How can an amoeba survive in hypotonic environment?
Amoebae survive in hypotonic environments because they have contractile vacuoles to pump excess water out of the cell.
To regulate osmotic pressure, most freshwater amoebae have a contractile vacuole (CV) that expels excess water from the cell.
This organelle is necessary because the surrounding water is hypotonic with respect to the contents of the cell.
Without a CV, the cell would fill with excess water and eventually burst.
Excess water enters the CV, which swells and moves to the edge of the cell.
The CV bursts and expels its water, and the cycle repeats.
I couldn't find a good video on amoebae, but here is a good video showing the operation of CVs in paramecia.