AQA GCSE BIOLOGY -2018 PAPER 1H
7. Figure 8 shows:
* a food chain for organisms in a river
* the biomass for organisms at each tropic level.
Figure 8
Algae --- invertebrate ---- small fish ---- large fish
Biomass in 840 g/m2
7.1. Draw a pyramid of biomass for the food chain in figure 8 on figure 9.
You should:
* use a suitable scale
* label the x-axis
* label each trophic level.
7.2. Calculate the percentage of the biomass lost between the algae and the large fish.
Give your answer to 2 significant figures.
840- 10 x 100
-----------
840
99 %
7.3. Give ONE way that biomass is lost between trophic levels.
Higher Tier Paper 2H
Monday 1 June 2020 Afternoon Time allowed: 1 hour 45 minutes
Materials
For this paper you must have:
• a ruler
• a scientific calculator
0 1 This question is about the decay of milk.
0 1 . 1 Name two types of microorganism that cause decay.
________________________________________________________________________________________________________________________________________________________________
[2 marks]
1 . 2 Cows’ milk is pH 6.6.
As milk decays, lipids in the milk are broken down.
One of the products of the breakdown of lipids causes the pH of milk to decrease.
Name the product that causes the pH to decrease.
______________________________________________________________________________________________________________________________________________________________________
A student investigated the effect of temperature on the time taken for different types of box
milk to decay.
This is the method used.
1. Put cows’ milk in six test tubes.
2. Keep each test tube at a different temperature.
3. Measure the pH of the milk in each tube every day for 12 days.
4. Record the number of days taken to reach pH 5.
5. Repeat steps 1 to 4 with goats’ milk and with almond milk.
1 . 3 Give one way the pH can be measured.
_________________________________________________________________________________________________________________________________________________________________
[1 mark]
0 1 . 4 Give two control variables the student should have used in this investigation.
[2 marks]
______________________________________________________________________________________________________________________________________________________________________
The student improved the investigation to produce valid results. box
Figure 1 shows the results.
1 . 5 Which type of milk stays fresh the longest at 10 °C?
___________________________________________________________________________________________________________________________________________________________________
1 . 6 Describe the effect of temperature on the time taken for goats’ milk to reach pH 5.
Use data from Figure 1 in your answer.
[2 marks]
________________________________________________________________________________________________________________________________________________________________
1 . 7 The time taken for cows’ milk to reach pH 5 at 10 °C is less than the time taken for
cows’ milk to reach pH 5 at 5 °C.
Suggest one reason why.
____________________________________________________________________________________________________________________________________________________________
1 . 8 Suggest two reasons why the different types of milk took different lengths of time to
reach pH 5.
______________________________________________________________________________________________________________________________________________________________________
4. A student carriedout an investigation using chicken eggs.
This is the method used.
1. Place 5 eggs in acid for 24 hours to dissolve the egg shell.
2. Measure and record the mass of each egg.
3. Place each egg into a separate beaker containing 200 cm³ of distilled water.
4. After 20 minutes, remove the eggs from the beakers and dry them gently wiht a paper towel.
5. Measure and record the mass of each egg.
Table 4 shows the results.
Table 4
Egg Mass of egg without
shell in grams Mass of egg after
20 minutes in grams
1 73.5 77.0
2 70.3 73.9
3. 72.4 75.7
4. 71.6 73.1
5. 70.5 73.8
75.7 - 72.4 X 100
72.4
= 3.3/72.4 X 100
= 4.6 %
4.1. Another student suggested that the result for egg 4 was anomalous.
Do you agree with the student?
Give a reason for your answer.
Ans: Yes, I am agree with the student, because the mass change is much lower than the others.
4.2. Calculate the percentage change in mass of egg 3.
Solution: 75.7 - 72.4 X 100
72.4
= 4.6 %
Percentage change in mass = 4.6 %
4.3 Explain why the masses of the eggs increased.
Ans: 1. Water entered by osmosis
2. From a dilute solution in the beaker to a more
concentrated solution in the egg.
3. Through a partially permeable membrane.