Cell differentiation

Pathogens are transmitted to animals and plants by a variety of methods.

A group of scientists collected and analysed data about climate change and the number of cases of diseases transmitted by animal vectors.

The scientists wanted to know whether the number of cases of each disease had increased as a result of climate change.

They found that the number of cases had increased for 103 different animal vector‑transmitted diseases.

The scientists concluded that climate change has increased the transmission of pathogens by animal vectors.

Suggest one additional piece of information that is needed to assess the validity of the scientists’ conclusion.

Suggest why climate change might result in more cases of diseases caused by animal vector‑transmitted pathogens.

Neutrophils are white blood cells that contribute to the immune response against infection.

Neutrophils produce oxidative bursts as part of their response to infection.

An oxidative burst is the rapid production of highly reactive particles, including hydrogen peroxide (H₂O₂), inside the cell.

State the location of the stem cells that differentiate into neutrophils.

The graph shows the change in hydrogen peroxide concentration in a neutrophil during an oxidative burst.

Use the graph to calculate the initial rate of increase of H₂O₂ concentration in the neutrophil during an oxidative burst.

Suggest how an oxidative burst helps neutrophils to perform their function.

Antibodies can bind to receptors on the cell surface membrane of a neutrophil.

The binding of an antibody to a receptor causes the neutrophil to engulf the pathogen that is bound to the antibody.

State the name given to antibodies that act in this way.

Plants lack immune cells, but they have other defences against pathogenic infection.

The sentences describe one form of plant defence against pathogens.

Complete the sentences using the most appropriate word or phrase.

When a pathogen is detected in plant tissue, a plant increases the production of a

polysaccharide called........ This polysaccharide is deposited

in channels called........, which pass through cell walls. This

deposition stops the pathogen moving between cells. The polysaccharide is also

deposited in the small gaps between sieve tube elements. These gaps are known as

........ This deposition stops the pathogen moving between

different regions of the plant.

Xylem vessels maintain the transpiration stream by transporting water up plant stems.

The sentences describe the role of meristems in producing xylem vessels.

Complete the sentences using the most appropriate words or phrases.

Meristem cells are located between xylem and........ tissues in

plants. Cells of either of these vascular tissues can be produced when meristem cells divide and

A pair of students dissect the vascular tissue of the primrose plant, Primula vulgaris.

State and explain one safety precaution that the students should take when dissecting the vascular tissue.

This is a light micrograph of a transverse section through the stem of P. vulgaris.

The diameter of one of the vascular bundles is shown by the line labelled V.

Calculate the actual diameter of the vascular bundle labelled V.

Give your answer in mm and to 2 significant figures.

A scientist plans to investigate the effect of temperature on the rate of transpiration in P. vulgaris.

The scientist uses a potometer in their investigation, as shown in the diagram below.

The scientist plans to calculate the rate of transpiration by measuring the distance moved by the air bubble.

The scientist carries out a preliminary trial by measuring the distance moved by the air bubble in 30 minutes at 20 C.

The bubble moves 18 mm in 30 minutes. The diameter of the capillary tubing in the potometer is 1 mm.

Calculate the rate of transpiration, in mm³ h^–1, during this preliminary trial.

Use the formula: Volume of cylinder = r²l

Rate of transpiration =........ mm³ h^–1

* Describe how the scientist could use the potometer to collect the data needed to assess the effect of temperature on the rate of transpiration in P. vulgaris.

Details of how to set up and use a potometer are not needed.

In your answer you should name an appropriate statistical test that could be used to analyse the data.

Extra answer space if required.

Many plants, such as Erica cinerea (bell heather), have evolved adaptations to limit water loss by transpiration.

This is a drawing of a leaf of E. cinerea.

State and explain how the leaf of E. cinerea is adapted to limit water loss by transpiration.

Bone marrow stem cells are a source of erythrocytes.

Which statement about bone marrow stem cells and their role in the production of erythrocytes is correct?

A Bone marrow stem cells are totipotent and can therefore differentiate into any type of cell.

B Erythrocytes are the only blood cell produced from bone marrow stem cells.

C Erythrocytes need to be replaced from bone marrow stem cells because erythrocytes are unable to undergo mitosis.

D In humans, differentiation of bone marrow stem cells into erythrocytes involves the synthesis of a haploid nucleus.

The figure shows a potometer used to measure the rate of transpiration in a leafy shoot.

Besides safety precautions, explain one practical precaution that should be taken when using a potometer.

A student carried out an investigation to measure the effect of air movement on the rate of transpiration.

The student used the apparatus shown in the figure, adding an electric fan to create air movement. They measured the distance travelled by the air-water meniscus in 5 minutes.

This was replicated five times with the fan switched off and then five times with the fan switched on.

The results are shown in the table.

Calculate the standard deviation for the distance travelled when the fan was switched

Give your answer to 2 significant figures.

What can you conclude from comparing the standard deviations of the two means?

The student carried out another investigation.

The student wanted to estimate the total leaf surface area of the shoot.

At the end of the investigation they removed all the leaves from the shoot.

They placed the leaves on graph paper and then counted squares to obtain an estimate of leaf area.

State two things the student would have to do to ensure that the estimate of leaf area was accurate.

In this investigation, the student calculated the rate of transpiration to be 30 mm³ min (ii)

They estimated the total leaf surface area of the shoot to be 37 cm².

Calculate the rate of transpiration in cm³ hr^–1 cm^–2.

Give your answer in standard form to 2 significant figures.

Rate =........ cm³ hr^–1 cm^–2

Plant growth requires the production of new xylem cells.

Describe how new xylem cells are produced.

* Explain how glucose produced in photosynthesis is translocated to parts of the plant where glucose is metabolised or stored.

Additional answer space if required.

Which of the following statements, A to D, does not correctly describe the structure or formation of plant vascular tissues?

A Companion cells are linked to xylem vessels by plasmodesmata.

B Mature sieve tube elements do not contain nuclei.

C Phloem and xylem are formed by differentiation of vascular meristems.

D Xylem vessels have non-lignified pits to allow movement in and out.

Your answer

The image below shows a micrograph of two different types of blood cell.

Questions 4 and 5 refer to this image.

Which of the following rows, A to D, shows the correct cell names from the image above?

Your answer

Which of the following statements, A to D, correctly explains why meristems can differentiate into xylem vessels in plant stems?

A Meristems are living and unspecialised.

B Meristems are living and specialised.

C Xylem vessels are dead and specialised.

D Xylem vessels are dead and unspecialised.

Your answer