Question 1

Life is believed to have originated at hydrothermal springs on the ocean floor rather than on or near the surface of Earth. What conditions made the hydrothermal springs the likely place for the beginning of life? Relate the conditions of the early oceans to the likely metabolism of the first cells.

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Question 2

Can gene frequencies change in the absence of selection? Why or why not?

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Question 3

All unicellular organisms belong to the same domain of life.

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Unicellular organisms are found across multiple domains of life, including Bacteria, Archaea, and Eukarya, indicating they do not belong to a single domain.

Question 4

Describe the hydrogen hypothesis and why it is favored over other hypotheses.

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Question 5

Carl Woese was an important figure in microbial classification and changed our understanding of the evolution and diversity of life. What breakthrough did he make that allowed us to infer evolutionary relationships between organisms? What assumptions was his breakthrough based on?

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Question 6

Rhodobacter cells perform photosynthesis in the presence of light and grow heterotrophically in the dark. After being cultured in total darkness for multiple generations, phenotypic and genotypic changes occur. What phenotypic changes occur and what evolutionary processes are driving them?

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Question 7

How does the Black Queen Hypothesis explain the effect of gene deletions on bacterial evolution?

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Question 8

The primary domains were founded based on comparative ribosomal RNA gene sequencing.

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The primary domains of life (Bacteria, Archaea, and Eukarya) were first proposed based on comparative ribosomal RNA gene sequencing. This technique revealed genetic differences among organisms that suggested three distinct lineages of life.

Question 9

What type of methods are used in microbial systematics? Why are multiple methods used to characterize and classify microbial species? Be sure to define the methods and describe the general strengths and weaknesses of each type.

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Question 10

Explain the endosymbiotic theory. What is the evolutionary value of endosymbiosis?

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Question 11

When exposed to UV light, oxygen gas produces ozone gas.

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This is true. Oxygen gas (O2) can be converted into ozone gas (O3) when it comes into contact with ultraviolet (UV) light. This typically occurs in the Earth's stratosphere, where UV radiation from the sun interacts with oxygen molecules to create ozone.

Question 12

Horizontal gene transfer is one plausible explanation as to why organisms in Archaea, Bacteria, and
Eukarya still share so many genes among such distinct domains.

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Horizontal gene transfer, also known as lateral gene transfer, refers to the transfer of genetic material between organisms that are not parent and offspring. This process can occur within the same domain or between different domains of life. As a result, genetic material can be shared among Archaea, Bacteria, and Eukarya, which may explain why these domains still share many genes despite their distinct evolutionary histories.

Question 13

How did cyanobacteria, oxygen, and ozone impact the evolution of eukaryotic cells?

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Question 14

Explain the strengths and limitations of using 16S rRNA for phylogenetic analyses.

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Question 15

Why is the biological species concept useful for Eukarya but not meaningful for Archaea and Bacteria? How are prokaryotic species defined?

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Question 16

Oxygen was a driving factor in the formation of eukaryotic cells.

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Oxygen played a crucial role in the formation of eukaryotic cells through the process of endosymbiosis, where an aerobic prokaryote was engulfed by another prokaryote leading to the evolution of a symbiotic relationship and eventually the development of eukaryotic cells with mitochondria.

Question 17

Approximately 3.7 billion years ago Archaea and Bacteria diverged as being distinct from each other.

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Archaea and Bacteria diverged around 3.7 billion years ago, according to scientific evidence.

Question 18

You have isolated a microbe from an environmental sample. The microbe has the ability to perform a new metabolic reaction at a very low temperature, so you are excited that it could be a new species. What experiments should you perform to determine if your isolate is truly a new species? What process will you follow to officially name your isolate?

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Quiz 13: Microbial Evolution and Systematics