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Question 1Nature of Science: scientific method, inquiry, data handling and evaluation

A student writes a hypothesis before starting an investigation. Which statement best describes the role of a hypothesis in scientific inquiry?

  1. It is a testable prediction that can be supported or rejected by evidence Correct answer.
  2. It is a final conclusion that is proved once the experiment is finished
  3. It is a fixed law that scientists are not allowed to change
  4. It is a personal opinion that does not need to be tested

Explanation

A hypothesis is a proposed, testable explanation or prediction made before data are collected. Evidence from the investigation can support it or lead to rejection and revision, so it is never treated as a proven final answer.

Question 2Nature of Science: scientific method, inquiry, data handling and evaluation

In a controlled experiment testing whether light affects plant growth, which is the independent variable?

  1. The temperature kept constant for all plants
  2. The final height of each plant
  3. The amount of light given to each plant Correct answer.
  4. The type of soil used for all plants

Explanation

The independent variable is the factor the investigator deliberately changes. Here the light amount is varied, while height is the measured dependent variable and soil and temperature are controlled variables.

Question 3Nature of Science: scientific method, inquiry, data handling and evaluation

A group repeats a measurement five times and obtains values that are very close to each other but all far from the true value. Which description fits these results?

  1. Accurate but not precise
  2. Both accurate and precise
  3. Neither precise nor accurate
  4. Precise but not accurate Correct answer.

Explanation

Precision describes how close repeated measurements are to one another, while accuracy describes how close they are to the true value. Closely grouped values that are all far from the true value are precise but inaccurate.

Question 4Nature of Science: scientific method, inquiry, data handling and evaluation

Which instrument would be most suitable for measuring the volume of a liquid to the nearest 0.1 cm³ in a school laboratory?

  1. A graduated measuring cylinder Correct answer.
  2. A metre rule
  3. A thermometer
  4. A top-pan balance

Explanation

A graduated measuring cylinder is designed to measure liquid volume and typically has graduations allowing readings to about 0.1 cm³. The other instruments measure length, mass, or temperature, not volume.

Question 5Nature of Science: scientific method, inquiry, data handling and evaluation

A student records the mass of a sample as 4.52 g using a balance. How many significant figures does this measurement have?

  1. One
  2. Three Correct answer.
  3. Two
  4. Four

Explanation

All nonzero digits in 4.52 are significant, and the zero is not present here. The digits 4, 5 and 2 are each significant, giving three significant figures.

Question 6Nature of Science: scientific method, inquiry, data handling and evaluation

Which action best improves the reliability of an investigation's results?

  1. Repeating the measurements and calculating a mean Correct answer.
  2. Using a larger piece of equipment
  3. Changing several variables at the same time
  4. Recording results only once but very carefully

Explanation

Reliability concerns how consistent results are when the investigation is repeated. Taking repeat readings and averaging them reduces the effect of random variation and gives a more dependable result.

Question 7Nature of Science: scientific method, inquiry, data handling and evaluation

A student wants to find the effect of temperature on the rate of a reaction. Which set of conditions gives a fair test?

  1. Vary temperature and volume together
  2. Vary temperature while keeping concentration and volume the same Correct answer.
  3. Keep temperature the same and vary concentration
  4. Vary temperature and concentration together

Explanation

A fair test changes only the independent variable and holds all other relevant factors constant. Varying temperature alone, with concentration and volume fixed, allows any change in rate to be attributed to temperature.

Question 8Nature of Science: scientific method, inquiry, data handling and evaluation

Which of these is an example of qualitative data?

  1. A description that a solution turned cloudy after mixing Correct answer.
  2. A time of 12.4 s recorded by a stopwatch
  3. A mass of 3.6 g measured on a balance
  4. A reading of 25 cm³ from a measuring cylinder

Explanation

Qualitative data are descriptive observations recorded without numerical measurement. A cloudy appearance is an observed quality, whereas volumes, times and masses are numerical, quantitative data.

Question 9Nature of Science: scientific method, inquiry, data handling and evaluation

A student plots a graph of extension against load and obtains a straight line through the origin. What does this indicate about the relationship?

  1. Extension increases only after a threshold load
  2. Extension is directly proportional to load Correct answer.
  3. Extension decreases as load increases
  4. Extension is unrelated to load

Explanation

A straight line passing through the origin shows that the two quantities change by the same ratio, meaning they are directly proportional. Doubling the load would double the extension.

