Question 1

Which step in the evolution of life is the most complex and probably occurred last?  
A) Formation of amino acids
B) Formation of protein-RNA systems
C) Formation of membrane-bound protocells
D) Spontaneous formation of organic compounds under abiotic conditions
E) Formation of ATP

Accepted Answer

The formation of membrane-bound protocells is the most complex step in the evolution of life as it involves the development of a protective barrier around genetic material and metabolic processes. This likely occurred later in the evolution of life as it requires the prior formation of simpler components such as amino acids and protein-RNA systems.

Question 2

Four of the following were likely in Earth's earliest atmosphere.Which one was not?  
A) Hydrogen
B) Nitrogen
C) Oxygen
D) Carbon dioxide
E) Water vapor

Accepted Answer

Earth's earliest atmosphere was likely composed of hydrogen, nitrogen, carbon dioxide, and water vapor. However, there was little to no oxygen present in the early atmosphere as it was mostly produced by photosynthetic organisms later on in Earth's history.

Question 3

A hypothesis currently getting a lot of attention concerning the origin of biological molecules is that they originated ____.  
A) in hot springs
B) under ice sheets in Antarctica
C) near hydrothermal oceanic vents
D) in salt lakes
E) in tidal pools

Accepted Answer

The hypothesis that biological molecules originated near hydrothermal oceanic vents is currently receiving a lot of attention. This hypothesis suggests that the high temperatures and rich chemical environment found near these vents could have provided the conditions necessary for the formation of complex organic molecules. Other locations, such as hot springs or tidal pools, have also been proposed as potential sites for the origin of biological molecules, but the hydrothermal vent hypothesis is currently the most widely accepted.

Question 4

The first eukaryotic fossils are dated to about ____.  
A) 2.7 billion years ago
B) 1.8 billion years ago
C) 1.5 billion years ago
D) 750 million years ago
E) 201 million years ago

Accepted Answer

The first eukaryotic fossils are dated to about 1.8 billion years ago.

Question 5

The "big bang" refers to  
A) an event marking the beginning of the universe.
B) the extinction of the dinosaurs.
C) the inevitable end of the universe.
D) the collision of the first galaxies forming the universe as it is today.
E) the inevitable death of large stars.

Accepted Answer

The "big bang" refers to the event marking the beginning of the universe, when it is believed that all matter and energy were created and the universe began to expand rapidly. This theory is supported by evidence such as the cosmic microwave background radiation and the observed redshift of distant galaxies.

Question 6

-The apparatus in the accompanying figure was used in the primitive Earth atmosphere simulation experiments performed by  
A) Stanley Miller and Harold Urey.
B) Günter Wächtershäuser.
C) Australian researchers.
D) Kwang Jeon.
E) Francis Crick and James Watson.

Accepted Answer

The apparatus in the accompanying figure was most likely used in the famous experiment conducted by Stanley Miller and Harold Urey in 1952. This experiment aimed to simulate the conditions of the early Earth's atmosphere to test the chemical origins of life. They demonstrated that organic compounds could be formed from inorganic precursors under conditions thought to resemble those of the early Earth.

Question 7

The ozone layer is valuable because it blocks  
A) heat.
B) UV radiation.
C) radio waves.
D) asteroids.
E) X-rays.

Accepted Answer

The ozone layer acts as a shield to block ultraviolet (UV) radiation from the sun, which is harmful to living beings on Earth. UV radiation can cause skin cancer, cataracts, and other negative effects on the environment. Therefore, the ozone layer is valuable for protecting life on our planet.

Question 8

The accumulation of free oxygen in the atmosphere ____.  
A) was a result of the accumulation of a by-product of a type of photosynthesis
B) caused the further spontaneous generation of life
C) provided the opportunity to extract more energy through anaerobic respiration
D) occurred immediately after the earth was formed
E) allowed for DNA to replace RNA as the primary data storage molecule

Accepted Answer

The accumulation of free oxygen in the atmosphere was a result of the accumulation of a by-product of a type of photosynthesis known as oxygenic photosynthesis, which is performed by cyanobacteria, algae, and plants. This process releases oxygen as a by-product, leading to an increase in atmospheric oxygen levels over time.

