Origin of Life on Earth

Question 1

What is life?

Answer 1

Something that

1. Metabolizes
2. Grows
3. Reproduces

Question 2

Is a virus considered life?

Answer 2

No. They reproduce, but don’t grow and don’t metabolizes.

Question 3

How do humans gain knowledge?

Answer 3

Experiential
-trial and error, 100% of pop. does it

Religious and Spiritual
-belief w/ no dissent, self-perpetuating, 98% of pop.

Scientific
-based on fact/reason, dissent encouraged, less than 1% of pop. engages in this

Question 4

What is the belief in spontaneous generation?

Answer 4

Belief in the 1800’s that non-life spontaneously created other life (rotting meat=flies) (Broth heated, cooled, and bacteria grows)

Question 5

Who disproved the theory of spontaneous generation?

Answer 5

Louis Pasteur

• Broth experiment.
• Flask with curved tube out of the end.
• Bacteria and dust gets trapped in S-curve.
• No growth.
• When tilted, the bacteria/dust makes contact with broth=growth

Question 6

What is the primordial soup hypothesis? From whom, does it originate?

Answer 6

That life evolved from simple organic compounds present on earth at the time of its infancy.

Oparin and Haldane came up with it.

Question 7

What are the basic elements of the primordial soup hypothesis?

Answer 7

• earth had a reducing atmosphere
• gases reacted with energy sources, yielding organic compounds
• compounds in seawater reacted further to form polymers
• polymers became organized to form earliest life

Question 8

How old is the earth and how do we know?

Answer 8

4. 6 billion years old
   - We know through radiometric dating of minerals in rocks
   - Igneous (not many as old as earth), meteorite, moon rocks
   - Radioisotope to decay product half life

Question 9

Why aren’t all igneous rocks the same age on earth?

Answer 9

Plate tectonics

Question 10

How do we know what earth was like when life arose?

Answer 10

Volcanoes

Question 11

How did volcanoes contribute to the primordial soup hypothesis?

Answer 11

Volcanoes spewed ammonia, methane, water, and hydrogen gas into the atmosphere.

• CH4+H2O=CO2+H2HCN+C2H2
• Lightning energy reacted with HCN+C2H2 to produce carbon compounds in water which eventually led to life
• CO2 created greenhouse effect and created atmosphere

Question 12

who tested the Oparin/Haldane primordial soup theory? What were the results?

Answer 12

1953-Stanley Miller-Urey experiment

• boiled water, and let electrical discharge go across container with CH4, NH3, H2O, H2.
• Gases go through condenser, and collected sampled had building blocks of life

Question 13

How were processes of creating life possible enhanced?

Answer 13

Hyrdrothermal vents provide high water temperature suitable for organic chemistry

Question 14

What stage was life in 3.5-3.8 bya?

Answer 14

• all life present used anaerobic metabolism
• primordial soup food grows thin
• origin of photoautotrophs b/c primordial soup running out
• O2 created absorbed as rust

Question 15

What is the primordial soup?

Answer 15

Building blocks of life created when lightning energy combined with gases in the atmosphere

• these building blocks went into the ocean where they
  1) combined to form life or
  2) underwent anaerobic fermentation to be used as food

Question 16

Where could early life live (3.5-3.8 bya)?

Answer 16

deep in the water or in shade b/c no O3 layer to block UV radiation

Question 17

Anaerobic photosynthetic bacteria developed as a result of the primordial soup food running out 2.8bya. What were the results of this?

Answer 17

Photosynthetic bacteria utlized abundant CO2 in atmosphere to produce sugar which was used as food and O2 a strong oxidizing agent.
-Fe2+ was an oxygen sponge and reacted with O2
to produce rust so O2 didn’t oxidize everything
-Produced Fe3+, which is now found in banded iron formations and used in production

Question 18

What did earliest life look like?

Answer 18

Earliest life was microbial

• Anaerobic metabolism of primordial soup molecules
• Glycolysis has very low yield so life grew slowly

Question 19

What is the origin of photosynthesis?

Answer 19

Cyanobacteria in deep water use sunlight to make their own sugar and use anaerobic glycolysis to use it which produced oxygen

Question 20

1.8 bya the ferrous iron, Fe2+, runs out. What occurs?

Answer 20

• O2 slowly makes it into atmosphere
• O2+Sunlight=O3 layer begins to form making surface waters and land less deadly
• O2 is deadly to anaerobes which either kills them off, forces them to areas w/o O2, or forces evolution of aerobic heterotrophs and aerobic autotrophs

Question 21

What occurred to life from 1.8-1.4 bya?

Answer 21

• first O2 in water and air
• ozone layer starts forming
• oxidative metabolism
• eukaryosis
• advent of sex
• biodiversity begins increasing

Question 22

What is the result/advantages of aerobic metabolism evolving?

Answer 22

lifeforms have 10x cellular energy

• more energy from oxidative metabolism
• faster growth and reproduction
• more diversity from sexual reproduction

Question 23

What are the two types of reproduction and how doe they both accomplish genetic diversity?

Answer 23

Sexual Reproduction

• Meiosis n+n=2n
• genetic diversity on which natural selection could operate

Asexual Reproduction
-only through random mutation

Question 24

How did eukaryotes evolve from prokaryotes?

Answer 24

Endosymbiosis Hypothesis

Question 25

What occurred 700-540 mya?

Answer 25

• origin of metazoa
• Edicaran fauna
• O2 levels surpass 10%
• Cambrian explosion

Question 26

How did metazoans originate from protists?

Answer 26

Unicellular flagellated protists make an aggregate

• form a hollow sphere
• specialized reproductive cells form
• cells fold in to make tissues