Gas exchange in plants and fish Flashcards
diffusion rate equation
diffusion rate = (surface area x conc gradient)/diffusion distance
how do insects limit water loss
-waterproof covering over their body surface
rigid outer skeleton covered with a waterproof cuticles
-small surface area to volume ratio
movement of oxygen through the insect-start outside
- oxygen enters the insect through spiracles and into the trachea. Spiracles close
- oxygen diffuses through the tracheae
- oxygen is delivered directly to the respiring tissues
adaptation of tracheoles
small tubes with thin walls so that the diffusion distance is reduced
highly branched so large SA
oxygen diffusion process in insects
- 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.
CO2 diffusion process in insects
- 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 insects get additional oxygen during flight
- at rest, water builds up in the tracheoles
- during flight the insect partially respires anaerobically to produce lactic acid
- lowes water potential of muscle cells
-as lactate builds up, water passes via osmosis from the tracheoles into the muscle cells - allows air into the tracheoles closer to muscle cells so reduces diffusion distance for oxygen when needed
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange (2)
- Many lamellae so there’s a large surface area
- Lamellae are thin for a short diffusion pathway
what is countercorrent flow?
blood and water flow in opposite directions
massively increases the fish’s ability to absorb oxygen from the water as a diffusion gradient is maintained
A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange. (6)
- large surface area provided by many lamellae
- thin layer of lamellae between blood and water so short diffusion distance
- water and blood flow in opposite directions so a concentration gradient is maintained
- as water is always next to blood with lower conc of oxygen, circulation replaces blood saturated with oxygen
- ventilation replaces water
Explain how the counter current mechanism in fish gills ensures the maximum amount of oxygen passes into the blood flowing through the gills (3)
- Water and blood flow in opposite directions
- Blood always passing water with a higher oxygen concentration
- concentration gradient maintained throughout the length of the gill lamellae
adaptations of leaf for gaseous exchange
flat- gives larger surface area to volume ratio
many stomata - pores to allow air to move in and out of the leaf
air spaces in leaf- short diffusion distance between mesophyll cells and air
diffusion of CO2 for photosynthesis
- 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 for plants
- 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.
plant adaptations to reduce water loss
- guard cells close the stomata to prevent water loss at night
- less CO2 is required at this time of day due to lack of light
- upper and lower surfaces have a waxy cuticle
- most stomata are distributed on the lower surface