Question 9

The first cells were ____.  
A) autotrophic
B) parasitic
C) anaerobic
D) aerobic
E) necrotic

Accepted Answer

The first cells were likely anaerobic, meaning they did not require oxygen to survive. This is supported by the fact that oxygen was not abundant in Earth's atmosphere until much later in history, and the earliest known fossils of cells are from anaerobic organisms. Autotrophic and parasitic behaviors likely developed later as evolution progressed. Necrotic is not a likely option as necrosis refers to the death of cells, not the creation of new ones. Aerobic metabolism, which requires oxygen, also evolved later.

Question 10

The by-product of the metabolism of cyanobacteria that had the most effect on the further evolution of life is ____.  
A) oxygen gas
B) carbon dioxide
C) water
D) nitrogen gas
E) hydrogen gas

Accepted Answer

The by-product of cyanobacteria metabolism that had the most significant effect on the further evolution of life is oxygen gas. Cyanobacteria were the first photosynthetic organisms to produce oxygen as a waste product during photosynthesis, which led to the eventual formation of the Earth's oxygen-rich atmosphere. The availability of oxygen allowed for the evolution of more complex organisms capable of aerobic respiration, leading to the diversity of life on Earth we see today.

Question 11

Four of the following statement about protocells are true.Which statement is false?  
A) They are simple membrane-bound sacs.
B) They contain DNA.
C) They are able to engage in metabolism.
D) They are able to reproduce.
E) They are able to capture energy.

Accepted Answer

Protocells do not contain DNA as they are a primitive form of life and DNA is a relatively complex molecule. Instead, they may have RNA molecules that perform similar functions.

Question 12

Analysis of genomes of modern species indicates that the first cells were similar to existing ____.  
A) viruses
B) fungi
C) prokaryotes
D) eukaryotes
E) algae

Accepted Answer

Analysis of genomes of modern species suggests that the first cells were similar to prokaryotes, which are single-celled organisms lacking a nucleus and other membrane-bound organelles. This is supported by the fact that modern bacteria and archaea, both types of prokaryotes, are the most genetically similar to the ancestors of all cellular life.

Question 13

The evolution of biochemical molecules started on Earth ____.  
A) after the appearance of prokaryotic cells
B) long before any cells emerged
C) after the appearance of eukaryotic cells
D) after the appearance of eukaryotic cells but before the appearance of multicellular organisms
E) after the appearance of multicellular organisms

Accepted Answer

The origin of life on Earth is believed to have occurred around 3.5-4 billion years ago, and the evolution of biochemical molecules likely started before the emergence of any cells. The first living organisms were likely simple prokaryotic cells that evolved from these molecules. The emergence of eukaryotic cells and multicellular organisms occurred much later in the history of life on Earth.

Question 14

-The spark discharge in the accompanying figure represents ____.  
A) sunlight energy in the environment.
B) heat energy in the environment.
C) electrical energy in the environment.
D) ionizing radiation in the environment.
E) the explosion of the hydrogen gas to release energy for the reactions.

Accepted Answer

The spark discharge in the figure represents electrical energy in the environment, as it is a common method to visually demonstrate electrical energy through the creation of a spark or arc between two points.

Question 15

A membranous sac that contains interacting organic molecules,hypothesized to have formed prior to the earliest life-forms:  
A) protocell.
B) archaea.
C) ribozyme.
D) chemotroph.
E) protist.

Accepted Answer

A protocell is a hypothetical and primitive cell-like structure that is believed to have arisen spontaneously from non-living matter on early Earth. It is composed of a membrane-bound compartment that contains interacting molecules, which can carry out some of the basic functions of life, such as metabolism and replication. The protocell is thought to have been a precursor to the first living cells and may have been able to evolve into more complex organisms over time. The other options (B) archaea, (C) ribozyme, (D) chemotroph, and (E) protist, do not refer to the specific structure described in the question.