Question 10Nature of Science: scientific method, inquiry, data handling and evaluation

The table below gives four repeated readings of a length in cm: 5.2, 5.4, 5.3, 5.3. What is the mean length?

  1. 5.35 cm
  2. 5.3 cm Correct answer.
  3. 5.2 cm
  4. 5.4 cm

Explanation

The mean is found by adding the readings and dividing by the number of readings: (5.2 + 5.4 + 5.3 + 5.3) ÷ 4 = 21.2 ÷ 4 = 5.3 cm. Reporting to the same precision as the readings gives 5.3 cm.

Question 11Nature of Science: scientific method, inquiry, data handling and evaluation

A student measures a reaction time as 8.0 s but the accepted value is 9.6 s. What is the percentage error of the measurement?

  1. 20.0%
  2. 83.3%
  3. 16.7% Correct answer.
  4. 1.6%

Explanation

Percentage error is the difference between the measured and accepted values divided by the accepted value, multiplied by 100. Here (9.6 − 8.0) ÷ 9.6 × 100 ≈ 16.7%.

Question 12Nature of Science: scientific method, inquiry, data handling and evaluation

Which statement correctly distinguishes a scientific law from a scientific theory?

  1. A theory is a temporary opinion, while a law can be overturned only by voting
  2. A law explains causes, while a theory only records observations
  3. A law is an untested guess, while a theory is a proven fact
  4. A law describes a consistent pattern, while a theory explains why that pattern occurs Correct answer.

Explanation

A scientific law is a concise statement of a regularly observed relationship, often expressed mathematically. A theory is a well-supported explanatory framework accounting for evidence and mechanisms, so the two serve different roles.

Question 13Nature of Science: scientific method, inquiry, data handling and evaluation

A student investigates how the height of a ramp affects the distance a toy car travels. Which is the dependent variable?

  1. The surface the car rolls on
  2. The height of the ramp
  3. The distance the car travels Correct answer.
  4. The mass of the toy car

Explanation

The dependent variable is the outcome measured in response to the change. Here the ramp height is deliberately varied, so the resulting travel distance is the dependent variable.

Question 14Nature of Science: scientific method, inquiry, data handling and evaluation

In a line graph showing temperature rising over time, the line is steep between 2 and 4 minutes and flat between 6 and 8 minutes. What does the flat section represent?

  1. Temperature remaining constant during that interval Correct answer.
  2. Temperature rising rapidly during that interval
  3. No data being recorded during that interval
  4. Temperature falling during that interval

Explanation

The gradient of a line on a graph shows the rate of change of the plotted quantity. A flat, horizontal section has zero gradient, meaning temperature does not change during that time.

Question 15Nature of Science: scientific method, inquiry, data handling and evaluation

A student wants to test whether a fertiliser increases plant growth. Which is the most appropriate control group?

  1. Plants of a different species given fertiliser
  2. Plants grown with twice the amount of fertiliser
  3. Plants grown under identical conditions without fertiliser Correct answer.
  4. Plants grown outdoors instead of indoors

Explanation

A control group is treated exactly like the experimental group except that the tested factor is absent. Comparing fertilised plants with identical unfertilised plants isolates the effect of the fertiliser.

Question 16Nature of Science: scientific method, inquiry, data handling and evaluation

Which statement best describes a random error in measurement?

  1. It can be removed entirely by careful calibration
  2. It shifts every reading in the same direction by the same amount
  3. It always produces readings that are too high
  4. It causes readings to scatter unpredictably around the true value Correct answer.

Explanation

Random errors arise from unpredictable fluctuations and cause repeated readings to spread around the true value. They can be reduced by taking many readings and averaging, but not eliminated completely.

Question 17Nature of Science: scientific method, inquiry, data handling and evaluation

A student claims that a plant grew taller because it was spoken to daily. Which additional evidence would most strengthen this causal claim?

  1. A record of the student's daily speaking schedule
  2. A comparison group of identical plants not spoken to, grown under the same conditions Correct answer.
  3. A second plant of a different species spoken to daily
  4. A photograph of the plant taken at the end of the experiment

Explanation

A causal claim requires a comparison that isolates the proposed cause. Identical plants grown under the same conditions but without speaking provide the control needed to attribute growth differences to the speaking.

Question 18Nature of Science: scientific method, inquiry, data handling and evaluation

A graph of two variables shows a strong correlation. Which conclusion is scientifically justified?

