Exam-style Questions: Ecological Concepts

1. The graph shows the changes in the size of the collared dove population in Britain following the introduction of these birds in 1955.

Exam-style Questions

a) Describe the pattern of population growth shown in the graph.

b) Explain how a named density dependent factor might have affected population size in the 1980s.

(Marks available: 5)

Answer

 

Answer outline and marking scheme for question: 1

Give yourself marks for mentioning any of the points below:

a) Description contains elements of slow increase and stability/slight decline;

Quantitative definition of change in rate of increase and peak.

(2 marks)

b) Identity of an appropriate density dependant factor (e.g. food supply/predation)

When population at high density leads to decrease;

When population at low density allows recovery.

(3 marks)

(Marks available: 5)

 

2. The diagram shows a profile along a transect showing succession on some coastal sand dunes.

Point

A

B

C

D

Index of diversity

1

2.3

5.4

6.1

 

Exam-style Questions

 

a) What data must be collected in order to be able to calculate an index of diversity of plants at one of the points along the transect?

b) Suggest an explanation for the trend in diversity along the transect.

(Marks available: 5)

Answer

 

Answer outline and marking scheme for question: 2

Give yourself marks for mentioning any of the points below:

a) The number of different plans/organisms of each species present;

Total number of species/plants of all species.

(2 marks)

b) Harsher/less stable environmental conditions at start;

Such as dry sand/high salt content/low nitrate/humus;

Few species able to tolerate these conditions.

(3 marks)

(Marks available: 5)

 

3. The wren is a small, insect-eating bird. The percentage change in size of the wren population from one year to the next was estimated over a number of years.

The number of days with snow lying in the previous winter was also recorded. This information is shown on the graph.

Exam-style Questions

 

a) (i) Describe the relationship between the number of days with snow lying and the change in population size.

(ii) Suggest and explain a reason for this relationship.

b) A comparison was made between the number of breeding pairs of wrens each year and their breeding success.

Number of breeding pairs of wrens/ millions

Percentage increase in population size

1.2

1.9

2.5

2.9

3.9

55

48

35

25

2

 

Suggest an explanation for the relationship between the size of the breeding population and breeding success.

(Marks available: 6)

Answer

 

Answer outline and marking scheme for question: 3

Give yourself marks for mentioning any of the points below:

a) (i) The more days of snow the lower the increase in the population/fewer birds (or converse).

Negative correlation/above 11-13 days of snow.

Negative change/decrease in population.

(ii) Fewer birds to breed.

Explanation using data (e.g. food hidden under snow/too cold for birds to survive).

b) More breeding pairs produces more competition.

Less breeding success.

(Marks available: 6)