SCSA Biology Science Inquiry Skills
15 sample questions with marking guides and sample answers · Avg. score: 70.9%
Most vinegar flies have wild type (reddish-brown) eyes. However, some mutants have white eyes and cannot see. Biologists conducted a laboratory experiment to compare the fitness of flies with wild type and white eyes.
Which of the following is the best hypothesis for the experiment?
Is there a difference in the fitness of flies with wild type and white eyes?
There is a difference in the fitness of flies with wild type and white eyes.
If flies cannot see, then they will have reduced fitness.
Do flies that cannot see have reduced fitness?
Reveal Answer
Is there a difference in the fitness of flies with wild type and white eyes?
A hypothesis must be a testable statement, not a question. This option represents a research question rather than a hypothesis.
There is a difference in the fitness of flies with wild type and white eyes.
This is the best hypothesis because it is a clear, testable statement that proposes a relationship between the variables being investigated (eye type and fitness).
If flies cannot see, then they will have reduced fitness.
While related to the experiment, this is formatted as a prediction (an "if-then" statement) rather than a formal hypothesis comparing the two specific phenotypes.
Do flies that cannot see have reduced fitness?
Like option A, this is phrased as a question. A scientific hypothesis must be a declarative statement that can be tested.
Most vinegar flies have wild type (reddish-brown) eyes. However, some mutants have white eyes and cannot see. Biologists conducted a laboratory experiment to compare the fitness of flies with wild type and white eyes.
The dependent variable in the experiment is the
laboratory conditions.
eye colour of the flies.
vision of the flies.
fitness of the flies.
Reveal Answer
laboratory conditions.
Laboratory conditions are typically controlled variables that are kept constant throughout the experiment to ensure a fair test, rather than the variable being measured.
eye colour of the flies.
Eye colour is likely the independent variable, which is the specific trait or condition being manipulated or categorized to observe its effects.
vision of the flies.
While vision might be related to eye colour, the dependent variable is the specific overall outcome being measured, which in this context is fitness.
fitness of the flies.
The dependent variable is the outcome that is measured or observed in an experiment. In this case, the fitness of the flies is the measured response to the independent variable.
A computer simulation was used to observe genotypic changes in the gene pool of 20 randomly selected rabbits. The simulation was set with these parameters:
- each rabbit's coat colour was either black or white
- black alleles were dominant; white alleles were recessive
- the number of rabbits was constant in each generation and breeding was random throughout the population
- an environmental factor was chosen in the simulation to provide selection pressure.
The table shows the results of the simulation at the start and after 20 generations.
| Initial population genotypes | Population genotypes after 20 generations |
|---|---|
| BB BB BB BB BB BB | BB BB |
| Bb Bb Bb Bb Bb Bb Bb Bb Bb Bb | Bb Bb Bb Bb Bb Bb Bb Bb |
| bb bb bb bb | bb bb bb bb bb bb bb bb bb bb |
Contrast the initial allele frequency with the allele frequency after 20 generations to draw a conclusion about the effect of the selection pressure on the rabbit population.
Reveal Answer
Initial allelic frequencies were B 0.55 and b 0.45.
Allelic frequencies after 20 generations were B 0.3 and b 0.7.
B decreased (from 0.55 to 0.3) and b increased (from 0.45 to 0.7).
This selection pressure was in favour of white rabbits as both genotype and allelic frequencies shifted toward the white phenotype and the white allele.
| Descriptor | Marks |
|---|---|
Provides the correct initial and final allele frequencies | 1 |
Identifies consequentially correct change in allele frequency | 1 |
States a consequentially valid conclusion | 1 |
The effect of an invasive species on plant biodiversity was investigated by collecting this data from an ecosystem.
| Percentage cover (invasive species) | |||||
|---|---|---|---|---|---|
| 0–20% | >20–40% | >40–60% | >60–80% | >80–100% | |
| Species richness | 7 | 7 | 7 | 4 | 2 |
| Simpson’s diversity index | 0.83 | 0.77 | 0.55 | 0.49 | 0.30 |
Contrast species richness in areas of low invasive species cover (0–20%) with areas of high invasive species cover (>80–100%).
Reveal Answer
Species richness is higher in areas with low invasive species cover (seven different species compared to two).
| Descriptor | Marks |
|---|---|
Identifies species richness is higher in areas with low invasive species cover | 1 |
Draw a conclusion about the effect of the invasive species on plant biodiversity in this ecosystem. Justify your response.