  1. The variables are associated, but causation cannot be concluded from correlation alone Correct answer.
  2. The correlation shows the data are accurate
  3. The relationship proves a scientific law
  4. One variable definitely causes the other

Explanation

Correlation shows that two variables change together, but a third factor could influence both. Establishing causation requires controlled experiments or further evidence ruling out alternative explanations.

Question 19Nature of Science: scientific method, inquiry, data handling and evaluation

A student reports a length as 12.34 cm when the ruler has markings every 0.1 cm. What is the main problem with this report?

  1. The value is too large to be a length
  2. The reading has too few significant figures
  3. The units should always be omitted
  4. The reading claims more precision than the instrument can provide Correct answer.

Explanation

A ruler marked every 0.1 cm allows an estimate to about one further decimal place, so 12.34 cm overstates the precision. Recording more digits than the instrument supports gives a misleading impression of certainty.

Question 20Nature of Science: scientific method, inquiry, data handling and evaluation

A scientist publishes results and other researchers repeat the investigation and obtain similar findings. What does this primarily demonstrate?

  1. The results are reproducible and more credible Correct answer.
  2. The experiment had no random error
  3. The measurements were all accurate
  4. The original hypothesis is now a law

Explanation

Reproducibility means independent researchers can obtain consistent results using the same method. Successful replication strengthens confidence in the findings but does not by itself prove accuracy or create a law.

Question 21Nature of Science: scientific method, inquiry, data handling and evaluation

An investigation tests how the concentration of acid affects reaction rate. The student measures the time for a cross to disappear behind the reacting mixture. Which improvement most reduces random error in the timing?

  1. Using a larger volume of acid in a wider beaker
  2. Recording only the first trial without repeats
  3. Carrying out the test at a different temperature each time
  4. Using a stopwatch with finer resolution and taking repeat timings Correct answer.

Explanation

Random error in timing comes from reaction time and reading uncertainty, so a finer-resolution stopwatch and repeated trials reduce its effect. Averaging repeated timings gives a more reliable value.

Question 22Nature of Science: scientific method, inquiry, data handling and evaluation

A student's results show one reading far outside the pattern of the others. Which action is most appropriate before calculating a mean?

  1. Change it to match the nearest other reading
  2. Include it without comment and ignore the pattern
  3. Delete it immediately because it does not fit the trend
  4. Investigate the anomalous reading and justify excluding it if a clear cause is found Correct answer.

Explanation

Anomalous results should be checked against the method to identify a cause such as a misreading or faulty equipment. Only with a justified reason should the value be excluded; altering data to fit a trend is unacceptable.

Question 23Nature of Science: scientific method, inquiry, data handling and evaluation

A graph plots volume on the y-axis against temperature in kelvin on the x-axis and gives a straight line that, when extrapolated, passes through the origin. What does the gradient of this line represent?

  1. The temperature at which volume is zero
  2. The change in volume per unit change in temperature Correct answer.
  3. The total volume at the highest temperature
  4. The rate of temperature increase per second

Explanation

The gradient of a straight-line graph is the change in the y-variable divided by the change in the x-variable. With volume against temperature, the gradient is the change in volume per unit change in temperature.

Question 24Nature of Science: scientific method, inquiry, data handling and evaluation

Two students measure the same quantity using different methods. Method A gives readings of 9.8, 9.9, 10.0 cm; method B gives 10.5, 10.5, 10.5 cm. The accepted value is 10.0 cm. Which conclusion is best supported?

  1. Method A is both more accurate and more precise than method B
  2. Method B is more accurate but less precise than method A
  3. Method B is more accurate and more precise than method A
  4. Method A is more accurate but less precise than method B Correct answer.

Explanation

Method A's readings centre on the accepted value of 10.0 cm, so it is accurate, but they spread from 9.8 to 10.0 cm, so it is less precise. Method B's readings agree perfectly with each other (precise) but are all 0.5 cm from the true value (inaccurate).

Question 25Nature of Science: scientific method, inquiry, data handling and evaluation

A student designs an investigation to test whether the angle of a ramp affects the speed of a trolley. Which feature of the design most limits the validity of the conclusion?

  1. Using a different trolley for each ramp angle Correct answer.
  2. Measuring the time with a stopwatch
  3. Repeating each angle three times
  4. Keeping the ramp surface the same for all trials

Explanation

Validity requires that only the independent variable changes while other relevant factors stay constant. Using a different trolley for each angle introduces a confounding variable, such as mass or friction, so any speed difference cannot be attributed to angle alone.

