Describe changes to the diaphragm upon inspiration. (2)
- Diaphragm contracts
- And flattens
Explain how the diaphragm causes air to move into the lungs. (3)
- Diaphragm contracts and flattens
- Increases the volume of the thorax
- Air moves down a pressure gradient and into the lungs
Describe how oxygen in the alveoli enters the blood capillaries. (2)
- Oxygen DIFFUSES through the epithelium of the alveoli
- and through the endothelium of the blood capillaries
Circulation of the blood helps to maintain this difference in oxygen concentration. Explain how. (1)
REPLACES blood with a high concentration of oxygen with blood with a low concentration of oxygen
Miner’s lung is a disease caused by breathing in dust in coal mines. The dust causes the alveolar epithelium to become thicker. People with miner’s lung have lower concentration of oxygen in their blood than healthy people.
Describe the path by which oxygen goes from an aveolus to the blood. (2)
- By diffusion
- Through the epithelium of the alevolus and through the endothelium of blood capillaries
Explain why people with miner’s lung have a lower concentration of oxygen in their blood. (1)
Thicker alveolar wall so longer diffusion pathway
In healthy lungs, a gradient is maintained between the concentration of oxygen in the alveoli and the concentration of oxygen in the lung capillaries.
Describe how ventilation helps to maintain this difference in concentration. (2)
- Air with a higher oxygen concentration DRAWN INTO lungs upon inspiration
- Air with a lower oxygen concentration REMOVED from lungs upon expiration.
Give one other way that helps to maintain the difference in oxygen concentration. (1)
Circulation OF BLOOD
Coal mining in Britain had been dramatically reduced by 1990.
Some scientists concluded that the rise in reported cases of miner’s lung after 1992 shows that the disease takes a long time to develop.
Evaluate this conclusion. (
- Long time between decrease in mining and increase in cases
- Correlation does not prove causation - other factors may influence miner’s lung
- Improved diagnosis methods
- Graph shows fluctuations
- Not all cases of miner’s lung reported
- Don’t know number of cases before 1990
The diaphragm helps to bring abou the increase in the total volume of air breathed out. Explain how. (3)
- Diaphragm relaxes
- Diaphragm domes
- Volume of the thorax decreases
Destruction of pahgocytes causes the lungs ti be more suspectible to infections. Explain why. (2)
- Phagocytes engulf and destroy pathogens
- Lung infections are caused by inhaling phagocytes/fibres
The reduced elasticity of the lungs causes breathing difficulty. Explain how. (2)
- MORE residual air in the lungs as they don’t deflate as much upon expiration
- Reduces OXYGEN concentration between the lungs and the environment
- Reduces rate of OXYGEN diffusion into the blood
Apart from reduced elasticity, explain how changes to the lung tissue reduce the effiency of gas exchange. (4)
- Alevolar walls thicken
- Longer diffusion pathway for gas exchange
- Scarred tissue
- Decreases surface area for gas exchange
Give one factor other than abestos, which increases the risk of developing lung cancer. (1)
Smoking
Explain an advantage of a counter-current mechanism. (2)
- Diffusion gradient maintained across the gills
- At every point of contact oxygen concentration in water is higher than the oxygen concentration in the blood
- (or) more oxygen diffuses into the blood
African lungfish are likely to survive for longer than Australian lungfish when living in pools that dry up. Explain why. (2)
- In African lungfish, more gas exchange by the lungs
- Gills inefficent in air (as gills need to be ventilated)
Gas exchange in fish takes place in gills. Explain how two features of gills allow efficent gas exchange. (2)
- thin EPITHELIUM so short diffusion pathway
- Many gill filaments and lamellae so large surface area for diffusion
- Counter-current mechanism to maintain diffusion gradient
Describe the relationship between body mass and oxygen uptake. (1)
- The higher the body mass, the lower the oxygen uptake per gram of body mass
- Negative corelation
Explain why the zoologist measured oxygen uptake per gram of body mass. (2)
- Allows for comparison
- As the mammals have different body masses
Heat from respiration helps mammals to maintain a constant body temperature. Use this information to explain the relationship between body mass and oxygen uptake as shown in the graph. (3)
- Smaller mammals have a larger SA:Vol
- Lose more heat per gram of body tissue
- Need to respire more to maintain temperature
- Oxygen is needed for respiration
Use information from the digram to suggest what stimulates the spiracles to open. (1)
- An INCREASE in the partial pressure of carbon dioxide.
Explain what causes the oxygen concentration in the trachae to fall when the spiracles are closed. (2)
- Oxygen used in respiration
- Oxygen moves into cells by diffusion
- More oxygen can’t enter through closed spiracles
The insect lives in dry conditions. Suggest an advantage of the pattern of spiracle movements shown in the diagram. (2)
- Spiracles not open all the time
- Less water loss
Explain how ventilation increases the rate of gas exchange in the alveoli. (2)
Maintains a greater diffusion gradient;
to allow faster diffusion
