?

Answer 6

No, it was only found in Carbon Dioxide and Water Vapour.

Question 7

When did oxygen begin to appear?

Answer 7

Approximately 2.3 BYA.

Question 8

What is the first appearance of oxygen evidenced by?

Answer 8

The presence of rusted iron found in ancient rocks that formed at the time. These unique layers can be found throughout the world and are known as banded iron formations.

Question 9

Why are iron banded formations evidence of oxygen?

Answer 9

Because in the absence of oxygen, iron cannot rust (oxidation causes rust), so therefore if rust is present, oxygen must be present.

Question 10

When did oxygen levels reach the levels they are at today?

Answer 10

Oxygen levels slowly increased from 2.3 BYA to the level they are today about 600 MYA.

Question 11

What is the first (of four) stage process of life?

Answer 11

Stage One: Origin of organic molecules (nucleotides and amino acids)

Question 12

What is important about the origin of organic molecules?

Answer 12

Organic molecules formed a primordial soup in early Earth’s oceans. The presence of the primordial soup is crucial to life’s beginning. This soup (and the creation of life) could not re-occur on Earth today.

Question 13

Where are organic molecules believed to have originated from?

Answer 13

These are believed to have first appeared 3.5 to 4 BYA, forming in the ancestral atmosphere of Earth. Some people believe the Earth was seeded via comets/asteroids introducing organic molecules to the Earth.

Question 14

Why could the primordial soup not occur today?

Answer 14

The lack of oxygen on Earth allowed molecules to avoid oxidation (gaining of oxygen), and no living organisms were around to metabolize organic soup.

Question 15

What are the three main hypotheses put forth to explain how the primordial soup developed?

Answer 15

1. Reducing atmosphere hypothesis (Miller and Urey, 1950s)
2. Extraterrestrial hypothesis
3. Deep sea vent hypothesis (Wächtershäuser, 1988 - first vents were not discovered until 1977)

Question 16

What is the Reducing atmosphere hypothesis?

Answer 16

Scientists in the 1950s thought that the ancestral atmosphere consisted of water vapout, hydrogen, methane, and ammonia. With oxygen absent, the atmosphere was reducing.
Miller and Urey recreated these conditions to see if they could produce organic molecules in the laboratory. Water vapour rase to a chamber of hydrogen, methane, and ammonia and electrodes were discharged to stimulate lightning. Gases were then cooled and condensed into a trap (should be the primordial soup).

Question 17

What did the Reducing atmosphere hypothesis find?

Answer 17

That simple organic compounds were found in the trap (e.g. sugars, amino acids, and nucleotides). Miller and Urey’s experiments indicated that the reducing atmosphere hypothesis had merit.

Question 18

What does new evidence suggest about the Reducing atmosphere hypothesis?

Answer 18

That the ancestral atmosphere was not a reducing environment. Instead, it was likely neutral-consisting of CO, carbon dioxide, nitrogen gas and water. Regardless, the neutral atmosphere achieved the same result: organic molecules were produced from CO, Carbon Dioxide, Nitrogen gas, and water.

Question 19

What is the Extraterrestrial hypothesis?

Answer 19

Some scientists believe that sufficient organic compounds could have come from asteroids and comets to produce a primordial soup. Meteorites contain substantial amounts of organic carbon. This organic carbon includes amino acids and nucleic acids. Opponents argue that most of this would be destroyed in the intense heating and collision.

Question 20

What is the Deep sea vent hypothesis?

Answer 20

Water, metals, and hydrogen sulfide exit deep sea thermal vents in excess of 300 degrees Celsius.
Precursors to organic molecules can be formed in the gradient between hot and cold water. For example, nitrogen gas can be reduced to ammonia in this environment. Ammonia is required for amino acid synthesis.

Question 21

What is the second (of four) stage process to life?

Answer 21

Nucleotides and amino acids became polymerized to form DNA, RNA, and proteins.

Question 22

Where did the second stage process to life occur?

Answer 22

Not in prebiotic soup but on solid surface (clay) or tidal pool.

Question 23

What happens in the second stage process to life?

Answer 23

When monomers are present (e.g. amino acids or nucleotides), formation of polypeptides and nucleic acid polymers may occur on the surface of clay. The chemical nature of clay is used in many industrial organic reactions.

Question 24

What is the third (of four) stage process to life?

Answer 24

Polymers became isolated by boundaries (i.e. first cell walls).

Question 25

What is important about the third stage process of life?

Answer 25

The boundary separated the environment from the internal polymers, thus creating their own micro-climate. This resulted in protobiont: first non-living structures that evolved into cells.

Question 26

What four characteristics do Protobionts have?

Answer 26

1. A membrane separating the external environment from internal contents
2. Polymers inside that contain information
3. Polymers also act as enzymes for additional reactions
4. Capable of replication (but not capable of precise self reproduction like living cells)

Question 27

What is the Coacervate hypothesis for protobiont formation?

