CHAPTER 25—THE ORIGIN OF LIFE
MULTIPLE CHOICE
1. Modern cells are thought to have arisen from
a.
protocells.
b.
pre-cells.
c.
gas and dust clouds.
d.
prokaryotic cells that predated protocells.
e.
prokaryotic cells that predated pre-cells.
2. Assuming geological evidence is accurate, life on Earth may have originated
a.
14 billion years ago.
b.
4.6 billion years ago.
c.
3.5 billion years ago.
d.
2.1 billion years ago.
e.
1.2 billion years ago.
3. Which of the following is the primary assumption made by researchers when designing experiments to
model how life may have arisen?
a.
The chemical reactions of living things are only possible in living systems.
b.
Living organisms are composed of elements commonly found in the universe and on
Earth.
c.
Conditions on Earth have not changed over time.
d.
Life arose on Earth from non-living matter.
e.
The development of living cells from nonliving matter was very rapid.
4. Where did Earth’s atmosphere originate?
a.
Earth’s gravity trapped gasses from passing comets.
b.
Gases were released from the Earth itself as it cooled.
c.
The atmosphere was derived from dust particles from the original gas cloud around the
planet.
d.
Earth’s gravity trapped gasses from passing comets, gases were released from the Earth
itself as it cooled, and the atmosphere was derived from dust particles from the original
gas cloud around the planet.
e.
Gases were released from the Earth itself as it cooled and the atmosphere was derived
from dust particles from the original gas cloud around the planet.
5. Why is the distance of the Earth from the sun so crucial for life as we know it?
a.
The distance provides the optimal temperature for water to occur in a liquid form.
b.
The distance allows the Earth’s orbit to have a year of a reasonable length.
c.
The distance allows for multiple seasons in temperate climates, which was crucial for
development of different chemicals used to build the first protocells.
d.
The distance provides ample opportunity for water to freeze into ice.
e.
The distance ensures that ample water is available for all of the organisms on Earth.
6. Why is the absence of atmospheric oxygen (O2) so important to the Oparin-Haldane hypothesis?
a.
Oxygen is corrosive and thus would have degraded many of the metallic compounds on
the surface, releasing toxic gasses into the new atmosphere.
b.
Oxygen is more reduced than hydrogen gas, methane, or ammonia.
c.
Oxygen would have supported microorganisms that help chemical decay proceed.
d.
Oxygen is able to reverse reactions by removing electrons and hydrogen from organic
molecules, thus destroying the first organic compounds as quickly as they developed.
e.
Oxygen would have caused multiple explosions, converting chemical energy into heat
energy and rendering that energy unavailable for driving the synthesis of organic
molecules.
7. Aside from the traditional hypothesis that life on Earth developed via organic compounds produced in
a reducing atmosphere, which of the following alternative hypotheses is most likely?
a.
Life could have arisen from the organic compounds formed around hydrothermal vents far
below the ocean floor.
b.
Life could have developed on another planet and was then delivered by meteorites.
c.
The organic compounds necessary for life were delivered to Earth by meteorites.
d.
Life on Earth may have arisen inside land-based volcanoes.
e.
The organic compounds necessary for life could only have been produced in an oxidizing
atmosphere
8. “Prebiotic soup” refers to
a.
the interior contents of protocells.
b.
the cytoplasm of early prokaryotic cells.
c.
the mix of gases in the atmosphere that gave rise to the first organic molecules.
d.
the polymerized slime coating ancient clay particles.
e.
the accumulation of organic molecules that formed in the oceans before there was life on
earth.
9. They famous Urey-Miller experiments provided crucial support for which hypothesis?
a.
the Endosymbiosis hypothesis
b.
the Oparin-Haldane hypothesis
c.
the RNA World hypothesis
d.
the Dickerson oxidizing atmosphere hypothesis
e.
the Hydrothermal vent hypothesis
10. After organic molecules have been formed in abundance, what is the next step that must occur in the
progression toward a living organism?
a.
evaporation of the water the organic compounds are dissolved in
b.
dehydration reactions linking macromolecule monomers into larger molecules
c.
increasing availability of organic compounds
d.
the formation of a semi-permeable membrane
e.
aggregation of the different organic compounds so all of the pre-cell building blocks are in
the same localized region
11. How might absorption of organic compounds into clays assist in their aggregation and organization
into membrane-bound protocells?
a.
Clays contain many minerals in extremely thin layers and readily repel ions, forcing
multiple chemical interactions.
b.
Clays are highly structured, contain water, and store potential energy that could drive the
chemical reactions forward.
c.
Clays lack water, forcing the concentration of the organic molecules and thus driving
multiple interactions.
d.
Clays are extremely resistant to temperature changes and thus would insulate the organic
compounds from temperature changes in the atmosphere.
e.
None of the above statements accurately explain clays’ possible roles in the formation of
protocells.
