7.1 Specialised exchange surfaceswhy is there a need

why is there a need for specialised exchange surfaces for multicellular organisms

• high metabolic activity, oxygen demands and carbon production

• low surface area too volume ratio, larger distance to travel

why do exchange surfaces have increased SA

provide area needed for exchange, overcome limitations of small SA:V ratio

why do exchange surfaces have thin layers

shorter diffusion distances

why do exchange surfaces have good blood supply

maintain steep concentration gradient for diffusion

why do exchange surfaces have good blood supply

to maintain diffusion gradient

example of increased surface area in exchange surfaces

root hair cells in plants or villi in small intestine

example of thin layers in exchange surfaces

alveoli in lungs or villi in small intestine

example of good blood supply in exchange surfaces

alveoli of lungs, gills of fish or villi of small intestines

example of ventilation in exchange surfaces

alveoli or gills of a fish (flow of water carry dissolved gases)