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CAIE IGCSE Biology 19.4 Populations Questions

Practise population questions by defining ecology terms, reading growth curves and calculating changes from population graphs or data tables.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • define and distinguish populations, communities and ecosystems using organisms, species and environments
  • identify food, competition, predation and disease as growth factors and predict their effects
  • label lag, exponential, stationary and death phases and link stages to birth–death balance
  • describe graph trends with values and calculate percentage change or halving time
  • infer population events from plotted changes using food, predation or limiting-factor evidence
  • explain sigmoid phases using reproduction, death rates and limiting factors such as resources, space or waste

Covered syllabus points

19.4.1—Population as a group of organisms19.4.2—Community as all of the populations19.4.3—Ecosystem as a unit containing19.4.4—Factors affecting the rate19.4.5—Lag, exponential (log), stationary19.4.6—Interpret graphs and diagrams19.4.7—Factors that lead to each phase

Question 1

[Maximum number: 2]

Carp are a type of fish. Researchers in Brazil measured the body lengths of a population of carp in a river in 1998 and again in 2008.

Histograms of their results are shown in Fig. 2.1.

Fig. 2.1

Fig. 2.1

Define the term population.

Question 2

[Maximum number: 4]

Fig. 5.1 shows Mackinlay's cuckoo-dove, Macropygia mackinlayi, which is found on most of the islands in the south-west of the Pacific Ocean.

Fig. 5.1

Fig. 5.1

Question (a)

(a)

Karkar Island is one island where Mackinlay's cuckoo-dove is found. This species is part of many communities that are adapted to the different habitats on the island.

[ 1 ]

Question (i)

(i)

Define the term community.

[ 1 ]

Question (b)

(b)

The highest point on Karkar Island is 1800 m above sea level.

In 1969, a researcher surveyed the bird species on Karkar Island. He recorded the vertical distribution of the birds between sea level and 1600 m .

In 2013, other researchers repeated the survey.
Fig. 5.2 shows the ranges of four species, as recorded in the two surveys. The vertical lines represent the range of heights where the birds were seen on the island.

Fig. 5.2

Fig. 5.2

[ 3 ]

Question (i)

(i)

Using the information in Fig. 5.2, suggest reasons for the change in the range of the island thrush (C) on Karkar Island.

[ 3 ]

Question 3

[Maximum number: 2]

Coral reefs are important ecosystems.

Complete the sentence about ecosystems.

An ecosystem can be defined as a unit containing the of organisms and their interacting together.

Fig. 6.1 is a photograph of a coral reef.

Fig. 6.1

Fig. 6.1

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