Biology Exam Answers: Cells, Photosynthesis, Genetics & Ecology

Biology Exam Answers: Cells, Photosynthesis, Genetics

Question 1

• 1(a)(i) C
• 1(a)(ii) D
• 1(a)(iii) D
• 1(a)(iv) A
• 1(b) C
• 1(c) A structure within a cell that has a specific function.
• 1(d) U releases energy; R moves the cell through water.

Question 2

• 2(a)(i) Time
• 2(a)(ii) Use a water bath at 70 °C.
• 2(b)

  B: It turns brick-black. This indicates it contains most glucose; glucose is needed for respiration and releases energy for muscle contraction during the race.

• 2(c) Fewer calories, so less weight gain.

Question 3

• 3(a) From light energy to chemical energy.
• 3(b)(i) Keep the plant in the dark for 12–48 hours so starch is used up in respiration.
• 3(b)(ii) LHS outside flask: blue-black. RHS inside flask: brown.
• 3(c) Nitrate: for making amino acids. Magnesium: for making chlorophyll.
• 3(d) Active transport requires energy.
• Waterlogged soil has no oxygen.
• Less respiration → less ATP.

Question 4

• 4(a)(i) Sucrose and amino acids
• 4(a)(ii)
  • Less respiration → less energy
  • Less protein made
  • Less growth/new cells
  • Less fruit produced
• 4(b)(i)

  Scale insects drop fast after ladybugs are introduced. Ladybugs feed on scale insects. Scale insect populations fluctuate but never reach zero. Insecticide increases scale numbers as ladybugs are killed. Ladybugs recover → scale insects drop again. Biological control is more effective than insecticide.

• 4(b)(ii)

  Lasts longer; specific → does not harm other organisms; no residue on crop; no bioaccumulation; pests do not become resistant.

Question 5

• 5(a)(i) All DNA of an organism.
• 5(a)(ii) Gene: section of DNA coding for a protein. Allele: alternative version of a gene.
• 5(b)(i)
  • Parents: Bb × Bb
  • Gametes: B or b × B or b
  • Offspring: BB, Bb, Bb, bb
  • Ratio: 3 black : 1 brown
• 5(b)(ii) 0.75 × 0.5 = 0.375
• 5(c) Cross with a blue-eyed (bb) female. If any blue-eyed offspring → male is Bb. If none after repeated crosses → male is BB.

Question 6

• 6(a)(i) 82/120 = 68%
• 6(a)(ii) Temperature changes day/night → more natural.
• 6(a)(iii) Leaf size.
• 6(b)(i) x-axis: Days. y-axis: Leaf area.
• 6(b)(ii)

  (6800 – 10) ÷ 100 = 67.9

• 6(b)(iii)

  No difference up to ~80 days. Growth decreases in B due to higher temperature. Enzymes denature above their optimum. Active site changes → slower reaction.

• 6(b)(iv)
  1. Trace outline on grid.
  2. Count squares.
  3. Multiply by 2 for both sides.

Question 7

• 7(a)(i) C
• 7(a)(ii) A
• 7(a)(iii) C
• 7(a)(iv) D
• 7(b) White blood cells engulf pathogens and produce antibodies. Antibodies are specific to the pathogen and either destroy pathogens or provide immunity.
• 7(c)(i) 5.0 × 10¹² in one litre; 5 × 10⁶ in 1 mm³ → = 1 × 10⁷.
• 7(c)(ii)

  No difference in platelets. More scab formation. More phagocytes that engulf pathogens. More lymphocytes that produce antibodies.

Question 8

• 8(a)(i) Community and their environment
• 8(a)(ii) All species in an area
• 8(a)(iii) A species in an area
• 8(b) Direction, plant, trophic, heat, respiration, manure, urea, bacteria

Question 9

• 9(a) Restriction enzymes; ligase joins DNA together.
• 9(b) GM involves asexual methods; GM uses enzymes.

Question 10

• 10
• C light and no light or different periods of light
• O same species of mass
• R calculate mean for each light
• M1 count number of seeds germinated
• M2 after stated time period
• S1 same temperature
• S2 same soil