Embedded Files
objectives
objectives
- List the features of gas exchange surfaces in animals
- Explain how air sacs in the lungs increase the surface area available for the absorption and release of gases
- State the differences in composition between inspired and expired air
Gas Exchange - Definition
Gas Exchange - Definition
Oxygen diffusing into the blood and carbon dioxide diffusing out
Labelling the Lungs
Labelling the Lungs
Label the Lung Diagram:
Diagram-of-gas-exchange-system.docSurface Area to Volume Ratio
Surface Area to Volume Ratio
Q. Why can small, unicellular organisms such as bacteria simply diffuse resources (e.g. oxygen) across their body surface?
Small organisms have a large surface area to volume ratio. Diffusion of resources, such as oxygen, is therefore very efficient.
Q. How do large, multicellular organisms, with small surface area to volume ratios, get sufficient resources, such as oxygen?
Large organisms with small surface area to volume ratios need specialised exchange surfaces such as lungs to obtain the resources they need.
Gas Exchange - Comparing Inhaled and Exhaled Air
Gas Exchange - Comparing Inhaled and Exhaled Air
We need Oxygen from the air for respiration and we need to remove Carbon Dioxide which is a waste gas of respiration.
Inhaled air (atmospheric air) and Exhaled air will therefore contain different amounts of Oxygen and Carbon Dioxide.
Below we can see that:
- Oxygen has decreased after it was exhaled
- Carbon Dioxide has increased
Alveoli
Alveoli
Gas exchange takes place in the alveoli – oxygen diffuses into the blood and carbon dioxide diffuses out of the blood.
Adaptations of Alveoli
Adaptations of Alveoli
Surface Area
Surface Area
- Alveoli increase the surface area immensely.
- Roughly half the size of a tennis court.
Short Diffusion Path
Short Diffusion Path
- One cell thick alveoli, one cell thick capillaries.
- Hence the surface across which diffusion occurs is thin and the rate is high.
Large Difference in Oxygen Concentration
Large Difference in Oxygen Concentration
Maintained by breathing (removes air high in CO2 and brings in air high in O2) and a continuous blood flow (takes away oxygenated blood and replaces it with blood with a high concentration of CO2)
Moist Surface
Moist Surface
Moist surfaces allow gases to dissolve and diffuse across the wall more effectively.
Summary Video
Summary Video
Gas Exchange worksheet
Gas Exchange worksheet
Complete the worksheet in your booklets
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