Investigating Ecosystems (DP IB Environmental Systems & Societies (ESS): SL)

Exam Questions

48 mins10 questions
1a1 mark

The figure below shows an example of a tool that can be used to help ecologists identify the organisms present within an ecosystem.

Dichotomous-Key-Example-table

State the name of this tool.

1b1 mark

Use the tool in part (a) to identify the organism shown in the figure below.

dichotomous-key-example

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21 mark

Distinguish between species richness and species diversity.

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3a
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1 mark

Some ecologists captured a random sample of 100 deer and marked them with ear tags.

They then release the marked deer back into the population and allowed them to mix with the unmarked deer.

After a set period of time, the ecologists recaptured a random sample of 50 deer and found that 10 of them were marked.

Using the Lincoln Index, estimate the population size of the deer.

3b1 mark

Outline one limitation of using the capture-mark-recapture method.

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43 marks

List three abiotic factors that can be measured in an aquatic ecosystem.

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1a1 mark

The figure below shows the data for a wolf population and the amount of suitable habitat that is available to the wolves.

wolf-population-habitat-graph

Suggest one possible method for estimating the wolf population size.

1b2 marks

Outline two reasons why collecting this type of data on wolves might be challenging.

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2a2 marks

Lichens are organisms that grow well on stone walls in unpolluted air. Lichens grow less well in polluted air.

Car exhaust fumes contain sulfur dioxide that pollutes air.

A scientist investigates the effect of pollution by cars in a city.

This is their method:

  • Measure the percentage area of a stone wall in the city centre covered by lichen

  • Repeat this measurement at different distances from the city centre

The table shows their results.

DIstance from city centre in km

Percentage area covered by lichen (%)

0

0

2

6

4

20

6

30

8

50

10

64

12

70

Explain the results shown in the table.

2b4 marks

Describe a method to measure the percentage of a stone wall covered by lichen.

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3a5 marks

Use the dichotomous key provided to identify the organisms below.

screenshot-2023-07-28-at-11-43-44

KEY

1 (a)

  Body is completely or partly covered in a shell

  Go to 2

(b)

  Body is not completely or partly covered in a shell

  Limax flavus

2 (a)

  Shell is attached to rocks by thin threads

  Mytilus edulis

(b)

  Shell is not attached to rocks by thin threads

  Go to 3

3 (a)

  Shell is a spire that comes to a point

  Buccinum undatum

(b)

  Shell is not a spire that comes to a point

  Go to 4

4 (a)

  Animal has tentacles

  Nautilus pompilius

(b)

  Animal has 2 tentacles

  Planorbis planorbis

3b3 marks

Identify three limitations of using dichotomous keys for identifying organisms.

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4a4 marks

A group of students compares the distribution of plant species in two fields using the following method:

  • Use random sampling

  • Use a 0.5 m × 0.5 m quadrat

  • Count the number of each species in a quadrat

  • Repeat this method for five quadrats in each field

The tables below show the students’ results.

Species

Field A

Number of plants in each quadrat

Number of plants per m2

First

Second

Third

Forth

Fifth

Mean

Dandelion

7

0

6

3

4

4

16

Buttercup

2

1

0

3

2

2

6

Violet

1

0

2

1

2

1

5

Heather

2

3

1

2

1

2

7

Species

Field B

Number of plants in each quadrat

Number of plants per m2

First

Second

Third

Forth

Fifth

Mean

Dandelion

7

3

2

1

2

 

 

Buttercup

0

0

0

0

0

0

0

Violet

0

0

0

1

0

0

0

Heather

0

0

0

0

0

0

0

i)

Describe how the students would obtain random samples from each field.

[2]

ii)

Calculate the mean number of dandelions per quadrat in field B.

[1]

iii)

Calculate the number of dandelions per m2 in field B.

[1]

4b3 marks

Describe the differences in species distribution in field A and field B.

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17 marks

Explain how a variety of ecological data collection methods could be used to show how an ecosystem changes as a result of human activity.

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29 marks

Evaluate methods for estimating biomass and energy at different trophic levels in ecosystems.

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