Question 26Nature of Science: scientific method, inquiry, data handling and evaluation

A student writes a hypothesis before carrying out an investigation into how light intensity affects the rate of photosynthesis in pondweed. Which statement is the best scientific hypothesis?

  1. The rate of photosynthesis can be measured by counting oxygen bubbles.
  2. As light intensity increases, the rate of bubble production will increase because more light energy is available for photosynthesis. Correct answer.
  3. Light intensity is measured in lux using a light meter.
  4. Pondweed is a plant and plants need light to survive.

Explanation

A scientific hypothesis is a testable prediction that links the independent variable to the dependent variable and gives a proposed reason for the expected pattern. Only the first statement predicts a specific relationship and offers a mechanism that can be checked by experiment. The other statements describe background facts or methods rather than a prediction to be tested.

Question 27Nature of Science: scientific method, inquiry, data handling and evaluation

During an investigation, a student records the colour of a precipitate as 'creamy white' and later records its mass as 2.4 g. Which statement correctly classifies the two observations?

  1. Both observations are qualitative because they describe a chemical substance.
  2. The colour is qualitative data while the mass is quantitative data. Correct answer.
  3. Both observations are quantitative because they were recorded during an experiment.
  4. The colour is quantitative data while the mass is qualitative data.

Explanation

Qualitative data describes qualities such as colour, texture or smell using words, whereas quantitative data is numerical and can be measured or counted. 'Creamy white' is a description and the mass of 2.4 g is a number with a unit, so the colour is qualitative and the mass is quantitative. Whether an observation was made during an experiment does not affect this classification.

Question 28Nature of Science: scientific method, inquiry, data handling and evaluation

A student measures the time for a marble to roll down a ramp five times and obtains 2.1 s, 2.2 s, 2.0 s, 2.1 s and 2.1 s. The stopwatch has a resolution of 0.1 s. Which statement best evaluates the quality of this data set?

  1. The readings are precise but there is no way to judge accuracy without a known or accepted value for comparison. Correct answer.
  2. The readings show a clear systematic error because they vary slightly.
  3. The readings are unreliable because a stopwatch cannot measure intervals of about two seconds.
  4. The readings are accurate because they are all close to each other.

Explanation

Precision refers to how closely repeated readings agree with each other, while accuracy refers to how close a reading is to the true or accepted value. The five readings cluster tightly together, which indicates good precision, but accuracy cannot be assessed without a reference value. Small variation between repeats is normal random variation rather than evidence of a systematic error.

Question 29Nature of Science: scientific method, inquiry, data handling and evaluation

A student investigating how the concentration of sugar solution affects osmosis in potato cylinders finds that one cylinder lost far more mass than all the others in its group. Which action is the most scientifically appropriate next step?

  1. Delete the reading from the results table so the mean is not affected.
  2. Change the conclusion so that it matches the unusual reading.
  3. Average the unusual reading with the other results and report it without comment.
  4. Repeat the measurement for that condition to check whether the result is reproducible before deciding whether to exclude it. Correct answer.

Explanation

An anomalous result should be checked by repeating the measurement under the same conditions, because it may be caused by a mistake or by genuine biological variation. Only after repetition can a scientist justify excluding a reading, and any exclusion should be explained. Silently removing or averaging the value without investigation hides possible errors or real effects.

Question 30Nature of Science: scientific method, inquiry, data handling and evaluation

A student plots a graph of the period of a pendulum against its length and obtains a curve. The student then plots the period squared against the length and obtains a straight line through the origin. Which conclusion is best supported by these graphs?

  1. The length of the pendulum has no effect on the period.
  2. The period is directly proportional to the length of the pendulum.
  3. The square of the period is directly proportional to the length of the pendulum. Correct answer.
  4. The period is inversely proportional to the length of the pendulum.

Explanation

A straight line through the origin on a graph of two variables shows that those two variables are directly proportional. Since the straight line appears when period squared is plotted against length, the square of the period is directly proportional to the length. The original curved graph shows that period itself is not directly proportional to length.

Question 31Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which structure controls the activities of a cell and contains the genetic material?

  1. The mitochondrion
  2. The cell membrane
  3. The nucleus Correct answer.
  4. The cytoplasm

Explanation

The nucleus houses the chromosomes, which carry the genetic instructions that direct the cell's activities, including protein synthesis and division. Other organelles carry out specific jobs but do not store the main genetic material in an animal cell.

