Biology - why do plants and algal have cell wall?

[MarcL]

Homework Statement

Suggest a hypothesis to explain why algal and plant cells have cell walls. Suppose that mutant individuals from each group lacked a cell wall. How could you use these individuals to test your hypothesis?

Homework Equations

There aren't really...

The Attempt at a Solution

My hypothesis was that it was to adapt to the aquatic environment. ( I don't really know how to explain it, isn't the cell wall in algal to protect them from osmotic pressure? ). The way to test it I said was to use the Benedict's test for reducing sugar because there's polysaccharides in plants ( again, not sure but in the chloroplasts?). I was reading my book and I didn't find an answer anywhere for this

 

[chemisttree]

Osmotic pressure happens because of the cell wall. No way an organism would evolve one to avoid it. Perhaps a thicker, more robust one.
I would start along the lines of homeostasis and concentration gradients.

I believe you will find polysaccs in the cell walls of algae as well as the cytoplasm.

 

[Akshay_Anti]

It is quite obvious that cell wall is to prevent cell membrane from bursting due to excess endosmosis... But why only the plant cells developed it and why not animal cells if it was an evolution over non walled membrane?