Pathogens are microorganisms that cause infectious diseases. What type of pathogen causes malaria? Tick (✓) one box. Bacterium: Fungus: Protist: Virus: Give two methods used to prevent people catching malaria. Give a reason why each method works. Method 1 Reason Method 2 Reason Describe two differences between a bacterial cell and a eukaryotic cell. 1 2 A scientist investigated the population growth of bacteria in a culture solution. At the start of the investigation the culture solution contained all the nutrients the bacteria needed. The scientist determined the number of living bacterial cells in the solution every hour over two days. Figure 5 shows the apparatus used. Describe why there are air holes in the cap of the culture bottle. Figure 6 shows the scientist’s results. Give one reason for what is happening to the number of bacteria at each of the stages. Stage A Stage B Stage C Stage D Figure 7 shows two cubes. Cube X represents a bacterial cell. Cube Y represents a small multicellular organism. A bacterial cell can absorb all the nutrients it needs by diffusion through its outer surface. Explain why a multicellular organism cannot absorb all the nutrients it needs by diffusion. You must include calculations in your answer. Use Figure 7.

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Pathogens are microorganisms that cause infectious diseases - AQA - GCSE Biology: Combined Science - Question 4 - 2019 - Paper 1

Question 4

Pathogens are microorganisms that cause infectious diseases. What type of pathogen causes malaria? Tick (✓) one box. Bacterium: Fungus: Protist: Virus: Give ... show full transcript

Worked Solution & Example Answer:Pathogens are microorganisms that cause infectious diseases - AQA - GCSE Biology: Combined Science - Question 4 - 2019 - Paper 1

Step 1

What type of pathogen causes malaria?

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Answer

The pathogen that causes malaria is a protist. This is the correct choice as malaria is caused by the parasite Plasmodium, which falls under the category of protists.

Step 2

Give two methods used to prevent people catching malaria. Give a reason why each method works.

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Answer

Method 1: Insecticide-treated nets. Reason: These nets kill or repel mosquitoes, the vectors transmitting malaria, thus preventing bites while people sleep.

Method 2: Vaccination against malaria. Reason: A vaccination helps develop immunity in individuals, reducing the likelihood of infection from malaria.

Step 3

Describe two differences between a bacterial cell and a eukaryotic cell.

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Answer

A bacterial cell does not have a nucleus, while a eukaryotic cell has a well-defined nucleus containing its genetic material.
Bacterial cells are generally smaller in size compared to eukaryotic cells, which can be quite large and complex.

Step 4

Describe why there are air holes in the cap of the culture bottle.

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Answer

Air holes in the cap of the culture bottle allow oxygen to enter, which is necessary for the bacteria to respire. This supports their growth by providing the essential gas for aerobic respiration.

Step 5

Give one reason for what is happening to the number of bacteria at each of the stages.

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Stage A: There is a rapid increase in the population size as cells divide quickly due to abundant nutrients.

Stage B: The population growth begins to level off as the nutrients become more limited, and waste products start to accumulate.

Stage C: The population size stabilizes as the rate of cell division equals the rate of cells dying.

Stage D: The population starts to decline as the nutrients are depleted and cells die from toxicity of waste products.

Step 6

Explain why a multicellular organism cannot absorb all the nutrients it needs by diffusion.

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Answer

A multicellular organism cannot absorb all the nutrients it needs by diffusion because of its larger size and complex structure. For instance, consider Cube X (bacterial cell) with a volume of 0.0002 cm³ and Cube Y (multicellular organism) with a volume of 11 cm³. The surface area to volume ratio for Cube X is higher than Cube Y, meaning a smaller cell can efficiently absorb nutrients through its surface. In contrast, as Cube Y has a lower ratio, diffusion alone cannot transport enough nutrients across its surface to meet its needs.

Calculating the ratio: For Cube X: Volume = 0.0002 cm³, Surface Area (assuming each edge length is 0.1 cm) = $6(0.1^2)$ = 0.06 cm², Ratio = 0.0002/0.06 = $3.33 × 10^{-3}$ .

For Cube Y: Volume = 11 cm³, Surface Area (assuming each edge length is 2.23 cm) = $6(2.23^2)$ = approximately 29.76 cm², Ratio = 11/29.76 = approximately $0.368$ .

Thus, the higher surface area to volume ratio of smaller cells allows for more efficient nutrient absorption.

Pathogens are microorganisms that cause infectious diseases - AQA - GCSE Biology: Combined Science - Question 4 - 2019 - Paper 1

Worked Solution & Example Answer:Pathogens are microorganisms that cause infectious diseases - AQA - GCSE Biology: Combined Science - Question 4 - 2019 - Paper 1

What type of pathogen causes malaria?

Give two methods used to prevent people catching malaria. Give a reason why each method works.

Describe two differences between a bacterial cell and a eukaryotic cell.

Describe why there are air holes in the cap of the culture bottle.

Give one reason for what is happening to the number of bacteria at each of the stages.

Explain why a multicellular organism cannot absorb all the nutrients it needs by diffusion.

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