Page 74 - Biology Form Two

Biology for Secondary Schools

7. Leave the set-ups undisturbed overnight.
8. Describe your observation.

9. Study Figure 3.4 and compare with your results.
Start of the experiment End of the experiment
BeakerREADING ONLY
Sugar solution Sugar solution
(a) Raw
Raw potato potato
Water Water
Beaker Beaker

(b) Sugar solution Sugar solution
Boiled Boiled
potato potato
Water Water
Beaker Beaker

(c)
Raw
Raw potato potato
FOR ONLINE
Water Water
Beaker
Figure 3.4: Experimental set-up to demonstrate osmosis

10. Prepare a brief report.

Questions

1. What differences did you observe in set-ups (a), (b), and (c)?

2. Explain your observation in each case.

The importance of osmosis
Osmosis is an important process in both plants and animals. In plants, osmosis
aids the absorption of water by the roots. Osmosis also aids the opening and

closing of the stomata. When guard cells absorb water the stomata open. When
they lose water, the stomata close. Osmosis also plays a key role during seed
germination. It enables the absorption of water that softens the seed coat, hence,
increasing seed permeability for dissolved minerals and oxygen. This promotes
the growth of seed embryo during germination.

68 Student’s Book - Form Two

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