CHS 2023 - Sec 4 BIOLOGY Prelim Exam PAPER 2 - Questions

Name: Index Number: Class: CATHOLIC HIGH SCHOOL Preliminary Examination Secondary 4 A BIOLOGY 6093/02 Paper 2 Thursday 24 August 2023 1 hour 45 minutes Additional Materials: - READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE ON THE MARGINS. Section A Answer all questions. Write your answers in the spaces provided on the Question Paper. Section B Answer all questions. Write your answers in the spaces provided on the Question Paper. Electronic calculators may be used. You are advised to spend no longer than one hour on Section A and no longer than 45 minutes on Section B. The number of marks is given in brackets [ ] at the end of each question or part question. For examiner’s use only: Section A / 50 Section B / 30 This paper consists of 19 printed pages. [Turn over

2 Section A Answer all questions. Write your answer in the spaces provided. 1 Some young grass plants were grown with their roots in a mineral solution that contained nitrate ions. The plants were divided into two batches, N and P. Cyanide, which inhibits aerobic respiration, was added to the solution given to the plants in batch P. The quantity of nitrate ions in the plants was determined at regular intervals for 70 hours. After 60 hours, the mineral solution was replaced by distilled water. The results are shown in Fig. 1.1. Fig. 1.1 Use the data in Fig. 1.1 to answer parts (a) to (c). (a) Calculate the rate of absorption of nitrate ions in batch N between 40 and 60 hours. Show your working. mg per hour [2]

3 (b) Explain why the absorption of nitrate ions by the plants in batch N differs from that in batch P; [4] (c) Explain why the mean quantity of nitrate ions in both batches of plants decreased after 60 hours. [2] [Total: 8 marks]

4 2 (a) Cartilage is present in some parts of the gas exchange system to prevent collapse due to pressure changes during inhalation. State two parts of the gas exchange system in which cartilage is located. and [1] (b) Fig. 2.1 shows the changes that occur in atmospheric pressure and oxygen concentration as altitude changes. The highest altitude at which people live permanently is 5100 m. Fig. 2.1 With reference to Fig. 2.1: (i) describe the effect of increasing altitude on both atmospheric pressure and the oxygen concentration [2] (ii) calculate the change in the atmospheric pressure when a person travels from sea level to an altitude of 3500 m. Show your working. answer [2] oxygen concentration / %

5 (c) When a person travels from 0 m (sea level) to a high altitude, gas exchange in the lungs is affected. A condition known as hypoxia results, where the body tissues do not receive an adequate oxygen supply. Explain how hypoxia occurs when a person ascends from sea level to a high altitude. [4] (d) At high altitudes, short-term responses by the body to hypoxia include: • a decrease in the volume of plasma in the blood • a decrease in the volume of blood pumped out of the heart per heart beat • an increase in the heart rate • an increase in the breathing rate. (i) Suggest why a decrease in the volume of plasma in the blood may reduce the effects of hypoxia [1] (ii) Explain why an increase in the heart rate occurs in response to hypoxia. [2] [Total: 12 marks]

6 3 (a) Fig. 3.1 shows a flower that reproduces using insect-pollination. Fig. 3.1 With reference to Fig. 3.1, describe two ways which the labeled parts differ in a wind-pollinated flower. 1 2 [2] (b) Mimulus is a plant genus containing a diverse range of species that have colourful flowers to attract pollinators, such as bees and hummingbirds. Pollinators transfer pollen between flowers for plant sexual reproduction. Table 3.1 compares some features of two closely-related species of Mimulus that both grow in the same region of North America. The features in which they differ are: • the altitude at which the two species grow • their flower characteristics, including petal colour and the distance from the opening of the flower to the nectar on which the pollinators feed • the percentages of pollinator visits that they receive from bees or from hummingbirds. Table 3.1 species of Mimulus altitude/ m petal colour distance to nectar/mm percentage of visits from pollinator type bee hummingbird M. lewisii 1600 – 3000 pink 14 100 0 M. cardinalis 0 – 2000 red 27 3 97

7 With reference to the data in Table 3.1, explain how the exchange of genetic materials between M. lewisii and M. cardinalis populations is prevented. [3] (c) Breeding experiments in the laboratory show that M. lewisii and M. cardinalis can breed together and produce offspring. The F1 hybrid offspring are fertile. Suggest, with reasons, what prediction can be made about the chromosome numbers of M. lewisii and M. cardinalis. [2] (d) The inheritance of the petal colour was investigated. Draw a genetic diagram to show a cross between two heterozygous parents with pink petals. Use the symbols R and r for the alleles representing red and white petals respectively. parental genotypes gametes offspring genotypes offspring phenotypes [3] [Total: 10 marks]

8 4 (a) Maize is an important food crop that has been improved both by selective breeding and by genetic engineering. (i) Outline how selective breeding has been used to improve maize. [2] (ii) Suggest two advantages of genetic engineering over selective breeding. 1 2 [2] (b) Fig. 4.1 shows part of a maize cob. The cob is made up of many individual seeds called kernels. Each kernel results from a separate fertilisation of a male and a female gamete. Some kernels are yellow and some are purple. Fig. 4.1 Name the type of variation shown in Fig. 4.1. Suggest a genetic explanation for this pattern of variation in colour. type of variation explanation [2]

9 (c) Mammoths are extinct mammals related to elephants. About three million years ago, the ancestors of mammoths migrated from Africa into Europe and Asia. There, about 1.7 million years ago, the steppe mammoth evolved and became adapted to the cooler conditions. Then, about 700 000 years ago, as the climate changed and the Arctic became much colder, the woolly mammoth evolved. Woolly mammoths showed a number of obvious adaptations to reduce heat loss, including thick fur, small ears and small tails. Fig. 4.2 shows the steppe mammoth (top) and the Woolly mammoth (bottom). Fig. 4.2 (not to scale) Adapted from https://prehistoric-fauna.com/Mammuthus-sungari (Steppe mammoth) and https://www.theboxplymouth.com/blog/press-release/mammoth-moment (Woolly mammoth)

10 Explain how variation and natural selection may have brought about the evolution of the woolly mammoth from the steppe mammoth. [4] [Total: 10 marks]