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Grade 12 · Science · curriculum collection

Grade 12 Science, NGSS domains

8 units for Grade 12 science, organised by NGSS disciplinary core idea domain: Physical Sciences, Life Sciences. Each unit has a short lesson, a practice worksheet and a review worksheet, both with answer keys.

8 units16 worksheets192 questions with answers
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Answer-checked and approved on 29 October 2026

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Aligned by StudyBrix at domain level. Not an official publication of, or endorsed by, the standards' authors. Framework: Next Generation Science Standards.

Units in teaching order

01

PS Physical Sciences

Electricity & circuits

Charge, current, voltage, resistance and electrical power.

Short lesson: Waves and electric circuits

Study guide for Grades 7 to 12: 20 key ideas, including electric current, potential difference and resistance; 3 practice questions.

Voltage is measured across a component; current is measured through a path. Never practise these concepts on household mains wiring.

  • Electric current. The rate at which electric charge passes a point.
  • Potential difference. Energy transferred per unit charge between two points.
  • Resistance. The ratio of potential difference to current for the stated operating conditions.
  • Series circuit. A circuit arrangement with components connected along one current path.

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. A theoretical 4 V ideal source supplies parallel ohmic resistors 39 Ω and 10 Ω. Find total source current. Round to 3 decimal places if needed. Answer in A.

  2. A steady DC device operates at 23 V and 8 A. Find power in W.

  3. A constant current of 9 A flows for 72 s. How much charge passes in C?

  4. Three ideal resistors of 75 Ω, 24 Ω and 48 Ω are in series. Find total resistance in Ω.

  5. Resistors of 19 Ω and 40 Ω are connected in parallel. Find the equivalent resistance in Ω as an exact fraction or integer.

  6. In a theoretical circuit, 16 Ω and 6 Ω are in series across an ideal 20 V source. Find their total electrical power. Round to 3 decimal places if needed. Answer in W.

  7. Two branches are connected in parallel to a battery. The branch currents are 2.3 A and 0.1 A. What current flows through the battery? (Assume ideal wires and an ideal battery.)

  8. An ideal ohmic resistor of 5 Ω carries 5 A. Find the voltage across it in V.

  9. A component has 6 V across it and current 2 A. Find electrical power.

  10. A 12 V ideal source is across a 3 Ω resistor. Find current in that branch.

  11. Waves and electric circuits: which term fits this description? A propagating pattern of electric and magnetic fields that can travel through vacuum.

    1. Diffraction
    2. Electromagnetic wave
    3. Closed circuit
    4. Resonance

  12. Why must the ideal-circuit assumptions be stated?

Answer key
  1. 0.503 A I = V/R₁ + V/R₂ 4/39 + 4/10 = 0.503
  2. 184 W 23 × 8 = 184
  3. 648 C 9 × 72 = 648
  4. 147 Ω 75 + 24 + 48 = 147
  5. 760/59 Ω 19 × 40 / (19 + 40) = 760/59
  6. 18.182 W P = V²/(R₁ + R₂) 20² / (16 + 6) = 18.182
  7. 2.4 A 2.3 + 0.1 = 2.4
  8. 25 V 5 × 5 = 25
  9. 12 W P = VI = 6 × 2 = 12 W.
  10. 4 A I = V/R = 12/3 = 4 A.
  11. Electromagnetic wave Electromagnetic wave: A propagating pattern of electric and magnetic fields that can travel through vacuum.
  12. Real sources, wires and components may have additional resistance or non-ideal behaviour that changes results.
Review worksheet: 12 questions

  1. A theoretical 25 V ideal source supplies parallel ohmic resistors 23 Ω and 32 Ω. Find total source current. Round to 3 decimal places if needed. Answer in A.

  2. A constant current of 4 A flows for 118 s. How much charge passes in C?

  3. A steady DC device operates at 48 V and 11 A. Find power in W.

  4. Resistors of 47 Ω and 48 Ω are connected in parallel. Find the equivalent resistance in Ω as an exact fraction or integer.

  5. Three ideal resistors of 77 Ω, 30 Ω and 58 Ω are in series. Find total resistance in Ω.

  6. In a theoretical circuit, 4 Ω and 11 Ω are in series across an ideal 37 V source. Find their total electrical power. Round to 3 decimal places if needed. Answer in W.

  7. An ideal ohmic resistor of 30 Ω carries 12 A. Find the voltage across it in V.

  8. Two different resistors are in series. The current through the first resistor is 1.3 A. What is the current through the second resistor? (Assume ideal wires and an ideal battery.)

  9. For two positive parallel resistors, equivalent resistance is what?

    1. Always equal to the largest
    2. Less than either branch resistance
    3. Greater than their sum

  10. Waves and electric circuits: which term fits this description? A circuit arrangement with branches connected across the same two nodes.

    1. Closed circuit
    2. Series circuit
    3. Parallel circuit
    4. Sound wave

  11. At fixed resistance, doubling voltage changes power by what factor, and why?

  12. Which unit measures potential difference?

    1. ampere
    2. coulomb
    3. ohm
    4. volt
Answer key
  1. 1.868 A I = V/R₁ + V/R₂ 25/23 + 25/32 = 1.868
  2. 472 C 4 × 118 = 472
  3. 528 W 48 × 11 = 528
  4. 2256/95 Ω 47 × 48 / (47 + 48) = 2256/95
  5. 165 Ω 77 + 30 + 58 = 165
  6. 91.267 W P = V²/(R₁ + R₂) 37² / (4 + 11) = 91.267
  7. 360 V 12 × 30 = 360
  8. 1.3 A Series: the same current, 1.3 A, flows through both.
  9. Less than either branch resistance An extra conducting path increases conductance.
  10. Parallel circuit Parallel circuit: A circuit arrangement with branches connected across the same two nodes.
  11. A factor of four because P = V²/R. Credit the square relationship and the fixed-resistance condition.
  12. volt

Related ready-made worksheets: Grade 12 Electricity & circuits worksheet

02

PS Physical Sciences

Chemistry

Moles, concentration, isotopes, gases and radioactive decay.

Short lesson: Solution dilution

Study guide for Grades 10 to 12: 2 worked examples and 2 practice questions. Solute amount is conserved; V₂ is final solution volume, not added solvent volume.

C₁V₁ = C₂V₂

Solute amount is conserved; V₂ is final solution volume, not added solvent volume.

Worked example

Dilute 130 mL of a 2 mol/L solution to 0.4 mol/L without losing solute. Find the final volume in mL.