Reveal Answer
The presence of the invasive species has a negative effect on biodiversity. While the same number of species were observed in the area when invasive species cover was 0–60% (7, as indicated by species richness), the SDI decreased from 0.83 to 0.3 as percentage cover increased. This indicates that overall, biodiversity decreased as percentage cover increased.
| Descriptor | Marks |
|---|---|
Identifies a relevant trend in the data | 1 |
Draws a valid conclusion about the effect of the invasive species | 1 |
Explain why having data on species richness and Simpson’s diversity index is more informative than a single measure for the purpose of this investigation. Refer to the table to support your response.
Reveal Answer
Species richness indicates the number of species that can coexist in the area; however, it doesn’t account for the abundance of each species, so one or two species may be dominating. SDI considers the number of species and their relative abundance (evenness), but the number of species is not obvious from the index.
Having both values is more informative because it allows the researcher to identify the number of species in the area (7) and infer evenness from the SDI. For example, the same number of species was present for 0–60% coverage (7), but the evenness was not the same, as the SDI decreased as % coverage got higher.
| Descriptor | Marks |
|---|---|
Recognises species richness is the total number of species present | 1 |
Recognises SDI considers species number and abundance/evenness | 1 |
Uses data to explain why data on species richness and SDI is more informative than a single measure | 1 |
A researcher captured, marked and released 36 frogs. The following day they captured 24 frogs and 18 were marked.
Calculate the approximate size of the frog population using the Lincoln index:
27
48
54
60
Reveal Answer
27
This answer results from incorrectly swapping the values for the total captured in the second sample () and the marked recaptures () in the formula ().
48
Using the Lincoln index formula , substitute the values (initially marked), (total captured second time), and (marked recaptures) to calculate .
54
This incorrect value likely results from simply adding the number of initially marked frogs to the number of marked frogs found in the second sample ().
60
This incorrect value results from adding the number of initially marked frogs to the total number of frogs captured in the second sample () instead of using the multiplication and division required by the formula.
The purpose of a 'control' in an experiment is to
determine the reliability of the experiment.
provide a comparison for the experimental treatment.
reduce the sample sizes needed for the experiment to be valid.
minimise the number of variables to be tested.
Reveal Answer
determine the reliability of the experiment.
Reliability is determined by repeating the experiment multiple times to check for consistent results, rather than by using a control group.
provide a comparison for the experimental treatment.
A control group provides a baseline where the independent variable is not applied, allowing researchers to see the actual effect of the experimental treatment by comparison.
reduce the sample sizes needed for the experiment to be valid.
Using a control group does not reduce the required sample size; in fact, larger sample sizes generally increase the statistical power and validity of an experiment.
minimise the number of variables to be tested.
While researchers keep certain variables constant to isolate the independent variable, the control group itself serves as a baseline for comparison, not a tool to reduce the number of variables.
A survey of grasshopper species was conducted across four eucalypt communities. Counts were conducted and the average abundance per 400 m recorded.
Grasshopper species (A–F)
| Community | A | B | C | D | E | F | Total |
|---|---|---|---|---|---|---|---|
| I | 32 | 18 | 1 | 3 | 0 | 46 | 100 |
| II | 3 | 2 | 0 | 1 | 3 | 12 | 21 |
| III | 3 | 2 | 28 | 3 | 18 | 51 | 105 |
| IV | 18 | 13 | 12 | 14 | 16 | 15 | 88 |
Which community has both the highest species richness and highest evenness for grasshoppers?
I
II
III
IV
Reveal Answer
I
Community I has a species richness of 5 (species E is absent), which is lower than communities III and IV. Additionally, it has low evenness because the population is dominated by species F and A.
II
Community II has a species richness of 5 (species C is absent), which is lower than the maximum richness observed in other communities. It also shows low evenness due to the dominance of species F.
III
Although Community III has the highest species richness (6 species), it has low evenness. The abundance is skewed heavily toward species F (51) and C (28), while other species have very low counts.
IV
Community IV has the highest species richness (all 6 species are present) and the highest evenness. The abundance counts for all species are very similar, ranging tightly between 12 and 18.
In rabbits, black fur is dominant to white fur. A male that is heterozygous for black fur is crossed with a female with white fur, producing 12 offspring.
Predict the number of offspring with white fur. Justify your response using a Punnett square.
