A scientist investigated cells from the fleshy scales of mature lily bulbs.
The scientist cut equal-sized pieces of tissue that did not contain any shoot tissue.
The scientist placed 20 pieces in each of eight dishes. Four dishes contained nutrient jelly with plant hormone. Four dishes contained nutrient jelly without plant hormone. All other conditions were kept the same.
After 21 days, the scientist counted the number of pieces that had formed shoots. Each new shoot contained specialised xylem and phloem cells.
| Plant hormone in jelly | Dish | Number of pieces that formed shoots out of 20 |
|---|---|---|
| Present | 1 | 16 |
| Present | 2 | 15 |
| Present | 3 | 3 |
| Present | 4 | 14 |
| Absent | 5 | 1 |
| Absent | 6 | 0 |
| Absent | 7 | 1 |
| Absent | 8 | 0 |
The scientist claimed that cells from mature bulb tissue can differentiate and that added plant hormone is required for this differentiation.
One result for the jelly with plant hormone is anomalous.
Calculate the mean percentage of pieces that formed shoots in the other dishes containing plant hormone.
Evaluate the scientist's claim using the results of the investigation.
For a second investigation, the scientist plans to use tissue from four more mature lily bulbs. Tissue from bulbs P and Q will be placed only in jelly with plant hormone. Tissue from bulbs R and S will be placed only in jelly without plant hormone.
Explain why this allocation could reduce the validity of the investigation. Suggest how the tissue should be allocated instead.
282 exam-style questions on AQA GCSE Biology 1.1 Cell structure, covering 1.1.1 Eukaryotes and prokaryotes, 1.1.2 Animal and plant cells, 1.1.3 Cell specialisation, 1.1.4 Cell differentiation, 1.1.5 Microscopy, and 1.1.6 Culturing microorganisms. Each one has a worked solution and a mark scheme showing where the marks go.