Life Science & Scientific Inquiry — Final exam worked answers

Question 1 · 3 points

Illustrative record: Group A receives 10 mL daily and bright light; Group B receives 5 mL and dim light. After seven days, A gains 4 cm and B gains 1 cm. Identify the intended variable, measured outcome, and confound. Propose a fairer comparison and explain what the current data do establish.

Worked answer

The record shows a 3 cm difference in height gain, but both water and light differ. It cannot isolate water’s effect. A revised comparison would keep light, species, starting conditions, and times comparable while changing only the defined water treatment; independent seedlings and recorded variation would strengthen the evidence.

Identify water amount as the intended factor.

Measure height change in centimeters over seven days.

Recognize light as an additional changed factor.

Match light and other conditions, then use several seedlings per group.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 2 · 3 points

Illustrative image record: a 4 cm scale bar represents 200 micrometers; the cell image spans 1.2 cm. A microscope setting lists a 10× eyepiece and a 40× objective. Calculate estimated cell length and total magnification. Explain why these are different quantities and state a calibration assumption.

Worked answer

The cell length is approximately 60 micrometers, and the stated total magnification is 400×. Length describes the specimen estimate; magnification describes image enlargement. Both assume the provided record is correct, and the scale calculation assumes uniform resizing of the cell and bar. Magnification alone does not supply the real cell length.

Find the ratio 1.2/4=0.3.

Multiply 0.3 by 200 micrometers.

Multiply lens factors 10×40.

Check that image and scale bar were resized together.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 3 · 3 points

Illustrative records: Treatment A height gains are 3, 4, and 5 cm; B gains are 1, 4, and 7 cm under the same stated interval. Calculate the means and numerical ranges. Describe one similarity, one difference, and what the summaries cannot establish.

Worked answer

Both means are 4 cm. A’s numerical range is 2 cm; B’s is 6 cm. The means agree but B’s observations are more spread out. These small illustrative sets do not establish why variability differs or whether a treatment caused the pattern. Keep individual records, examine methods, and use more independent observations.

A sum is 12 cm and B sum is 12 cm.

Divide each by three.

Subtract smallest from largest in each set.

Compare spread without inventing a cause.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 4 · 3 points

Illustrative observation: covered soil loses 5 g over a day; uncovered soil loses 12 g in the same setting. Starting water, container, and temperature are stated comparable. A claim says a cover always prevents all evaporation. Write a better claim, cite numerical evidence, explain a plausible mechanism, and identify a limit.

Worked answer

The cover is associated with 7 g less measured water loss in this comparison. Reducing exposed soil can reduce evaporation under comparable conditions, but the covered sample still lost 5 g. The record therefore does not support “all evaporation prevented” or “always.” Repeated matched trials and checks for other loss pathways would strengthen the explanation.

Calculate the measured loss difference: 12−5=7 g.

State reduced loss in the observed setting.

Connect the cover with reduced exposure under the model.

Notice that 5 g was still lost and other settings were not tested.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 5 · 3 points

Illustrative records: A is a seed with cells that later germinates; B is a battery toy that moves; C is a bacterium with a membrane and DNA but no enclosed nucleus. Use several characteristics to classify living status and explain why movement and a nucleus are not sufficient tests.

Worked answer

A and C are living under the supplied records. A’s cellular organization and germination support that conclusion despite its earlier dormancy. C can function without an enclosed nucleus because it is prokaryotic. B’s movement alone does not establish cellular life. The comparison relies on the supplied biological observations, not a rule that every moving object is alive.

Identify cellular organization in A and C.

Use germination as evidence of a seed’s life process.

Separate powered toy motion from cellular activity.

Recognize C as a prokaryotic organism.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 6 · 3 points

Illustrative record: a living cell divides into two cells; each later divides once. A student claims the resulting four cells must be four times the original mass. Use cell theory to explain the number change and evaluate the mass claim.

Worked answer

The sequence fits new cells arising from existing cells and gives four cells after the two division rounds. The mass claim is unsupported: cells can differ in size, and growth requires material uptake. Cell count alone does not establish four times the starting mass. Additional mass or size observations would be needed.

Count one to two to four cells.

Connect new cells with previous cells dividing.

Distinguish cell production from total mass.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 7 · 3 points

Illustrative cell record: the membrane is damaged and substances leak outward; ribosomes remain visible. A draft says visible ribosomes prove the whole cell functions normally. Explain the membrane’s role, evaluate the draft, and identify a useful further observation.

