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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
Step 2
Give two methods used to prevent people catching malaria. Give a reason why each method works.
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.
Answer
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A bacterial cell does not have a nucleus, while a eukaryotic cell has a well-defined nucleus containing its genetic material.
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Bacterial cells are generally smaller in size compared to eukaryotic cells, which can be quite large and complex.
Step 4
Step 5
Give one reason for what is happening to the number of bacteria at each of the stages.
Answer
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.
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) = = 0.06 cm², Ratio = 0.0002/0.06 = .
For Cube Y: Volume = 11 cm³, Surface Area (assuming each edge length is 2.23 cm) = = approximately 29.76 cm², Ratio = 11/29.76 = approximately .
Thus, the higher surface area to volume ratio of smaller cells allows for more efficient nutrient absorption.