Question 1

The chemical composition of ancient sediments suggests that oxygen was essentially absent from the atmosphere of the early Earth; how can its abundance in today's atmosphere be explained?

Accepted Answer

The production of oxygen as a byproduct of photosynthesis by cyanobacteria and some eukaryotes is the most widely accepted explanation for the increase in atmospheric oxygen levels over time.

Question 2

Because plants lack the ability to directly use the _____ present in the atmosphere, their abundance often depends on bacterial populations present within the soil.

Accepted Answer

Plants require nitrogen to grow, but they are unable to use the nitrogen present in the atmosphere. Instead, they rely on bacterial populations in the soil to convert atmospheric nitrogen into a form that they can use, such as ammonia or nitrates. Without these bacteria, plants would not be able to access the nitrogen they need, which could limit their growth and abundance.

Question 3

Prokaryotes obtain their nutrition in a variety of ways; all of the following methods except _____ have been observed.

Accepted Answer

All of the listed methods are observed in prokaryotes, including consuming other organisms (heterotrophy), acquiring carbon from nonliving sources (autotrophy), and photosynthesis. Prokaryotes are also capable of using noncarbon-based nutritional systems, such as chemosynthesis or lithotrophy, which involve obtaining energy from inorganic substances rather than organic compounds. Therefore, the incorrect statement is that "all of the following methods except using noncarbon-based nutritional systems have been observed."

Question 4

Prokaryotic genomes

Accepted Answer

Prokaryotic genomes are relatively small and contain only DNA that is actively used. Unlike eukaryotic genomes, they do not have much non-coding or junk DNA.

Question 5

Which of the following would you most likely find surviving in a boiling-hot spring?

Accepted Answer

Archaea are known for their ability to survive in extreme environments, such as boiling-hot springs, due to their unique biochemical and structural adaptations.

Question 6

What do these products have in common-soy sauce, yogurt, swiss cheese, and buttermilk?

Accepted Answer

The common factor among these products is that they are all produced through bacterial fermentation. Soy sauce is made from soybeans and wheat that are fermented with a specific type of mold, while yogurt, buttermilk, and Swiss cheese are all fermented with specific strains of bacteria.

Question 7

The photograph below shows Sulfolubus, an archaean that lives in environments with very high temperatures. 
What hypothesis can explain the extreme habitats of the archaeans?

Accepted Answer

The answer of The photograph below shows Sulfolubus, an archaean...

Question 8

The workers shown in the photograph below are involved in bioremediation; what explanation could account for their specific actions?

Accepted Answer

The answer of The workers shown in the photograph below...

Question 9

Prokaryotes differ in several ways from eukaryotes; one of the most distinctive is

Accepted Answer

Prokaryotes lack a true nucleus that encloses the cell's DNA. This distinguishes them from eukaryotes, which have a well-defined nucleus that separates the DNA from the cytoplasm. Prokaryotic DNA is typically arranged in a single circular chromosome that is located in the nucleoid region of the cell.

Question 10

Which of the following terms describes organisms that can survive in extremely salty environments?

Accepted Answer

Halophiles are organisms that can survive in extremely salty environments, such as salt lakes or salt pans. A thermophile is an organism that can survive in very high temperatures, while methanogens are organisms that produce methane gas and can be found in environments such as marshes and sewage treatment plants. Therefore, the correct answer is B) halophiles.

Question 11

Bacterial cells can typically be described by one of the following three shapes:

Accepted Answer

The three basic shapes of bacterial cells are the rod (also known as bacillus), sphere (also known as cocci), and corkscrew (also known as spirillum). The other options listed are not correct as they do not accurately describe the shapes of bacterial cells.

Question 12

The group with the greatest diversity in the strategies used to obtain carbon and energy is the

Accepted Answer

Prokaryotes encompass a wide variety of organisms, including bacteria and archaea, which utilize a vast array of strategies to obtain carbon and energy. Some prokaryotes are autotrophic, obtaining their carbon from inorganic sources such as carbon dioxide, while others are heterotrophic, obtaining their carbon from organic sources such as other organisms or dead organic matter. Prokaryotes also utilize a wide variety of energy sources, including sunlight, organic compounds, and even inorganic compounds such as sulfur or iron. In contrast, the other three groups listed have more limited strategies for obtaining carbon and energy. Fungi and Plantae are mainly photoautotrophic, while Animalia are mainly heterotrophic.

Question 13

What best explains why bacteria can reproduce so much more rapidly than an organism like a mushroom?

Accepted Answer

Mushrooms reproduce sexually, requiring the meeting of compatible mating types, which is a slower process compared to the asexual reproduction of bacteria, allowing bacteria to reproduce more rapidly.

Question 14

A distinguishing difference between bacteria and archaeans is

Accepted Answer

Bacteria have peptidoglycan in their cell walls, while archaeans do not. Instead, archaeans have a variety of different molecules in their cell walls, such as pseudopeptidoglycan, S-layer proteins, or glycoproteins.

Question 15

Which of the following statements about bacteria is false?

Accepted Answer

Bacteria do not have organelles, so their membranes cannot be used to produce medicines. This statement is false.

Question 16

When success is defined as the greatest number of living individuals, Earth's most successful inhabitants are the

Accepted Answer

Bacteria and archaea have been around for billions of years, far longer than any other living organisms on Earth. They also inhabit a wide variety of environments, from the depths of the ocean to the insides of animals, and are incredibly diverse in terms of their genetic makeup and metabolic capabilities. As a result, there are trillions upon trillions of individual bacterial and archaeal cells on Earth at any given time, making them the most successful inhabitants in terms of sheer numbers.

Question 17

In addition to the Bacteria, which other kingdom is comprised exclusively of prokaryotic organisms?

Accepted Answer

The kingdom Archaea is comprised exclusively of prokaryotic organisms, just like the kingdom Bacteria.

Question 18

Microscopic examination can often resolve questions in taxonomy, for example, cells that possess a nucleus are never classified as

Accepted Answer

Cells that possess a nucleus are classified as eukaryotes, hence options A, D are incorrect. Fungi are also eukaryotic organisms, hence option B is incorrect. The only option left is C, which is correct, as archaeans are prokaryotic organisms that lack a true nucleus.

Question 19

Carbon and energy are among the most basic life resources and organisms that have been classified with respect to how they are obtained. What term describes an organism that obtains these substances from rock?

Accepted Answer

Organisms that obtain carbon and energy from inorganic sources through oxidation reactions are called chemoautotrophs. They obtain these substances from sources such as rock or chemicals in the environment. Option A refers to organisms that obtain carbon from organic compounds and energy from chemical reactions, option B refers to organisms that obtain both carbon and energy from sunlight, and option C refers to organisms that obtain carbon from organic compounds and energy from sunlight.

Question 20

Bacteria can be distinguished from most other organisms because

Accepted Answer

Bacterial DNA is not enclosed within a nucleus or any other membrane-bound organelle, which distinguishes them from eukaryotic cells.

Quiz 2: Biological Diversity, Bacteria, and Archaea