The Challenges of Size (OCR GCSE Biology A (Gateway))

Fanconi anaemia is a genetic disorder. It results in the bone marrow being destroyed.
This causes a decrease in the numbers of red blood cells, white blood cells and platelets.

Explain two possible symptoms of Fanconi anaemia.

1 ...................................
2 ...................................

Table 19.1 shows normal ranges for blood components in people without Fanconi anaemia.

Table 19.1

(i) Suggest why there is such a wide range of white blood cell numbers.

[2]

(ii) The diagram shows a microscope slide containing blood from a patient.

The square cover slip is 10mm wide and the thickness of the blood underneath is 0.001mm.

Calculate the volume of blood under the cover slip.

Volume of blood = ...................... mm³ [1]

(iii) Under the cover slip are 1000 white blood cells.

Does the blood sample provide evidence that the patient has Fanconi anaemia?

Use Table 19.1 and your answer to part (b)(ii) to justify your answer.

[3]

There are many different genetic disorders that can affect blood cells. Details of three of these are found in Table 19.2.

Table 19.2

 A blood smear from another patient shows that he has 3 × 10⁶ red blood cells per mm³ of blood. Neither of his parents have a blood disorder.

Use Table 19.1 and Table 19.2 to explain which blood disorder the patient could have.

Name of disorder ...........................
Explanation ............................

The diagram shows a cross-section of a plant stem.

A greenfly feeds on the plant by piercing through to the tissue shown in the cross-section of a plant stem.

(i) What is the name of the tissue in the stem that the greenfly is trying to reach with its mouthpart?

Tick (✓) one box

[1]

(ii) Explain why plants infested with greenfly have very poor growth.

 [2]

 A gardener carries out an experiment using two similar tomato plants. The tomato plants are grown in pots.

She puts one inside a glasshouse and one outside beside the glasshouse.

To decide which plant loses the most water, the gardener looks to see which plant wilts first.

The diagrams show a plant before and after it has wilted.

(i) On a windy day, the plant outside the glasshouse wilts first.

Explain why.

 [2]

(ii) The gardener’s results do not provide very accurate information about the effect of wind on water loss.

How could the gardener improve the design of her experiment?

 [3]

Fifty years ago scientists experimenting on plants had to inject dyes to measure water flow.

Now they can use modern methods such as MRI and X-ray imaging.

Scientists are now developing new ideas on how water flows through a plant that are different from theories developed fifty years ago.

Explain why.

The diagram shows structures on the surface of a leaf.

(i) Photosynthesis occurs in the guard cells but not the epidermal cells.

Explain why this is important in the control of the rate of transpiration in the plant.

[4]

(ii) Explain why guard cells are an example of specialised cells.

[2]

An experiment was done to look at the effect of ‘ringing’ on a tree trunk. Ringing removes a strip of plant tissue from around the stem of the tree.

The diagram shows where the stem is ringed.

The results were recorded after one week.

The diagram shows the results.

What conclusions can be made about the results?

Some students investigate the effect of the surface area : volume ratio on the rate of diffusion in animal cells.

They use hydrochloric acid and gelatine cubes that have been stained blue using a pH indicator solution. The indicator will turn red in acidic conditions.

They put different sized cubes into 3 different test tubes of hydrochloric acid and time how long it takes for the cubes to completely change to red.

Fig. 16.1 shows the apparatus they use.

Fig. 16.1

The table shows the students’ results.

(i) Calculate the surface area : volume ratio for the cube with sides of 2mm.

surface area : volume ratio = ..................... [2]

(ii) What conclusion can be made about the effect of surface area : volume ratio on the rate of diffusion?

[1]

(iii) Emphysema causes some of the walls of alveoli in the lungs to break down. This produces a smaller number of larger air sacs.

Use the results to explain the effect of emphysema on oxygen diffusing into the blood.

[2]

In a condition called sickle cell anaemia, the red blood cells can change shape. This reduces the amount of oxygen getting to cells in the body.

Fig. 16.2 shows a red blood cell and a sickled red blood cell.

Fig. 16.2

Explain why sickle cell anaemia reduces the amount of oxygen getting to cells in the body.

The diagram shows a simple potometer.

The apparatus can be used to investigate the effect of light intensity on transpiration rates.

(i) Describe what happens during transpiration.

[2]

(ii) Describe how the apparatus can be used to investigate the effect of light on transpiration rates.

[3]

(iii) The heat sink is a transparent tube of cold water.

Explain why a heat sink is used in this experiment.

[2]

The table shows the results from using the potometer.

(i) The mean distance the gas bubble moved along the tube at 10cm from the light was 72mm.

The diameter of the narrow tube was 1mm.

Calculate the volume of water taken up by the plant.

Use the equation: volume = πr²l
where r is the radius of the tube and l is the distance the bubble moves
π = 3.14

Give your answer to 2 significant figures.

Volume of water = ................. mm³ /minute [3]

(ii) Identify the anomalous reading in their recorded results and suggest a possible reason for this.

[2]

(iii) How should the scientists deal with this anomalous reading when they process the data?

[1]

(iv) The scientists described their results for 20cm as 73 ± 2. Explain why they did this.

[2]

Stomata are found on the surface of leaves.

The diagram shows some of the surface cells of a leaf.

(i) Write down the name of the cell labelled X.

[1]

(ii) Describe two functions of stomata.

[2]

Rheumatic fever is a rare disease in the UK.

Look at this information.

(i) Put ticks (✓) in the two boxes that best describe rheumatic fever.

[1]

(ii) White blood cells make protein molecules that can kill the bacteria.

What is the name of these protein molecules?

[1]

(iii) The diagram shows one of the valves that can be made leaky.

People who have this leaky valve often have these symptoms:

• they get out of breath easily

• they do not seem to have much energy and feel tired.

Write about the job of this valve and how damage to the valve may cause these symptoms.

[4]

Look at the graph.

• It gives data about people of different ages.

• It shows the number of cases of rheumatic fever.

• It also shows the number of new cases of heart problems caused by rheumatic fever.

  

(i) What is the age of people that most commonly have rheumatic fever?

Answer = ........................................ years [1]

(ii) How many years after getting rheumatic fever is it most common to get heart problems?

How can you tell this from the graph?

[2]

One treatment for the heart valve problem is to lower the patient’s blood pressure.

Blood pressure can be lowered by taking a drug to increase the amount of water excreted by the body.

Which organ would be targeted by the drug and what would be the effect on urine?

Organ targeted ..........................................................
effect on urine .............................................................

Look at the diagram. It represents the human circulatory system.

Describe how the diagram shows that humans have a double circulatory system.

Look at the diagrams of the circulation systems in an amphibian, bird and fish.

Which of these has a circulatory system most similar to humans?

Tick (✓) one box.

Explain your choice.

Scientists investigate how exercise affects blood flow to different organs in the body.

This is their method.

• Ask a healthy person to sit in a room at 20°C

• Measure the blood flow to different organs in the person’s body

• Repeat this with the person exercising at a constant speed on a treadmill in the same room.

The table shows the scientists’ results.

(i) By how many times has the total blood flow increased by doing exercise?

Give your answer to the nearest whole number.

Number of times the total blood flow has increased = ......................................... [2]

(ii) The table shows that blood flow to other organs has decreased by nearly 5 times when a person is doing exercise.

The blood flow to the muscles has increased by more than eighteen times.

Explain these changes to blood flow rate.

[2]