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Adaptations for Respiration
THE RESPIRATORY SURFACE
All aerobic organisms must take in oxygen and eliminate carbon dioxide. Among
the protists and very small multicellular animals, there is generally a direct
exchange of respiratory gases across the cell membrane. In larger animals,
however, the exchange of gases takes place at a specialized respiratory surface.
The respiratory surface, whether external or internal, must be in contact with free
oxygen. The surface must also be thin, and it must be constantly moist. At the
moist membrane surface, oxygen dissolves and diffuses through the membrane.
1. Describe the required characteristics of a respiratory surface.
2. What happens to gases at the respiratory surface?
3. What happens if the respiratory surface dries out?
PROTOZOA
Among the protozoa, respiration is accomplished by the diffusion of dissolved
oxygen and carbon dioxide through the cell membrane. Oxygen dissolved in the
surrounding water diffuses into the organism and is carried throughout the cell by
cyclosis and diffusion. Carbon dioxide, which is produced within the cell,
diffuses out through the cell membrane into the surrounding medium.
1. What is the respiratory surface for protozoa?
2. How do protozoa obtain oxygen?
3. How is oxygen transported throughout the cytoplasm in protozoans?
HYDRA
The hydra’s saclike body is composed of two cell layers, both of which are in
direct contact with the environment. Dissolved oxygen diffuses from the
surrounding water into the cells of the body, and carbon dioxide diffuses out
through the cell membranes into the environment.
1. What is the respiratory surface in the hydra?
2. Explain why a hydra, a multicellular organism, does not require a respiratory
system?
MULTICELLULAR ANIMALS AND RESPIRATORY PIGMENTS
Most multicellular air-breathing animals maintain a moist respiratory surface
internally. In addition, many animals have special respiratory pigments, such as
hemoglobin in their blood. These pigments increase the capacity of the blood to
carry oxygen and carbon dioxide.
1. Explain how most air-breathing multicellular animals are able to maintain a
moist respiratory surface.
2. The most common respiratory pigment is _________________________.
STRUCTURE OF THE HUMAN RESPIRATORY SYSTEM
“ORGAN”
Nose
Uvula
Epiglottis
Larnyx
Trachea
Bronchus/Bronchi
Bronchioles
Airsacs/Alveolus/Alveoli
DESCRIPTION AND FUNCTION
1. In humans, the respiratory surface is made up of the walls of the
________________________, which are only one cell thick.
2. The vocal cords are in the ________________________________.
3. The large muscle that separates the chest (thoracic) and abdominal cavities is the
______________________________________.
4. The two subdivisions of the trachea that enter the lungs are the
__________________________.
PHASES OF HUMAN RESPIRATION
Breathing is the process by which air moves into and out of the lungs. The
breathing process and the rate of breathing are mainly controlled by the
respiratory center in the medulla of the brain. Nerves go from the respiratory
center to the diaphragm and rib muscles. The respiratory center is sensitive to the
concentration of CO2 in the blood. When the CO2 concentration rises, the
respiratory center causes the rate of breathing to increase so that more O2 enters
the blood and more CO2 is removed. When the carbon dioxide concentration
decreases, the rate of breathing also decreases.
The exchange of gases between the lungs and the blood is known as external
respiration. The exchange of respiratory gases between the blood and the cells is
known as internal respiration.
1. Describe what happens during inhalation and during exhalation, including the
changes in pressure that occur in the chest cavity.
2. Explain the difference between external and internal respiration.
3. How does the respiratory center of the brain control the breathing rate?
4. Explain the effect of strenuous muscular activity on breathing rate.