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Cambridge IGCSE Biology practice

Paper 3 structured question: Populations

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Populations

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Paper 3Theory (Core)2 marks

A population of bacteria is growing in a nutrient-limited environment. The population size changes over time following a sigmoid growth curve.

Diagram Description

Sigmoid Growth Curve

The graph shows population size on the y-axis and time on the x-axis. The curve has four phases: lag phase (initial flat section), exponential phase (steep upward slope), stationary phase (plateau), and death phase (downward slope).

  1. a

    Identify the lag phase on the sigmoid growth curve.

    Aim for approximately 1 distinct marking point.

    [1]
  2. b

    Identify the exponential phase on the sigmoid growth curve.

    Aim for approximately 1 distinct marking point.

    [1]

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Paper 3 structured question: Populations

Paper 3Theory (Core)2 marks

Diagram Description

Sigmoid Growth Curve Phases

The curve shows four phases: lag phase (flat), exponential phase (rising steeply), stationary phase (plateau), and death phase (declining).

  1. a

    Identify the stationary phase on the sigmoid growth curve.

    Aim for approximately 1 distinct marking point.

    [1]
  2. b

    Identify the death phase on the sigmoid growth curve.

    Aim for approximately 1 distinct marking point.

    [1]