IB Diploma Biology chapter 4: D Continuity and change MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

125 exam-style questions on D Continuity and change, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

125 questions · 11 topics · 10 per test

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What chapter 4 covers

Ten D Continuity and change questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. A fish stock of 80 000 tonnes gains 12% of its mass each year through reproduction and growth. Fishing removes 9000 tonnes per year. Ignoring other losses, what happens to the stock in one year, and is the harvesting sustainable?

  1. A
    it rises by 600 tonnes, but the harvesting is not sustainable because fish are being removed
  2. B
    it rises by 600 tonnes, so the harvesting is sustainable
  3. C
    it rises by 9600 tonnes, so the harvesting is sustainable
  4. D
    it falls by 600 tonnes, so the harvesting is not sustainable
Show answer

Answer: B. Gain = 12% of 80 000 = 9600 tonnes. Net change = 9600 − 9000 = +600 tonnes. Harvesting is sustainable when the rate of removal does not exceed the rate of replacement, even though fish are being caught.

2. Over 50 years the mean temperature in a mountain region rises by 1.3 °C. Temperature falls by about 6.5 °C for every 1000 m increase in altitude. By about how far upslope would the zone with the original temperature have moved?

  1. A
    20 m
  2. B
    8450 m
  3. C
    5 m
  4. D
    200 m
Show answer

Answer: D. The zone with the original temperature has shifted to where it is 1.3 °C cooler: 1.3 ÷ 6.5 × 1000 = 200 m higher. This helps to explain why montane species now live at greater altitudes.

3. Which statement about evolution by natural selection is correct?

  1. A
    it makes the population evolve towards a goal that the environment requires, by producing the alleles that are needed
  2. B
    it changes the frequency of alleles over generations, because individuals with advantageous heritable traits leave more offspring
  3. C
    it occurs only when new mutations arise in response to a change in the environment, and not otherwise
  4. D
    it changes individuals during their lifetimes when they use a trait more, and the changed trait is then inherited by their offspring
Show answer

Answer: B. Natural selection acts on existing heritable variation: the individuals best suited to their environment survive and reproduce more, so their alleles become more common. Acquired characteristics are not inherited.

4. Which is an example of a positive feedback cycle in global warming?

  1. A
    warming reduces the use of fossil fuels for heating, so less CO2 is released
  2. B
    warming melts reflective snow and ice, so more solar radiation is absorbed, causing more warming
  3. C
    higher CO2 increases photosynthesis, which removes CO2 from the atmosphere
  4. D
    warming increases cloud cover, which reflects sunlight and cools the Earth
Show answer

Answer: B. Positive feedback amplifies the change: melting ice exposes darker surfaces that absorb more energy. Reduced fuel use, more photosynthesis and more cloud would all reduce warming, so they are negative feedbacks or not feedbacks.

5. Muscle cells and skin cells of one person contain the same genes but make different proteins. What is the best explanation?

  1. A
    the genes of muscle cells mutate in a different way from those of skin cells, so different proteins are produced
  2. B
    translation of mRNA is impossible in one of the cell types, so it makes no proteins from its genes
  3. C
    muscle cells lose the genes for skin proteins during development, and skin cells lose the genes for muscle proteins
  4. D
    different genes are transcribed in each cell type, so only some of the genes in each cell are expressed
Show answer

Answer: D. Every cell has the full set of genes, but transcription is regulated so that each cell type expresses only some of them.

6. A forest originally covered 4.0 million km2 and now covers 3.2 million km2. If it loses the same percentage of its current area over the next 50 years, what area will remain?

  1. A
    2.56 million km2
  2. B
    2.8 million km2
  3. C
    2.4 million km2
  4. D
    2.0 million km2
Show answer

Answer: A. The percentage change so far is (3.2 − 4.0) ÷ 4.0 × 100 = −20%. Losing 20% of 3.2 leaves 3.2 × 0.80 = 2.56. Subtracting the same 0.8 again would give 2.4, but the same percentage is a smaller absolute loss.

7. A DNA sequence changes from ATGCCTA to ATGCGTA. What type of mutation is this?

  1. A
    a deletion: one base has been lost, so the length of the sequence is now shorter
  2. B
    a frameshift: the number of bases is unchanged, but the reading frame is altered
  3. C
    an insertion: a base has been added, so every codon after this position is changed
  4. D
    a base substitution: one base has been replaced by a different base and the length is unchanged
Show answer

Answer: D. Substitution swaps one base for another (here C for G). Insertions add and deletions remove bases.

8. A cell line grown in the laboratory with no mutagens still shows about one new mutation per 109 bases in each round of replication. What is the most likely cause?

  1. A
    exercise of the cells, which alters the base sequence of DNA when the cell becomes more active
  2. B
    the nutrients in the growth medium, which change the base sequence when they are absorbed into the cell
  3. C
    errors made by DNA polymerase during replication that are not corrected by DNA repair
  4. D
    transcription of the genes, which changes the base sequence of the DNA template as it is read
Show answer

Answer: C. Mistakes in copying or repairing DNA are a natural source of mutation, even without mutagens.

9. Mosquito populations became resistant after an insecticide was used for many years. Which explanation is correct?

  1. A
    individual mosquitoes became tolerant of the chemical during their lives and passed the acquired tolerance to their offspring
  2. B
    the insecticide caused mutations for resistance in the mosquitoes that were sprayed, and these were passed to offspring
  3. C
    the mosquitoes needed to survive, so the population produced the resistance alleles that it required and every mosquito became resistant at once
  4. D
    resistance alleles arose by random mutation, some mosquitoes survived and reproduced, and the allele became more common
Show answer

Answer: D. Selection acts on existing heritable variation. Changes acquired during an individual's life are not encoded in genes, so they are not inherited.

10. Two pure-breeding pea plants, one tall and one short, are crossed. The F1 plants are self-pollinated. What ratio of tall to short is expected in the F2?

  1. A
    1 : 1
  2. B
    1 : 2 : 1
  3. C
    3 : 1
  4. D
    all tall
Show answer

Answer: C. TT × tt gives all Tt in F1. Tt × Tt gives 1 TT : 2 Tt : 1 tt, which is 3 tall : 1 short (1 : 2 : 1 is the genotype ratio).

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D Continuity and change: questions students ask

How many D Continuity and change MCQs are there?

125, each with the answer and a short explanation, across 11 topics: D1.1 DNA replication, D1.2 Protein synthesis, D1.3 Mutations and gene editing, D2.1 Cell and nuclear division, D2.3 Water potential, D3.1 Reproduction, D3.2 Inheritance, D3.3 Homeostasis, D4.1 Natural selection, D4.2 Stability and change, D4.3 Climate change. Every chapter test draws ten of them, so you can take it many times.

Is the IB Diploma Biology chapter 4 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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