2 × 130 ÷ 0.4 = 650

Answer: 650 mL

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. An ideal gas occupies 13 L at 330 K. With pressure and amount fixed, find its volume at 990 K in L.

  2. An ideal decay model starts with 172 mg. What expected mass remains after 2 half-lives, in mg?

  3. Dilute 100 mL of a 1.6 mol/L solution to 0.4 mol/L without losing solute. Find the final volume in mL.

  4. A hypothetical element has isotopes of mass 71 u (15%) and 76 u (85%). Calculate its mean atomic mass in u.

  5. A solution contains 7 mol of solute in a final solution volume of 20 L. Find concentration in mol/L as a fraction or decimal.

  6. A sample has mass 108 g and molar mass 6 g/mol. Find its amount in mol.

  7. Atomic structure and chemical language: which term fits this description? A pure substance made from two or more elements chemically combined in a fixed ratio.

    1. Covalent bond
    2. Proton
    3. Exothermic reaction
    4. Compound

  8. Dilute 100 mL of 0.80 mol/L solution to a final volume of 400 mL. Find the new concentration in mol/L.

  9. An ideal gas occupies 13 L at 290 K. With pressure and amount fixed, find its volume at 580 K in L.

  10. An ideal decay model starts with 96 mg. What expected mass remains after 4 half-lives, in mg?

  11. Dilute 280 mL of a 2.7 mol/L solution to 0.9 mol/L without losing solute. Find the final volume in mL.

  12. A hypothetical element has isotopes of mass 81 u (95%) and 83 u (5%). Calculate its mean atomic mass in u.

Answer key
  1. 39 L 13 × 990 / 330 = 39
  2. 43 mg 172 ÷ 2^2 = 43
  3. 400 mL 1.6 × 100 ÷ 0.4 = 400
  4. 75.25 u 71 × 0.15 + 76 × 0.85 = 75.25
  5. 7/20 mol/L 7/20 = 7/20
  6. 18 mol 108/6 = 18
  7. Compound Compound: A pure substance made from two or more elements chemically combined in a fixed ratio.
  8. 0.2 0.80 × 100/400 = 0.20
  9. 26 L 13 × 580 / 290 = 26
  10. 6 mg 96 ÷ 2^4 = 6
  11. 840 mL 2.7 × 280 ÷ 0.9 = 840
  12. 81.1 u 81 × 0.95 + 83 × 0.05 = 81.1
Review worksheet: 12 questions

  1. An ideal gas occupies 21 L at 320 K. With pressure and amount fixed, find its volume at 640 K in L.

  2. An ideal decay model starts with 52 mg. What expected mass remains after 1 half-lives, in mg?

  3. Dilute 300 mL of a 1.5 mol/L solution to 0.3 mol/L without losing solute. Find the final volume in mL.

  4. A solution contains 30 mol of solute in a final solution volume of 7 L. Find concentration in mol/L as a fraction or decimal.

  5. A hypothetical element has isotopes of mass 22 u (45%) and 24 u (55%). Calculate its mean atomic mass in u.

  6. A sample has mass 576 g and molar mass 36 g/mol. Find its amount in mol.

  7. Atomic structure and chemical language: which term fits this description? An atom or bonded group with a net electric charge.

    1. Electrolyte
    2. Concentration
    3. Molecule
    4. Ion

  8. A 0.50 mol/L solution has volume 0.40 L. How many moles of solute are present?

  9. An ideal gas occupies 10 L at 380 K. With pressure and amount fixed, find its volume at 1140 K in L.

  10. An ideal decay model starts with 752 mg. What expected mass remains after 4 half-lives, in mg?

  11. Dilute 110 mL of a 4.2 mol/L solution to 0.6 mol/L without losing solute. Find the final volume in mL.

  12. A solution contains 10 mol of solute in a final solution volume of 8 L. Find concentration in mol/L as a fraction or decimal.

Answer key
  1. 42 L 21 × 640 / 320 = 42
  2. 26 mg 52 ÷ 2^1 = 26
  3. 1500 mL 1.5 × 300 ÷ 0.3 = 1500
  4. 30/7 mol/L 30/7 = 30/7
  5. 23.1 u 22 × 0.45 + 24 × 0.55 = 23.1
  6. 16 mol 576/36 = 16
  7. Ion Ion: An atom or bonded group with a net electric charge.
  8. 0.2 0.50 × 0.40 = 0.20
  9. 30 L 10 × 1140 / 380 = 30
  10. 47 mg 752 ÷ 2^4 = 47
  11. 770 mL 4.2 × 110 ÷ 0.6 = 770
  12. 5/4 mol/L 10/8 = 5/4

Related ready-made worksheets: Grade 12 Chemistry worksheet

03

PS Physical Sciences

Analytical chemistry

Concentration, titration, chromatography and yield.

Short lesson: Chromatography and evidence

Study guide for Grades 9 to 12: 4 key ideas, including separation, rf and comparison; 2 worked examples and 3 practice questions. Interpret a supplied chromatogram without claiming one spot proves identity.

  • Separation. Components distribute differently between a mobile phase and a stationary phase.
  • Rf. In a planar example, Rf = distance traveled by spot / distance traveled by solvent front from the same origin.
  • Comparison. Rf values are comparable only under matching conditions.
  • Limits. Co-migration is possible, so matching spots alone need not prove identical substances.

Worked example

A spot travels 3.0 cm while the solvent front travels 6.0 cm from the same baseline. Find Rf.

Rf = 3.0/6.0 = 0.50.

Answer: 0.5

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. A 153 g sample is 39% desired substance by mass. Find the desired substance mass. Round to 3 decimal places if needed. Answer in g.

  2. An aqueous solution has concentration 1.3 mol/L. A model aliquot has volume 134 mL. Find the solute amount. Round to 3 decimal places if needed. Answer in mol.

  3. The theoretical dry pure product mass is 92 g; the actual dry pure product mass is 48 g. Find percentage yield. Round to 3 decimal places if needed. Answer in %.

  4. A model solution contains 2.3 mol in a final volume of 0.18 L. Find its molar concentration. Round to 3 decimal places if needed. Answer in mol/L.

  5. A supplied valid-range calibration is S = 4c + 0.5. The signal is 0.9. Find c in the calibration's arbitrary concentration units. Round to 3 decimal places if needed.

  6. Five repeated measurements of the mass of the same sample (g) are: Trial 1 = 7.29; Trial 2 = 6.59; Trial 3 = 6.63; Trial 4 = 6.63; Trial 5 = 6.59. Leave out the outlier (trial 1) and find the mean of the other four. Round to 2 decimal places.

