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Edexcel IGCSE Biology 4.2 comparing population size

Practise population-size sampling by planning quadrat methods, controlling variables and calculating means or densities from field data.

Syllabus
First assessment 2019
Course
Biology 4BI1

Exam points

  • Describe quadrat sampling with random coordinates, counts, repeats and a calculated mean.
  • Calculate or compare population size from tables, percentages or numbers per square metre.
  • Select controlled variables such as quadrat area, sampling time, habitat type or method.

4.2 Comparing population size question 1

[Maximum number: 4]

Limpets are marine animals that attach to rocks on coastal shores.

The diagram shows a food web that contains limpets.

Figure for Question 4.2 Comparing population size question 1 — Edexcel IGCSE Biology

Question (a)

(a)

Some scientists think that food webs on rocky shores are at risk from an increase in greenhouse gases.

The scientists record these two factors during August every year for 17 years.
- the number of limpets per m2m^{2} on a rocky shore
- the mean temperature at the same rocky shore

The graph shows the scientists' results.

Figure for Question (a) — Edexcel IGCSE Biology
[ 4 ]

Question (i)

(i)

Describe how the scientists could determine the number of limpets on the rocky shore.

[ 3 ]

Question (ii)

(ii)

Give one factor the scientists should control when comparing the number of limpets per m2m^{2} each year.

[ 1 ]
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