Transport Systems (Edexcel IGCSE Biology)

Separate: Biology Only

The diagram shows a cross‐section through a leaf.

Which layer contains palisade mesophyll cells?

(1)

Which set of environmental conditions would produce the fastest rate of transpiration from this leaf?

(1)

Separate: Biology Only

Scientists investigate the effect of changing carbon dioxide concentration on the density of stomata of wheat plants.

They grow wheat plants from seed in different concentrations of carbon dioxide.

After three weeks, they take a leaf from each plant and calculate the mean density of stomata.

State the independent variable in this investigation.

(1)

Give two abiotic variables that the scientists could control.

(2)

To calculate the mean density of stomata, leaf sections are viewed with a microscope.

The number of stomata within six circular areas of the leaf are counted.

The results for one leaf are shown in the table.

The radius of each circular area is 0.40 mm.

area of circle = πr²

[π = 3.14]

Calculate the mean density of stomata on the leaf surface. Give your answer in stomata per mm².

(3)

The investigation shows that in increased carbon dioxide concentrations there is a lower mean density of stomata.

The scientist concludes that in hot dry areas, with increased carbon dioxide concentrations, it would be an advantage for wheat to have a lower mean density of stomata.

Discuss the scientist’s conclusion.

(4)

Separate: Biology Only

The diagram shows the path that the water takes when it is absorbed from the soil into the xylem of a plant.

Explain how root hair cells are adapted for efficient absorption of water.

(2)

Explain how water is transported from the soil to the leaves.

(4)

Separate: Biology Only

Describe how you could determine the rate of water loss from a leafy shoot.

The diagram shows a magnified image of a root hair cell from a young plant.

Give the names of structures labelled W, X, Y and Z.

The actual length of the cell, along the line between A and B, is 1000 μm.

Calculate the magnification of this drawing.

Separate: Biology Only

Explain the role of the root hair cell in absorption of water from the soil.

(3)

Sometimes gardeners give their plants too much water. The water fills up the air spaces in the soil around the plant roots. Explain how this can lead to plants failing to grow properly.

(3)

P. multocida is a bacterium that causes cholera in chickens.

The diagram shows the bacterium.

Give two structures in this bacterium that are also found in all eukaryotic cells.

Separate: Biology Only

Scientists investigated the survival of chickens injected with normal P. multocida or with weakened P. multocida.

The table shows the scientists’ results.

What is a correct conclusion about P. multocida from these results?

(1)

The scientists took the living chickens that had been injected with weakened P. multocida and then injected them with normal P. multocida.

The chickens did not die, as they were now immune.

Explain why these chickens did not die.

(4)

The diagram shows the human heart with four blood vessels labelled A, B, C and D.

Which blood vessel brings oxygenated blood to the heart? 

(1)

Which blood vessel contains blood at the highest pressure?

(1)

(1)

Describe the function of the semi-lunar valves.

(2)

In the heart of a foetus, the two upper chambers (atria) are linked by a hole so that blood can pass between them.

Explain why this hole is normally closed before the baby is born.

(2)

Sometimes the hole does not close.

Explain what effect this will have on the baby.

(3)

Sickle cell anaemia is a condition in which some of the person’s red blood cells develop abnormally.

The diagram shows red blood cells from a healthy person and red blood cells from a person with sickle cell anaemia.

A person with sickle cell anaemia often suffers pain as some of their blood vessels become blocked by the sickle cells.

Suggest why the person’s blood vessels may become blocked.

(1)

People with sickle cell anaemia have symptoms of tiredness and joint pain that get worse if they are exposed to cold temperatures and high altitudes.

Suggest why these symptoms get worse.

(3)

Sickle cell anaemia is caused by a single recessive allele.

State what is meant by the term recessive.

(1)

A man and a woman who are both heterozygous for the sickle cell allele have a child.

Calculate the probability that the child will be female and not have sickle cell anaemia.

(2)

Sickle cell anaemia is more common in countries where malaria is found. This is because having an allele for sickle cell anaemia can reduce the likelihood of developing malaria.

Which type of organism causes malaria?

What is the name of the pigment found in red blood cells?

Give two differences in structure between red blood cells and white blood cells.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Suggest why cardiomyopathy can cause heart failure (lines 6 to 7).

During the transplant procedure the patient’s heart is removed, leaving behind a section of the right and left atria.

Describe the functions of the atria in the body.

Describe how the blood in the pulmonary artery differs from the blood in the aorta.

Explain the function of the heart-lung bypass machine (lines 11 to 12).

Explain why the patient needs to be given immunosuppressants (lines 19 to 20).

Explain why patients should not smoke after their heart transplant (lines 28 to 29).

State what is meant by the term balanced diet.

Calculate the number of patients in the United Kingdom who have a heart transplant in one year that are still alive five years later (lines 2 to 3 and lines 35 to 36).

Suggest why patients are advised to avoid strenuous activities after their heart transplant (line 24).

Suggest why patients are more likely to be at risk of food poisoning after their heart transplant (lines 32 to 33).

Aerobic respiration uses oxygen and produces ATP.

Complete the word equation for aerobic respiration.

oxygen + .......................... → .......................... + .......................... + ATP

A scientist investigates the rates of aerobic respiration of some animals.

The scientist calculates the rate of respiration per gram of each animal.

The results are shown in the table.

Explain why a mouse uses more oxygen per gram than a human.

The structure of a frog heart is different from the structure of a human heart.

The diagram shows a section of a frog heart with arrows showing the direction of blood flow.

