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Figure 1 shows the number of possible DNA base sequences for strands of different lengths.
Use Figure 1 to state the number of possible DNA base sequences for a strand of four nucleotide positions.
Use the pattern in Figure 1 to explain how a short DNA molecule can store a large amount of information.
Explain how complementary base pairing, based on hydrogen bonding, allows genetic information to be replicated and expressed.
A research group summarized its estimates for the ages of the first living cells and the last universal common ancestor (LUCA) in Figure 1. The estimates are ranges in Ga, where 1 Ga is one billion years before the present. The estimate for the first living cells was based on fossilized evidence in ancient seafloor hydrothermal-vent precipitates; the estimate for LUCA was based on conserved sequences from genomic analysis.
Using Figure 1, state the estimated age range for each of the first living cells and LUCA.
State the interval in which the two estimates overlap.
State what the fossilized evidence in ancient seafloor hydrothermal-vent precipitates indicates.
State what conserved sequences from genomic analysis indicate about LUCA.
Using Figure 1, state what the age estimates show about the time scale over which life has been evolving.
A botanical team reviewed a classification in which flowering plant species A and B were grouped together because their flowers have a similar shape. The team compared the same 12-base region of DNA in the three species.
| Species pair | Number of base differences |
|---|---|
| A and B | 12 |
| A and C | 2 |
| B and C | 10 |
Identify the pair with the most similar DNA sequences.
Does the DNA evidence support classifying A and B as the closest relatives among these three species? Justify your answer using one comparison from the table.
Suggest why classification based on flower shape could have been misleading.
Researchers record the percentage of beetles in a population with an inherited pale-colour characteristic.
| Generation | Beetles with pale colour / % |
|---|---|
| 1 | 32 |
| 5 | 47 |
One adult beetle develops greater leg-muscle mass through repeated exercise. This change is not passed to its offspring.
Calculate the increase in the percentage of beetles with pale colour from generation 1 to generation 5, in percentage points.
State what is meant by evolution.
Explain why the change in leg-muscle mass in the adult beetle does not count as evolution.
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