Biology

Which part of an animal cell controls the activities of the cell and contains the genetic material?

• AMitochondria
• BNucleus✓
• CCytoplasm
• DCell membrane

Answer: The nucleus contains the chromosomes (DNA) and controls the cell's activities.

Which structure is found in a plant cell but NOT in an animal cell?

• AMitochondria
• BCell wall✓
• CRibosome
• DCell membrane

Answer: Plant cells have a cellulose cell wall, chloroplasts and a permanent vacuole; animal cells do not.

What is the role of red blood cells?

• ACarrying oxygen✓
• BFighting infection
• CClotting blood
• DProducing antibodies

Answer: Red blood cells contain haemoglobin, which binds oxygen and transports it around the body.

Which process do plants use to make glucose using light energy?

• ARespiration
• BPhotosynthesis✓
• CDigestion
• DTranspiration

Answer: Photosynthesis: carbon dioxide + water → glucose + oxygen, using light energy absorbed by chlorophyll.

Aerobic respiration releases energy using which gas?

• AOxygen✓
• BNitrogen
• CCarbon dioxide
• DHydrogen

Answer: Aerobic respiration uses oxygen: glucose + oxygen → carbon dioxide + water, releasing energy.

Which enzyme breaks down starch into sugars?

• ACatalase
• BAmylase✓
• CProtease
• DLipase

Answer: Amylase (a carbohydrase) digests starch into smaller sugars such as maltose.

What is the name of the random change in DNA that can lead to variation?

• AMutation✓
• BMitosis
• CDiffusion
• DMeiosis

Answer: A mutation is a random change in the DNA base sequence and is a source of genetic variation.

In a food chain, what do the arrows represent?

• AThe direction of energy transfer✓
• BThe flow of water
• CPredator chasing prey
• DThe movement of animals

Answer: Arrows in a food chain show the direction in which energy (and biomass) is transferred.

Which hormone reduces blood glucose concentration?

• ATestosterone
• BGlucagon
• CInsulin✓
• DAdrenaline

Answer: Insulin, released by the pancreas, causes cells to take up glucose, lowering blood glucose.

Which type of cell division produces gametes (sex cells)?

• ABudding
• BMitosis
• CMeiosis✓
• DBinary fission

Answer: Meiosis produces four genetically different gametes, each with half the number of chromosomes.

Antibiotics are used to treat infections caused by which type of pathogen?

• ABacteria✓
• BViruses
• CAll pathogens
• DFungi only

Answer: Antibiotics kill bacteria; they do not work against viruses.

Which part of a plant absorbs water and mineral ions from the soil?

• AStomata
• BRoot hair cells✓
• CXylem vessels
• DPhloem

Answer: Root hair cells have a large surface area to absorb water (by osmosis) and mineral ions.

What is homeostasis?

• AThe transfer of energy in ecosystems
• BThe breakdown of glucose
• CThe maintenance of a constant internal environment✓
• DThe growth of an organism

Answer: Homeostasis is the regulation of internal conditions (e.g. temperature, blood glucose, water) to keep them stable.

Natural selection leading to changes in a species over time is known as:

• APollination
• BExtinction
• CEvolution✓
• DAdaptation

Answer: Evolution by natural selection: organisms best adapted to their environment are more likely to survive and reproduce.

Which blood vessels carry blood away from the heart?

• AArteries✓
• BVenules
• CVeins
• DCapillaries

Answer: Arteries carry blood away from the heart at high pressure and have thick, muscular walls.

A plant cell is 0.05 mm wide. On a student's drawing the same cell measures 10 mm across. What is the magnification of the drawing?

• A×0.5
• B×20
• C×200✓
• D×2000

Answer: Magnification = image size ÷ actual size = 10 mm ÷ 0.05 mm = 200, written ×200. Multiplying the two sizes together instead of dividing, or slipping a decimal place when dividing by 0.05, produces the other values.

A photograph of a cell has a magnification of ×400. The cell measures 20 mm across on the photograph. What is the real width of the cell?

• A0.005 mm
• B0.05 mm✓
• C0.5 mm
• D8000 mm

Answer: Rearranging magnification = image size ÷ actual size gives actual size = image size ÷ magnification = 20 mm ÷ 400 = 0.05 mm. Multiplying 20 by 400 instead of dividing gives 8000 mm, which is 8 metres wide.

A model organism is a cube with sides of 2 cm. What is its surface area to volume ratio?

• A1:3
• B1.5:1
• C3:1✓
• D4:1

Answer: A cube has 6 faces, so surface area = 6 × 2 cm × 2 cm = 24 cm². Volume = 2 cm × 2 cm × 2 cm = 8 cm³. The ratio 24:8 cancels down to 3:1. Dividing volume by surface area instead gives the inverted ratio, and forgetting to square the side length when finding the surface area gives 1.5:1.

In an investigation, pondweed released 45 cm³ of oxygen in 15 minutes. What was the mean rate of photosynthesis, measured as volume of oxygen released per minute?

• A0.33 cm³/min
• B3 cm³/min✓
• C30 cm³/min
• D675 cm³/min

Answer: Rate = volume ÷ time = 45 cm³ ÷ 15 minutes = 3 cm³ per minute. Dividing the time by the volume gives 0.33 and multiplying them gives 675.

A potato cylinder had a mass of 4.0 g at the start of an osmosis experiment and a mass of 4.6 g after 30 minutes in distilled water. What is the percentage change in mass?

