Saving account? Interest rate?

One question that occurs to my mind after reading the different topics here.

Picture this:

I open a saving account and save 20K Canadian dollars on that account. A year later, that amount has grown due to the interest rate regardless of which bank and/or against what rate. ( I wonder which bank will be propriate enough and I think of RBC myself! looks robust and trustworthy!)

I also transfer or add 10K to my bank account itself and I leave 20K behind on my saving account where I live.

So, what will happen now and what should I do or pay attention to?

Do I have to pay tax over due to my 20K on a Canadian saving account immediately or at the end of the next calender year? and if so, will the taxation be due to the whole 20K plus interest or only due on the interest?