Reveal Answer
| B | b | |
|---|---|---|
| b | Bb | bb |
| b | Bb | bb |
50% Bb: heterozygous black fur
50% bb: white fur
0.5 x 12 offspring = 6 white rabbits
| Descriptor | Marks |
|---|---|
identifies parental genotypes | 1 |
provides an appropriate Punnett square | 1 |
predicts number of offspring with white fur | 1 |
Use the following information to answer the question.
A bacterial plasmid was modified by inserting a gene for an enzyme that provides resistance to the antibiotic ampicillin. A nutrient solution containing cells of the bacterium Escherichia coli was obtained. E. coli is naturally sensitive to the antibiotic ampicillin. The solution was divided into two equal volumes. The bacteria in one half of the solution were left untreated. Plasmids were added to the other half of the solution and the bacteria were treated to increase their chance of taking up the plasmids.
The next day, the bacterial cells were spread on agar plates as follows:
- Plate 1 – Untreated bacterial cells on nutrient agar
- Plate 2 – Untreated bacterial cells on nutrient agar with ampicillin
- Plate 3 – Treated bacterial cells on nutrient agar with ampicillin
- Plate 4 – Treated bacterial cells on nutrient agar
The plates were incubated overnight.
In order to collect only bacterial cells that had taken up the plasmid successfully, a sample should be taken from
Plate 1.
Plate 2.
Plate 3.
Plate 4.
Reveal Answer
Plate 1.
Plate 1 contains untreated cells on plain nutrient agar. These cells were never exposed to the plasmid, and all of them will grow, so you cannot collect cells with the plasmid from this plate.
Plate 2.
Plate 2 contains untreated cells on agar with ampicillin. Since the cells naturally lack resistance and were not given the plasmid, no cells will survive or grow on this plate.
Plate 3.
Plate 3 contains treated cells on agar with ampicillin. The ampicillin acts as a selective marker, killing any cells that failed to take up the plasmid and allowing only the successfully transformed, resistant cells to grow.
Plate 4.
Plate 4 contains treated cells on plain nutrient agar. Because there is no ampicillin to kill off the unsuccessful cells, both cells that took up the plasmid and those that did not will grow together.
Allele frequencies were monitored in two large populations of field mice from neighbouring forests over a 10-year period. Results are shown.
Forest X
| Year | Genotype AA | Genotype Aa | Genotype aa | Allele frequency A | Allele frequency a |
|---|---|---|---|---|---|
| 2013 | 52 | 146 | 102 | 0.42 | 0.58 |
| 2014 | 48 | 144 | 108 | 0.40 | 0.60 |
| 2015 | 55 | 147 | 98 | 0.43 | 0.57 |
| 2016 | 60 | 150 | 90 | 0.45 | 0.55 |
| 2017 | 58 | 142 | 100 | 0.43 | 0.57 |
| 2018 | 58 | 148 | 94 | 0.44 | 0.56 |
| 2019 | 59 | 152 | 89 | 0.45 | 0.55 |
| 2020 | 60 | 148 | 92 | 0.45 | 0.55 |
| 2021 | 65 | 149 | 86 | 0.46 | 0.54 |
| 2022 | 66 | 149 | 85 | 0.47 | 0.53 |
Forest Y
| Year | Genotype AA | Genotype Aa | Genotype aa | Allele frequency A | Allele frequency a |
|---|---|---|---|---|---|
| 2013 | 0 | 0 | 300 | 0.00 | 1.00 |
| 2014 | 0 | 0 | 300 | 0.00 | 1.00 |
| 2015 | 0 | 0 | 300 | 0.00 | 1.00 |
| 2016 | 0 | 15 | 285 | 0.03 | 0.98 |
| 2017 | 3 | 46 | 251 | 0.09 | 0.91 |
| 2018 | 14 | 60 | 226 | ||
| 2019 | 31 | 91 | 178 | 0.26 | 0.75 |
| 2020 | 48 | 104 | 148 | 0.33 | 0.67 |
| 2021 | 60 | 122 | 118 | 0.40 | 0.60 |
| 2022 | 66 | 137 | 97 | 0.45 | 0.55 |
Calculate the allele frequencies for forest Y in 2018. Show your working.
Reveal Answer
Frequency (a) =
Frequency (A) =
| Descriptor | Marks |
|---|---|
Provides appropriate working | 1 |
Calculates the frequencies of both alleles | 1 |
Identify temporal trends in allele frequency for forests X and Y and infer reasons for the observed differences.
