Gas Exchange Flashcards
As an organism gets larger…
Surface area to volume ratio decreases
What is Fick’s law?
Rate of diffusion = (SA x concentration gradient) / diffusion distance
What do insects have to limit water loss?
Waterproof covering and relatively small surface area to volume ratio
What is the movement of water through an insect? (4)
- Oxygen enters the insect through the spiracles and into the trachea
- Spiracles close
- Oxygen diffuses through the tracheae into the tracheoles ( down conc. gradient)
- Oxygen is delivered directly to the respiring tissues
Oxygen diffusion in insects (3)
- Tissues respire using oxygen, which reduces the concentration of oxygen at the tissue
- Oxygen moves from an area of higher concentration to lower concentration so moves from the tracheae to the tissue
- This lowers the oxygen concentration in the tracheae so oxygen moves into the tracheae from outside the insect via the spiracles
Carbon dioxide diffusion in insects (3)
- Respiration produces CO2, increasing the concentration at the tissue
- CO2 moves from an area of high concentration at the tissue to the low concentration in the tracheae
- CO2 then moves from high concentration in tracheae to low concentration outside the insect via the spiracles
How does an insect get additional oxygen during flight?
- during flight the insect may partly respire anaerobically and produce some lactate
- this lowers the water potential of the muscle cells. As the lactate builds up, water passes via osmosis from the tracheoles into the muscle cells
- this adaptation draws air into the tracheoles closer to the to the muscle cells and therefore reduces the diffusion distance for oxygen when it’s most needed
What are the two adaptations of the tracheoles in insects ?
- thin walls so that the diffusion distance is reduced
- highly branched so large surface area
Explain two ways ways in which the structure of fish gills is adapted for efficient gas exchange (2)
- Many filaments/ lamellae, so there’s a large surface area
- Lamellae are thin for a short diffusion pathway
Explain the counter- current flow mechanism in fish
- Water and blood flow in opposite directions
- Water with a high concentration of oxygen is always next to the blood with a low concentration of oxygen
- This maintains a favourable concentration gradient along the whole length of the gill
Explain how the gills of a fish are adapted for efficient gas exchange (6)
- Large surface area provided by many lamellae making diffusion more efficient
- Thin epithelium of lamellae, so short diffusion distance
- Water and blood flow in opposite directions so that a concentration gradient is maintained along the whole length of the gill
- As water with a high concentration of oxygen is always next to the blood with a low concentration of oxygen
- Circulation replaces blood saturated with oxygen
- Ventilation replaces water
What are the 3 adaptations of a leaf for gas exchange?
- Flat- gives larger surface area to volume ratio
- Many stomata- pores to allow air to move in and out of leaf
- Air spaces in leaf so short diffusion distance between mesophyll cells and air
Diffusion of co2 for photosynthesis (3)
- Mesophyll cells photosynthesise and this reduces the concentration of co2 in the cells
- CO2 diffuses from the air spaces into the cells
- This in turn reduces the co2 concentration in the air spaces causing co2 to move into the air spaces from the air outside the leaf, through the stomata
Diffusion of o2 in plants (3)
- Mesophyll cells produce o2 as a result of photosynthesis
- O2 diffuses into the air spaces from the cells
- This increases the concentration of o2 in the air spaces, causing o2 to move from the air spaces to outside the leaf via the stomata
How do stomata close?
- guard cells carry out photosynthesis
- this produces sugars which lowers the water potential
- water moves into guard cell causing them to swell
- stomata close