Question 32Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

A student views a cell with a regular box-like shape, a thick outer wall and green structures inside. Which type of cell is being observed?

  1. A nerve cell
  2. A red blood cell
  3. A plant cell Correct answer.
  4. A sperm cell

Explanation

Plant cells have a rigid cellulose cell wall giving a regular shape, and chloroplasts that appear green. Animal cells such as nerve, red blood and sperm cells lack a cell wall and chloroplasts.

Question 33Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which food test gives a brick-red colour when a reducing sugar such as glucose is present?

  1. Benedict's test Correct answer.
  2. Biuret test
  3. Emulsion test
  4. Iodine test

Explanation

Benedict's solution is blue and turns brick-red on heating with a reducing sugar. The colour change comes from reduction of copper(II) ions to copper(I) oxide.

Question 34Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Vitamin C is needed in the diet mainly to help the body do which of the following?

  1. Absorb calcium to harden bones
  2. Clot blood at the site of a wound
  3. Form collagen and maintain healthy connective tissue Correct answer.
  4. Produce haemoglobin in red blood cells

Explanation

Vitamin C is required for the formation of collagen, the protein that strengthens skin, blood vessels and gums. A deficiency causes scurvy, with bleeding gums and poor wound healing.

Question 35Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

In which part of the human digestive system is most water absorbed from undigested food?

  1. The duodenum
  2. The stomach
  3. The large intestine Correct answer.
  4. The oesophagus

Explanation

The large intestine absorbs most of the remaining water from undigested material, turning it into faeces. This conserves water that would otherwise be lost from the body.

Question 36Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which gas is taken into the blood in the lungs and used by cells for aerobic respiration?

  1. Water vapour
  2. Nitrogen
  3. Oxygen Correct answer.
  4. Carbon dioxide

Explanation

Oxygen diffuses from the alveoli into the blood, where it binds to haemoglobin and is carried to cells. Cells use oxygen in aerobic respiration to release energy from glucose.

Question 37Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which blood vessel carries blood away from the heart to the body's organs?

  1. A capillary
  2. A lymph vessel
  3. A vein
  4. An artery Correct answer.

Explanation

Arteries carry blood away from the heart under high pressure and have thick, elastic walls. Veins return blood to the heart, while capillaries are the tiny vessels where exchange occurs.

Question 38Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which organ removes urea from the blood and produces urine?

  1. The lung
  2. The liver
  3. The kidney Correct answer.
  4. The pancreas

Explanation

The kidneys filter the blood, removing urea and excess salts and water to form urine. Urea is made in the liver from excess amino acids but is excreted by the kidneys.

Question 39Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

A student measures the rate of respiration in germinating seeds by recording how quickly a coloured liquid moves along a tube connected to the seeds. Why does the liquid move?

  1. Oxygen is used up, lowering the pressure in the sealed tube Correct answer.
  2. The seeds release oxygen, increasing the pressure
  3. Carbon dioxide is used up, raising the pressure in the sealed tube
  4. Water vapour condenses and pushes the liquid along

Explanation

As the seeds respire aerobically they take in oxygen and release carbon dioxide, which is absorbed by a chemical such as soda lime. The net loss of gas lowers the pressure inside the sealed tube, so the external liquid is pushed inwards.

Question 40Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Why do villi in the small intestine greatly increase the rate of absorption of digested food?

  1. They increase the surface area and have thin walls close to blood capillaries Correct answer.
  2. They produce acid that dissolves food particles
  3. They store glucose until it is needed by the body
  4. They churn food to mix it with bile

Explanation

Villi are finger-like projections that multiply the surface area for absorption. Each has a very thin wall and a dense network of capillaries, so dissolved nutrients can diffuse a short distance into the blood quickly.

Question 41Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Enzymes in the digestive system break large food molecules into smaller ones. Which statement best explains why this is necessary?

  1. Large molecules are toxic until they are broken down
  2. Smaller molecules contain more energy than large ones
  3. Large molecules cannot be tasted by the tongue
  4. Smaller molecules can pass through the gut wall into the blood Correct answer.

Explanation

Digestion converts large insoluble molecules into small soluble ones that can be absorbed across the gut lining into the bloodstream. The energy content is unchanged; only the size and solubility of the molecules change.

Question 42Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which change increases the rate at which an enzyme digests its substrate in a controlled experiment?

