-multicellular organism so has a small surface area to volume ratio, large diffusion, high demand and body surface impermeable.
-Therefore, cannot perform has exchange (O2 in / CO2 out ) via their surface, they require a specialised has exchange system called gills.
![](https://img.wattpad.com/cover/272714285-288-k56915.jpg)
YOU ARE READING
A-level Biology Notes
General FictionTopics 1-4 of A-level Biology AQA New specification