YTSS PURE BIO 1

NAME: ( ) CLASS: YISHUN TOWN SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SEC 4 EXPRESS BIOLOGY (6093/2) DATE : 26 August 2024 DAY : Monday DURATION: 1 hr 45 min MARKS: 80 marks READ THESE INSTRUCTIONS FIRST Write your name, class and register number in the spaces provided at the top of this page. Section A Answer all the questions. Write your answers in the spaces provided. Section B Answer one question. Write your answers in the spaces provided. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. You may use an approved calculator. Section A Section B TOTAL This question paper consists of 18 printed pages

2 SECTION A (70 MARKS) Answer all questions in this section. 1 The malarial pathogen, P. falciparum, enters red blood cells after a person becomes infected. Fig. 1.1 shows a sample of an infected person’s blood with 3 red blood cells which are infected with P. falciparum. Fig. 1.1 (a) With reference to Fig. 1.1, suggest two ways how the presence of P. falciparum affects a red blood cell. [2] 1. ...……………………………………………………………………………………… …………………………………………………………………………………………… 2. ...……………………………………………………………………………………… …………………………………………………………………………………………… (b) Using your answers from (a), explain how the change might affect the function of the red blood cell. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… (c) State three other components of blood not shown in Fig. 1.1. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… infected red blood cells

3 2 Plants have specialised cells for the efficient transport of manufactured food. Table 2.1 shows some of the features of two different types of cells found in plant tissue, which are adapted for the efficient transport of manufactured food. Key ✓ present  absent Table 2.1 (a) Name three substances that are transported by these specialised cells. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… (b) Identify both cell types: [2] Cell type A:………………………………………… Cell type B:………………………………………… (c) Explain how both cells work together to perform their function. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… feature of cell cell type A cell type B cytoplasm ✓ ✓ nucleus  ✓ mitochondria none many cellulose in the cell wall ✓ ✓ ribosomes  ✓

4 3 Fig. 3.1 shows some common morning glory flowers in two different colours. Fig. 3.1 The gene that determines flower colour in the morning glory plant has two alleles: • a dominant allele that results in purple flowers, A • a recessive allele that results in red flowers, a Two heterozygous morning glory plants were crossed and their F1 generation is grown in an open field. (a) Using your knowledge of monohybrid inheritance, complete the genetic diagram to predict the ratio of the colour of the flowers of the F1 generation. [4] Phenotype of parents: …………………………. …………………………. Genotype of parents: ………… ………… Gametes: ………… ………… ………… ………… Genotype of F1 generation: ………… ………… ………… ………… Phenotype of F1 generation: ………… ………… ………… ………… Ratio of F1 generation: ……………………………………………………………………………

5 (b) A student observed the flower colour of all the morning glory plants in the field and recorded 660 plants with purple flowers and 440 plants with red flowers. (i) State the observed ratio. [1] …………………………………………………………………………………………… (ii) Suggest why the ratio in (a) is different from the ratio in (b)(i). [2] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… (c) State the expected ratio of the plants that are homozygous dominant to the plants that are heterozygous for flower colour in the F1 generation in (a). Hence, use it to calculate the expected number of heterozygotes in the open field. Show your working. [2] Ratio: …………………………………… Expected number of heterozygotes: ………………………… (d) A particular morning glory plant in Japan has over 20 different flower colour phenotypes, including shades of blue, purple, red and pink. The flower colour of Japanese morning glory is controlled by at least four genes. The flower colour can change gradually after the flowers open each morning and can change with fluctuations in the carbon dioxide concentration of the surrounding air. A student concluded that the flower colour phenotype in Japanese morning glory shows continuous variation. Suggest two reasons why the student made this conclusion. [2] 1. …………………………………………………………………...………………….... …………………………………………………………………………………………… 2. ...…………………………………………………………………………………….... ……………………………………………………………………………………………

6 4 Scientists investigated the response of stomata to changing carbon dioxide (CO 2) concentrations in the butterfly pea plant. The scientists placed butterfly pea plants in chambers. They measured the width of open stomata (stomatal apertures) after the plants had been exposed to different CO 2 concentrations for 40 minutes. Other environmental factors were kept constant. The relationship between CO 2 concentration and the average width of stomatal apertures is shown in Fig. 4.1. Fig. 4.1 (a) State two key environmental factors that were kept constant. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… (b) In 2016, a study measured the atmospheric CO2 concentration as 400 ppm. In the future, climate change may reduce water availability and increase atmospheric CO2 concentrations in some habitats. Suggest how the stomatal response shown in Fig. 4.1 would allow the butterfly pea plant to survive the effects of climate change. [2] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… average width of stomatal aperture / µm CO2 concentration / ppm

7 rate of release of oxygen / arbitrary units (au) temperature / oC (c) In another experiment, scientists investigated the effect of temperature on a certain process in the butterfly pea plant. Fig. 4.2 shows how the rate of release of oxygen by a plant varies with temperature on a sunny day. Fig. 4.2 (i) Calculate the average increase in rate of release of oxygen as the temperature increases from 5°C to 20°C. Show your working. Give your answer to two decimal places. [2] (ii) Suggest why the rate of release of oxygen levels off and then decreases after 20°C. [3] …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… (iii) On Fig. 4.2, sketch a curve to show the rate of release of oxygen on a cloudy day. [1]

8 5 The potato plant is an important food crop. Crop yield (amount of crop harvested) is reduced if the leaves of the plant are eaten by the larvae of the potato bug. Scientists used genetic engineering to create two genetically modified (GM) vari