3.4.7 Investigating diversity Questions

Specification route: 3.4.7
Question bank: 27 questions
Course stage: AS / Year 12

Sample questions

QUESTION 1 · 3.4.7 · LEVEL 2

Historically, genetic diversity was estimated by comparing the frequency of observable characteristics. What modern techniques are now used for more accurate comparisons?

Comparing the base sequences of DNA or mRNA, and the amino acid sequences of proteins.
Comparing the fossil record and embryological development.
Calculating the species richness and index of diversity using quadrats.
Observing variations in courtship behaviours across populations.

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Modern technology allows us to look at the molecules that actually code for those observable characteristics.

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Answer: Comparing the base sequences of DNA or mRNA, and the amino acid sequences of proteins.

Genetic diversity within, or between species, can be made by comparing: the frequency of measurable or observable characteristics; the base sequence of DNA; the base sequence of mRNA; the amino acid sequence of the proteins.

QUESTION 2 · 3.4.7 · LEVEL 2

When undertaking quantitative investigations of variation within a species, why is it essential to collect data from random samples?

To avoid bias and ensure the data accurately represents the whole population.
To calculate the standard deviation more easily.
To increase the mutation rate within the observed sample.
To guarantee that every single individual in the population is counted.

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If you only measure the tallest plants, your average will not reflect the true population.

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Answer: To avoid bias and ensure the data accurately represents the whole population.

Quantitative investigations of variation within a species involve: collecting data from random samples. Random sampling avoids investigator bias.

QUESTION 3 · 3.4.7 · LEVEL 4

Scientists discover two morphologically identical populations of frogs. They compare the sequence of amino acids in a specific respiratory protein. Why might this protein sequence be identical even if their DNA sequences are slightly different?

Because the genetic code is degenerate; different DNA base triplets can code for the exact same amino acids.
Because amino acid sequences evolve much faster than DNA sequences.
Because mRNA splicing completely standardizes all proteins in eukaryotic organisms.
Because the frogs occupy the exact same environmental niche.

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Multiple 'words' in the DNA dictionary can translate to the same 'meaning' in a protein.

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Answer: Because the genetic code is degenerate; different DNA base triplets can code for the exact same amino acids.

Genetic diversity within, or between species, can be made by comparing... the base sequence of DNA... the amino acid sequence. Due to the degenerate nature of the genetic code, a silent mutation in DNA will not alter the amino acid sequence.

QUESTION 4 · 3.4.7 · LEVEL 5

When comparing two means from normally distributed data, what does it signify if their standard deviations overlap significantly?

It suggests that the difference between the two means is unlikely to be statistically significant.
It proves that the two samples were drawn from entirely completely different species.
It indicates that a mutation has occurred within the sampled populations.
It guarantees that the investigator bias was removed during the sampling process.

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If the spreads overlap a lot, the 'true' mean of both populations could easily be the same number.

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Answer: It suggests that the difference between the two means is unlikely to be statistically significant.

Students should be able to... interpret data relating to similarities and differences in the base sequences of DNA... Standard deviation indicates the spread of data around the mean. If standard deviations overlap heavily, differences in means are likely due to chance.

QUESTION 5 · 3.4.7 · LEVEL 3

A researcher wants to investigate the variation in leaf length of a specific plant species in a field. How can they ensure their sample is truly random to avoid investigator bias?

By laying out a grid using tape measures and using a random number generator to select coordinates for sampling.
By throwing a quadrat randomly over the shoulder and measuring whatever plants it lands on.
By selecting only the plants that look the healthiest and most representative of the species.
By walking in a straight line and measuring every tenth plant encountered.

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Human choice must be completely removed from the selection process.

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Answer: By laying out a grid using tape measures and using a random number generator to select coordinates for sampling.

Quantitative investigations of variation within a species involve: collecting data from random samples. Throwing quadrats is biased (humans influence the throw). Grid coordinates combined with random number generation is strictly objective.

QUESTION 6 · 3.4.7 · LEVEL 3

Why is comparing the base sequence of mRNA often considered more useful than comparing observable characteristics when investigating genetic diversity?

Observable characteristics are often polygenic and highly influenced by the environment, whereas mRNA directly reflects the transcribed genetic code.
Observable characteristics cannot be quantified, whereas mRNA sequences can easily be weighed.
mRNA is completely unaffected by mutations, providing a perfect historical record of the species.
Comparing characteristics requires the death of the organism, whereas mRNA can be extracted non-invasively.

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Looks can be deceiving due to external factors like diet or climate.

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Answer: Observable characteristics are often polygenic and highly influenced by the environment, whereas mRNA directly reflects the transcribed genetic code.

Comparing observable characteristics has limitations because many characteristics are polygenic (coded by multiple genes) and environmental factors can modify them. Direct DNA/mRNA sequencing provides an unambiguous, objective measure of genetic diversity.

QUESTION 7 · 3.4.7 · LEVEL 3

Advances in immunology allow scientists to investigate evolutionary relationships. How is this achieved?

By comparing the cross-reactivity of antibodies with proteins from different species to measure similarity.
By injecting DNA directly into a white blood cell and observing the mutation rate.
By using antibiotics to sequence the genome of different bacterial species.
By counting the number of phagocytes present in a randomly sampled population.

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Proteins have specific 3D shapes. Antibodies bind to specific shapes (antigens).

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Answer: By comparing the cross-reactivity of antibodies with proteins from different species to measure similarity.

Genetic diversity within, or between species, can be made by comparing... immunological comparisons of proteins. Antibodies specific to the proteins of one species will bind strongly to the highly similar proteins of a closely related species.

QUESTION 8 · 3.4.7 · LEVEL 2

When investigating variation, why must data be collected from random samples?

To ensure the sample is representative of the whole population and to eliminate investigator bias.
To deliberately select only the extreme phenotypes for analysis.
To artificially increase the standard deviation of the resulting data.
To ensure that every individual in the population is eventually measured.

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If a researcher chooses where to place a quadrat, they might subconsciously pick areas with more plants.

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Answer: To ensure the sample is representative of the whole population and to eliminate investigator bias.

Quantitative investigations of variation within a species involve: collecting data from random samples. This removes human bias and ensures mathematical reliability.

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