Section 4, Part A

Question 1

Define prokaryote

Answer 1

A member of the domain Bacteria or Archaea; a unicellular organism lacking a nucleus and containing relatively few organelles or cytoskeletal components

Question 2

How do prokaryotes and eukaryotes differ?

Answer 2

• Compared to to prokaryotic cells, most eukaryotic cells are large, have many more organelles, and have a cytoskeleton
• Eukaryotes have a membrane-bound nucleus (prokaryotes do not)
• Multicellularity is rare in Bacteria, nonexistent in Archaea, and has evolved multiple times in Eukarya
• Prokaryotes reproduce asexually via fission, when eukaryotes reproduce asexually they do so via mitosis and cell division; many eukaryotes undergo meiosis and reproduce sexually
  [552-553, 5th ed]

Question 3

What are the oldest fossils? Name them

Answer 3

• 3.5 billion years ago

- Stromatolites, prokaryotic life likely formed in warm hydrothermal vents at the bottom of the ocean [powerpoint]

Question 4

Were the earliest prokaryotic organisms likely to be autotrophic or heterotrophic?

Answer 4

Autotrophic - heterotrophs are dependent on molecules produced by autotrophs [powerpoint]

Question 5

Were the earliest prokaryotic organisms likely to use aerobic cellular respiration as a pathway for harvesting energy? Why or why not?

Answer 5

The first prokaryotic organisms used anaerobic respiration as a pathway for harvesting energy. These organisms evolved before the Earth’s atmosphere became more oxygenated. [page 542, 5th ed]

Question 6

How did the evolution of oxygenic photosynthesis in some prokaryotes dramatically change Earth’s environment? What is the geologic evidence for this change? (Oxygenation) What were the consequences of this change for other prokaryotic organisms?

Answer 6

Oxygen is an efficient electron acceptor, so cellular respiration using oxygen produces more energy. [page 542, 5th ed/powerpoint]

Question 7

Describe stromatolite

Answer 7

A stromatolite is an accreted mass of microorganisms (cyanobacteria) which have grown so closely together that they form a mat. Stromatolites typically form in layers, creating a characteristic stratified look. [http://www.wisegeek.com/what-is-a-stromatolite.htm]

Question 8

What are banded iron formations?

Answer 8

Banded Iron formations occur in Proterozoic rocks, ranging in age from 1.8 to 2.5 billion years old. They are composed of alternating layers of iron-rich material (commonly magnetite) and silica (chert). [http://jersey.uoregon.edu/~mstrick/
RogueComCollege/RCC_Lectures/Banded_Iron.html]

Question 9

Name the first organisms to perform oxygenic photosynthesis. When and where did these first become numerous on Earth?

Answer 9

• Cyanobacteria, which first became numerous in the oceans between 2.5 - 2.7 billion years ago.
• These bacteria were responsible for the change which brought about a high concentration of oxygen in the Earth’s atmosphere.

Question 10

How are the three domains of life related, and which are prokaryotic?

Answer 10

• Bacteria and Archaea are prokaryotic (and usually unicellular), but Archaea are more closely related on the phylogenetic tree to Eukarya. [528, 5th ed]

Question 11

List the differences between Bacteria and Archaea

Answer 11

• Bacteria’s plasma membrane lipids are composed of glycerol bonded to unbranched fatty acids by ester linkages
• Bacteria’s cell walls, when present, contain peptidoglycan
• Archaea’s RNA polymerase is composed of >10 subunits (Bacteria has 5)
• Archaea’s translation is initiated with methionine [Table 29.1, page 529, 5th ed]