Worked answer

The membrane helps maintain regulated exchanges and internal conditions. Leakage suggests disruption even though ribosomes remain visible. Presence of one structure does not prove normal system function. Measurements of exchange, internal conditions, and cell activity would help assess the extent of damage.

Locate the exchange boundary.

Connect uncontrolled leakage with disrupted internal conditions.

Separate visible presence from measured function.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 8 · 3 points

Illustrative records: A has wall, enclosed nucleus, and chloroplasts; B has wall and DNA without an enclosed nucleus; C has membrane and enclosed nucleus without a wall. Identify categories supported by the combination of features and qualify the conclusions.

Worked answer

A fits the supplied photosynthetic plant model; B fits a prokaryotic cell; C fits a typical animal model. These are supported model comparisons, not a complete identification of species. Other organisms and specialized cells can share selected features, and microscope resolution and sample context matter.

A’s combination fits a photosynthetic plant-cell model.

B’s DNA location fits a prokaryotic model.

C fits a typical animal-cell model but needs sample context.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 9 · 3 points

Illustrative model: equal-pressure compartments A and B start with equal volumes; A has 5 nonpenetrating solute particles per volume unit and B has 10. Water can cross; solute cannot. Predict initial net water movement, identify what crosses, and explain why equilibrium need not mean no motion.

Worked answer

Initial net water movement tends from A toward B under these simplified conditions. Water crosses; the stipulated solute does not. This can change concentrations and pressures, limiting later flow. At equilibrium water molecules can still move both ways even when there is no net change. The conclusion depends on the stated permeability and pressure assumptions.

Compare nonpenetrating solute concentrations.

Apply the stipulated water permeability.

Separate net movement from individual crossings.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 10 · 3 points

Illustrative sealed-chamber data for a short study: carbon dioxide reading begins at 400 units, falls to 350 under light, and rises to 370 during a later dark interval. Readings share one calibrated unit; plant condition and temperature are otherwise stated comparable. Calculate both changes and explain them through net processes without claiming either process was observed directly.

Worked answer

The light interval shows a 50-unit decrease, consistent with net photosynthetic uptake exceeding respiratory release. The dark interval shows a 20-unit increase, consistent with respiration without the same light-driven uptake. These net gas measurements do not separately measure each process; leaks, other organisms, and instrument conditions would need checking in an actual investigation.

Light change: 350−400=−50 units.

Dark change: 370−350=+20 units.

Compare photosynthetic uptake and respiratory release under the model.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 11 · 3 points

Illustrative model: digestion makes small food molecules available; an intestinal surface absorbs them; circulation transports them; muscle cells use materials and energy during contraction. Identify relevant levels of organization and explain why no listed system independently completes the entire process.

Worked answer

The digestive system processes and absorbs food molecules, the circulatory system transports them, and muscle cells use them in cellular work. Organs contain interacting tissues, and tissues contain specialized cells. The pathway connects levels and systems; neither an intestine nor a muscle cell independently performs every step. The diagram is a selected model, not a complete anatomical description.

Identify digestive and circulatory organ-system roles.

Locate exchange surfaces within organs and tissues.

Connect transport to cellular use.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 12 · 3 points

Illustrative comparison: Sample A remains in one large piece; equal-mass Sample B is divided into small pieces. Both experience the same stated enzyme conditions; B breaks down faster. Explain a surface-area mechanism, distinguish observation from inference, and connect digestion with absorption.

Worked answer

Faster breakdown in B is consistent with increased exposed surface for enzyme contact under the stated conditions. The result is evidence about breakdown rate, not proof that absorption or energy use has already occurred. Further measurements could check the products and their passage across an exchange surface. Other changed conditions would weaken the isolated surface-area explanation.

Identify comparable mass and conditions.

Connect smaller pieces with more exposed surface.

Separate breakdown from later boundary crossing.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 13 · 3 points

Illustrative draft: air enters lungs; oxygen then moves directly from lungs to every muscle cell; no vessels or heart are drawn. Repair the pathway, label gas exchanges, and distinguish the pathway from cellular respiration.

Worked answer

Oxygen enters lung air spaces, crosses into blood, is transported through the heart and vessels, and reaches tissues by exchange. Carbon dioxide can follow a return pathway toward lung release. Cellular respiration occurs in cells and uses food and oxygen in the aerobic model; it is not simply the act of breathing. The diagram is simplified and does not show every anatomical detail.

