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4 (a) Figure 4 shows the structures in a leaf - Edexcel - GCSE Biology - Question 4 - 2019 - Paper 1
Question 4
4 (a) Figure 4 shows the structures in a leaf. Explain how structure Z is involved in defence against pathogens. (2) (b) Chemicals can be extracted from plants. So... show full transcript
Worked Solution & Example Answer:4 (a) Figure 4 shows the structures in a leaf - Edexcel - GCSE Biology - Question 4 - 2019 - Paper 1
Step 1
Explain how structure Z is involved in defence against pathogens.
Answer
Structure Z refers to the waxy cuticle found on the surface of leaves. This waxy layer serves as a physical barrier that prevents pathogens from entering the leaf. By acting as a waterproof surface, it helps to reduce the chances of infection, thus playing a crucial role in the plant's defense mechanism.
Step 2
Step 3
Explain why the scientist worked near to a Bunsen burner.
Answer
The scientist worked near a Bunsen burner to create an updraft of air that minimizes the risk of airborne contaminants settling on the agar plates. The heat from the flame helps to sterilize the surrounding air, further ensuring that no unwanted microorganisms interfere with the experiment.
Step 4
Calculate the area of the zone of inhibition for chemical A.
Answer
To calculate the area of the zone of inhibition for chemical A, we use the formula for the area of a circle:
Given that radius (r) is 12 mm and using π = 3.14, we have:
Thus, the area of inhibition for chemical A is 452.16 mm².
Step 5
Give two variables the scientist needed to control to make this conclusion valid.
Answer
- The concentration of each chemical used in the experiment should be kept consistent across both agar plates.
- The volume of bacteria spread on each agar plate should be the same to ensure a fair comparison.
Step 6
Explain one advantage of producing these genetically modified crop plants.
Answer
One advantage of producing genetically modified crop plants that produce toxic chemicals in their leaves is that they can provide enhanced protection against pests and diseases. This reduces the need for chemical pesticides, leading to potentially lower environmental impact and reduced production costs for farmers.