AP Biology PowerPoint Question Sheet—Ch. 25 The Origin of Life
1. What were some of the first elements produced? Mainly hydrogen, some helium and lithium
2. Go to http://en.wikipedia.org/wiki/Big_Bang
 When did the big bang occur? 13.798 ± 0.037 billion years ago, which is thus
considered the age of the universe.
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What are the core ideas of the Big Bang? Core ideas: 1) the expansion, 2) the early hot
state, 3) the formation of light elements, and 4) the formation of galaxies
What did Georges Lemaitre do? First proposed what became the Big Bang theory in
what he called his "hypothesis of the primeval atom". Over time, scientists built on
his initial ideas to form the modern synthesis.
What did Fred Hoyle do? Agreed that Universe was expanding, but rejected Big Bang
Theory. Argued that there was no “beginning” of the universe. Produced the other
main theory for the explanation of the expansion of the universe, “Steady State
Theory”. The validity of the Steady State Theory vs. The Big Bang Theory was debated
for a long period of time, but now it is believed that the Big Bang Theory is the most
plausible hypothesis.
 In a couple of sentences define the big bang? Synopsis of the theory: 1) Universe was in
hot, dense state and started expanding (Big Bang Theory), 2) Proton and neutrons
formed nuclei quickly as temperatures cooled, 3) Giant clouds of these elements
combined by gravity to form stars and galaxies (which later form heavier elements
inside of these stars and galaxies), 4) Galaxies continue to move away from each other
due to this initial explosion, 5) Thus, the universe is still continually expanding
3. What are some properties that protobionts exhibit?
 Precursors to cells.
 They were able to carry out chemical reactions enclosed within a border across which
materials could be exchanged.
 Borders formed in the same manner as hydrophobic molecules aggregate to form
membranes (as phospholipids form plasma membranes).
 Exhibited some of the properties associated with life, including simple reproduction,
metabolism, and excitability
 Liposomes are experimentially (and abiotically) produced protobionts
4. Describe Stanley Miller’s and Harold Urey’s experiment.
 Coined as the “lightning experiment”. Note: I wouldn’t necessarily use this term when
describing it on a test. It just makes the experiment easier to remember.
 The Miller-Urey experiment demonstrated the abiotic synthesis of organic
compounds.
 Water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2) were all sealed inside
a sterile array of glass tubes and flasks connected in a loop, with one flask half-full of
liquid water and another flask containing a pair of electrodes.
 The liquid water was heated to induce evaporation, sparks were fired between the
electrodes to simulate lightning through the atmosphere and water vapor, and then
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the atmosphere was cooled again so that the water could condense and trickle back
into the first flask in a continuous cycle.
Within a day, the mixture had turned pink in color, and at the end of two weeks of
continuous operation, Miller and Urey observed that as much as 10–15% of
the carbon within the system was now in the form of organic compounds.
Two percent of the carbon had formed amino acids that are used to make proteins in
living cells, with glycine as the most abundant. Nucleic acids were not formed within
the reaction. But the common 20 amino acids were formed, in various concentrations.
5. What did Wachtershauser propose?
 Iron-Sulfur World Theory and suggested that life might have originated at
hydrothermal vents (underwater geysers).
 Iron sulfide can donate electrons to dissolved carbon dioxide to form larger organic
compounds.
 This may have been the beginnings of metabolic reactions.
 This is an attractive hypothesis because of the abundance of CH4 (methane) and NH3
(ammonia) present in hydrothermal vent regions, a condition that was not provided
by the Earth's primitive atmosphere.
6. Go to http://en.wikipedia.org/wiki/liposome
 What is a liposome? A liposome is a type of protobiont (precursor to cells). It is an
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artificially-prepared vesicle composed of a lipid bilayer.
Who first described liposomes? Liposomes were first described by British
haematologist Alec D Bangham in 1961 (published 1964), at the Babraham Institute,
in Cambridge.
7. What was accepted as the first genetic material? RNA (RNA World Hypothesis). Reasoning for
this is that RNA can act as both an enzyme (ribozyme) and hereditary material.
 Arguments against DNA being the original genetic material is that for the pathway
from DNA to RNA to proteins, some of the proteins made are actually required in the
transcription from DNA to RNA. DNA on its own would not have been able to make
those proteins.
8. Go to http://3dbiology.pbworks.com/w/page/912247/Existing%20Models
 What is a glycocalyx A capsule or slime layer. It is a covering outside the cell wall
(typically just referred to as the capsule).
 Find on the bacteria diagram
9. Name the consequences of Oxygen production.
 Life can no longer arise from nonliving materials because oxygen is a very
electronegative element (it “wants” the electrons more than the other elements that
were around at this time; therefore, it would have taken the place of most of the
reactants during these reactions).
 Organisms that can tolerate oxygen are at an advantage. Obligate anaerobes either
became extinct or found anaerobic (without oxygen) environments.
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Some oxygen formed ozone, O3, which filtered out UV radiation like the oceans do.
This took away one of the main energy sources that allowed chemical evolution to
occur.
 Basically, the presence of oxygen stopped the creation of organic material from
inorganic material.
What is aerobic respiration? Using oxygen to create ATP. This process is much more efficient
than anaerobic respiration.
What is endosymbiosis? The word “endo” means into and “symbiosis” refers to a symbiotic
relationship. The engulfing of a prokaryote by a eukaryote to create mitochondria and
chloroplast. The process that created mitochondria occurred before chloroplast (all
eukaryotes have mitochondria, meaning that the introduction to mitochondria occurred in a
more distant common ancestor than did chloroplast introduction).
Go to http://en.wikipedia.org/wiki/chloroplast
 Name the parts of a chloroplast
i. Outer and inner membrane (would expect 2 membranes from endosymbiosis)
ii. Thylakoid – discs responsible for light absorption
1. Granum (stack of thylakoids)
iii. Stroma – fluid filled space
iv. Nucleoid – area where DNA is found
v. Ribosomes – make proteins
 Click on chloroplast DNA—Single, circular loop which is just like that of prokaryotes
(would be expected from endosymbiosis)
Why is sexual reproduction important in the evolution of the earth? Sexual reproduction
ensures genetic variability and exchange of genetic material. As a result, evolution occurs
more rapidly.
When did many phyla of living animals appear in the fossil record? Cambrian Period (Cambrian
Explosion)
What did continental drift allow?
 These movements cause changes in climate, ocean currents, the formation of glaciers
and other geological phenomenon.
 Allowed for allopatric speciation on a global scale
When did the greatest mass extinction occur? 250 million years ago “Great Oxygen
Catastrophe”
Describe the Mesozoic.
 Contained the Cretaceous, Jurassic, and Triassic periods
 Occurred from 65.5 to 250 million ago
 During this time, dinosaurs dominated and angiosperms (flowering plants) appeared