Question 16

RNA is believed to have preceded DNA because _____.  
A) DNA contains thymine and RNA does not.
B) DNA is double stranded and requires more components.
C) DNA can store more protein-building instructions in less space.
D) RNA can also function as an enzyme.
E) RNA cannot replicate itself.

Accepted Answer

RNA is believed to have preceded DNA because it can function as an enzyme, which suggests it could have catalyzed its own replication and other biochemical reactions in early life forms.

Question 17

Life probably would never have emerged on Earth if the ancient atmosphere had been the same as the present one in regard to the content of ____.  
A) carbon dioxide
B) hydrogen
C) oxygen
D) nitrogen
E) carbon monoxide

Accepted Answer

The presence of oxygen in the atmosphere would have prevented the emergence of life on Earth because oxygen reacts with and destroys organic molecules, which are the building blocks of life. The first life forms on Earth likely emerged in an oxygen-free environment. Therefore, if the ancient atmosphere had the same amount of oxygen as present, life would not have emerged.

Question 18

Aerobic respiration became established as a result of the evolution of ____.  
A) the first protocells
B) the first true cells
C) metabolism
D) the nuclear envelope
E) the oxygen-producing pathway of photosynthesis

Accepted Answer

Aerobic respiration requires oxygen as a final electron acceptor, which is produced by the oxygen-producing pathway of photosynthesis. Therefore, the evolution of this pathway led to the establishment of aerobic respiration.

Question 19

-The area labeled "spark discharge" in the accompanying figure contained all of the following gases found in the ancient Earth atmosphere except:  
A) carbon dioxide.
B) methane.
C) ammonia.
D) water vapor.
E) hydrogen gas.

Accepted Answer

The "spark discharge" experiments, which simulated conditions thought to be present on early Earth, primarily used a mixture of gases that included methane (CH4), ammonia (NH3), water vapor (H2O), and hydrogen gas (H2), but not carbon dioxide (CO2). These experiments aimed to demonstrate how organic molecules could have formed from simple inorganic molecules under early Earth conditions.

Question 20

The formation of amino acids under abiotic conditions was important because they serve as ____.  
A) a supply of structural units for proteins
B) enzymes to catalyze reactions
C) subunits in the formation of DNA
D) subunits in the formation of RNA
E) subunits for the formation of lipids

Accepted Answer

Amino acids serve as the building blocks for proteins, providing the structural units necessary for their formation. They are not enzymes themselves, although they can be incorporated into enzymes as active sites. While they can be incorporated into both DNA and RNA, they are not subunits of those molecules. They are also not subunits for the formation of lipids.

Quiz 19: Life's Origin and Early Evolution

Which step in the evolution of life is the most complex and probably occurred last?

Four of the following were likely in Earth's earliest atmosphere.Which one was not?

A hypothesis currently getting a lot of attention concerning the origin of biological molecules is that they originated ____.

The first eukaryotic fossils are dated to about ____.

The "big bang" refers to

-The apparatus in the accompanying figure was used in the primitive Earth atmosphere simulation experiments performed by

The ozone layer is valuable because it blocks

The accumulation of free oxygen in the atmosphere ____.

The first cells were ____.

The by-product of the metabolism of cyanobacteria that had the most effect on the further evolution of life is ____.

Four of the following statement about protocells are true.Which statement is false?

Analysis of genomes of modern species indicates that the first cells were similar to existing ____.

The evolution of biochemical molecules started on Earth ____.

-The spark discharge in the accompanying figure represents ____.

A membranous sac that contains interacting organic molecules,hypothesized to have formed prior to the earliest life-forms:

RNA is believed to have preceded DNA because _____.

Life probably would never have emerged on Earth if the ancient atmosphere had been the same as the present one in regard to the content of ____.

Aerobic respiration became established as a result of the evolution of ____.

-The area labeled "spark discharge" in the accompanying figure contained all of the following gases found in the ancient Earth atmosphere except:

The formation of amino acids under abiotic conditions was important because they serve as ____.