Fresh water is less concentrated of
than sea water it (fresh
water) to be less
than the intra-cellular
making cells to . Sea water, on
other hand, since is very concentrated
to dehydrate the .

The vacuoles of are internal
structures in water storage
when necessary liberate to
the cytoplasm. thus can dilute
cytoplasm for it enter into
osmotic with the
environment. of fresh water
need vacuoles more their
intracellular is in relation to
exterior. Without the
mechanism provided by vacuoles,
protozoans of water would absorb
much water and die.