  7. In the supplied complete neutralization equation H₂A + 2OH⁻ → A²⁻ + 2H₂O, how much OH⁻ reacts with 0.09 mol H₂A? Round to 3 decimal places if needed. Answer in mol.

  8. A 68 mL aliquot at 0.9 mol/L is diluted to 136 mL total without reaction or loss. Find the final concentration. Round to 3 decimal places if needed. Answer in mol/L.

  9. Measured from the same origin, a spot travels 27 mm and the solvent front 31 mm. Find Rf. Round to 3 decimal places if needed.

  10. A spot travels 3.0 cm while the solvent front travels 6.0 cm from the same baseline. Find Rf.

  11. For A + 2B → C, 3 mol A and 4 mol B are available. Find the maximum moles of C.

  12. At equivalence, must acid and base volumes always be equal?

    1. No; concentration and stoichiometry also matter.
    2. Yes, by definition.
    3. Only if the glass is clear.
Answer key
  1. 59.67 g component mass = sample mass × purity/100 153 × 39/100 = 59.67
  2. 0.174 mol n = cV; V(L) = V(mL)/1000 1.3 × (134/1000) = 0.174
  3. 52.174 % yield % = actual/theoretical × 100 48/92 × 100 = 52.174
  4. 12.778 mol/L c = n/V 2.3/0.18 = 12.778
  5. 0.1 c = (S − b)/m for S = mc + b (0.9 − 0.5)/4 = 0.1
  6. 6.61 g (6.59 + 6.63 + 6.63 + 6.59) ÷ 4 ≈ 6.61
  7. 0.18 mol H₂A + 2OH⁻ → A²⁻ + 2H₂O; n(OH⁻) = 2n(H₂A) 2 × 0.09 = 0.18
  8. 0.45 mol/L c₂ = c₁V₁/V₂ 0.9 × 68/136 = 0.45
  9. 0.871 Rf = spot distance / solvent-front distance 27/31 = 0.871
  10. 0.5 Rf = 3.0/6.0 = 0.50.
  11. 2 mol B allows 4/2 = 2 mol C; A would allow 3, so B limits.
  12. No; concentration and stoichiometry also matter. Equal reacted moles do not imply equal volumes.
Review worksheet: 12 questions

  1. An aqueous solution has concentration 1 mol/L. A model aliquot has volume 425 mL. Find the solute amount. Round to 3 decimal places if needed. Answer in mol.

  2. A model solution contains 3.3 mol in a final volume of 1.23 L. Find its molar concentration. Round to 3 decimal places if needed. Answer in mol/L.

  3. A supplied valid-range calibration is S = 2c + 0.2. The signal is 3.3. Find c in the calibration's arbitrary concentration units. Round to 3 decimal places if needed.

  4. The theoretical dry pure product mass is 177 g; the actual dry pure product mass is 146 g. Find percentage yield. Round to 3 decimal places if needed. Answer in %.

  5. Five repeated measurements of the mass of the same sample (g) are: Trial 1 = 16.33; Trial 2 = 17.08; Trial 3 = 17.06; Trial 4 = 17.06; Trial 5 = 17.08. Leave out the outlier (trial 1) and find the mean of the other four. Round to 2 decimal places.

  6. Measured from the same origin, a spot travels 1 mm and the solvent front 31 mm. Find Rf. Round to 3 decimal places if needed.

  7. A 298 g sample is 60% desired substance by mass. Find the desired substance mass. Round to 3 decimal places if needed. Answer in g.

  8. A 42 mL aliquot at 0.2 mol/L is diluted to 168 mL total without reaction or loss. Find the final concentration. Round to 3 decimal places if needed. Answer in mol/L.

  9. In the supplied complete neutralization equation H₂A + 2OH⁻ → A²⁻ + 2H₂O, how much OH⁻ reacts with 0.46 mol H₂A? Round to 3 decimal places if needed. Answer in mol.

  10. Does one visible spot prove a sample is pure?

    1. Only if the spot is round.
    2. Not necessarily; components can co-migrate or be undetected.
    3. Yes, always.

  11. Why should actual and theoretical yield use the same product identity and units?

  12. A 1:1 reaction uses 0.004 mol titrant to react with 0.020 L analyte. Find analyte concentration.

Answer key
  1. 0.425 mol n = cV; V(L) = V(mL)/1000 1 × (425/1000) = 0.425
  2. 2.683 mol/L c = n/V 3.3/1.23 = 2.683
  3. 1.55 c = (S − b)/m for S = mc + b (3.3 − 0.2)/2 = 1.55
  4. 82.486 % yield % = actual/theoretical × 100 146/177 × 100 = 82.486
  5. 17.07 g (17.08 + 17.06 + 17.06 + 17.08) ÷ 4 ≈ 17.07
  6. 0.032 Rf = spot distance / solvent-front distance 1/31 = 0.032
  7. 178.8 g component mass = sample mass × purity/100 298 × 60/100 = 178.8
  8. 0.05 mol/L c₂ = c₁V₁/V₂ 0.2 × 42/168 = 0.05
  9. 0.92 mol H₂A + 2OH⁻ → A²⁻ + 2H₂O; n(OH⁻) = 2n(H₂A) 2 × 0.46 = 0.92
  10. Not necessarily; components can co-migrate or be undetected. Method resolution and detection impose limits.
  11. Comparing different substances or quantities gives a meaningless ratio. State the shared comparison basis.
  12. 0.2 mol/L The analyte amount is 0.004 mol; divide by 0.020 L.

Related ready-made worksheets: Grade 12 Analytical chemistry worksheet

04

PS Physical Sciences

Physical chemistry

Energy changes, reaction rates, equilibrium and gases.

Short lesson: Acids, bases and logarithmic pH

Study guide for Grades 9 to 12: 4 key ideas, including brønsted-Lowry, pH and strength; 2 worked examples and 3 practice questions. State the model, temperature and difference between strength and concentration.

  • Brønsted-Lowry. An acid donates a proton and a base accepts one.
  • pH. For dilute idealized aqueous school problems, pH ≈ −log₁₀[H₃O⁺], with concentration in mol/L relative to the standard state.
  • Strength. Strong describes extent of ionization under the stated conditions; concentrated describes amount per volume.
  • Water. At 25 °C in the familiar dilute model, pH + pOH ≈ 14. Neutral pH changes with temperature.

Worked example

A Brønsted-Lowry acid does what?

The definition concerns proton transfer.

Answer: Donates a proton.

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. For A ⇌ B, use Kc = [B]/[A]. Equilibrium concentrations are [A] = 0.8 and [B] = 0.6 mol/L. Find Kc. Round to 3 decimal places if needed.

