IB Diploma · Biology A2.1
IB Biology A2.1: Orig. of cells — Practice Questions & Answers
IB Biology A2.1 Origins of cells HL notes: spontaneous origin of carbon compounds, protocells, RNA world, LUCA, and first cells at hydrothermal vents.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
Which gas was significantly less abundant in early Earth's atmosphere compared to today?
- Oxygen
- Nitrogen
- Carbon dioxide
- Methane
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WhyOxygen was scarce in early Earth's atmosphere and only accumulated later through photosynthesis.
2
Multiple choice
The Miller-Urey experiment demonstrated the formation of:
- Amino acids and other organic molecules.
- Proteins
- Lipids
- Polysaccharides
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WhyThe Miller-Urey experiment showed amino acids and other organic molecules can form from simple gases under early Earth conditions.
3
Multiple choice
Viruses are considered non-living because they lack:
- Independent metabolism
- Genetic material
- Ability to evolve
- The ability to interact with host cell receptors
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WhyViruses are considered non-living because they lack independent metabolism and cannot reproduce without a host cell.
4
Multiple choice
A key challenge in explaining the origin of cells is their:
- Complex structure and self-replication.
- Small size
- Simple structure
- Lack of genetic material
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WhyExplaining cell origins is difficult because cells are highly complex and capable of self-replication.
5
Multiple choice
The formation of vesicles by fatty acids allowed for:
- Compartmentalization of chemical reactions.
- Increased energy production
- Enhanced protein synthesis
- Faster DNA replication
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WhyFatty acid vesicles enclosed reactants, allowing compartmentalisation of chemical reactions in early protocells.
6
Multiple choice
The "RNA world" hypothesis suggests that early life relied on:
- RNA as both genetic material and catalyst.
- DNA as genetic material
- Proteins as catalysts
- Lipids as energy sources
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WhyThe RNA world hypothesis proposes RNA served as both genetic material and catalyst in early life.
7
Multiple choice
Ribozymes demonstrate that RNA can function as:
- Enzymes.
- Storage molecules
- Structural components
- Transport molecules
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WhyRibozymes are catalytic RNA molecules, showing that RNA can act as an enzyme.
8
Multiple choice
The universal genetic code provides evidence for:
- A common ancestor for all life.
- Multiple independent origins of life
- Recent evolution of all organisms
- Rapid genetic divergence
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WhyThe near-universal genetic code shared by all organisms is strong evidence for a common ancestor.
9
Multiple choice
The immense length of time life has evolved on Earth highlights:
- The gradual accumulation of adaptations
- The lack of significant environmental changes over time
- The simplicity of early life forms
- The rapid rate of evolutionary change
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WhyThe vast span of evolutionary time allowed the gradual accumulation of many small adaptations.
10
Multiple choice
Fossil evidence and genomic analysis suggest that the LUCA likely evolved near:
- Hydrothermal vents.
- Terrestrial volcanic regions
- Frozen ice caps
- Terrestrial deserts
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WhyEvidence suggests the last universal common ancestor evolved near hydrothermal vents rich in energy and chemicals.
Key terms in Orig. of cells
Spontaneous formation: The origin of organic carbon compounds by non-biological chemistry, without enzymes, on the early Earth.
Miller–Urey experiment: A 1950s experiment that produced amino acids from a simulated early atmosphere energised by electrical discharge.
Protocell: A simple, membrane-bound compartment that separates an internal environment from its surroundings but is not yet fully living.
Self-assembly: The spontaneous organisation of amphipathic molecules, such as phospholipids, into bilayers and vesicles in water.
Ribozyme: An RNA molecule that acts as a catalyst, speeding up biochemical reactions.
RNA world hypothesis: The proposal that early life used RNA for both information storage and catalysis before DNA and proteins evolved.
LUCA: The last universal common ancestor; the population from which all current life is descended.
Hydrothermal vent: A deep-sea site releasing mineral-rich, energy-bearing fluids, proposed as a setting for the first cells.
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