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1 (a) Explain why a leaf is considered to be an organ. [2]
(b) Explain how layer B and layer C in Fig. 1.1 are adapted for their functions. [6] [Image_1: Diagram of leaf cross-section]
(c) A student placed a plant in a very hot room for 12 hours. There was a bright light in the room and the plant was not given any water during the 12-hour period. Fig. 1.2 shows a series of sketches that the student made of the stomata during the investigation. [Image_2: Series of stomata sketches]
(i) Identify the cell labelled D on Fig. 1.2. [1]
(ii) State the main function of the stomata. [1]
(iii) State the advantage to the plant of the change to the stomata shown in Fig. 1.2. [1]
(d) The student increased the humidity in the room and repeated the investigation. Predict and explain the effect of high humidity on the stomata. [3]
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2 (a) Draw a circle on Fig. 2.1 to identify one pair of bases. [1] [Image_3: Diagram of DNA molecule]
(b) The percentage of T bases in the DNA of a species is 29%. Calculate the percentage of bases that would be base G in the DNA of this species. Space for working. [1]
(c) (i) State the name given to a length of DNA that codes for a protein. [1]
(ii) Explain how proteins are made by a cell. [5]
(iii) DNA controls cell function by controlling the production of proteins. State two types of cell membrane proteins. [2]
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3 (a) Antibiotic resistance is an increasing problem worldwide. Erythromycin is an antibiotic.
Fig. 3.1 shows the daily doses of erythromycin per 1000 people over a 13-year period. The number of bacterial infections resistant to erythromycin per 1000 people is also shown. [Image_4: Graph of antibiotic resistance]
(i) Calculate the percentage change in the number of bacterial infections resistant to erythromycin per 1000 people between 1993 and 1995. Give your answer to two significant figures. Space for working. [3]
(ii) Describe the data shown in Fig. 3.1. [3]
(iii) Suggest reasons for the change in the number of bacterial infections resistant to erythromycin from 1993 to 1995 shown in Fig. 3.1. [2]
(iv) Explain how bacteria become resistant to antibiotics. [5]
(b) (i) Bacteria are prokaryotes. State two features of all prokaryotes. [2]
(ii) Some bacteria have a flagellum. State the function of a flagellum. [1]
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4 (a) A student recorded the information about an aquatic habitat. Fig. 4.1 shows the student’s notes. [Image_5: Notes on aquatic habitat]
(i) Construct a food web to show the feeding relationships described in Fig. 4.1. [4]
(ii) Complete Table 4.1 using the information in Fig. 4.1 by identifying the names of the missing trophic levels and one organism at each different trophic level. [Table_1: Trophic levels] [3]
(iii) Outline how the energy in the primary consumers in this aquatic food web is used to produce biomass in the secondary consumers. [3]
(iv) Humans also eat salmon. Predict the impact on the feeding relationships shown in Fig. 4.1 of overharvesting of salmon. [3]
(b) Describe what is meant by the term decomposer. [1]
(c) Animals such as salmon can be farmed for meat. Explain why it is more energy efficient for humans to eat crop plants than to eat livestock that have been fed on crop plants. [4]
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5 (a) State the name and function of the cell structure labelled A in Fig. 5.1. [2] [Image_6: Photomicrograph of cell structure]
(b) State the two pieces of information needed to calculate the actual length of cell structure A in Fig. 5.1. [1]
(c) The actual length of cell structure A is 0.000 75 mm. Convert this value to micrometres (\(\mu m\)). [1]
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6 (a) A student investigated plant growth responses in roots and shoots. They used this method: • Damp cotton wool was placed in two Petri dishes. • Three bean seedlings were attached to the cotton wool in each Petri dish. • Each seedling was orientated so that the roots pointed in a different direction in each Petri dish. • Petri dish 1 was kept on its side in a fixed position. • Petri dish 2 was kept on its side and rotated constantly. • Both Petri dishes were kept in the dark. • After two days the seedlings were observed. Fig. 6.1 is a diagram of the apparatus. [Image_7: Diagram of apparatus]
Fig. 6.2 shows the seedlings after two days. [Image_8: Seedlings after two days]
(i) Describe the pattern of growth of the bean roots and shoots in Petri dish 1 shown in Fig. 6.2. [1]
(ii) State the name of the growth responses observed in the bean roots and shoots. [1]
(iii) Explain how auxin causes the difference in the pattern of growth shown by the shoots of seedlings B and E shown in Fig. 6.2. [5]
(b) Seeds require oxygen and water to germinate. (i) State one other environmental condition that affects germination. [1]
(ii) Suggest why oxygen and water are required for germination. [2]
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7 Complete the sentences about enzymes by writing a suitable word or phrase in each of the spaces provided. Enzymes are involved in chemical digestion which produces small ... molecules that can be absorbed into the blood. Two examples of protease enzymes are pepsin and trypsin. Pepsin is produced by the ... and requires acidic conditions. These conditions are created by the release of ..., which provides the optimum pH for pepsin activity and also kills harmful .... The ... produces trypsin which breaks down protein in ... pH conditions. These conditions are created by a substance called ..., which neutralises the gastric juices and also has an important role in the ... of fats and oils. [8]
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