Add lung exchange into blood.

Add heart and transport vessels.

Add tissue exchange and cellular use.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 14 · 3 points

Illustrative paper hinge: String A bends a joint when pulled; String B straightens it when pulled. The hinge and attachments are unchanged. Explain the represented mechanism, connect it with muscles, and state two limits of the analogy.

Worked answer

The strings represent pulls that can rotate the hinge in opposite directions, analogous to coordinated muscle actions. The model does not show nerves, living tissue, energy transfers, changing forces, or exact anatomical scale. It illustrates a mechanical relationship without establishing individual performance or health.

Identify the hinge as a turning point.

Connect each pull with an opposing action.

State missing tissues and cellular processes.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 15 · 3 points

Illustrative processing record for one model interval: 100 water units enter a filtrate; 96 return to the blood pathway; 4 leave through the urine pathway. Check the model balance, calculate the returned fraction, and explain why it is not a real intake recommendation.

Worked answer

The model balances its 100 input units with 100 output units, and 96% return through the stated pathway. It represents selective processing rather than all filtrate being excreted. The numbers are invented for one boundary and interval; they do not describe a person’s whole water budget or prescribe fluid intake.

Add outputs: 96+4=100.

Calculate returned share: 96/100×100%.

Identify the simplified boundary and invented units.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 16 · 3 points

Illustrative timing trials are 0.20, 0.25, and 0.30 seconds for one defined task. A draft labels the mean a complete measure of the person’s intelligence. Calculate mean and range, describe the measured pathway in general, and correct the claim.

Worked answer

Mean response time is 0.25 s and numerical range is 0.10 s. A stimulus-response task involves detection, processing, and action plus measurement conditions. These values cannot establish overall intelligence or health; attention, equipment, and task demands also matter. They describe only the supplied fictional trials.

Mean: 0.75/3=0.25 s.

Range: 0.30−0.20=0.10 s.

Separate the task measure from an unsupported personal conclusion.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 17 · 3 points

Illustrative artificial-system record: a quantity rises from 20 to 24 units; a detector activates an output that lowers it to 21. The stated working range is 19–22 units. Explain the direction of feedback, the final relation to the range, and why these are not human clinical values.

Worked answer

The response opposes the rise, so it represents negative feedback. The final 21 lies within the stated working range. The units and thresholds are invented for an artificial system; they do not evaluate a learner’s body. The model illustrates a relationship while omitting the complexity of living regulation.

Identify the initial rise.

Connect the activated output with the opposing decrease.

Compare 21 with the invented range.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 18 · 3 points

Illustrative model: a response recognizes Symbol A; Symbol B differs; after repeated A exposure the model response begins faster. No clinical records are represented. Explain specific recognition and memory, distinguish the observation from a universal protection claim, and state a model limit.

Worked answer

The model illustrates target-specific recognition and a memory-related faster response to A. It does not establish an identical response to B or guaranteed protection in a real person. Matching symbols simplify molecular interactions and omit many defense pathways. The supplied pattern is educational evidence about the model, not a clinical assessment.

Identify the repeated target A.

Compare response timing under the stated model.

Avoid assigning the same result to B or every real infection.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 19 · 3 points

Illustrative organisms: A produces new individuals from parent tissue without gamete fusion; B begins with fusion of two gametes. A later develops one new mutation. Classify the mechanisms, explain how A can vary, and distinguish offspring production from successful reproduction over a life cycle.

Worked answer

A represents asexual reproduction and B sexual reproduction. A’s new mutation shows that asexual offspring are not guaranteed identical in every detail. The records describe production mechanisms, but later survival and reproductive success depend on development and conditions. More information is needed to compare outcomes, not merely count starting cells.

Identify no fusion in A and fusion in B.

Connect A’s new mutation with variation.

Consider later survival and reproductive stages.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 20 · 3 points

Illustrative seven-day data: Treatment A has 18 germinated seeds of 20; B has 12 of 20. Species and other conditions are stated matched; the treatment is water amount. Calculate both percentages, describe the measured difference, and qualify the claim about lifelong plant success.

Worked answer

A has 90% germination and B 60%, a 30-percentage-point difference in this illustrative comparison. It supports a treatment-related germination question under the matched conditions, but does not establish adult survival, universal species response, or every causal detail. Replicate independent groups and record later growth separately.

