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(a) A gardener decided to kill the dandelion plants growing in his lawn - Edexcel - GCSE Biology - Question 7 - 2020 - Paper 1
Question 7
(a) A gardener decided to kill the dandelion plants growing in his lawn. The gardener set up a trial to see which concentration of weed killer would kill the most d... show full transcript
Worked Solution & Example Answer:(a) A gardener decided to kill the dandelion plants growing in his lawn - Edexcel - GCSE Biology - Question 7 - 2020 - Paper 1
Step 1
Give one variable the gardener should control when completing this trial.
Answer
One variable that the gardener should control is the amount of light each area receives. This ensures that all plants are exposed to the same light conditions, eliminating light as a confounding factor in plant growth.
Step 2
State and explain the conclusions the gardener can make based on his trial.
Answer
The gardener can conclude that an 80% concentration of weed killer is the most effective solution in killing dandelion plants. The results show that after applying this concentration, the number of dandelions reduced to zero.
Furthermore, it can be inferred that as the concentration of the weed killer increases, the number of surviving dandelions decreases, indicating a direct relationship between weed killer concentration and its effectiveness.
Step 3
Explain how plant hormones work as weed killers.
Answer
Plant hormones, such as auxins, disrupt the normal growth patterns of plants. When applied in excessive amounts, these hormones can lead to uncontrolled growth, causing plants to grow unevenly. This results in the plants becoming unable to sustain themselves, ultimately killing them. Therefore, the application of these hormones in weed killers effectively eliminates unwanted plants by thwarting their physiological growth processes.
Step 4
Explain how phototropism is controlled in plant shoots.
Answer
Phototropism in plant shoots is controlled by the differential distribution of the hormone auxin. When light shines on a plant, auxin is redistributed towards the shaded side of the shoot. This causes the cells on the shaded side to elongate more than those on the illuminated side, resulting in the plant bending towards the light source. This adaptive response allows the plant to optimize light capture for photosynthesis.