Reveal Answer
Allele frequencies remained relatively constant in forest X over the 10-year period, with a slight increase in allele A over time. This suggests genetic drift is occurring and the changes are likely due to chance rather than the environment favouring a particular phenotype.
This contrasts with forest Y, where the frequency of allele A increases significantly over time after it first appears in 2016. The allele may have been introduced to forest Y due to migration (mice moving in from a neighbouring forest) or mutation. Either way, it is evident that the allele A provided a selective advantage to mice in forest Y, resulting in its frequency increasing over time.
| Descriptor | Marks |
|---|---|
Identifies allele frequencies remain relatively constant in forest X over time | 1 |
Infers a reason for the temporal change in forest X | 1 |
Identifies allele A first appeared in forest Y in 2016 | 1 |
Infers this is due to migration (gene flow) or mutation | 1 |
Identifies the frequency of allele A increases over time in forest Y | 1 |
Infers allele A provides a selective advantage to mice in forest Y | 1 |
In an experiment investigating the effect of different temperatures on DNA structure, which one of the following is the independent variable?
rate of DNA denaturation
mass of DNA in the sample
number of nucleotide bases in the DNA sequence
temperatures at which the experiment is conducted
Reveal Answer
rate of DNA denaturation
Incorrect. The rate of DNA denaturation is what is being measured as the outcome, making it the dependent variable rather than the independent variable.
mass of DNA in the sample
Incorrect. The mass of DNA is a factor that should be kept constant across all trials to ensure a fair test, making it a controlled variable.
number of nucleotide bases in the DNA sequence
Incorrect. The length and sequence of the DNA should remain constant throughout the experiment, so this represents a controlled variable.
temperatures at which the experiment is conducted
Correct. The independent variable is the factor intentionally manipulated by the experimenter, which in this case is the different temperatures being tested.
The table provides population data for a species of fairy-wren.
| Year | Population on 1st January | Births | Deaths | Immigration | Emigration |
|---|---|---|---|---|---|
| 2022 | 15 200 | 7600 | 4310 | 790 | 24 |
The population growth rate in 2022 was closest to
17%
27%
55%
73%
Reveal Answer
17%
This value is incorrect. It results from miscalculating the net change or using the wrong denominator in the growth rate formula.
27%
The population growth rate is calculated as . Using the data: , which rounds to 27%.
55%
This calculation incorrectly considers only the population inputs (Births + Immigration) divided by the initial population (), failing to subtract deaths and emigration.
73%
This option is incorrect and likely represents the complement of the correct answer (), rather than the actual growth rate.
Use the following information to answer the question.
Populations of the koala (Phascolarctos cinereus) can be found along the eastern coast of Australia. In the late 1800s, habitat destruction and hunting reduced the number of koalas dramatically. In an effort to save the koala from extinction, a small number of individual koalas were introduced to French Island, Victoria. The number of koalas on the island quickly grew. Scientists measured the genetic diversity within the island population and found it to be low when compared to populations of koalas in New South Wales and Queensland.
When completing the research on the French Island koalas, the scientists would have needed to take into account bioethical issues. The scientists were aware that they would need to communicate all results, whether favourable or unfavourable.
Which one of the following principles of bioethics would the scientists be addressing?
non-maleficence
beneficence
integrity
respect
Reveal Answer
non-maleficence
Non-maleficence is the principle of avoiding harm or minimizing harm to subjects, which does not directly relate to the honest reporting of all research results.
beneficence
Beneficence focuses on maximizing benefits and minimizing risks for participants or society, rather than the ethical obligation to report all data honestly.
integrity
Integrity is the bioethical principle that requires the honest reporting of all sources of information and communication of results, regardless of whether they are favourable or unfavourable.
respect
Respect involves considering the intrinsic value of living things and their autonomy or welfare, which is not the principle governing the transparent communication of research findings.
Use the following information to answer the question.
Students investigated the proteins found in several different types of human cells.
Students completed their investigation and analysed their results. They suggested their results were affected by systematic errors.
Systematic errors
result in a spread of readings.
affect the precision of a measurement.
are easy to identify and eliminate.
cause readings to differ from the true value by a consistent amount each time.
Reveal Answer
result in a spread of readings.
