llustration of freshwater flat-worm

Question

What is an illustration of freshwater flat-worm? Due to that habitat illustrate the physiological problem that such animals must resolve?

Answer 1

Platyhelminthes of freshwater such as planarias contain an internal environment very concentrated in solutes than the exterior and therefore they present a tendency to gain water. Such organisms then require a drainage system to evade cell death caused by extreme water.

The problem is resolved by the presence of protonephridia situated all along longitudinal channels in the animal body. Protonephridia contain ciliated cells, the flame cells, which push water external the body via excretory pores.