Cambridge International A Level Biology Revision Guide

Chapter 18: Biodiversity, classification and conservation
a Calculate the mean percentage cover for the first two species in the table. [1]
b Explain why the percentage cover for all the species in each quadrat adds up to more than 100%. [1]
c Suggest why the percentage cover was recorded to the nearest 5%. [1]
d Could these results be used to obtain a valid estimate of the species density for each species?
Explain your answer. [4]
e State four factors that influence plant biodiversity in a field ecosystem. [4]
[Total: 11]
6 A sample of 39 ground beetles was captured from an area of waste ground measuring 100 × 25 metres.
Each animal was marked and then released. A second sample of 35 was caught on the following day.
Of these, 20 had been marked.
a Use these results to estimate the number of ground beetles in the population. Show your working. [2]
b State three assumptions that must be made in order to make this estimate. [3]
c Describe a method that you could use to check that the mark–release–recapture method gives a valid
estimate of the ground beetle population in the area of waste ground. [4]
[Total: 9]
7 Light is an important abiotic factor that determines the distribution and abundance of plants. Some
plants are adapted to grow in areas of low light intensity. They are known as shade plants. Some students
investigated the abundance of dog’s mercury, Mercurialis perennis, under forest trees in eight different
locations. At each location, they used ten randomly positioned quadrats to measure the percentage cover
of this shade plant.
Location
Light intensity
at ground level /
percentage of full sun
Mean percentage
cover of M. perennis
A 90 10
B 50 65
C 30 90
D 20 80
E 80 34
F 88 20
G 93 10
H 100 0
457
a Draw a scatter graph to see if there is a correlation between light intensity beneath the canopy and
abundance of M. perennis. [2]
b State a null hypothesis for this investigation. [1]
c Use the data in the table to calculate the Spearman rank correlation, r s
. Show all your working. [4]
d What can you conclude from your calculation? You will need to consult Table P2.8 on page 504 to
help you answer this question. [3]
[Total: 10]