Oct/Nov 2023

What characteristics do bacteria have?

Features of organisms

The apparatus illustrated was used by a student to determine how the rate of water loss from the leafy stem changed as wind speed increased. Which graph could have been drawn from the results?

Transpiration and translocation

In children, a deficiency disease can lead to bones that are soft and misshapen. What is the name of this deficiency disease, and what causes it?

Diet

The diagram illustrates the human digestive system. At which parts do ingestion and egestion take place?

Human digestive system

Which graph most accurately shows how pH affects the activity of gastric protease?

Effects of temperature and pH

The graph illustrates how lung volume changed during breathing while a person was resting and then after they started to exercise. As the person moved from rest to exercise, the amount of air taken in with each breath rose from $x$ dm$^3$ to $y$ dm$^3$. From the graph, which numbers should be used to fill the gaps in the sentence correctly?

Human gas exchange

What substances are produced by anaerobic respiration in muscle?

Anaerobic respiration

Which label indicates the site where lactic acid is broken down?

Anaerobic respiration

Two individuals completed a brief session of exercise on a treadmill. Both people ran on the treadmill for the same length of time and at the same speed. The graph illustrates the pulse rates of these two individuals before, during and after the exercise period. Which interpretation of the graph is correct?

Heart

Which blood vessels transport deoxygenated blood?

Blood vessels

How is the microorganism responsible for cholera described, and by what route is it passed on?

Disease

A group of students was given several arthropod specimens. They counted how many legs each arthropod had. Their findings are given in the table. Number of legs and number of arthropods with that number of legs: - 6 legs: 10 - 8 legs: 4 - 10 legs: 4 - 20 or more legs: 2 Which statement about the arthropods is correct?

Features of organisms

The chart shows data for a car travelling at $110\,\text{km h}^{-1}$ with a driver who has not taken alcohol. It indicates the distance the car covers from the moment the driver spots a hazard and responds by applying the brakes, and then the distance it will continue to travel before it comes to a complete stop. If that same driver drinks alcohol before setting off, the distance covered before reacting to the hazard rises by $20\%$. What would the car’s total stopping distance be in that case?

Mammalian nervous system

Medicines can be used to treat infections in the body. What are antibiotics used to treat?

Antibiotics

Human immunodeficiency virus (HIV) damages the immune system, causing a reduction in lymphocyte numbers. A diagnosis of AIDS may be made once lymphocyte numbers fall below $200$ cells mm$^{-3}$ of blood. The graph shows the lymphocyte numbers after HIV infection in a patient. After how many years from infection would this patient be diagnosed with AIDS?

Immunity

A treatment known as dialysis is used by some people to remove waste products and extra salts from their blood. In these individuals, which body part is not working properly?

Urinary system

What change takes place in the eye when a person focuses on a vehicle that is moving towards them from far away?

Mammalian sense organs

A beam of light was directed into a person’s eye for $50$ seconds. While this was happening, the light intensity was altered. The graph illustrates how the person’s pupil size changed. Which statement accounts for the change in pupil size?

Mammalian sense organs

The graph represents a person's blood sugar level across eight hours. No exercise was done during this period. Which statement accounts for the shape of the graph between $X$ and $Y$?

Blood glucose control

Which actions might cause the hair erector muscles in the skin to contract?

Temperature control

An investigation into the growth of a young plant shoot was arranged, as shown. What will the shoot look like after $48$ hours?

Coordination and response in plants

A scientist collects four pairs of samples from a wild cherry tree. In which pair of samples might there be cells with different genotypes?

Variation

The diagram presents two plant cells, X and Y. Cell X has a greater water potential than Y. In what direction, and through which process, will water move between these two cells?

Diffusion and osmosis

The diagram illustrates how many carrot plants can be grown from small sections of carrot root. Which row is correct for this method of plant reproduction?

Asexual and sexual reproduction

During plant reproduction, these processes happen. What is the correct sequence in which they occur?

Sexual reproduction in plants

Which hormone triggers an egg cell to be released from the ovary?

Mammalian hormones

The diagram depicts a baby just before birth. Which labelled structures are the cervix and the uterus?

Sexual reproduction in humans

In a DNA molecule, the strands are held together by bonds between base pairs. Which base pairs occur in DNA?

DNA

In humans, the inheritance of the ABO blood groups is determined by three alleles ($I^{A}$, $I^{B}$ and $I^{O}$), of which only two may occur in any one individual. What blood groups could the children of a homozygous group A woman and a heterozygous group B man have?

Inheritance

The antibiotic penicillin is made by a fungus named Penicillium. The graph illustrates how the masses of Penicillium fungus, penicillin and sugar change in a fermenter during the manufacture of one batch of antibiotic. What does each curve on the graph represent?

