Page 137 - Biology Form Two

Biology for Secondary Schools

Activity 6.2: Observe the parts of the lungs. The composition of inhaled air
mammalian respiratory system is different from that of exhaled air, as
shown in Table 6.3.
Materials
Table 6.3: Composition of inhaled
FOR ONLINE READING ONLY
Dissected mouse and chart showing and exhaled air
the mammalian respiratory system, Constituent Inhaled Exhaled
notebook, and pencil air air
Oxygen gas 20.95% 16.40%
Procedure
1. Observe the displayed specimen Carbon 0.03% 4.00%
of the respiratory system of the dioxide gas 78.10% 78.10%
Nitrogen gas
mouse.
Noble gases 0.94% 0.94%
2. Describe what you have observed.
3. Identify all the structures of the Inhalation
mouse respiratory system that you
have observed. Inhalation helps to bring air into the
respiratory system. During inhalation,
4. Compare the displayed system air enters the body through the nasal

with the chart. cavity. As air passes through the nasal
5. Write short notes on your cavity, it is moistened and warmed

observation. to body temperature. This is possible
due to the presence of mucus which
Mechanism of gas exchange in protects the tissue from direct contact
mammals with air. Mucus has a high amount of

Task 6.3 water. Therefore, as air crosses these
surfaces of the mucus membranes, it
Search the library and internet sources picks up water. This process helps to
for information on inhalation and equilibrate the air temperature with the
exhalation in mammals. Prepare a body temperature, hence reducing any
summary of your search. damage that cold, hot, or dry air can

cause. Mucus also helps in trapping
Gas exchange in mammals occurs as dust particles that enter the nose.
a result of inhalation and exhalation.
Inhalation is a process of breathing During inhalation the muscles of
in air into the lungs. Exhalation is a the diaphragm contract, pulling the
process of breathing out air from the diaphragm downwards. As this happens,

Student’s Book - Form Two 131

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