  2. A reactant concentration decreases from 0.97 to 0.79 mol/L in 5 s. Find its positive average disappearance rate. Round to 3 decimal places if needed. Answer in mol/(L·s).

  3. For one reaction as written, a bond model requires 868 kJ/mol to break bonds and releases 401 kJ/mol on forming bonds. Estimate ΔH. Round to 3 decimal places if needed. Answer in kJ/mol.

  4. An ideal gas has initial pressure 73 kPa and volume 6.5 L. At fixed amount and temperature its volume becomes 6.8 L. Find the new pressure. Round to 3 decimal places if needed. Answer in kPa.

  5. The given standard reduction potentials are 1.35 V for the cathode and -0.46 V for the anode. Find E°cell. Round to 3 decimal places if needed. Answer in V.

  6. In the dilute school model, [H₃O⁺] = 7 × 10^−2 mol/L. Calculate pH. Round to 3 decimal places if needed.

  7. Use PV = nRT and R = 8.314 kPa·L/(mol·K). Find the ideal-gas volume for 1.5 mol at 373 K and 124 kPa. Round to 3 decimal places if needed. Answer in L.

  8. At 25 °C, use the dilute model pH + pOH = 14. A solution has pH 3.2. Find pOH. Round to 3 decimal places if needed.

  9. At fixed temperature, does a catalyst change the equilibrium constant?

    1. Yes, always doubles it.
    2. No.
    3. Only by making matter vanish.

  10. At dynamic equilibrium, what is equal?

    1. All coefficients in the equation.
    2. All reactant and product concentrations.
    3. The forward and reverse rates.

  11. Why should temperature be stated before asserting that neutral water has pH 7?

  12. Why should amounts be recalculated after a significant addition before using the ratio expression?

Answer key
  1. 0.75 Kc = [B]/[A] for A ⇌ B 0.6/0.8 = 0.75
  2. 0.036 mol/(L·s) r = (c₁ − c₂)/Δt (0.97 − 0.79)/5 = 0.036
  3. 467 kJ/mol ΔH ≈ bonds broken − bonds formed 868 − 401 = 467
  4. 69.779 kPa P₂ = P₁V₁/V₂ 73 × 6.5/6.8 = 69.779
  5. 1.81 V E°cell = E°cathode − E°anode 1.35 − (-0.46) = 1.81
  6. 1.155 pH ≈ −log₁₀([H₃O⁺]/(1 mol/L)) 2 − log₁₀(7) = 1.155
  7. 37.514 L V = nRT/P; R = 8.314 kPa·L/(mol·K) 1.5 × 8.314 × 373/124 = 37.514
  8. 10.8 pOH ≈ 14 − pH at 25 °C 14 − 3.2 = 10.8
  9. No. The catalyst changes rates, not the thermodynamic equilibrium constant.
  10. The forward and reverse rates. Equal opposing rates maintain constant macroscopic composition.
  11. Water's ionization constant changes with temperature. Neutral means equal hydronium and hydroxide activities, not universally pH 7.
  12. Added acid or base changes the quantities of the conjugate pair. Initial concentrations need not remain the relevant ratio.
Review worksheet: 12 questions

  1. A reactant concentration decreases from 0.43 to 0.37 mol/L in 17 s. Find its positive average disappearance rate. Round to 3 decimal places if needed. Answer in mol/(L·s).

  2. An ideal gas has initial pressure 118 kPa and volume 2.1 L. At fixed amount and temperature its volume becomes 7.2 L. Find the new pressure. Round to 3 decimal places if needed. Answer in kPa.

  3. The given standard reduction potentials are 0.44 V for the cathode and -0.05 V for the anode. Find E°cell. Round to 3 decimal places if needed. Answer in V.

  4. For one reaction as written, a bond model requires 339 kJ/mol to break bonds and releases 968 kJ/mol on forming bonds. Estimate ΔH. Round to 3 decimal places if needed. Answer in kJ/mol.

  5. For A ⇌ B, use Kc = [B]/[A]. Equilibrium concentrations are [A] = 0.4 and [B] = 4.1 mol/L. Find Kc. Round to 3 decimal places if needed.

  6. Use PV = nRT and R = 8.314 kPa·L/(mol·K). Find the ideal-gas volume for 2.5 mol at 332 K and 93 kPa. Round to 3 decimal places if needed. Answer in L.

  7. At 25 °C, use the dilute model pH + pOH = 14. A solution has pH 7.8. Find pOH. Round to 3 decimal places if needed.

  8. In the dilute school model, [H₃O⁺] = 3 × 10^−5 mol/L. Calculate pH. Round to 3 decimal places if needed.

  9. At 25 °C with pH + pOH = 14, find pOH for pH 5.

  10. Why should pure solids be omitted from the simple K expression in a heterogeneous equilibrium?

  11. A bond-enthalpy model requires 450 kJ/mol to break bonds and releases 610 kJ/mol forming bonds. Estimate ΔH.

  12. Explain why a positive calculated standard cell potential is not a guarantee of a large measured current.

Answer key
  1. 0.004 mol/(L·s) r = (c₁ − c₂)/Δt (0.43 − 0.37)/17 = 0.004
  2. 34.417 kPa P₂ = P₁V₁/V₂ 118 × 2.1/7.2 = 34.417
  3. 0.49 V E°cell = E°cathode − E°anode 0.44 − (-0.05) = 0.49
  4. -629 kJ/mol ΔH ≈ bonds broken − bonds formed 339 − 968 = -629
  5. 10.25 Kc = [B]/[A] for A ⇌ B 4.1/0.4 = 10.25
  6. 74.2 L V = nRT/P; R = 8.314 kPa·L/(mol·K) 2.5 × 8.314 × 332/93 = 74.2
  7. 6.2 pOH ≈ 14 − pH at 25 °C 14 − 7.8 = 6.2
  8. 4.523 pH ≈ −log₁₀([H₃O⁺]/(1 mol/L)) 5 − log₁₀(3) = 4.523
  9. 9 14 − 5 = 9.
  10. Their activity is taken as approximately constant in that model. Do not claim solids are chemically inactive.
  11. -160 kJ/mol 450 − 610 = −160 kJ/mol.
  12. Current also depends on resistance, kinetics, concentrations and cell design. Distinguish thermodynamic tendency from actual operating rate.

Related ready-made worksheets: Grade 12 Physical chemistry worksheet

05

LS Life Sciences

Cells & microscopy

Cells, organelles, microscopes and cell division.