Biotechnology

The diagram illustrates a food chain. mahogany tree $\rightarrow$ caterpillar $\rightarrow$ songbird $\rightarrow$ hawk. Which organisms are found in the greatest numbers in this food chain?

Energy flow

Some bacteria and fungi function as decomposers. What is formed when decomposers decompose plant and animal protein?

Nutrient cycles

What does the term community mean?

Ecosystems and biodiversity

Which row shows how ions and molecules are transported by active transport?

Active transport

The list below shows some changes that may take place in a lake polluted with nitrogen-containing fertiliser. In what order do these changes happen?

Effects of humans on ecosystems

A student performed two tests on a liquid sample. After Benedict’s solution was added to part of the liquid and the mixture was heated, it became red. When biuret reagent was then added to the remaining liquid, it changed to mauve (purple). Which conclusion is correct?

Biological molecules

Enzymes take part in many reactions inside living cells. Which statement explains the way enzymes act?

Enzyme action

The diagram illustrates the movement of substances involved in photosynthesis in a leaf. Which row gives the correct labels for the diagram?

Photosynthesis

The diagram shows a plant cell. Compared with the rest of the cell, which row gives the concentrations of oxygen and magnesium within structure P during daytime?

Photosynthesis

The diagram depicts a root hair cell. In what way does the shape of the cell benefit the plant?

Specialised cells, tissues and organs

Which structures are characterised by having both cytoplasm and cell walls?

Cell structure and function

Which alteration in conditions will lower the rate of transpiration?

Transpiration and translocation

Which of the following are the correct definitions of digestion and assimilation? 1 the taking of food into the body via the mouth 2 the splitting of large insoluble food molecules into smaller soluble molecules 3 the absorption and use of food molecules in the cells of the body 4 the passage of food molecules across the wall of the intestine into the blood and lymph

Absorption and assimilation

Which organ makes an acid that destroys bacteria in food that has been eaten?

Human digestive system

The table presents the absorption rates of two different sugars, arabinose and glucose, in living and dead intestines. In each case, the sugar concentrations inside the intestines were identical. What are the main methods by which arabinose and glucose are absorbed in living intestine?

Active transport

Which table illustrates muscle movement during inspiration?

Human gas exchange

Which apparatus can be used to investigate how carbon dioxide is produced by the anaerobic respiration of yeast?

Anaerobic respiration

The diagram shows the equation for aerobic respiration. $\ldots\ldots 1 \ldots\ldots + \ldots\ldots 2 \ldots\ldots \rightarrow \ldots\ldots 3 \ldots\ldots + \ldots\ldots 4 \ldots\ldots$ Which words correctly fill gaps 1-4?

Aerobic respiration

The graph illustrates one person’s pulse rate across a time interval in which they are resting, riding an exercise bike, and then resting once more. At what point did the person cease pedalling?

Circulatory system

Which row gives the names of the blood vessels that carry blood to and from the liver and the kidney?

Blood vessels

What does the term pathogen mean?

Disease

Which statement gives the definition of a species?

Concept and use of a classification system

Malaria can be controlled through the use of mosquito nets treated with insecticide and placed over beds. Using these bed nets lowers the number of bites from infected mosquitoes. The graph illustrates the effect of using bed nets on the average number of mosquito bites in a group of people. Which conclusion can be drawn from these data?

Disease

Antibiotics are effective against which kind of infection or disease?

Antibiotics

The graph illustrates how the concentration of antibodies in a child’s blood changes over time. It indicates the changes in antibody concentration after the child has been vaccinated against a specific disease and after the child has been infected by the pathogen responsible for that disease. From the graph, which statement is correct?

Immunity

Which label indicates the place where urea is produced?

Excretion

A student was asked to compare a typical spinal reflex response with a voluntary movement. He has made one error in his comparison. Which row contains the incorrect statement?

Mammalian nervous system

A person is in a room that is darkened. After five seconds, a light is switched on. Five seconds later, the light is switched off once more. Which graph shows the changes in the diameters of their pupils?

Mammalian sense organs

Statements describing the body’s reaction to changes in temperature are given. 1. Arterioles in the skin surface constrict. 2. Arterioles in the skin surface dilate. 3. Hair erector muscles contract. 4. Hair erector muscles relax. 5. Sweat evaporates from the skin. 6. Muscles contract spontaneously. Which statements are part of the body’s response to hot weather?

Temperature control

The diagram illustrates how the concentration of glycogen stored in the liver of a human varies with time. These changes help keep the concentration of glucose in the blood constant. In which periods does the concentration of glucose in the blood rise above the average level?

Blood glucose control

The diagram illustrates some seedlings that have been grown in light. Which statement describes how auxin is distributed in the seedlings?

Coordination and response in plants

A plant contains 20 chromosomes in its leaf cells. It reproduces sexually and also asexually. What is the correct chromosome number in the gametes and in the cells involved in asexual reproduction?

