Life Science: Biology — Midterm exam worked answers
Student exam paperAn independent assessment of the core chapters listed below, followed by corrections and discussion.
12 questions · 28 points · suggested 60 minutes
Student instructions
- Suggested time: 60 minutes; allow breaks or accommodations and record them.
- Work independently with a calculator, blank paper and the reference relationships printed in this paper. Grades 9, 11 and 12 may also use the course-linked NYSED reference tables. Use no lesson notes or answer key during an assessed attempt.
- Show reasoning and units for written tasks. All supplied datasets are illustrative; do not present them as measurements you collected.
- Objective items: 1 point each. Written items: 3 points each, one per criterion. A parent or teacher marks the written work; the app never grades an explanation automatically.
- Sample exam: try the whole paper before opening the worked key, then revisit the linked chapters. The sample and final are different papers; this is a course assessment, not an official Regents examination.
Reference relationships
| Relationship or tool | Conditions |
|---|---|
| Cell geometry | Cube area=6L², volume=L³, area/volume=6/L. A geometry model simplifies actual shapes. |
| Genetic probabilities | Specify genotypes and the inheritance model. Each offspring is a probability event; ratios are not guaranteed small-family counts. |
| Population accounting | New population=old+births+immigration−deaths−emigration. |
| Energy transfer | Next-level production=available production×the supplied efficiency, not a universal fixed 10%. |
| Molecular pathways | Replication copies DNA; transcription makes RNA; translation makes polypeptide. Track matter and energy separately. |
Coverage and marks
| Chapter | Questions | Points |
|---|---|---|
| Investigating the Chemistry of Life | 1, 2, 3 | 7 |
| Cells, Membranes & Exchange | 4, 5, 6 | 7 |
| Body Systems, Signals & Homeostasis | 7, 8, 9 | 7 |
| Matter & Energy in Living Systems | 10, 11, 12 | 7 |
Parent / teacher marking guide
- Mark objective answers after submission. Written marks remain pending until a parent or teacher applies the three-point criteria.
- Accept scientifically equivalent wording and valid alternative methods. Award stated method credit for a correct model or substitution even if later arithmetic fails.
- A raw percentage describes this paper only; it is not a validated course grade or a certification. Review chapter-level evidence and the learner’s independent explanations.
- Record support and accommodations, save corrections and reassess with different tasks. Do not count copied solutions as independent mastery.
Question 1 · 1 point
Which type of bond forms when two atoms share a pair of electrons?
- Metallic bond
- Ionic bond
- Covalent bond
- Hydrogen bond
Worked answer
Covalent bond
In a covalent bond, two atoms share a pair of electrons — as oxygen does with two hydrogens in water.
1 point for the correct objective answer; no written-method marks for this item.
Question 2 · 3 points
Three independent reaction rates are 8, 10, and 9 units/min. How should you summarize them?
Worked answer
Mean 9 units/min; observed range 8–10, n = 3.
Mean = (8 + 10 + 9) ÷ 3 = 9 units/min.
Report the observed range, 8–10 units/min, and number of replicates.
Do not infer an exact universal rate from this small group.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Mean = (8 + 10 + 9) ÷ 3 = 9 units/min.
- 1 point: reach a scientifically supported conclusion: Mean 9 units/min; observed range 8–10, n = 3.
Question 3 · 3 points
Evaluate the evidence in this supplied classroom investigation: Investigate Enzyme Activity with Replicates. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
Means are 3, 8, 15, and 1 units/min; ranges are 2–4, 7–9, 14–16, and 0–2. The highest tested mean occurs at 35°C, but the optimum might lie between tested temperatures. High heat can disrupt enzyme structure, yet low activity alone does not prove permanent denaturation. Compare a cooled sample with a fresh control and check other measurement conditions.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.
Question 4 · 1 point
A microscope has a 10× eyepiece and a 40× objective lens. What is the total magnification?
Worked answer
400 ×
Total magnification = eyepiece × objective = 10 × 40 = 400×.
1 point for the correct objective answer; no written-method marks for this item.
Question 5 · 3 points
A bacterium that is truly 0.05 mm long appears 20 mm long through a microscope whose eyepiece magnifies 10×. What is the magnification of the objective lens in use?
Worked answer
The objective lens magnifies 40×. (Check: 10 × 40 = 400×, which matches the 400× found from the sizes.)