Short lesson: Cell structures and their jobs

Study guide for Grades 9 to 12: 2 worked examples and 2 practice questions. Link each structure to its job.

structure ↔ function · plant cells add wall, chloroplasts, large vacuole · bacteria lack a nucleus

Link each structure to its job. Plant and animal cells share most organelles; prokaryotes such as bacteria have ribosomes and a membrane but no nucleus or membrane-bound organelles.

Worked example

Which structure is found in plant cells but not in animal cells: the cell wall or the cell membrane?

Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.

Answer: the cell wall

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. Why is DNA replication not the same event as cell division?

  2. Which structure is found in plant cells but not in animal cells: the cell wall or the mitochondrion?

    1. the cell wall
    2. the mitochondrion

  3. What separates during mitotic anaphase?

    1. Entire species.
    2. Sister chromatids.
    3. Only all cell membranes.

  4. Which structure does a typical bacterial cell have: the Golgi apparatus or the cell membrane?

    1. the cell membrane
    2. the Golgi apparatus

  5. Which outcome fits the standard role of mitosis in growth and repair?

    1. Creating four gametes in all cases.
    2. Halving chromosome number for every daughter cell.
    3. Producing genetically similar daughter nuclei, apart from mutations.

  6. Which structure is found in plant cells but not in animal cells: the large central vacuole or the nucleus?

    1. the large central vacuole
    2. the nucleus

  7. Does every mature cell divide at the same rate?

    1. Only if cells are the same color.
    2. Yes, all once per hour.
    3. No.

  8. Which structure is found in plant cells but not in animal cells: the cell wall or the nucleus?

    1. the cell wall
    2. the nucleus

  9. Starting with one cell, two complete rounds of division produce how many cells if none die?

  10. Which structure is found in plant cells but not in animal cells: the mitochondrion or the chloroplast?

    1. the mitochondrion
    2. the chloroplast

  11. When is DNA copied for a typical mitotic division?

    1. Before mitosis, during S phase.
    2. Never.
    3. Only after all daughter nuclei have separated.

  12. Which structure is found in plant cells but not in animal cells: the large central vacuole or the cell membrane?

    1. the large central vacuole
    2. the cell membrane
Answer key
  1. Replication copies genetic material; division distributes material into daughter cells. Distinguish copying from physical separation.
  2. the cell wall Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  3. Sister chromatids. Chromatids separate and move toward opposite poles.
  4. the cell membrane Bacteria are prokaryotes: they have ribosomes and a cell membrane but no nucleus, mitochondria or Golgi apparatus.
  5. Producing genetically similar daughter nuclei, apart from mutations. Mitosis differs from the chromosome-reduction process of meiosis.
  6. the large central vacuole Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  7. No. Division rates differ by cell type and conditions.
  8. the cell wall Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  9. 4 Each cell divides into two: one cell becomes two, then those two become four cells.
  10. the chloroplast Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  11. Before mitosis, during S phase. Replication precedes mitotic chromosome separation.
  12. the large central vacuole Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
Review worksheet: 12 questions

  1. Which cell structure gives a plant cell a rigid outer layer for support?

    1. the mitochondrion
    2. the chloroplast
    3. the cell wall
    4. the cell membrane

  2. A diploid parent cell has 8 chromosomes. In the standard mitosis model, how many chromosomes does each daughter nucleus receive?

  3. Which structure does a typical bacterial cell have: the ribosome or the mitochondrion?

    1. the ribosome
    2. the mitochondrion

  4. Why must a question specify whether it counts chromosomes or chromatids after replication?

  5. Which structure does a typical bacterial cell have: the nucleus or the cell membrane?

    1. the cell membrane
    2. the nucleus

  6. Which structure is found in plant cells but not in animal cells: the nucleus or the large central vacuole?

    1. the nucleus
    2. the large central vacuole

  7. Which structure does a typical bacterial cell have: the mitochondrion or the cell membrane?

    1. the mitochondrion
    2. the cell membrane

  8. Which cell structure contains most of the cell’s DNA and controls its activities?

    1. the large central vacuole
    2. the nucleus
    3. the cell wall
    4. the mitochondrion

  9. Which structure is found in plant cells but not in animal cells: the chloroplast or the cell membrane?

    1. the chloroplast
    2. the cell membrane

  10. Which structure is found in plant cells but not in animal cells: the nucleus or the chloroplast?

    1. the chloroplast
    2. the nucleus

  11. Which structure is found in plant cells but not in animal cells: the ribosome or the chloroplast?

    1. the ribosome
    2. the chloroplast

  12. Which structure is found in plant cells but not in animal cells: the chloroplast or the mitochondrion?

    1. the chloroplast
    2. the mitochondrion
Answer key
  1. the cell wall The cell wall gives a plant cell a rigid outer layer for support.
  2. 8 Mitosis preserves the chromosome number in this model.
  3. the ribosome Bacteria are prokaryotes: they have ribosomes and a cell membrane but no nucleus, mitochondria or Golgi apparatus.
  4. A replicated chromosome consists of sister chromatids, so the counts differ by the convention used. The counting unit and stage must be clear.
  5. the cell membrane Bacteria are prokaryotes: they have ribosomes and a cell membrane but no nucleus, mitochondria or Golgi apparatus.
  6. the large central vacuole Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  7. the cell membrane Bacteria are prokaryotes: they have ribosomes and a cell membrane but no nucleus, mitochondria or Golgi apparatus.
  8. the nucleus The nucleus contains most of the cell’s DNA and controls its activities.
  9. the chloroplast Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  10. the chloroplast Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  11. the chloroplast Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
  12. the chloroplast Cell walls, chloroplasts and a large central vacuole are typical of plant cells; both plant and animal cells have a nucleus, mitochondria, ribosomes and a cell membrane.
06

LS Life Sciences

Human biology & physiology

Body systems: breathing, circulation, digestion and control.

Short lesson: Homeostasis and negative feedback

Study guide for Grades 9 to 12: 4 key ideas, including homeostasis, feedback and pathway; 2 worked examples and 3 practice questions. Describe regulation as a dynamic process, not a perfectly fixed value.

  • Homeostasis. Internal conditions are regulated within workable ranges despite changes.
  • Feedback. Negative feedback tends to counter a deviation from a regulated state.
  • Pathway. A simple control model includes a sensor, a coordinating process and an effector.
  • Limits. Feedback models simplify physiology and are not diagnostic tools.

Worked example

What does negative feedback tend to do?

The response reduces the triggering difference in a simple control model.

Answer: Counter a deviation.

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. A supplied fictional chart shows response level 3 units initially and 12 later. What is the factor increase?