Asexual and sexual reproduction

The diagram illustrates an experiment. At the beginning of the experiment, a starch suspension is white and iodine solution is yellow/brown. After $6$ hours, the starch suspension is blue/black. Why has the starch suspension changed colour?

Biological molecules

What are the characteristics of sexual reproduction? 1. fusion between diploid nuclei 2. fusion between haploid nuclei 3. formation of clones 4. formation of genetically different offspring

Asexual and sexual reproduction

Which flower structure makes pollen?

Sexual reproduction in plants

The diagram illustrates the female reproductive system. Which row gives the correct labels for the diagram?

Sexual reproduction in humans

The diagram illustrates a fetus inside the uterus. Which structures are necessary for nourishing the fetus, and which structures are necessary for supporting it and shielding it from mechanical shocks?

Sexual reproduction in humans

Which statements are correct? 1. Every chromosome has one DNA molecule. 2. A gene is a length of DNA located on a chromosome. 3. A gene includes smaller regions known as alleles.

Inheritance

The diagram illustrates the inheritance of the allele, E, for polydactyly (having extra fingers), which is dominant to the allele for no extra fingers, e. What genotypes do persons M and N have?

Inheritance

Three flasks were arranged as shown at $35\,^{\circ}\text{C}$. A balloon was fitted to the mouth of each flask. Flask 1 contains water, yeast and sugar. Flask 2 contains water and sugar. Flask 3 contains water and yeast. The degree of balloon inflation was noted after one hour. In what order are the balloons arranged from the one that is most inflated to the one that is least inflated?

Anaerobic respiration

In a tree, insect larvae tunnel through its leaves. The insects that emerge are then consumed by birds, and parasitic fleas live among the birds’ feathers. For this food chain, which pyramid represents biomass and which pyramid represents numbers?

Energy flow

The fossil fuels used as energy sources today were formed from the remains of plants and animals that became buried millions of years ago. What was the original source of the energy stored in these fossil fuels?

Photosynthesis

Which term is used to describe the number of different species living in an area?

Ecosystems and biodiversity

The table gives the relative concentrations of two mineral ions in a root cell and in the water in the soil surrounding the plant root. Water around root: magnesium ions $23$ arbitrary units, nitrate ions $19$ arbitrary units. Inside root cell: magnesium ions $2475$ arbitrary units, nitrate ions $1306$ arbitrary units. What is required for the plant root to raise the concentration of the mineral ions in its cells?

Active transport

When large amounts of nitrates are carried into rivers, these changes may happen and fish may die. 1. Water plants die and sink to the river bed. 2. Bacteria increase very quickly. 3. The concentration of oxygen in the water falls. 4. More single-celled water plants grow, turning the water green. In what sequence do these changes happen?

Effects of humans on ecosystems

Certain health conditions may be identified by carrying out chemical tests for protein and glucose in urine. Which row gives the outcomes for a person whose urine contains protein and glucose?

Urinary system

Which statement gives a description of enzyme-catalysed reactions?

Enzyme action

The diagram illustrates an aphid feeding on sugar inside a leaf. As the aphid feeds, what is the sequence in which its mouthparts move through the leaf tissues?

Leaf structure

Which processes require plants to have either nitrate ions or magnesium ions?

Mineral nutrition

Which row identifies the processes by which nitrate ions and water from soil enter a root hair cell?

Uptake and transport of water and ions

Human blood is made up of several different components, each with its own role.

Blood

Fig. 2.1 presents the life cycle of the plant Coffea arabica. This plant makes seeds that are used to produce coffee.

Sexual reproduction in plants

Fig. 3.1 uses a bar chart to show what percentage of total human body mass is contributed by the five most frequent elements in the human body.

Biological molecules

Dust may irritate receptor cells in the lining of the nose or throat, which can set off a sneeze. When sneezing occurs, air is expelled from the lungs forcefully and the eyelids shut.

Variation

Fig. 5.1 shows two structures that are part of the human digestive system.

Human digestive system

Fig. 6.1 presents a biological molecule.

DNA

A plant root hair cell is carrying out aerobic respiration. Name the structures inside the cell that perform aerobic respiration.

Aerobic respiration

The size of a population may change over time. Table 8.1 indicates how the estimated worldwide populations of humans and tigers are thought to have altered from 1970 to 2000.

Conservation

Cholera is brought about by an organism type that can be transferred from one host to another.

Cell structure and function

Fig. 2.1 depicts a reindeer. Reindeer inhabit treeless regions of the Arctic. In certain months of the year, reindeer feed mainly on grasses, ferns and mosses. Wolves and brown bears eat reindeer.

Energy flow

Fig. 3.1 presents diagrams showing the flow of blood into and out of three major organs through blood vessels P to U.

