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CAIE IGCSE Biology 19.4.7 Explaining Sigmoid Growth Phases

Practise explaining each growth-curve phase using reproduction, death and limiting factors such as food, space and waste.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • explain the lag phase through low population size and initially limited reproduction
  • link exponential growth to plentiful resources and a birth rate above the death rate
  • explain stationary or death phases using competition, depleted resources, waste and changing birth or death rates

19.4.7—Factors that lead to each phase question 1

[Maximum number: 3]

Genetically modified bacteria were grown in a fermenter. The number of bacteria was measured, and the data are shown in Fig. 5.1.

Fig. 5.1

Fig. 5.1

Describe and explain the change in bacterial population size from 24 hours to 50 hours shown in Fig. 5.1.

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