A: 18/20×100=90%.

B: 12/20×100=60%.

Difference is 30 percentage points.

Limit the claim to the stipulated germination interval.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 21 · 3 points

Illustrative draft places a chromosome inside one gene and says every body cell with the same DNA performs the same task. Repair the nested relationship and explain cell specialization without inventing separate inherited genomes for every cell type.

Worked answer

Gene regions are parts of chromosome DNA, not containers for whole chromosomes. Cells with broadly similar genetic information can use different portions and develop different structures and roles. The model does not show every gene, product, or interaction, so a shared genome does not imply identical activity in all cells.

Place gene regions along chromosome DNA.

Connect information use with functional products.

Distinguish shared information from identical activity.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 22 · 3 points

Illustrative cell starts with six chromosomes. DNA is copied, corresponding copies separate normally, and the cell forms two daughters. State each daughter’s chromosome count and distinguish DNA copying from permanent doubling of the chromosome set.

Worked answer

Each daughter receives six chromosomes in the stipulated normal model. Replication supplied DNA copies so both receive the set; it does not leave each daughter with twelve chromosomes. The result depends on normal distribution and does not describe every real division error or specialized cell.

Begin with the six-chromosome set.

Represent each as copied before separation.

Distribute one corresponding copy to each daughter.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 23 · 3 points

Illustrative species has eight chromosomes in a diploid body cell, arranged in four pairs. Normal gametes form and two fuse. Find gamete and zygote counts and explain how different gametes can carry different combinations.

Worked answer

Each modeled gamete has four chromosomes; fusion yields a zygote with eight. Different pair distributions and exchanges can produce varied combinations despite equal counts. Equal chromosome count does not imply identical allele versions. The conclusion assumes the stipulated normal diploid life cycle, not every organism’s reproductive arrangement.

Divide the paired set into one per pair: four.

Combine two gamete sets: four plus four equals eight.

Connect distributions with varied inherited combinations.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 24 · 3 points

Illustrative cross: Aa×aa; A is completely dominant and gametes have equal modeled probabilities. List possible genotypes, calculate recessive phenotype probability, and explain why four offspring need not split exactly two and two.

Worked answer

The expected genotype probabilities are 50% Aa and 50% aa; the recessive phenotype probability is 50%. Four independent offspring need not contain exactly two of each. These predictions depend on the fictional single-region model and supplied dominance rule; they are not general predictions for complex human traits.

Aa contributes A or a; aa contributes a.

Combinations are Aa and aa with equal probabilities.

Apply the stipulated phenotype rule and separate probability from count.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 25 · 3 points

Illustrative identical-genotype seedlings: one group receives adequate light and averages 8 cm; another receives low light and averages 5 cm. No sequence change is recorded. Explain the supported environmental comparison and correct a claim that every shorter plant must have acquired a heritable mutation.

Worked answer

The supplied record supports an environmental growth comparison, with a 3 cm mean difference under the stated light conditions. It does not document a sequence change or heritable mutation. Actual causal interpretation still depends on the fairness of the comparison and variation. A trait difference alone cannot establish mutation or transmission to offspring.

Calculate the observed 3 cm mean difference.

Use the stated equal-genotype information.

Separate environmental response from undocumented mutation and transmission.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 26 · 3 points

Illustrative web: grass feeds insects and rabbits; insects and seeds feed mice; mice and rabbits feed foxes. An insect decline is recorded, but other resource counts are missing. Trace one affected pathway and explain why the exact mouse or fox change cannot be determined.

Worked answer

The insect decline can affect the mouse pathway and indirectly foxes, but mice also have seeds and foxes also have rabbits. The web does not give dependence strengths, alternative resource changes, movement, or timing. It supports a conditional mechanism, not an exact population forecast.

Follow insect→mouse→fox under the stated arrows.

Identify seeds as another mouse resource and rabbits as another fox resource.

Request counts, rates, and interval information.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 27 · 3 points

Illustrative energy model: producers provide 2,000 units; first consumers receive 300; second consumers receive 60 during the same interval. Calculate both transfer percentages and explain why the ten-percent shortcut and an energy-destruction claim are wrong.

Worked answer

The two modeled transfers are 15% and 20%. They are not both ten percent. Lower energy reaching the next position does not mean energy was destroyed; organisms use energy and transfer it into other pathways and heat. The model does not give the full separate budget or exact organism counts.