Blood vessels

Fig. 4.1 presents a Siamese fighting fish that lives in fresh water.

Nuclear division

A student is studying how an enzyme is used in fruit juice production. The student does the following: chops one apple into small pieces; places the same number of pieces into each of three beakers, A, B and C; adds $2\,\text{cm}^3$ of a dilute enzyme solution to the apple in beakers A and B; adds $2\,\text{cm}^3$ of distilled water to the apple in beaker C; keeps each beaker in a water-bath at a fixed temperature for 30 minutes; then filters the juice from each beaker into a separate measuring cylinder and notes the volume of juice gathered in each measuring cylinder.

Enzyme action

Fig. 6.1 shows a plant leaf in cross-section.

Leaf structure

Mangrove trees develop in forests that make up an important coastal ecosystem. Mangrove forests show high biodiversity, with many different animal species living there.

Ecosystems and biodiversity

Hydrogen peroxide is a poisonous waste substance present in cells. The enzyme catalase, which is found in cells, decomposes hydrogen peroxide to form water and oxygen. hydrogen peroxide  catalase  water + oxygen If potato tissue is placed into a hydrogen peroxide solution in a test-tube, the catalase in the potato cells makes oxygen bubbles form. When detergent is added to the hydrogen peroxide solution, the oxygen bubbles become trapped and build up as a bubble layer that moves up the test-tube. The height of this layer shows how much catalase activity has taken place. A student used this method to investigate the activity of the catalase in potato tissue by following these instructions: • Label three large test-tubes A, B and C. • Add $5\text{ cm}^3$ of hydrogen peroxide solution to each test-tube. Hydrogen peroxide is an irritant that may damage eyes and skin. • Add $1\text{ cm}^3$ of detergent to the hydrogen peroxide solution in each test-tube. • Cut three pieces of potato measuring $10\text{ mm} \times 10\text{ mm} \times 10\text{ mm}$. • Put one of the pieces of potato into test-tube A. • Start the timer immediately and watch the potato piece. Oxygen bubbles will rise to the surface and make a layer at the top of the hydrogen peroxide solution. • Measure the height of this layer at 2, 4 and 6 minutes from the start and record these values. The height of the bubble layer should be measured from the top of the hydrogen peroxide solution to the top of the bubble layer, as shown in Fig. 1.1.

Enzyme action

Bacteria may be cultivated on agar jelly inside a Petri dish. As they grow and multiply, the transparent agar jelly turns cloudy. Antibiotics can stop bacteria from growing. Circles of filter paper soaked in an antibiotic solution can be placed on the agar surface. If the region around a disc stays clear, the antibiotic has stopped the bacteria from growing. The larger the clear region, the more effective the antibiotic is. A student investigated the effect of distilled water (E) and four different antibiotics (F, G, H and J) on some bacteria using the method described. They prepared three identical Petri dishes and measured the diameter of the clear regions around the filter paper discs after a few days. No clear region was seen around disc E in any of the Petri dishes. Fig. 2.1 shows the results for Petri dish 3.

Antibiotics

Fig. 3.1 shows a photomicrograph of a kidney section containing several kidney tubules.

Urinary system

Certain animals living in cold environments must limit how much heat escapes from their bodies. A student explored how an insulating material affects heat loss from an animal. A test-tube was used to model the animal, and wool, which is known to be a good insulator, was used. A line was marked on the test-tube 2 cm below the top. The wool was put into a beaker, and the test-tube was inserted so that it was fully surrounded by wool, as shown in Fig. 1.1. A second marked test-tube was set in a test-tube rack, as shown in Fig. 1.1. No insulation was used for this one. Hot water was poured into both test-tubes up to the marked lines. The timer was started immediately, and the temperature of the water in each test-tube was measured.

Temperature control

A pulse oximeter is a device that clips onto the tip of a finger. It records the heart rate (pulse rate) in beats per minute and the percentage of oxygen in the blood (%SpO$_2$). A student used a pulse oximeter to study how exercise affects heart rate and the percentage of oxygen in the blood. Before exercising, the student took three readings from the pulse oximeter (0, 1 and 2 minutes). They then exercised for five minutes. At the end of five minutes, they took four more readings at one minute intervals (7, 8, 9 and 10 minutes). Some of the results are shown in Table 2.1. The photograph in Fig. 2.1 shows the pulse oximeter readings at 1 minute.

Circulatory system

As a seed begins to germinate, the radicle appears first and starts to develop into the root. A student chose to study how the radicle grows during germination. The student used a seed that had already been germinating for several days. Eight evenly spaced lines were drawn on the radicle, as shown in Fig. 3.1. The seed was then kept in suitable conditions in the dark, with the radicle directed vertically downwards. Two days later, the radicle had grown as shown in Fig. 3.1.

Coordination and response in plants