Incorrect. Random errors cause a spread or scatter of readings, whereas systematic errors shift all measurements in the same direction.
affect the precision of a measurement.
Incorrect. Systematic errors affect the accuracy of a measurement, while random errors affect its precision.
are easy to identify and eliminate.
Incorrect. Systematic errors are often difficult to identify because the measurements may still appear highly precise despite being consistently inaccurate.
cause readings to differ from the true value by a consistent amount each time.
Correct. By definition, a systematic error consistently shifts all measurements by the same amount and in the same direction from the true value.
The path to human insulin
In the 1970s, recombinant deoxyribonucleic acid methods for cloning and expressing genes in the bacteria Escherichia coli were under intense development. An important question that arose at the time was: Can humans design and chemically synthesise genes that function in bacteria? This question was answered in the late 1970s with the successful expression of human insulin using E. coli. For the first time, this provided a practical source of recombinant human insulin for the treatment of diabetes. Prior to this, insulin was isolated from either cows or pigs.
When recombinant human insulin was first developed, researchers had knowledge of the amino acid sequence and the structure of insulin. Researchers investigated cloning the human insulin gene using plasmids found in E. coli. They knew of the presence of an EcoR1 recognition site (GAATTC) within these plasmids.
When research began, the safety of recombinant plasmids was being actively discussed. Safety regulations were put in place to identify, evaluate, minimise and manage the risks involved. Researchers tested the first recombinant human insulin in cell cultures in the laboratory and in live animals. This was followed by clinical trials where information was gained about the effectiveness and side effects of using this insulin to treat diabetes.
The first recombinant human insulin that was produced and tested established that the use of recombinant plasmids was successful. Facilities were built for recombinant plasmid research and the commercial production of recombinant human insulin. One of insulin’s first researchers, Arthur Riggs, stated, ‘It is interesting to think about how much progress has been made since [the 1970s]. For example, in 2020, the genes for insulin can be made in a few hours by automated instruments, then cloned and expressed by a single person in about a week’.
What is meant by recombinant deoxyribonucleic acid in the context of this article?
Reveal Answer
Human DNA is incorporated with bacterial DNA.
| Descriptor | Marks |
|---|---|
States that human DNA is incorporated with bacterial DNA | 1 |
The article states that the researchers knew the structure of insulin and the amino acid sequence before they created the recombinant human insulin in the laboratory.
How would the researchers have used this information to genetically engineer a human insulin gene and how might this engineered insulin gene have differed from a natural insulin gene isolated from human DNA?
Reveal Answer
Researchers would work backwards from the amino acid sequence to determine the possible mRNA or DNA. The DNA sequence might differ due to the code being redundant or degenerate OR the natural gene would include introns.
| Descriptor | Marks |
|---|---|
States that researchers would work backwards from the amino acid sequence to determine the possible mRNA or DNA | 1 |
States that the DNA sequence might differ due to the code being redundant/degenerate OR the natural gene would include introns | 1 |
Outline the steps that are required for the human insulin gene to be cloned and expressed in bacteria in 2020.
Reveal Answer
A suitable answer was that the steps to clone and express the gene in bacteria are as follows.
- Isolate human insulin gene from human or artificially synthesise human insulin gene from known sequence.
- Insulin gene inserted into plasmid using restriction enzymes to cut and ligases to join to form recombinant plasmid, which are then placed back into bacteria. These bacteria are then grown in culture.
| Descriptor | Marks |
|---|---|
Identifies isolating the human insulin gene from a human or artificially synthesising it from a known sequence | 1 |
Identifies inserting the insulin gene into a plasmid using restriction enzymes to cut and ligases to join, forming a recombinant plasmid | 1 |
Identifies placing recombinant plasmids back into bacteria and growing the bacteria in culture | 1 |
What ethical response would have been expected from the researchers in the 1970s if, during their clinical trials, they discovered that the recombinant human insulin was significantly more effective than using insulin from either cows or pigs?
Reveal Answer
Some suitable ethical responses were:
- Researchers should stop the clinical trial and people who are being given the animal insulin should be offered the more effective recombinant version of the insulin.
- Stop production of insulin from animals to protect their welfare.
- Release information to public to increase informed decision.
| Descriptor | Marks |
|---|---|
Provides a suitable ethical response (e.g., stop the clinical trial and offer the recombinant version to those on animal insulin, stop production from animals to protect welfare, or release information to the public to increase informed decision-making) | 1 |