Answer 27

Charged polymers (e.g. hydrophobic fatty acids) spontaneously associate with each other (this can be demonstrated in a lab)

Question 28

What is the Microsphere hypothesis for protobiont formation?

Answer 28

Small water filled vesicles with macromolecule boundary. Example: when a hot solution of protein is cooled, a microsphere may develop with a water filled interior and an outer layer of protein.

Question 29

What is the Liposome hypothesis for protobiont formation?

Answer 29

Similar to microspheres, but with a lipid outer layer. Researchers have shown that clay can catalyze the formation of liposomes that grow and divide.

Question 30

What are protobionts?

Answer 30

The precursor to cells. They are abiotic, and contain organic molecules. They have primitive cell-like membrane structures and have some properties of life. They have no RNA or DNA.

Question 31

What are the three scenarios for Protobiont formation?

Answer 31

Coacervates (water membrane), microspheres (protein membrane), lipospheres (lipid membrane).

Question 32

What is the fourth (of four) stage process to life?

Answer 32

Polymers that were enclosed in membranes evolved cellular properties.

Question 33

What did Protobionts develop in the fourth stage process?

Answer 33

Protobionts developed metabolic functions and self replication.

Question 34

What and why do scientists favour a certain macromolecule as the first one of Protobionts?

Answer 34

Scientists favour RNA because it can perform three functions:

1. Store information
2. Self-replication
3. Enzymatic activity

Question 35

What (other than RNA) macromolecules could be considered the first macromolecule of Protobionts?

Answer 35

DNA or proteins. They aren’t though.

Question 36

What are the four stage processes to life?

Answer 36

1. Form nucleotides and animo acids
2. Nucleotides and amino acids (monomers) become polymerized
3. Polymers become enclosed in membranes
4. Membrane bound polymers acquire cellular properties

Question 37

What were the first organisms?

Answer 37

Prokaryotes: single celled microorganisms with anaerobic metabolism (little free oxygen available 3.8-3.5 BYA).

Question 38

Why were the first organisms hypothesized to be anaerobic heterotrophs?

Answer 38

Because they wouldn’t require oxygen and to take in molecules - easier for primitive cells to use organic molecules in primordial soup than to evolve additional metabolic pathways to make organic molecules (like autotrophs). The organisms were also most likely thermophiles, as oceans were continuously heated by heavy impacts of meteorites.

Question 39

How did the first organisms metabolize organic molecules?

Answer 39

They were Anaerobic heterotrophs. They metabolized the organic molecules from the primordial soup via fermentation. Organic molecules were made slowly, and anaerobic heterotrophs would have exhausted the supply quickly.

Question 40

Who had the advantage in early Earth: Autotrophs or Heterotrophs?

Answer 40

Organic molecules were made slowly, and anaerobic heterotrophs would have exhausted the supply quickly. Therefore, cells that evolved the ability to synthesize organic molecules from inorganic sources would have an advantage (Autotrophs).

Question 41

What are two types of anaerobic autotrophs?

Answer 41

Chemoautotrophs and photoautotrophs.

Question 42

What are anaerobic chemoautotrophs?

Answer 42

Prokaryotes that obtain carbon from carbon dioxide, but obtain energy from the reduction of inorganic chemical bonds (not from sunlight). These types of organisms can be found near hydrothermal vents or geysers.

Question 43

What is an example of an anaerobic chemoautotroph?

Answer 43

Species of the genus Sulfolobus, which oxidize H2S for energy to reduce carbon dioxide to produce organic compounds.

Question 44

What are anaerobic photoautotrophs?

Answer 44

Organisms that obtain energy from sunlight to fix carbon dioxide into carbon compounds.

Question 45

What do both anaerobic chemoautotrophy and photoautotrophy require and what happened to the supply?

Answer 45

Reduced elements or compounds (e.g. H2S and H2) to provide energy. This supply was likely exhausted an anaerobic autotrophs became abundant in ancestral oceans, similar to the depletion of organic compounds in the primordial soup by microbial heterotrophs. Because of this, alternative energy harvesting approaches evolved.

Question 46

Give a summary of the origin of life.

Answer 46

Earth formed (4 BYA), Earth cooled and water formed (4 BYA), primordial soup formed first organics (3.5 BYA), origin of protobiont (3.5 BYA), first living organism (anaerobic heterotroph, 3.5 BYA), anaerobic autotrophs (chemo and photo, 3.5 BYA)

Question 47

What followed the anaerobes in the development of life?

Answer 47

Photoautotrophs with oxygenic photosynthesis. Oxygen was a by-product of this new process.

Question 48

What was the key innovation by photoautotrophs for the development of life?

Answer 48

The use of water as the electron donor (water is split). This was an advantage because water was very plentiful. This happened 3.5 BYA. Oxygen was a by-product.