  2. A fictional circulation model has 81 beats/min and 44 mL/beat. Find its flow in mL/min. These are supplied model values, not diagnostic ranges. Round to 3 decimal places if needed. Answer in mL/min.

  3. Why can a delay in feedback produce overshoot?

  4. Why is saying all hormonal responses are slow too absolute?

  5. What does an antibody bind in the simplified model?

    1. A matching antigenic feature.
    2. Only air molecules in all cases.
    3. Any object regardless of structure.

  6. A fictional circulation model has 87 beats/min and 63 mL/beat. Find its flow in mL/min. These are supplied model values, not diagnostic ranges. Round to 3 decimal places if needed. Answer in mL/min.

  7. Why should a thermostat analogy not be treated as a complete model of human physiology?

  8. Why does a hormone not produce the same response in every cell it passes?

    1. Cells differ in receptors and response machinery.
    2. Blood never reaches tissues.
    3. Hormones choose morally better cells.

  9. Which is an example of a physical barrier in innate defense?

    1. Only a worksheet score.
    2. Intact skin.
    3. Only a memory antibody.

  10. A fictional circulation model has 60 beats/min and 42 mL/beat. Find its flow in mL/min. These are supplied model values, not diagnostic ranges. Round to 3 decimal places if needed. Answer in mL/min.

  11. Why is a classroom blood-glucose example not a personal medical instruction?

  12. A supplied signal travels 12 distance units in 3 time units. Find its average model speed.

Answer key
  1. 4 12/3 = 4; these units are model data, not clinical interpretation.
  2. 3564 mL/min flow = beats per minute × volume per beat 81 × 44 = 3564
  3. A response may continue after the system has approached its target because information or effects are delayed. A causal explanation is needed.
  4. Hormones differ in mechanisms and response timing. The textbook contrast is a generalization, not a universal law.
  5. A matching antigenic feature. Binding depends on molecular compatibility.
  6. 5481 mL/min flow = beats per minute × volume per beat 87 × 63 = 5481
  7. Real organisms have interacting signals, changing conditions and multiple control pathways. Analogies illuminate some features but omit others.
  8. Cells differ in receptors and response machinery. Target-cell properties determine response.
  9. Intact skin. Skin is one component of barrier protection.
  10. 2520 mL/min flow = beats per minute × volume per beat 60 × 42 = 2520
  11. It cannot account for an individual's condition, medicines or clinical measurements. Keep the learning model distinct from care decisions.
  12. 4 12/3 = 4 distance units per time unit.
Review worksheet: 12 questions

  1. A fictional circulation model has 84 beats/min and 87 mL/beat. Find its flow in mL/min. These are supplied model values, not diagnostic ranges. Round to 3 decimal places if needed. Answer in mL/min.

  2. Does homeostasis mean every internal value is exactly constant?

    1. Yes, with no fluctuations.
    2. No; regulation operates within ranges.
    3. Only because cells stop working.

  3. Which statement is accurate?

    1. Hormones are conscious decisions.
    2. Only neurons contain chemicals.
    3. Both nervous and endocrine signaling depend on molecular interactions.

  4. Which is the more accurate description?

    1. Innate and adaptive components interact.
    2. The two systems can never communicate.
    3. Only one cell type handles every defense.

  5. A fictional circulation model has 99 beats/min and 80 mL/beat. Find its flow in mL/min. These are supplied model values, not diagnostic ranges. Round to 3 decimal places if needed. Answer in mL/min.

  6. Which would fit a simple negative-feedback response to an increase?

    1. No relation to the measured quantity.
    2. A response always doubling the increase.
    3. A response tending to decrease the regulated quantity.

  7. Why does an organism benefit from coordinating responses across tissues?

  8. Which feature is associated with adaptive immunity?

    1. Only external bones.
    2. No interaction with antigens.
    3. Specific recognition and memory.

  9. A fictional circulation model has 95 beats/min and 67 mL/beat. Find its flow in mL/min. These are supplied model values, not diagnostic ranges. Round to 3 decimal places if needed. Answer in mL/min.

  10. A supplied control model has target 10 units and measurement 13 units. What is measurement minus target?

  11. What is a synapse in a basic nervous-system model?

    1. A junction where a neuron communicates with another cell.
    2. Only a bone connection.
    3. A whole organ with no cells.

  12. Does immune memory mean an organism can never become ill again?

    1. Yes, without exceptions.
    2. No.
    3. Only after any one exposure.
Answer key
  1. 7308 mL/min flow = beats per minute × volume per beat 84 × 87 = 7308
  2. No; regulation operates within ranges. Biological values vary while being regulated.
  3. Both nervous and endocrine signaling depend on molecular interactions. All biological signaling has a physical and chemical basis.
  4. Innate and adaptive components interact. Immune responses involve coordinated components.
  5. 7920 mL/min flow = beats per minute × volume per beat 99 × 80 = 7920
  6. A response tending to decrease the regulated quantity. The response opposes the deviation in this simplified case.
  7. Different tissues can adjust their activities to changing conditions together. Avoid purpose-only language without explaining coordination.
  8. Specific recognition and memory. Adaptive responses can change after prior exposure.
  9. 6365 mL/min flow = beats per minute × volume per beat 95 × 67 = 6365
  10. 3 13 − 10 = +3 units.
  11. A junction where a neuron communicates with another cell. Synapses mediate communication between cells.
  12. No. Protection depends on many biological factors and can be incomplete.

Related ready-made worksheets: Grade 12 Human biology & physiology worksheet

07

LS Life Sciences

Genetics & inheritance

DNA, inheritance, genotypes and variation.

Short lesson: Meiosis and chromosome sets

Study guide for Grades 9 to 12: 4 key ideas, including reduction, divisions and variation; 2 worked examples and 3 practice questions. Track sets of chromosomes rather than assuming gametes are identical.

  • Reduction. Meiosis reduces chromosome-set number in the usual diploid-to-haploid model.
  • Divisions. One DNA replication is followed by two division stages.
  • Variation. Crossing over and independent assortment can create different genetic combinations.
  • Fertilization. Fusion of haploid gametes can restore the diploid chromosome number.

Worked example

A diploid cell has 12 chromosomes. In the standard model, how many are in a haploid gamete?

Half of 12 is 6.

Answer: 6

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. What separates in meiosis I in the standard model?

