EXCHANGE SURFACES VERIFIED SOLUTIONS 2023/2024

EXCHANGE SURFACES VERIFIED SOLUTIONS 2023/2024 Why do multicellular organisms need specialised exchange surfaces but single celled organisms don't? - ANSWER single celled organisms can exchange materials across their CSM to meet requirements - metabolic activity low → O2 needs low + CO2 produced is low - large SA:V ratio Multicellular organisms are the opposite - high metabolic rate (active + maintain temp) - small SA:V ratio 3 main features of an efficient exchange surface - ANSWER • increased surface area • thin layer • good blood supply/ventilation to maintain gradient how to calculate surface area to volume ration using a sphere - ANSWER - calculate SA with 4π² - calculate volume with 4/3πr³ - ratio = surface area/volume can see as radius gets bigger the SA:V ration decreases How does increased SA aid diffusion? - ANSWER larger SA:V ratio bigger area for exchange e.g root hair cells, villi How do thin layers aid diffusion? - ANSWER reduces diffusion distance e.g in alveoli How does a good blood supply aid diffusion? - ANSWER Increases concentration gradient substances constantly delivered and removed e.g alveoli, gills, villi Nasal cavity features - ANSWER - large SA with good blood supply - goblet cells secrete mucus to trap dust + bacteria - moist surface so gases dissolve helping them to pass across the gas exchange surface