Total magnification = apparent size ÷ true size = 20 mm ÷ 0.05 mm = 400×.
Total magnification also equals eyepiece × objective, so objective = total ÷ eyepiece.
objective = 400 ÷ 10 = 40×.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Total magnification = apparent size ÷ true size = 20 mm ÷ 0.05 mm = 400×.
- 1 point: reach a scientifically supported conclusion: The objective lens magnifies 40×. (Check: 10 × 40 = 400×, which matches the 400× found from the sizes.)
Question 6 · 3 points
Evaluate the evidence in this supplied classroom investigation: Interpret Membrane Exchange Data. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
Mean changes are +10%, +2%, and −8%. A linear interpolation places zero around 1.2 model units. This is an estimate for this tissue and method, not an exact measurement of every cell’s contents. Net mass can be affected by solution on the surface, tissue damage, solute movement, and a nonlinear response. Osmosis concerns water movement, not equal movement of all solutes.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.
Question 7 · 1 point
In a negative feedback loop, the response
- permanently raises the set point
- reverses the change and pushes the condition back toward its set point
- amplifies the change until a process finishes
- has no effect on the condition
Worked answer
reverses the change and pushes the condition back toward its set point
Negative feedback counteracts (reverses) the change, restoring the set point — the most common form of homeostatic control.
1 point for the correct objective answer; no written-method marks for this item.
Question 8 · 3 points
A cell needs glucose and oxygen for respiration. Trace their different entry routes.
Worked answer
Different systems supply the reactants; respiration occurs in the cells.
Digestion and absorption supply glucose to circulation.
Ventilation and lung gas exchange supply oxygen to circulation.
Blood carries both toward tissues; exchange delivers them to cells.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: Digestion and absorption supply glucose to circulation.
- 1 point: reach a scientifically supported conclusion: Different systems supply the reactants; respiration occurs in the cells.
Question 9 · 3 points
Evaluate the evidence in this supplied classroom investigation: Evaluate a Feedback Model. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
The condition rises from 90 to 145, the signal rises, and the condition later returns to 90 while the signal decreases. This is consistent with a negative-feedback model. Other changing processes could also contribute. A controlled model test could compare normal versus blocked receptor response with the same input; direct response evidence would strengthen the proposed link.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.
Question 10 · 1 point
Under stated standard biochemical conditions, ATP hydrolysis releases 7.3 kcal/mol. Using that value, how much free energy is released by 5 mol?
Worked answer
36.5 kcal
5 × 7.3 = 36.5 kcal under the stated conditions; actual cellular values depend on conditions.
1 point for the correct objective answer; no written-method marks for this item.
Question 11 · 3 points
An ATP molecule undergoes hydrolysis to ADP and phosphate. Account for phosphates and energy.
Worked answer
Phosphate matter is conserved; the favorable energy change belongs to the whole reaction.
ATP has three phosphate groups; ADP retains two and inorganic phosphate is released.
Water participates in hydrolysis.
The complete reaction can release free energy that supports coupled work.
Marking criteria
- 1 point: identify the appropriate model or mechanism for this task.
- 1 point: show the calculation or evidence in the worked steps: ATP has three phosphate groups; ADP retains two and inorganic phosphate is released.
- 1 point: reach a scientifically supported conclusion: Phosphate matter is conserved; the favorable energy change belongs to the whole reaction.
Question 12 · 3 points
Evaluate the evidence in this supplied classroom investigation: Account for Carbon and Gas Exchange. State a supported claim, cite two specific entries from the dataset, and identify one limitation plus an improvement.
Worked answer
The high-light net change is +5 units/hour. If respiration consumes 3 units/hour as in darkness, estimated gross production is 8 units/hour. Net zero could mean equal production and consumption. Photosynthesis transfers light energy into chemical processes; respiration transfers chemical energy into ATP and heat. If respiration changes in light, the gross estimate must be revised.
Read the column labels and compare entries using their stated units.
Connect the observed pattern to the investigation mechanism, not just a repeated description.
Evaluate the supplied example data; do not claim they establish every real-world case.
Marking criteria
- 1 point: a claim consistent with the supplied dataset and scientific mechanism.
- 1 point: cite and correctly compare at least two specific data entries.
- 1 point: a relevant limitation and improvement addressing it.