Climate & Natural Vegetation (Cambridge (CIE) IGCSE Geography)

Students from Brazil who lived near Tijuca National Park did some fieldwork to study the tropical rainforest ecosystem. They visited three sites which are described and located in Fig. 1.1.

The students decided to investigate the effect of vegetation cover at the three sites. They agreed on the following hypotheses:

Hypothesis 1: Humidity is greater where there is more vegetation cover. Humidity is the amount of water vapour in the air.

Hypothesis 2: Infiltration is quicker where there is more vegetation cover.

(i) To obtain data the students made each of their measurements five times at each site. Explain why this would make their results more reliable.

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(ii) To measure the amount of vegetation cover the students used the piece of equipment shown in Fig. 1.2.

Fig 1.2

What is this piece of equipment called? Tick (✓) your answer below.

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(iii) To measure humidity the students did a simple test which a student described in his fieldwork notebook, Fig. 1.3. Suggest one weakness of this test. 

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The results of the students’ measurements of humidity and infiltration rates are shown in Table 1.1 (below).

Table 1.1 for Question 1 Results of students’ measurements

Site A

Site B

Site C

(i)

Which site has the highest amount of vegetation cover? Circle your answer.

site A    site B    site C

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(ii)

One set of measurement results is shown below.

At which site and for which measurement (1–5) were these results recorded? Site .............. Measurement number ..............

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iii)

Use the results in Table 1.1 to calculate the average infiltration time at site B. Show your calculation below.

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Using their results from Table 1.1 the students plotted the graphs shown in Fig. 1.4 below

Table 1.1 for Question 1 Results of students’ measurements

Site A

Site B

Site C

(i) Use the information in Table 1.1 to plot the following on Fig. 1.4:

• the percentage of vegetation cover and the percentage of bare ground in measurement 3 at site C • how long the cobalt chloride paper took to turn pink (humidity measurement) in measurement 5 at site B • the infiltration time in measurement 5 at site C.

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(ii) Before they made a conclusion to Hypothesis 1 the teacher reminded the students that the less time the paper took to turn pink the greater the humidity of the air. What conclusion would the students make about Hypothesis 1: Humidity is greater where there is more vegetation cover? Support your decision with evidence from Fig. 1.4 and Table 1.1. 

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(iii) The students decided that Hypothesis 2: Infiltration is quicker where there is more vegetation cover was correct.

What evidence from Fig. 1.4 and Table 1.1 supports their conclusion?

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Suggest why infiltration times are different at sites A and C. Look at Fig. 1.1 to help you to answer.

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Fig. 1.1.

Whilst doing their fieldwork the students saw many different plant species in the tropical rainforest. As an extension activity, they returned to their three fieldwork sites and counted the number of different species using the reference sheet shown in Fig. 1.5. Their results are shown in Table 1.2.

Fig 1.5

Table 1.2 for Question 1 Different species* identified by students

*Species reference number in Fig. 1.5

Key ✓ species seen at the site

(i) One student wanted to show the number of different plant species seen at each site. Which one of the following would be suitable to show the information in Table 1.2? Tick (✓) your choice.

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(ii) Suggest two reasons why the number and types of plant species vary between the sites. Look at Fig. 1.1 to help you to answer.

1 ........................................................................................................................................ 2 ........................................................................................................................................

Fig. 1.1.

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