AP Bio Quiz Ch 20

1. A ribozyme is a molecule of RNA that has catalytic properties.

True

False

A ribozyme is a type of RNA molecule that can catalyze chemical reactions. Unlike most other enzymes, which are made of proteins, ribozymes are made of RNA. They can perform various functions, such as cleaving RNA molecules or synthesizing new RNA strands. The discovery of ribozymes has provided evidence for the RNA world hypothesis, which suggests that RNA may have played a central role in the early evolution of life on Earth. Therefore, the statement that a ribozyme is a molecule of RNA that has catalytic properties is true.

Explanation

A ribozyme is a type of RNA molecule that can catalyze chemical reactions. Unlike most other enzymes, which are made of proteins, ribozymes are made of RNA. They can perform various functions, such as cleaving RNA molecules or synthesizing new RNA strands. The discovery of ribozymes has provided evidence for the RNA world hypothesis, which suggests that RNA may have played a central role in the early evolution of life on Earth. Therefore, the statement that a ribozyme is a molecule of RNA that has catalytic properties is true.

2. The person who performed an experiment that proved that amino acids could be produced in the laboratory from a reducing atmosphere and electrical sparks was

Stanley Miller.

Graham Cairns-Smith.

Thomas Cech.

Aleksander Oparin.

Sidney Fox.

Stanley Miller is the correct answer because he conducted the famous Miller-Urey experiment in 1953, which demonstrated that amino acids, the building blocks of proteins, could be synthesized in a laboratory setting. In the experiment, Miller simulated the conditions of early Earth by creating a reducing atmosphere of methane, ammonia, and water vapor, and then subjected it to electrical sparks to simulate lightning. This experiment provided evidence for the possibility of organic molecules forming spontaneously on Earth, supporting the theory of chemical evolution and the origin of life.

Explanation

Stanley Miller is the correct answer because he conducted the famous Miller-Urey experiment in 1953, which demonstrated that amino acids, the building blocks of proteins, could be synthesized in a laboratory setting. In the experiment, Miller simulated the conditions of early Earth by creating a reducing atmosphere of methane, ammonia, and water vapor, and then subjected it to electrical sparks to simulate lightning. This experiment provided evidence for the possibility of organic molecules forming spontaneously on Earth, supporting the theory of chemical evolution and the origin of life.

3. Which of the following kinds of molecules is thought to have been absent from the primitive reducing atmosphere?

Water vapor (H2O)

Carbon dioxide (CO2)

Hydrogen (H2)

Oxygen (O2)

Nitrogen (N2)

Oxygen (O2) is thought to have been absent from the primitive reducing atmosphere. This is because the primitive atmosphere was primarily composed of gases such as hydrogen (H2), methane (CH4), ammonia (NH3), and water vapor (H2O). Oxygen is a highly reactive gas and would have been consumed by the oxidation reactions occurring in the early Earth. It was only after the emergence of photosynthetic organisms that oxygen began to accumulate in the atmosphere.

Explanation

Oxygen (O2) is thought to have been absent from the primitive reducing atmosphere. This is because the primitive atmosphere was primarily composed of gases such as hydrogen (H2), methane (CH4), ammonia (NH3), and water vapor (H2O). Oxygen is a highly reactive gas and would have been consumed by the oxidation reactions occurring in the early Earth. It was only after the emergence of photosynthetic organisms that oxygen began to accumulate in the atmosphere.

4. The oxidizing atmosphere probably developed about _____ billion years ago.

1.5

2.5

3.5

4.5

The oxidizing atmosphere probably developed about 2.5 billion years ago. This suggests that at this point in time, there was a significant increase in the presence of oxygen in the Earth's atmosphere. This development is believed to have been a result of the emergence of photosynthetic organisms, such as cyanobacteria, which released oxygen as a byproduct of their metabolic processes. This increase in oxygen had significant implications for the evolution of life on Earth, leading to the development of more complex organisms that rely on oxygen for respiration.

Explanation

The oxidizing atmosphere probably developed about 2.5 billion years ago. This suggests that at this point in time, there was a significant increase in the presence of oxygen in the Earth's atmosphere. This development is believed to have been a result of the emergence of photosynthetic organisms, such as cyanobacteria, which released oxygen as a byproduct of their metabolic processes. This increase in oxygen had significant implications for the evolution of life on Earth, leading to the development of more complex organisms that rely on oxygen for respiration.