What is the name of the blood vessel labelled X?

(1)

Give one difference between the structure of the frog heart and a human heart.

(1)

Humans can run for long periods of time. Frogs can only move for short periods of time.

Explain how the structure of the heart of a frog means that it is unable to move for long periods of time.

(5)

Human blood contains red blood cells and white blood cells.

The table shows the number of these blood cells in a sample of blood.

Complete the table to give the number of white blood cells per mm³ in standard form.

(1)

What is the number of red blood cells in 1000 cm³ of this person's blood?

(1)

The table gives names, descriptions and symptoms of two blood conditions.

Explain why a person with anaemia is often tired.

(2)

Explain why a person with leukopenia is more likely to get an infection.

(2)

Cholesterol is needed in the diet for making cell membranes.

State the role of the cell membrane.

Too much cholesterol is a health risk because fatty deposits build up in arteries.

The lumen of an artery had a diameter of 4.0 mm before the build-up of a fatty deposit.

The fatty deposit covers 45 % of the original area of the lumen.

Calculate the area in mm² of the lumen that is available for blood flow.

[area of the lumen = πr²]

[π = 3.14]

A scientist tests the blood cholesterol concentration in a sample of men between 25 and 34 years old.

The scientist groups the men in ranges of blood cholesterol concentration and counts the number of men in each range.

The table gives the scientist’s results.

Plot a suitable graph on the grid to show these results.

(5)

Which range of blood cholesterol levels is the mode for this sample? 

(1)

A blood cholesterol level greater than 239 mg per 100 cm³ means a person has a higher risk of heart disease.

Calculate the percentage of men in the sample at a higher risk of heart disease. 

(2)

Statins are drugs that reduce blood cholesterol levels.

A scientist investigates the use of one type of statin on the risk of having a heart attack.

He gives the statin to one group of people and gives a control substance to another group of people.

He calculates the percentage of people in each group that has a heart attack during the next four years.

The table gives the scientist’s results.

A conclusion from this data is that statins reduce the risk of heart attacks.

Discuss this conclusion.

The diagram shows the human circulation system with some blood vessels labelled A to J. The arrows show the direction of blood flow.

The table gives some statements about the content of blood vessels in this circulation system.

Complete the table by giving the letter of the blood vessel that matches each statement.

(5)

State two ways in which the structure of blood vessel A differs from the structure of blood vessel J.

(2)

Muscles in the legs contain capillaries.

A scientist investigates how long-term training affects the number of capillaries in an athlete’s leg muscles.

The scientist determines the mean number of capillaries per mm² in samples of leg muscle from the athlete before and after a period of training.

The table shows the scientist’s results.

The scientist concludes that training improves the athletic performance.

Discuss this conclusion.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

César Astudillo from Collado Villalba, Spain, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons. Image cropped and colour removed.

Name the type of cell that produces antibodies. (Lines 8 and 9)

Separate: Biology Only

Human blood groups are controlled by three alleles, I^A, I^B and I^O.
The I^A and I^B alleles are codominant and the I^O allele is recessive

State what is meant by the term codominant.

(1)

Two parents have genotypes of I^AI^O and I^BI^O.

Which of these are all the possible blood groups of their children?

(1)

Calculate the number of blood donations collected per year from the high‐income countries. (Lines 14 and 15)

Give your answer in standard form.

Some scientists have suggested that spherical artificial red blood cells transport oxygen less efficiently than normal human red blood cells.

Explain why the shape of the artificial red blood cells reduces the efficiency of oxygen transport compared to normal human red blood cells. (Lines 18 and 19)

Separate: Biology Only

Suggest why artificial blood does not clot when stored. (Lines 26 and 27)

Explain why the artificial red blood cells are suspended in sodium chloride solution instead of in water. (Line 20)

Separate: Biology Only

Explain why stem cells can be used to make large quantities of red blood cells. (Lines 22 and 23)

(2)

Suggest why the scientists made red blood cells with blood group O. (Lines 22 and 23)

(2)

Give two substances found in blood plasma that are not present in the artificial blood. (Lines 28 and 29)

Separate: Biology Only

Schistosomiasis

Which process is affected if kidneys are damaged (line 8)?

Suggest three ways to reduce the risk of being infected by schistosomes.

Name two different blood cells that would be found in the urine of infected people (line 17).

An infected person has a body mass of 120 kg. What dose of drugs would be effective for this person (lines 19 to 20)?

Using the estimated number of people in the world who have schistosomiasis (lines 21 to 22), calculate the number of people who die each year from schistosomiasis.

Which of these is the correct description of a plasmid?

Separate: Biology Only

Explain how a vaccine could protect people from schistosomiasis (lines 24 to 25).

Suggest what is given to the control group (lines 27 to 29).

(1)

A scientist claims that the investigation proves the vaccine is effective against schistosomiasis (lines 27 to 29).

Comment on this claim.

(3)

Separate: Biology Only

A student investigates the rate of evaporation from a clay pot and the rate of transpiration by a plant. The clay pot is porous and has small holes that allow water to evaporate.

The student keeps the clay pot and the plant in the same conditions next to a closed window. He measures the rates at different times of the day.

The table shows the student’s results.

The student uses this apparatus to measure the rate of evaporation from the clay pot.

Explain the changes in the rate of evaporation from the clay pot.

(2)

Suggest how the student could measure the rate of evaporation from the clay pot.

(3)

Separate: Biology Only

(2)

Draw a labelled diagram of the apparatus the student could use to determine the rate of transpiration by a plant.

(4)