300/2,000×100=15%.

60/300×100=20%.

Identify other energy pathways and the stated boundary.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 28 · 3 points

Illustrative pond interval: rain adds 40 L; runoff adds 20 L; evaporation removes 25 L; outflow removes 15 L. Other pathways are excluded. Calculate storage change, label inputs and outputs, and explain the conservation distinction.

Worked answer

The modeled pond gains 20 L. Rain and runoff are inputs, while evaporation and outflow cross outward. The changing pond amount is consistent with matter conservation because the pond is only one boundary. The result assumes the stated pathways are complete for the interval and does not predict future weather or every real pond exchange.

Inputs: 40+20=60 L.

Outputs: 25+15=40 L.

Change: 60−40=+20 L.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 29 · 3 points

Illustrative dry-material study over the same interval: matched samples each start at 20 g; A ends at 14 g and B at 18 g. Moisture treatment differs; other conditions are stated matched. Calculate mass losses and explain the supported pattern with a boundary limitation.

Worked answer

A shows 6 g loss and B 2 g, so A lost 4 g more in this illustrative comparison. This is consistent with a treatment-related decomposition question under the stated matching. It does not identify every organism or destination of matter. Check replication, dry-mass method, and material transfers before generalizing to every soil.

A loss: 20−14=6 g.

B loss: 20−18=2 g.

Compare dry-mass method and missing destinations.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 30 · 3 points

Illustrative interval: population begins at 50; births add 12; immigration adds 5; deaths remove 8; emigration removes 4. No other pathways are stipulated. Calculate ending count and explain why a before-after count alone cannot identify all pathways.

Worked answer

The modeled population ends at 55, a net increase of five. The same net change could result from other combinations of births, deaths, and movement. Before-after counts alone do not identify the mechanism; pathway observations, boundaries, and detection methods are needed. This model does not establish a permanent habitat capacity.

Gains: 12+5=17.

Losses: 8+4=12.

End: 50+17−12=55.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 31 · 3 points

Illustrative records show plant cover falling from 80% to 50% while herbivore count rises from 10 to 20; drought also occurs. Describe the changes, explain two plausible contributions, and propose evidence that separates them.

Worked answer

Herbivory could reduce cover, while drought could also limit plant growth. The two recorded changes do not isolate either cause. Compare feeding observations, water conditions, and suitable reference plots across repeated intervals. Plant cover and counts are different measures, and the model should not claim a single cause from their association alone.

Cover falls 30 percentage points.

Herbivore count doubles.

Compare feeding effects with drought and a suitable matched observation.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 32 · 3 points

Illustrative equal-effort samples: A has species counts 8,1,1; B has 4,3,3. Both samples include ten individuals and three detected species. Compare richness, total abundance, and distribution without claiming one number proves universal stability.

Worked answer

The samples have equal richness and total count but different distributions. B is more even under the stated observations. These facts do not establish every functional relationship, genetic diversity, or response to future disturbances. Comparable repeated surveys and role-specific evidence would improve a resilience argument.

Richness is three in each.

Total abundance is ten in each.

A is more dominated by one species; B is more evenly distributed.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 33 · 3 points

Illustrative matched-rain model: Area A sends 18 L to surface runoff and Area B 10 L after a vegetation treatment. Starting conditions are stated comparable, but only one trial is supplied. Calculate the difference, explain a plausible pathway, and qualify a universal water-quality claim.

Worked answer

B has 8 L less recorded runoff in this illustrative trial. Vegetation-associated retention or infiltration could contribute under the stated comparison. The record does not establish all causal details, repeated performance, or absence of contaminants. More matched trials and separate water-quality measures are needed for stronger claims.

Difference: 18−10=8 L.

Connect vegetation and soil with possible infiltration or retention.

Separate runoff amount from all water-quality properties and identify the single-trial limit.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 34 · 3 points

Illustrative four 1 m² plots contain 2, 4, 3, and 3 plants of one species. A habitat area is 20 m². Find sample density, calculate an extrapolated count, and state the assumptions that prevent calling it a complete census.

Worked answer

The sample density is 3 plants/m² and the extrapolated count is 60 plants. It is an estimate assuming the plots represent the 20 m² habitat and detection is adequate. Patchiness, omitted zones, or missed plants could change the result. The supplied data do not establish an exact total.

Total count: 12 across 4 m².

Density: 12/4=3 plants/m².

