Page 77 - Biology Form Two

Biology for Secondary Schools

Exercise 3.1 (iv) transport of water from the roots to
different parts of the plant through
1. Explain the importance of transport the xylen.
of materials in the human body.
Activity 3.4: Demonstrate mass flow
2. Why are isotonic solutions ideal
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for treating dehydration? in plants

3. Explain the effects of osmosis in Materials
animal cells. Potted plant and scalpel or knife

4. Differentiate a hypotonic solution Procedure
from a hypertonic solution. 1. Remove a ring of bark from the
potted plant as shown in Figure
Mass flow 3.8. The bark contains phloem.
This is the bulk movement of substances
from one region to another due to Safety precautions
differences in pressure between the Observe safety precautions
two regions. Mass flow occurs within when working with sharp
a cell or along a vessel. This mode objects.
of transport is important in large and
complex organisms where substances
are required in large amounts. Mass
flow occurs when the materials need
to be transported over a long distance.
Thus, diffusion alone is not sufficient
to ensure physiological processes. ring of bark
removed
Examples of systems where mass flow
occurs include

(i) the blood circulatory system in
animals; Figure 3.8: Potted plant with a ring of bark
(ii) the lymphatic system in animals; removed

(iii) transport of manufactured food 2. Leave the plant undisturbed for a
material in plants from the site of week.
manufacture, mostly in the leaves 3. Observe the plant. What do you
to the point of utilisation through observe in the upper part of the
the phloem. (This process is called shoot? Compare your results with
translocation) and Figure 3.9.

Student’s Book - Form Two 71

05/10/2024 15:36:26
BIOLOGY FORM 2 NEW.indd 71
BIOLOGY FORM 2 NEW.indd 71 05/10/2024 15:36:26