12. What happens when phospholipids are placed in an aqueous solution?
a.
They disperse throughout the solution and form polar bonds with other organic molecules
present in the solution.
b.
They move to the water’s surface and form a single-layered membrane between the water
and the atmosphere.
c.
They repel one another.
d.
They spontaneously form bilayers.
e.
The hydrophobic tales force the phospholipids to form “beads” at the surface, much like
you see when vegetable oil is added to an aqueous solution.
13. Ribozymes may have originally developed by
a.
ATP synthesis.
b.
the chance assembly of RNA molecules.
c.
cellular respiration.
d.
glycolysis.
e.
electron transfer systems.
14. Which of the following was probably the first information storage molecule?
a.
DNA
b.
RNA
c.
protein
d.
carbohydrates
e.
lipids
15. Why do some scientists believe that RNA was the first information storage molecule?
a.
because some viruses use RNA as their information storage molecule
b.
because RNA can be a catalyst as well as an information storage molecule
c.
because amino acids cannot form peptide bonds without ribosomes to catalyze their
formation
d.
because RNA is a less stable molecule than DNA
e.
because proteins are made of far more amino acid monomers (over 20) than RNA (4)
16. If RNA was the first information storage molecule, what macromolecule would have been the “next”
molecule produced in the progression toward living cells?
a.
DNA
b.
lipids
c.
carbohydrates
d.
sugars
e.
proteins
17. What evidence do we have for the development of photosynthetic cells that used water as an electron
source at least 3 billion years ago?
a.
fossils of the first eukaryotic cells
b.
the discovery of the first plant fossils
c.
the discovery of stromatolites
d.
fossils of the first animals
e.
fossils of the earliest chloroplasts
18. Aerobic bacteria most likely evolved
a.
directly from early protocells.
b.
around hydrothermal vents.
c.
much later than cyanobacteria.
d.
in a prebiotic soup.
e.
through the process of endosymbiosis.
19. Which mineral ion is required for ribozymes to become active and begin self-replication?
a.
ferrous iron
b.
ferric iron
c.
zinc
d.
magnesium
e.
selenium
20. The RNA world proposal suggests that the first information molecules were
a.
transfer RNA.
b.
ribosomes.
c.
messenger RNA.
d.
ribozymes.
e.
unpaired strands of DNA.
21. Who developed the modern endosymbiotic theory?
a.
Charles Darwin
b.
Lynn Margulis
c.
Richard Dickerson
d.
Wendy Johnson
e.
Stanley Miller
22. The hypothesis that mitochondria and chloroplasts originated from the phagocytic activity of
prokaryotes that was not followed by digestion is called the
a.
theory of natural selection.
b.
endosymbiotic hypothesis.
c.
ribozymes-first hypothesis
d.
Oparin-Haldane hypothesis.
e.
stromatolite hypothesis
23. According to the endosymbiont hypothesis,
a.
most of the genes from the endocytosized bacteria moved to the nucleus.
b.
the host anaerobe became dependent on the endocytosized bacteria.
c.
the endocytosized bacteria became dependent on the host cell.
d.
the endocytosized bacteria were all photosynthetic.
e.
most of the genes from the endocytosized bacteria moved to the nucleus, the host anaerobe
became dependent on the endocytosized bacteria, and the endocytosized bacteria became
dependent on the host cell.
24. Even though the three domain taxonomic system used in this book is widely accepted, there is a key
relationship between common ancestry domains that is unclear. That relationship is
a.
between Archaea and Eukarya.
b.
between Archaea and Bacteria.
c.
between Bacteria and Eukarya.
d.
between Archaea, Eukarya, and Bacteria.
e.
whether the three domains all have a common ancestor.
25. Which feature of Archaea is shared with Bacteria but not with Eukarya?
a.
the sequestration of DNA into a nucleus
b.
the common occurrence of introns
c.
the chemical structure of the cell walls
d.
the plasma membrane structure
e.
a genome comprised of a single, circular molecule of DNA
26. The development of multicellular organisms likely originated
a.
from colonies of unicellular organisms of the same species.
b.
from endocytosis of other cells followed by mitosis.
c.
from cooperation between different species of cells.
d.
from colonies of numerous species of cells.
e.
from endosymbiotic eukaryotes.
27. The nuclear membrane of eukaryotes originated from
a.
captured aerobic bacteria.
b.
prebiotic soup.
c.
captured cyanobacteria.
d.
invaginations of the plasma membrane.
e.
the large circular chromosome of the prokaryotic ancestor.
28. Why is the protein-first hypothesis not accepted by most scientists?
a.
Proteins cannot be catalysts.
b.
There is no known mechanism of protein self-replication.
c.
Of all of the macromolecules, only DNA can self-replicate.
d.
There is no evidence that proteins can store information.
e.
Proteins are too complex to have been the first “polymers of life.”
