Question 1
Name the three processes involved in the growth of a plant.
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- cell division (1)
- elongation (1)
- differentiation (1)
Question 2
Explain why cell differentiation is important in the development of an organism.
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- cells become specialised / gain structures for a particular job (1)
- so different cells can carry out different functions / the organism can have different tissues and organs (1)
Question 3
The table shows the mass of girls aged 12 months on some percentile lines. A girl's mass was on the 50th percentile at 6 months old. At 12 months old her mass is 7.0 kg. Use the table to suggest why a doctor would want to check her growth.
| Percentile | 2nd | 25th | 50th | 75th | 98th |
|---|---|---|---|---|---|
| Mass in kg | 7.0 | 8.2 | 8.9 | 9.7 | 11.3 |
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- she has moved from the 50th percentile to the 2nd percentile (1) allow she has dropped down across the percentile lines
- a large change in percentile may show she is not growing properly / has a health problem (1)
Question 4
A baby has a mass of 3.5 kg at birth. At 6 weeks old the baby's mass is 4.2 kg. Calculate the percentage gain in mass.
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- change in mass = 4.2 − 3.5 = 0.7 kg and 0.7 ÷ 3.5 × 100 (1)
- 20% (1) correct answer with no working scores 2
Question 5
Many newborn babies lose some mass in the first few days. A baby had a mass of 3.5 kg at birth and 3.22 kg at 5 days old. Calculate the percentage loss in mass.
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- change in mass = 3.5 − 3.22 = 0.28 kg and 0.28 ÷ 3.5 × 100 (1)
- 8% (1) correct answer with no working scores 2; do not accept 8.7% (divided by final mass)
Question 6
Describe the function of embryonic stem cells, stem cells in adult animals and meristems in plants.
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- embryonic stem cells can differentiate into any type of cell / produce all the specialised cells of the developing embryo (1)
- stem cells in adult animals can differentiate into a limited range of cell types to replace damaged or worn-out cells, such as blood cells from bone marrow (1)
- meristems produce cells that can differentiate into any type of plant cell, allowing the plant to keep growing (1) allow found at tips of roots and shoots for growth
Question 7
Discuss the potential benefits and risks associated with the use of stem cells in medicine.
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| Level | Marks | What the answer does |
|---|---|---|
| 3 | 5–6 | Gives a balanced discussion with several benefits and several risks, which are explained, and may include a reasoned conclusion. Scientific terms are used accurately. |
| 2 | 3–4 | Gives at least one benefit and one risk, with some explanation. The discussion may be one-sided or lack detail. |
| 1 | 1–2 | States one or two simple points about benefits or risks, with little or no explanation. |
Indicative content
- benefits: could treat conditions such as diabetes or paralysis
- benefits: could replace damaged or diseased cells with healthy cells
- benefits: new tissues could be grown for transplants
- risks: stem cells may divide out of control and form a tumour
- risks: viruses in donated stem cells could be passed to the patient
- risks: the immune system may reject cells from another person
- ethical or religious objections to using embryos
- a conclusion that weighs the benefits against the risks