• A0.6%
• B13%
• C15%✓
• D115%

Answer: Percentage change = change in mass ÷ starting mass × 100 = 0.6 g ÷ 4.0 g × 100 = 15% increase. Dividing by the final mass rather than the starting mass gives 13%, and leaving out the × 100 leaves 0.6.

A student places ten 1 m² quadrats at random in a field of 800 m² and records a mean of 8 daisies per quadrat. What is the best estimate of the number of daisies in the whole field?

• A80
• B100
• C640
• D6400✓

Answer: Estimated total = mean number per m² × total area = 8 × 800 = 6400 daisies. Multiplying by the number of quadrats rather than by the area of the field gives 80, and dividing the area by the mean gives 100.

Along a transect a student counts the buttercups in five 1 m² quadrats and records 3, 5, 6, 8 and 8 plants. The area being studied is 250 m². Using the mean count, what is the best estimate of the total number of buttercups?

• A42
• B1500✓
• C2000
• D7500

Answer: The mean count is (3 + 5 + 6 + 8 + 8) ÷ 5 = 30 ÷ 5 = 6 plants per m². Estimated total = 6 × 250 = 1500 buttercups. Using the raw total of 30 instead of the mean gives 7500, and using the largest single count gives 2000.

Cardiac output = stroke volume × heart rate. A person has a stroke volume of 70 cm³ and a heart rate of 65 beats per minute. What is their cardiac output?

• A135 cm³/min
• B455 cm³/min
• C4550 cm³/min✓
• D45 500 cm³/min

Answer: Cardiac output = 70 cm³ × 65 beats per minute = 4550 cm³ per minute. Adding the two figures instead of multiplying them gives 135.

Producers in a food chain transfer 20 000 kJ of energy. The primary consumers that eat them transfer 1800 kJ. What percentage of the producers' energy is transferred to the primary consumers?

• A0.09%
• B9%✓
• C11%
• D18%

Answer: Percentage transferred = 1800 kJ ÷ 20 000 kJ × 100 = 9%. Leaving out the × 100 gives 0.09, and dividing the larger figure by the smaller one gives about 11.

In the osmosis required practical, why are the potato cylinders gently blotted with paper towel before they are reweighed?

• ATo remove surface liquid, which would add to the measured mass✓
• BTo warm the cylinders so that osmosis carries on at the same rate
• CTo kill the cells so that they stop respiring during the weighing
• DTo make certain that every cylinder is exactly the same length

Answer: Solution clinging to the outside of a cylinder is weighed along with it, which makes the change in mass look bigger than it really is. Blotting removes that surface liquid. The cells stay alive, and the cylinders are cut to the same size before the experiment begins.

When using a light microscope, why should the lowest-power objective lens be used first?

• AIt gives the widest field of view, so the specimen is much easier to find✓
• BIt magnifies the specimen most, so fine detail shows straight away
• CIt uses less light, which stops the specimen being damaged by the lamp bulb
• DIt focuses the specimen automatically without using the fine focus dial

Answer: A low-power objective shows a large area of the slide, so the specimen can be found and roughly focused first. Higher-power objectives show a much smaller area and sit very close to the slide.

A student heats a food sample with Benedict's solution in a water bath. The mixture turns from blue to brick-red. What does this result show?

• AStarch is present, because iodine has turned blue-black
• BProtein is present, because biuret solution has turned purple
• CLipid is present, because a cloudy white emulsion has formed
• DA reducing sugar is present, because the colour is brick-red✓

Answer: Benedict's solution is the test for reducing sugars. On heating it changes from blue through green, yellow and orange to brick-red, and brick-red shows a high concentration of a reducing sugar such as glucose. Iodine, biuret and the emulsion test were not used here.

In the required practical on the rate of photosynthesis, a lamp is moved to different distances from a piece of pondweed. A clear glass tank of water is placed between the lamp and the pondweed. Why is the tank of water used?

• AIt increases the light intensity that reaches the pondweed leaves
• BIt supplies the extra carbon dioxide the pondweed needs
• CIt makes the oxygen bubbles much easier to see and count
• DIt absorbs heat from the lamp so temperature stays constant✓

Answer: A lamp transfers energy by heating as well as by light. The water absorbs most of that heat, so the temperature of the pondweed stays constant and temperature remains a control variable while light intensity is changed.

A graph shows the activity of the enzyme amylase plotted against pH. Activity is almost zero at pH 3, rises to a clear peak at pH 7, then falls back to zero at pH 10. Which conclusion do these results support?

• AThe enzyme is most active at pH 3 and is denatured by pH 7
• BThe enzyme works equally well at every pH value tested
• CThe enzyme is most active at pH 7 and is denatured by pH 10✓
• DThe enzyme is most active at pH 10 because activity is highest there

Answer: The peak of the curve gives the optimum pH, which is 7 for this enzyme. Away from the optimum the active site changes shape, and by pH 10 the activity has fallen to zero because the enzyme has been denatured.

Why should quadrats be placed using random numbers rather than being put down where the plants look most plentiful?

• ARandom placement avoids bias, so the sample represents the whole area✓
• BRandom placement guarantees that every plant in the whole area is counted
• CRandom placement means far fewer quadrats are needed for certainty
• DRandom placement spreads the plants out evenly across the area

Answer: Choosing where to put a quadrat by eye biases the sample towards the patches that look interesting, so the results would not represent the whole area. Random coordinates take that choice away from the student.