(a) DCPIP is an indicator and can be used to determine the rate of respiration of organisms such
as yeast.
(i) State the category of indicators to which DCPIP belongs.
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(ii) Describe the colour change that occurs in DCPIP during experiments to determine the
rate of respiration.
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(b) An investigation was carried out to determine the effect of temperature on the rate of
respiration of yeast.
• A suspension of yeast cells was added to a test‑tube containing glucose solution.
• A further four test‑tubes were set up in the same way.
• One test‑tube was placed in a water‑bath at 10 °C for 5 minutes.
• DCPIP was added to the test‑tube and the time taken for the DCPIP to change colour
was measured.
• The experiment was repeated using the other test‑tubes at 20° C, 30 °C, 40 °C and 50 °C.
The results are shown in Fig. 6.1.
unmarked) captured in second sample
m = number of marked individuals recaptured in
Question
Biology
CAIE2024
n = number of individuals (both marked and
Question
Biology
CAIE2024
N = estimate of population size
n = number of individuals captured in first sample
Question
Biology
CAIE2024
(cid:44)(cid:1)(cid:1)(cid:1)(cid:1)(cid:9)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:3)(cid:5)(cid:44)
(d) A light trap was used to estimate the total size of a population of B. betularia in a woodland.
On night one, 24 moths were captured. These were marked with a small spot of harmless
paint. On night two, 29 moths were captured, and 8 of these showed a spot of paint.
Use the Lincoln index formula provided to calculate the size of the population.
Show your working.
n #n
N = 1 2 Key to symbols:
m
Populations of the moth Biston betularia live in Europe and in North America. The most common
phenotype on both continents is a pale wing colour with light‑grey shading (the typical form).
A moth phenotype with dark wing colour (the melanic form) also occurs on both continents.
Fig. 10.1 shows the typical form of the moth.
Fig. 10.2 shows the melanic form of the moth.
Fig. 10.1 Fig. 10.2
(a) Two melanic European moths were crossed together. The wing colours of the offspring were
(cid:44)(cid:1)(cid:1)(cid:1)(cid:1)(cid:9)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:2)(cid:8)(cid:44)
(b) Fig. 7.3 shows the evolutionary relationships between three species of American spadefoot
toad.
Spea multiplicata
Spea hammondii
Spea bombifrons
(cid:44)(cid:1)(cid:1)(cid:1)(cid:1)(cid:9)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:6)(cid:44)
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(c) The experiment was repeated with A. thaliana plants that were left in darkness from 14 to 96
hours. The results are shown in Fig. 2.2.
100
Key
day
open night
stomata 50
/ %
The leaves of many plants have stomata that show a regular daily rhythm of opening and closing
over a period of 24 hours.
(a) Explain why it is important for plants to open and close their stomata in a daily rhythm.
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(b) Fig. 2.1 shows the results of an experiment to monitor this rhythm over three days and nights
for the plant Arabidopsis thaliana. The percentage of open stomata is shown. Each day
consisted of 14 hours of light (white bar) and each night consisted of 10 hours of darkness
(black bar).
100
Key
day
open night
stomata 50
/ %