29. What is an alternative to RNA as the first polymer of life?
a.
nucleotides
b.
non-genetic polymers
c.
polymers that do not form a double helix
d.
other genetic polymers containing different sugars
e.
other genetic polymers containing different amino acids
30. Which of the following does NOT describe modern, living cells?
a.
a semi-permeable membrane keeping the internal environment of the cell separate from
the external environment
b.
nucleic acids linked in a sequence to form at least one large molecule
c.
a requirement for the nucleic acids to be contained behind a nuclear membrane
d.
multiple pathways for converting energy from one form into another
e.
a method of converting the nucleic acid sequences into proteins
31. What do some scientists believe led to the increase in the level of oxygen in the atmosphere?
a.
the first photosynthetic reactions
b.
photosynthetic cells that used water and not H2S as a source of electrons
c.
The development of cellular respiration pathways in cells
d.
the use of glycolysis in cells
e.
photosynthetic pathways that stripped oxygen off of carbon dioxide and retained only the
carbon in subsequent steps
32. Evidence for the endosymbiotic theory does NOT include which of the following?
a.
DNA in prokaryotes, mitochondria, and chloroplasts is arranged in a single, circular
genome.
b.
Endocytosized cells have been directly observed to survive in the cytoplasm of the host
cell.
c.
Endocytosized organelles have been directly observed to survive in the cytoplasm of the
host cell.
d.
Fossils of prokaryotic cells in the process of endocytosizing cyanobacteria have been
discovered.
e.
There are some rRNA sequences that are similar between prokaryotes, mitochondria, and
chloroplasts.
33. Which of the following was probably NOT a natural energy source that drove the chemical reactions
leading to the first organic molecules?
a.
sunlight
b.
electrical storms (lightning)
c.
photosynthesis
d.
radioactive decay
e.
heat energy released from Earth’s core
34. According to the Oparin-Haldane hypothesis, which of the following was probably NOT a major
component of Earth’s early atmosphere?
a.
O2 (oxygen)
b.
H2 (hydrogen)
c.
CH4 (methane)
d.
H2O (in vapor form)
e.
NH3 (ammonia)
35. Which of the following statements about endosymbiosis is FALSE?
a.
endosymbiosis has taken place many times among true, multicellular animals
b.
genes from organelles that originated through endosymbiosis are largely transferred to the
host cell nucleus
c.
The genes that code for ribosomes in mitochondria and chloroplasts are more like those in
prokaryotes than in eukaryotes
d.
mitochondria and chloroplasts divide on their own through binary fission
e.
endoysymbiosis occurred many times in unicellular animals
SHORT ANSWER
36. Why can the hypothesis that life evolved on another planet and was transported by meteorites not be
falsified?
37. If life evolved in hydrothermal vents, is it likely the first cells were in the Domain Archaea?
38. Distinguish between stromatolites and biosignatures.
39. Explain the endosymbiotic hypothesis.
40. What key assumption of the endosymbiotic theory is observed in living animals?
MODIFIED TRUE/FALSE
If the statement is true, answer “T”. If the statement is false, answer “F” and make it correct by
changing the underlined word(s) and writing the correct word(s) in the answer blank(s).
41. Scientists believe life arose spontaneously from nonliving matter.
42. Scientists agree that life originated on Earth.
43. Proteins may have been the first information-storage molecules because they can self-replicate as well
as catalyze reactions.
44. Clays do not facilitate the formation of phospholipid bilayers.
45. Phospholipids created in a laboratory can self-assemble into bilayers.
46. Stromatolites are fossils of ancient, photosynthetic cyanobacteria.
47. Most scientists believe that prokaryotes evolved from eukaryotes.
48. Mitochondria probably developed before the atmosphere was oxygen rich.
49. The development of the Golgi, endoplasmic reticulum, and nucleus are part of the endosymbiotic
theory.
50. Archaea genomes contain introns.
51. The first truly living cells must have been prokaryotic in structure.
52. Multi-cellularity is believed to have evolved multiple times on Earth.
ESSAY
53. Describe the supporting evidence for the endosymbiotic theory.
54. Define the Oparin-Haldane hypothesis and explain how it has been tested in a laboratory.
512
MATCHING
Match each phrase below with one of the following terms:
a.
ribozymes
f.
stromatolite
b.
protocells
g.
cyanobacteria
c.
prebiotic soup
h.
endosymbionts
d.
hydrothermal vent
i.
archaeans
e.
lipid bilayer
j.
enzymes
55. The first water-splitting photosynthesizers
56. The precursors of mitochnodria and chloroplats
57. The likely first information molecules
58. The first result of lightning strikes in a reducing atmosphere the reducing atmosphere hypothesis
59. These share a common ancestor with the first eukaryotic cells
60. Rock structures where the earliest evidence of life is found
61. The basic chemical structure that serves for the containment of cells and cell-like objects