Estimated larger count: 3×20=60.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 35 · 3 points

Illustrative plans within a 100-token budget: A costs 80 and reduces runoff from 20 to 8 L; B costs 60 and reduces it from 20 to 10 L. Both satisfy the same stated space requirement; later maintenance is unknown. Calculate reductions, compare reduction per token, and recommend a feasible option under an explicit criterion with a next test.

Worked answer

A provides the larger total reduction in the model, while B gives a slightly larger reduction per token. Both fit the initial budget. Either can be supported under an explicit priority, but maintenance, repeated performance, and real-setting transfer remain unknown. Recommend a matched repeated test and a maintenance estimate; fictional tokens are not actual prices.

A reduction: 12 L; B: 10 L.

A ratio: 12/80=0.15 L/token; B: 10/60≈0.167 L/token.

Choose using total reduction or cost efficiency and identify maintenance uncertainty.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 36 · 3 points

Illustrative upright undisturbed layers: bottom contains Species A; middle A and B; top B. No numerical ages or complete regional survey are supplied. State relative order, describe detected species patterns, and qualify an extinction claim.

Worked answer

The bottom layer is relatively oldest and the top youngest under the stated assumptions. A is not detected in the top record, while B occurs in middle and top. This local pattern alone does not prove A became extinct everywhere or supply exact dates. Preservation, sampling, and other locations need consideration.

Order bottom before middle before top.

A is detected in lower two; B in upper two.

Separate local non-detection from global extinction.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 37 · 3 points

Illustrative inherited-color model: generation one has 20 dark of 100 beetles; generation two has 50 dark of 100. Dark beetles are harder to detect on the stated ground, and greater reproductive contribution is recorded. Calculate frequencies, explain selection, and state why the evidence is stronger than a color change in one beetle.

Worked answer

The dark variant rises from 20% to 50%, a 30-percentage-point increase. The supplied inheritance and reproductive evidence support selection in this model, with visibility as the proposed mechanism. It concerns population proportions across generations, not one individual choosing a new trait. Real studies would also test other changes and sampling limits.

Frequencies are 20% and 50%.

Increase is 30 percentage points.

Connect inherited variation, visibility, and reproductive contribution across generations.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 38 · 3 points

Illustrative tree: A splits from a lineage before B and C split from each other. No times, branch-length scale, or actual species identities are supplied. Identify the closest pair in the model, explain why C need not descend from living B, and state what timing cannot be inferred.

Worked answer

B and C share the more recent common ancestor in the stated topology. C is not represented as descending from living B; both connect through an ancestral lineage. Exact dates or elapsed times cannot be inferred because no time scale is supplied. The diagram is a hypothesis whose supporting evidence would need examination.

Find the shared B–C node.

Treat living B and C as tips, not parent and child.

Respect the missing time scale.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 39 · 3 points

Illustrative plants: A averages 12 seeds in favorable soil; B averages 9 in poorer soil. A proposal says breeding only A proves an inherited yield improvement. Explain the confound, propose a stronger comparison, and identify a diversity tradeoff.

Worked answer

The observed yield difference does not isolate an inherited advantage because soil differs. Compare parent and offspring performance under suitable matched conditions and independent replicates. Selecting only a narrow group may reduce variation, so measure other outcomes and possible vulnerabilities rather than declaring universal improvement from one trait.

Notice unequal soil conditions.

Compare replicated offspring under matched conditions.

Consider narrowing inherited variation.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.

Question 40 · 3 points

Illustrative inherited-seed model: generation one has 30 of 100 plants with Variant A; generation two has 45 of 100. A contributes more surviving offspring under the stated conditions, but movement and other populations were not measured. Calculate the change, explain a selection mechanism, identify an alternative or limit, and propose a next observation.

Worked answer

Variant A rises from 30% to 45%, a 15-percentage-point increase. Given the supplied inherited trait and greater surviving-offspring contribution, selection is a supported mechanism in this model. Unmeasured movement or sampling can also affect frequencies. Record reproductive outcomes across more generations and compare movement or matched conditions before generalizing beyond this fictional population.

Find frequencies: 30% and 45%.

Change is 15 percentage points.

Connect inheritance and reproductive contribution; examine movement and other evidence.

Marking criteria

• Accurate biological concept or distinction.
• Evidence, calculation, or model connected with an explained claim.
• A correct limitation, assumption, or needed additional observation.