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What is primarily responsible for the vast number of habitats occupied by microbes compared to larger organisms?
What is the estimated age of the Earth based on meteorite dating?
Which geologic formation provided the first direct evidence of cellular life?
What is considered the first self-replicating entity in the context of the origin of life?
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Which gases were prevalent in Earth's early atmosphere during the origin of life?
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What approach do biologists primarily rely on to reconstruct early life events given the sparse fossil record?
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What concept describes the process of reformulating hypotheses based on new data in microbial evolution?
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Which of the following molecules is not considered essential in the early evolution of cellular life?
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What microbe is considered a candidate for the extant relative of the endosymbiotic cyanobacterium that evolved into chloroplasts?
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Which theory combines the endosymbiotic origin of mitochondria with genome fusion?
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According to the serial endosymbiotic theory (SET), which process is suggested to have developed first?
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What role did anaerobic spirochetes play in the early development of eukaryotes according to the SET?
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What is unique about the cyanobacterium Prochloron regarding its chlorophyll content?
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What significant characteristic does RNA possess that supports the idea of a precellular RNA world?
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What are ribozymes?
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Which statement accurately describes the relationship between RNA and DNA?
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What evidence supports the RNA world hypothesis?
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What role does rRNA play in modern cells?
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What were scientists unable to recreate in experiments simulating early Earth conditions?
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Why do some scientists question the RNA world hypothesis?
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What is the primary function of RNase P discovered in Escherichia coli?
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What was the significance of adding montmorillonite to a solution of nucleotides in 1996?
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Which type of metabolism is believed to be a remnant of ancient life forms?
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Approximately how many years ago did the evolution of cyanobacteria and oxygenic photosynthesis occur?
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What is one key characteristic of mitochondria and chloroplasts that supports the endosymbiotic hypothesis?
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What evidence supports that mitochondria are derived from α-proteobacteria?
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What role did the host cell possibly provide in the endosymbiotic relationship with mitochondria?
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Which of the following components is NOT associated with mitochondria?
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How did the intracellular bacterium contribute to the host cell's survival?
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Study Notes
Microbial Evolution
- Microbial life is very diverse & occupies many more habitats than larger organisms
- Microbial evolution is studied using the scientific method
The Origin of Life
- Earth is 4.5 to 4.6 billion years old, but life may not have existed for the first hundred million years
- The first direct evidence of cellular life was found in South Africa and Australia from around 3.5 billion years ago
- Microbial fossil record is sparse, so scientists rely on indirect evidence
The First Self-Replicating Entity: The RNA World
- The first self-replicating entity was likely simpler than any modern cell
- It likely evolved in a hot, anoxic environment rich in gases like hydrogen, methane, and ammonia
- DNA, RNA, and proteins are the three essential cellular molecules, and RNA is thought to be the first molecule to have both replicative and enzymatic activity
- In 1981, self-splicing RNA was discovered, showing RNA's catalytic activity
- The RNA world hypothesis suggests RNA was the first self-replicating molecule, capable of storage, copy, expression, and enzymatic activity
- RNA may have given rise to double-stranded DNA, which is more stable
- Two pieces of evidence support the RNA world hypothesis: ATP is a ribonucleotide and RNA can regulate gene expression
- Critics argue that the conditions on early Earth would have prevented the stable formation of RNA components like ribose and pyrimidines
Early Cellular Life
- Early cellular life was primitive but complex
- Cells needed to derive energy from harsh, anoxic environments
- FeS-based metabolism seen in some hyperthermophilic archaea may be a remnant of the first form of chemiosmosis
- Photosynthesis evolved early, with evidence of cyanobacteria and oxygenic photosynthesis from 3 billion years ago
- Stromatolites, layered rocks formed by cyanobacteria, provide evidence of early photosynthetic life
The Endosymbiotic Origin of Mitochondria and Chloroplasts
- The endosymbiotic hypothesis is generally accepted as the origin of mitochondria and chloroplasts
- Both organelles have bacterial-like ribosomes and a single, circular chromosome, supporting their bacterial origin
- Mitochondria are believed to have descended from an α-proteobacterium that became engulfed by a precursor cell
- The engulfed bacterium may have provided a function essential to the host cell, like aerobic respiration
- Chloroplasts likely evolved from an endosymbiotic cyanobacterium with Prochloron being a potential candidate
- The serial endosymbiotic theory (SET) proposes that eucaryotes evolved in a series of endosymbiotic steps
- Motility, nuclei, mitochondria, and chloroplasts all evolved through separate endosymbiotic events
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Description
Explore the fascinating journey of microbial life, its evolution, and the origin of life on Earth. This quiz delves into the evidence of early life forms, the RNA world hypothesis, and the role of essential molecules like DNA, RNA, and proteins in evolution. Test your knowledge and understanding of these foundational concepts in biology.