    1. Only cell-wall layers.
    2. All sister chromatids in the same way as meiosis II.
    3. Homologous chromosomes.

  2. Using base-pairing rules, which sequence pairs with the DNA strand TGTTGAC, read base by base in the same order?

    1. ACACCTG
    2. ACAACTG
    3. ACAACUG
    4. TGTTGAC

  3. A fictional diploid organism has 60 chromosomes in a normal somatic nucleus. In the standard meiosis model, how many chromosomes are in a haploid gamete? Round to 3 decimal places if needed.

  4. In the simple Aa × Aa inheritance model with independent outcomes, the probability of aa is 1/4. Among 264 offspring, find the expected aa count, not a guaranteed outcome. Round to 3 decimal places if needed.

  5. In a canonical double-stranded DNA sample, adenine is 6% of all bases. Find the guanine percentage, assuming A = T and C = G. Round to 3 decimal places if needed. Answer in %.

  6. In pea plants, the allele for a tall stem (T) is dominant over the allele for a short stem (t). Two plants, tt × tt, are crossed. What percentage of the offspring are expected to show a tall stem?

  7. Which process produces RNA using DNA information?

    1. Translation.
    2. Transcription.
    3. Osmosis.

  8. A stated model has red RR, white WW and pink RW flowers. What pattern is described?

    1. Complete dominance of red.
    2. Incomplete dominance.
    3. No inheritance.

  9. For Aa × aa, what fraction is expected to be heterozygous?

  10. In meiosis II, what usually separates?

    1. Homologous species.
    2. Sister chromatids.
    3. Only all mitochondria.

  11. Using base-pairing rules, which sequence pairs with the DNA strand TTCATC, read base by base in the same order?

    1. AAGAAG
    2. AAGUAG
    3. AAGTAG
    4. TTCATC

  12. A fictional diploid organism has 88 chromosomes in a normal somatic nucleus. In the standard meiosis model, how many chromosomes are in a haploid gamete? Round to 3 decimal places if needed.

Answer key
  1. Homologous chromosomes. The first division separates homologous pairs.
  2. ACAACTG TGTTGAC → ACAACTG (A-T, C-G)
  3. 30 haploid chromosome count = diploid count/2 60/2 = 30
  4. 66 expected aa count = offspring count × 1/4 264 × 1/4 = 66
  5. 44 % G% = (100 − 2A%)/2 (100 − 2 × 6)/2 = 44
  6. 0 % tt × tt → tt, tt, tt, tt → 0/4 = 0%
  7. Transcription. Transcription copies sequence information into RNA.
  8. Incomplete dominance. The heterozygote has an intermediate phenotype.
  9. 1/2 The first parent contributes A in half the gametes; the second contributes a.
  10. Sister chromatids. The second division separates sister chromatids.
  11. AAGTAG TTCATC → AAGTAG (A-T, C-G)
  12. 44 haploid chromosome count = diploid count/2 88/2 = 44
Review worksheet: 12 questions

  1. In the simple Aa × Aa inheritance model with independent outcomes, the probability of aa is 1/4. Among 760 offspring, find the expected aa count, not a guaranteed outcome. Round to 3 decimal places if needed.

  2. In a canonical double-stranded DNA sample, adenine is 28% of all bases. Find the guanine percentage, assuming A = T and C = G. Round to 3 decimal places if needed. Answer in %.

  3. In pea plants, the allele for yellow seeds (Y) is dominant over the allele for green seeds (y). Two plants, YY × Yy, are crossed. What percentage of the offspring are expected to have the genotype Yy?

  4. Using base-pairing rules, which sequence pairs with the DNA strand CTCGAA, read base by base in the same order?

    1. GAGCTG
    2. GAGCUU
    3. CTCGAA
    4. GAGCTT

  5. A fictional diploid organism has 98 chromosomes in a normal somatic nucleus. In the standard meiosis model, how many chromosomes are in a haploid gamete? Round to 3 decimal places if needed.

  6. For RW × RW in that flower model, what percentage is expected to be pink?

  7. Why can the same gene be present in two cell types while their protein production differs?

  8. Why must the organism or chromosome number be stated before solving a gamete-count question?

  9. In a stated complete-dominance model, which genotype is heterozygous?

    1. Aa.
    2. AA.
    3. aa.

  10. In the simple Aa × Aa inheritance model with independent outcomes, the probability of aa is 1/4. Among 252 offspring, find the expected aa count, not a guaranteed outcome. Round to 3 decimal places if needed.

  11. In a canonical double-stranded DNA sample, adenine is 16% of all bases. Find the guanine percentage, assuming A = T and C = G. Round to 3 decimal places if needed. Answer in %.

  12. In pea plants, the allele for yellow seeds (Y) is dominant over the allele for green seeds (y). Two plants, YY × Yy, are crossed. What percentage of the offspring are expected to have the genotype YY?

Answer key
  1. 190 expected aa count = offspring count × 1/4 760 × 1/4 = 190
  2. 22 % G% = (100 − 2A%)/2 (100 − 2 × 28)/2 = 22
  3. 50 % YY × Yy → YY, Yy, YY, Yy → 2/4 = 50%
  4. GAGCTT CTCGAA → GAGCTT (A-T, C-G)
  5. 49 haploid chromosome count = diploid count/2 98/2 = 49
  6. 50 % Two of four equally likely genotype combinations are RW.
  7. Gene expression can be regulated differently in each cell type. Presence of a gene is not identical to its expression level.
  8. Different species have different chromosome complements. A human number cannot be silently applied to every organism.
  9. Aa. Heterozygous means two different alleles at the locus.
  10. 63 expected aa count = offspring count × 1/4 252 × 1/4 = 63
  11. 34 % G% = (100 − 2A%)/2 (100 − 2 × 16)/2 = 34
  12. 50 % YY × Yy → YY, Yy, YY, Yy → 2/4 = 50%

Related ready-made worksheets: Grade 12 Genetics & inheritance worksheet

08

LS Life Sciences

Ecology & populations

Ecosystems, food webs, populations and biodiversity.

Short lesson: Population change and carrying capacity

Study guide for Grades 9 to 12: 4 key ideas, including balance, limits and carrying capacity; 2 worked examples and 3 practice questions. Use births, deaths and movement as separate terms.

  • Balance. Population change = births + immigration − deaths − emigration over the stated interval.
  • Limits. Resources and interactions can constrain growth; growth is not indefinitely exponential in a finite environment.
  • Carrying capacity. Carrying capacity is a model-dependent environmental support level, not an eternally fixed number.
  • Data. A change in count can reflect detection differences as well as real demographic change.

Worked example

A model starts with 100 organisms, has 20 births, 5 immigrants, 10 deaths and 3 emigrants. Find the final population.

100 + 20 + 5 − 10 − 3 = 112.

