Fieldwork and sampling techniquesIB MYP Biology: Subtopic test

1. 1
   Students in Dubai are estimating the number of daisies on a rectangular school field that measures 40 m by 25 m. They used a 1 m² quadrat at five positions and counted 4, 7, 5, 6 and 3 daisies.

   (a)

   How should the students place the quadrats to avoid bias?

   [1 mark]

   • AUse random coordinates from a random number generator
   • BPlace them where daisies look most common
   • CPlace them next to each other in one corner
   • DPlace them only in the shade

   (b)

   What is the mean number of daisies per quadrat?

   [1 mark]

   • A25
   • B4
   • C6
   • D5

   (c)

   Calculate the estimated number of daisies on the whole field.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A researcher is estimating the number of ground beetles in an olive grove in Crete. In the first sample she caught 40 beetles, marked each with a tiny spot of non-toxic paint and released them. A week later she caught 36 beetles, and 9 of them carried a paint spot.

   (a)

   Which calculation gives the estimated population of beetles?

   [1 mark]

   • A36 × 9 ÷ 40
   • B40 × 36 ÷ 9
   • C(40 + 36) ÷ 9
   • D40 × 9 ÷ 36

   (b)

   Which assumption must be true for this method to give a reliable estimate?

   [1 mark]

   • AMarked beetles are more likely to be caught again
   • BThe population changes greatly between the two samples
   • CMarked beetles mix randomly back into the population
   • DThe paint harms the marked beetles

   (c)

   Calculate the estimated number of ground beetles in the olive grove.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Students studied a coastal sand dune in Portugal. They laid a 50 m tape from the shoreline inland and used a 1 m² grid quadrat every 10 m, estimating by eye the percentage of the ground covered by marram grass. The cover was 5% at 0 m, 15% at 10 m, 35% at 20 m, 60% at 30 m, 80% at 40 m and 90% at 50 m. They used one transect and the same student estimated every quadrat.

   (a)

   Describe the trend in the cover of marram grass moving inland and give one reason why a transect was suitable for this study.

   [3 marks]

   (b)

   Evaluate the students' method by identifying two sources of error or bias, and suggest an improvement for each.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Rangers at a nature reserve in southern Spain are monitoring two species. In a large meadow they want to estimate how many wild orchids grow there. They also want to estimate the population of a rare lizard that is easily disturbed and lives in rocky ground, where it cannot be counted directly.

   (a)

   Describe how the rangers could estimate the number of orchids in the meadow using quadrats.

   [6 marks]

   (b)

   Evaluate the use of the mark-release-recapture method to monitor the rare lizard.

   [6 marks]

   Total for question 4: 12 marks

End of questions