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(a) Explain, using only features visible in Fig. 1.1, why \textit{Ranunculus cymbalaria} is classified as a dicotyledonous plant rather than as a monocotyledonous plant. [2]
(b) Suggest why there are few starch grains in the cells of W compared with a large number of starch grains in the cells of S. [3]
(c) Describe how enzymes in root cells synthesise starch. [3]
(d) As temperature is increased, for example from 10 °C to 30 °C, enzyme activity increases.
Explain how increasing temperature affects enzyme activity. [2]
[Image_1: Fig. 1.1 shows a buttercup, \textit{Ranunculus cymbalaria}. Fig. 1.1B shows details of a flower of the same plant.]
[Image_2: Fig. 1.2 shows a transverse section through a buttercup root at the end of the cold winter (W) and at the end of the warm, moist summer (S).]
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(a) Define the term excretion.
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(b) Explain how, when the patient is receiving dialysis treatment
(i) the loss of plasma proteins and red blood cells is prevented,
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(ii) the normal glucose concentration of the blood is maintained.
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Fig. 2.1 shows a dialysis machine for treating people who have kidney failure. The dialysate (dialysis fluid) is a solution of glucose and salts.
(c) A person with kidney failure received regular dialysis treatment for 17 days.
Fig. 2.2 shows how the concentration of urea in the blood changed over the 17 days.
(i) State how many times the person received dialysis treatment.
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(ii) Calculate the decrease in the concentration of urea in the blood from the beginning of dialysis until the end of the treatment.
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(iii) Describe the changes that occur in the urea concentration in the blood over the period shown in Fig. 2.2. You will gain credit for using the data in Fig. 2.2 in your answer.
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(iv) Explain the changes in urea concentration in the blood as shown in Fig. 2.2.
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(a) In the space below write a balanced chemical equation for anaerobic respiration in muscles.
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Some students investigated the breathing of a 16-year old male athlete. Fig. 3.1 shows the pattern of his breathing for 60 seconds when resting. Fig. 3.2 shows the pattern of his breathing while he took some exercise for 60 seconds.
[Image_1: Fig. 3.1 shows a graph of volume of air in dm^3 over time in seconds. The peaks are less frequent compared to Fig. 3.2]
[Image_2: Fig. 3.2 shows a graph of volume of air in dm^3 over time in seconds with more frequent peaks compared to Fig. 3.1]
Table 3.1 shows a summary of the results obtained by the students.
[Table_1]
| | breathing at rest | breathing during exercise |
|-------------------------|-------------------|---------------------------|
| volume of air breathed in with each breath / dm$^3$ | 0.5 | ................................ |
| rate of breathing / number of breaths per minute | 11 | ................................ |
| volume of air breathed in per minute / dm$^3$ | 5.5 | ................................ |
(b) Using information from Fig. 3.2, complete Table 3.1.
Write your answers in Table 3.1. [3]
(c) Explain the effect of exercise on the student’s breathing.
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(d) During strenuous exercise, the hormone adrenaline causes changes in the pulse rate and in the concentration of glucose in the blood.
Explain the importance of these changes during strenuous exercise.
pulse rate
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concentration of glucose in the blood
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The human immunodeficiency virus (HIV) infects white blood cells. The virus is reproduced inside these white blood cells.
(a) Describe what may happen to viruses that leave infected white blood cells. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. [2]
(b) Describe the possible long-term effects of HIV on the immune system. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. [3]
(c) People with HIV may be treated with a variety of drugs.
(i) Define the term drug. .................................................................................................................................................................................. .................................................................................................................................................................................. [1]
(ii) Explain why antibiotics cannot be used to control HIV. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. .................................................................................................................................................................................. [2]
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(a) (i) Describe the changes that occur to the oxygen concentration in the river as shown in Fig. 5.1. You will gain credit for using the data in Fig. 5.1 in your answer.
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(a) (ii) Name the invertebrate animal that is only found in water with the highest oxygen concentration.
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(a) (iii) Name the two invertebrate animals that tolerate the lowest oxygen concentrations.
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(a) (iv) Suggest and explain the changes in the number of different species of invertebrate animals along the river, as shown in Table 5.1.
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(b) Explain how bacteria breakdown these nutrient molecules.
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(c) Explain two ways in which the concentration of nitrate ions may be reduced as the water flows through the reed beds.
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(d) Some bacteria that live in reed beds release methane. Other sources of methane are cattle and flooded rice fields.
Explain the environmental consequences of an increase in the methane concentration in the atmosphere.
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(a) Define the term \textit{self-pollination}.
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Snapdragon plants have flowers with three colours: red, pink and white.
Some students investigated the inheritance of flower colour in snapdragons.
In \textit{cross 1} they cross-pollinated plants that were homozygous for red flowers with plants that were homozygous for white flowers. They collected and planted the seeds from cross 1. All of the resulting plants had pink flowers.
In \textit{cross 2} they self-pollinated all the pink-flowered plants and found that in the next generation there were red-flowered plants, white-flowered plants and pink-flowered plants.
(b) Complete the genetic diagrams to show how flower colour is inherited in snapdragon plants.
Use the symbol $I^{R}$ for the allele for red flowers and $I^{W}$ for the allele for white flowers.
\textit{cross 1} parental phenotypes red flowers $\times$ white flowers
parental genotypes ............ $\times$ ............
gametes
offspring genotypes ..............
offspring phenotypes pink flowers
\textit{cross 2} parental phenotypes pink flowers $\times$ pink flowers
parental genotypes ............ $\times$ ............
gametes
offspring genotypes .........................................................................................................
ratio of offspring phenotypes ......................................................................................................... [4]
(c) Another student cross-pollinated pink-flowered plants with white-flowered plants.
Complete the genetic diagram to show the results that the student would expect.
phenotypes pink flowers $\times$ white flowers
genotypes ............ $\times$ ............
gametes
offspring genotypes .........................................................................................................
ratio of offspring phenotypes ......................................................................................................... [3]
(d) Explain the advantages of sexual reproduction to a species of flowering plant, such as the snapdragon.
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