Answer: 112

Read the full study guide

Worksheets

A practice worksheet and a review worksheet, 12 and 12 questions.

Worksheets (PDF)Answer keys (PDF)
Practice worksheet: 12 questions

  1. A fictional population starts at 735. During one interval: 15 births, 32 arrivals, 27 deaths and 17 departures. Find the final count. Round to 3 decimal places if needed.

  2. Supplied fictional records give M = 25 initially marked, C = 57 in a later sample, and R = 16 marked in that sample. Use N ≈ MC/R under the stated assumptions. No animals are to be handled. Round to 3 decimal places if needed.

  3. In this simplified food chain: algae → zooplankton → herring → seal. What is the role of “algae” in this chain?

    1. quaternary consumer
    2. tertiary consumer
    3. primary consumer
    4. producer

  4. Why is unlimited exponential growth unrealistic in a finite habitat?

    1. Organisms contain no matter.
    2. Mathematics never models biology.
    3. Resources and other constraints become important.

  5. A fictional population starts at 279. During one interval: 55 births, 2 arrivals, 34 deaths and 29 departures. Find the final count. Round to 3 decimal places if needed.

  6. Supplied fictional records give M = 49 initially marked, C = 96 in a later sample, and R = 17 marked in that sample. Use N ≈ MC/R under the stated assumptions. No animals are to be handled. Round to 3 decimal places if needed.

  7. In this simplified food chain: algae → zooplankton → herring → seal. If the population of “herring” suddenly drops, what is the most likely short-term effect on the population of “seal”?

    1. It will most likely increase.
    2. It will most likely decrease.
    3. It will not be affected at all.

  8. What does emigration mean?

    1. Every birth.
    2. Entering it.
    3. Leaving the population area.

  9. A fictional population starts at 431. During one interval: 18 births, 22 arrivals, 57 deaths and 38 departures. Find the final count. Round to 3 decimal places if needed.

  10. Supplied fictional records give M = 32 initially marked, C = 52 in a later sample, and R = 18 marked in that sample. Use N ≈ MC/R under the stated assumptions. No animals are to be handled. Round to 3 decimal places if needed.

  11. In this simplified food chain: willow shrubs → moose → wolf. At which trophic level is “willow shrubs”? (Producers are level 1.)

  12. Births plus immigration total 30 and deaths plus emigration total 45. What is net change?

Answer key
  1. 738 N₂ = N₁ + births + immigration − deaths − emigration 735 + 15 + 32 − 27 − 17 = 738
  2. 89.063 N ≈ MC/R 25 × 57/16 = 89.063
  3. producer Level 1 in this chain: producer.
  4. Resources and other constraints become important. Finite resources and interactions limit growth.
  5. 273 N₂ = N₁ + births + immigration − deaths − emigration 279 + 55 + 2 − 34 − 29 = 273
  6. 276.706 N ≈ MC/R 49 × 96/17 = 276.706
  7. It will most likely decrease. With less food available, the predator population is likely to decrease.
  8. Leaving the population area. Emigration is outward movement.
  9. 376 N₂ = N₁ + births + immigration − deaths − emigration 431 + 18 + 22 − 57 − 38 = 376
  10. 92.444 N ≈ MC/R 32 × 52/18 = 92.444
  11. 1 Count from the producer: willow shrubs → moose → wolf.
  12. -15 30 − 45 = −15 individuals.
Review worksheet: 12 questions

  1. A fictional population starts at 769. During one interval: 29 births, 28 arrivals, 52 deaths and 13 departures. Find the final count. Round to 3 decimal places if needed.

  2. Supplied fictional records give M = 75 initially marked, C = 84 in a later sample, and R = 11 marked in that sample. Use N ≈ MC/R under the stated assumptions. No animals are to be handled. Round to 3 decimal places if needed.

  3. In this simplified food chain: grass → rabbit → fox. What is the role of “rabbit” in this chain?

    1. tertiary consumer
    2. producer
    3. secondary consumer
    4. primary consumer

  4. A population changes from 80 to 100. Find its percentage increase.

  5. A fictional population starts at 419. During one interval: 22 births, 7 arrivals, 35 deaths and 13 departures. Find the final count. Round to 3 decimal places if needed.

  6. Supplied fictional records give M = 53 initially marked, C = 42 in a later sample, and R = 23 marked in that sample. Use N ≈ MC/R under the stated assumptions. No animals are to be handled. Round to 3 decimal places if needed.

  7. In this simplified food chain: grass → grasshopper → frog → snake → hawk. If the population of “frog” suddenly drops, what is the most likely short-term effect on the population of “snake”?

    1. It will most likely increase.
    2. It will not be affected at all.
    3. It will most likely decrease.

  8. Why can carrying capacity change over time?

  9. A fictional population starts at 259. During one interval: 75 births, 33 arrivals, 31 deaths and 28 departures. Find the final count. Round to 3 decimal places if needed.

  10. Supplied fictional records give M = 77 initially marked, C = 90 in a later sample, and R = 63 marked in that sample. Use N ≈ MC/R under the stated assumptions. No animals are to be handled. Round to 3 decimal places if needed.

  11. In this simplified food chain: kelp → sea urchin → sea otter. If the population of “kelp” suddenly drops, what is the most likely short-term effect on the population of “sea urchin”?

    1. It will most likely decrease.
    2. It will not be affected at all.
    3. It will most likely increase.

  12. Why should a survey method remain comparable across years?

Answer key
  1. 761 N₂ = N₁ + births + immigration − deaths − emigration 769 + 29 + 28 − 52 − 13 = 761
  2. 572.727 N ≈ MC/R 75 × 84/11 = 572.727
  3. primary consumer Level 2 in this chain: primary consumer.
  4. 25 % (100 − 80)/80 × 100 = 25%.
  5. 400 N₂ = N₁ + births + immigration − deaths − emigration 419 + 22 + 7 − 35 − 13 = 400
  6. 96.783 N ≈ MC/R 53 × 42/23 = 96.783
  7. It will most likely decrease. With less food available, the predator population is likely to decrease.
  8. Environmental conditions, resources and interactions can change. It is not a universal permanent constant for a species.
  9. 308 N₂ = N₁ + births + immigration − deaths − emigration 259 + 75 + 33 − 31 − 28 = 308
  10. 110 N ≈ MC/R 77 × 90/63 = 110
  11. It will most likely decrease. With less food available, the predator population is likely to decrease.
  12. Changed detection methods can mimic a population trend. Separate observation effects from actual demographic changes.

Related ready-made worksheets: Grade 12 Ecology & populations worksheet