  1. Raising the temperature from 20°C towards the optimum Correct answer.
  2. Adding a strong acid to a stomach enzyme working at pH 2
  3. Boiling the enzyme before adding the substrate
  4. Cooling the mixture below 5°C

Explanation

Enzyme activity rises with temperature up to an optimum because particles collide more frequently with more energy. Beyond the optimum the enzyme denatures and activity falls sharply.

Question 43Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which sequence correctly describes the pathway of air from the nose to the alveoli?

  1. Alveoli, bronchioles, bronchi, trachea
  2. Bronchi, trachea, alveoli, bronchioles
  3. Trachea, bronchi, bronchioles, alveoli Correct answer.
  4. Bronchioles, alveoli, bronchi, trachea

Explanation

Inhaled air passes from the nose through the trachea, which divides into two bronchi, then into many finer bronchioles ending in alveoli. The alveoli are the gas exchange surfaces.

Question 44Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

During exercise, a person's breathing rate and depth increase. Which explanation is correct?

  1. The heart signals the lungs to cool the body
  2. Lower oxygen levels directly make the diaphragm contract faster
  3. More carbon dioxide in the blood is detected and stimulates faster, deeper breathing Correct answer.
  4. The lungs detect lactic acid and expand more

Explanation

Muscles respire faster during exercise, releasing more carbon dioxide into the blood. Chemoreceptors detect the raised carbon dioxide concentration and trigger faster, deeper breathing to remove it.

Question 45Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which feature of red blood cells makes them efficient at transporting oxygen?

  1. They have a large nucleus that stores oxygen
  2. They have a cell wall that traps oxygen
  3. They contain haemoglobin and have no nucleus, leaving more room for it Correct answer.
  4. They contain chloroplasts that release oxygen

Explanation

Red blood cells are packed with the pigment haemoglobin, which binds oxygen in the lungs and releases it in tissues. Losing the nucleus during development frees space for more haemoglobin.

Question 46Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Why does the left ventricle have a thicker muscular wall than the right ventricle?

  1. It receives blood directly from the lungs
  2. It holds a larger volume of blood than the right ventricle
  3. It pumps blood at higher pressure to the whole body rather than just to the lungs Correct answer.
  4. It contains valves that the right ventricle lacks

Explanation

The left ventricle pumps oxygenated blood into the aorta and around the whole body, requiring high pressure, so its wall is thick and muscular. The right ventricle only pumps blood the short distance to the lungs.

Question 47Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

A person with a narrowed coronary artery may experience chest pain during exercise. Which explanation is correct?

  1. The coronary artery carries deoxygenated blood away from the heart
  2. Heart muscle receives less oxygen than it needs during exertion Correct answer.
  3. The heart stops producing urine during exercise
  4. Too much oxygen reaches the heart muscle and damages it

Explanation

The coronary arteries supply the heart muscle itself with oxygenated blood. If narrowed, less oxygen reaches the muscle, especially when exercise raises demand, causing pain known as angina.

Question 48Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

Which process allows glucose and amino acids to be reabsorbed from the filtrate back into the blood in the kidney?

  1. Excretion of urea into the filtrate
  2. Filtration in the glomerulus
  3. Ultrafiltration under high pressure
  4. Selective reabsorption along the tubule Correct answer.

Explanation

After filtration, useful substances such as glucose, amino acids and most water are selectively reabsorbed from the tubule back into the blood. Only waste and excess substances remain to form urine.

Question 49Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

On a hot day a person sweats more and produces a smaller volume of more concentrated urine. Which statement explains this?

  1. Less water is lost through sweat, so urine becomes dilute
  2. More water is lost through sweat, so the kidneys reabsorb more water to conserve it Correct answer.
  3. The kidneys produce more urine to cool the blood
  4. Sweat glands remove urea, so the kidneys work less

Explanation

Sweating removes water and salts, reducing the water content of the blood. The kidneys respond by reabsorbing more water, so a smaller volume of more concentrated urine is produced to conserve body water.

Question 50Biological systems: cells, nutrition, digestion, respiration, circulation, excretion

A cell is placed in a solution with a higher water concentration than its cytoplasm. What will happen to the cell?

  1. Water leaves by osmosis and the cell shrinks
  2. Water enters by osmosis and the cell may swell Correct answer.
  3. Salts move in until concentrations are equal
  4. No water moves because the cell is partially permeable

Explanation

Osmosis is the movement of water from a region of higher water concentration to a region of lower water concentration through a partially permeable membrane. The surrounding solution has more water than the cytoplasm, so water enters and the cell swells.