Teacher's notes and answers to questions in the book - Hodder Plus ...

WJEC GCSE Additional Science Teacher’s Notes
Ethano-orcein stain is made by grinding 1.5 g of solid orcein with a pestle and mortar. In a
fume cupboard, mix 90 cm 3 of glacial ethanoic acid with 110 cm 3 of distilled water and bring to
the boil. Pour the boiling mixture over the orcein and stir very thoroughly (still in the fume
cupboard). Leave overnight, then filter and store in a tightly-stoppered dark bottle. An
alternative is lactopropionicorcein stain.
_Do animals and plants grow in the same way_______
(pages 23–24)
Discussion points
1. What are the advantages to a plant of a branched growth form Why might a compact form be better
for animals
Branched growth allows greater spread for light capture (irrelevant in animals). Plants are
sedentary and so cannot escape predators. A branched form allows parts of the plant to be
lost/damaged without destroying the whole. Animals have no need of a branched form and
such a form would inhibit movement.
2. Why is being able to grow throughout life a particular advantage to plants, and why would it not be so
advantageous for animals
This again could be linked to the need to re-grow parts eaten by animals. It also ensures the
best chance of reaching light. Neither is necessary in animals, and increasing size would mean
constantly increasing food demands, as well as making it difficult to support the body and
possibly to feed. Small animals do not have the adaptations to cope with becoming larger.
Questions
4. Describe the pattern shown in the graph (Figure 2.21).
Growth rate starts very high but declines rapidly until the age of 3–4, then more gradually until
the age of 12. Between the ages of 12–14 the rate increases again, then declines steadily until
the age of 20.
5. Suggest an explanation for the shape of the graph between the ages of 12 and 14.
Puberty occurs and this is associated with rapid growth.
_What are stem cells (pages 24–25)_______________
TASK How should we use stem cells, if at all (page 25)
This activity is included to meet the needs of the specification, to discuss the future potential
and ethical issues surrounding stem cell technology.
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