5. Which statement is NOT true about the RNA-first hypothesis?

It is supported by the discovery that RNA can act as a catalyst.

It is supported by the fact that some viruses have RNA as their genetic material.

It suggests that there was an "RNA world" about 4 billion years ago.

The RNA-first hypothesis suggests that RNA was the first genetic material and played a crucial role in the development of life on Earth. It is supported by the discovery that RNA can act as a catalyst and the fact that some viruses have RNA as their genetic material. It also proposes the existence of an "RNA world" about 4 billion years ago. However, it does not state that first RNA, then DNA, then proteins would have been necessary to interact in the chemical evolution that led to the development of the first cells. This statement contradicts the RNA-first hypothesis.

Explanation

The RNA-first hypothesis suggests that RNA was the first genetic material and played a crucial role in the development of life on Earth. It is supported by the discovery that RNA can act as a catalyst and the fact that some viruses have RNA as their genetic material. It also proposes the existence of an "RNA world" about 4 billion years ago. However, it does not state that first RNA, then DNA, then proteins would have been necessary to interact in the chemical evolution that led to the development of the first cells. This statement contradicts the RNA-first hypothesis.

6. Which of these would have been most likely to develop only after the formation of a true cell?

Autotroph

Heterotroph

Protocell

Microsphere

Proteinoid

Autotrophs are organisms that can produce their own food through photosynthesis or chemosynthesis. This process requires the presence of a true cell with specialized organelles such as chloroplasts or other structures to carry out photosynthesis. Heterotrophs, protocells, microspheres, and proteinoids are all simpler structures that could have existed before the formation of a true cell. Therefore, autotrophs would have most likely developed only after the formation of a true cell.

Explanation

Autotrophs are organisms that can produce their own food through photosynthesis or chemosynthesis. This process requires the presence of a true cell with specialized organelles such as chloroplasts or other structures to carry out photosynthesis. Heterotrophs, protocells, microspheres, and proteinoids are all simpler structures that could have existed before the formation of a true cell. Therefore, autotrophs would have most likely developed only after the formation of a true cell.

7. Prokaryotic cells are represented by fossils that are dated back as far as _____ billion years ago.

1.5

2.8

3.8

4.8

Prokaryotic cells are represented by fossils that are dated back as far as 3.8 billion years ago. This suggests that prokaryotic life forms were present on Earth at that time, indicating their early evolution and existence. The age of these fossils provides evidence for the ancient origins of prokaryotic cells and their significance in the history of life on Earth.

Explanation

Prokaryotic cells are represented by fossils that are dated back as far as 3.8 billion years ago. This suggests that prokaryotic life forms were present on Earth at that time, indicating their early evolution and existence. The age of these fossils provides evidence for the ancient origins of prokaryotic cells and their significance in the history of life on Earth.

8. The dilemma of whether proteins or nucleic acids directed the first synthesis of the other is avoided by the

Protein-first hypothesis.

RNA-first hypothesis.

Clay-catalyst hypothesis.

The clay-catalyst hypothesis suggests that clay minerals played a crucial role in the first synthesis of proteins and nucleic acids. According to this hypothesis, clay minerals acted as catalysts, facilitating the formation of complex organic molecules from simpler building blocks. This hypothesis avoids the dilemma of whether proteins or nucleic acids came first because it proposes that both were synthesized simultaneously with the help of clay minerals. Therefore, the clay-catalyst hypothesis provides a plausible explanation for the origin of both proteins and nucleic acids without favoring one over the other.

Explanation

The clay-catalyst hypothesis suggests that clay minerals played a crucial role in the first synthesis of proteins and nucleic acids. According to this hypothesis, clay minerals acted as catalysts, facilitating the formation of complex organic molecules from simpler building blocks. This hypothesis avoids the dilemma of whether proteins or nucleic acids came first because it proposes that both were synthesized simultaneously with the help of clay minerals. Therefore, the clay-catalyst hypothesis provides a plausible explanation for the origin of both proteins and nucleic acids without favoring one over the other.