When we were in Toronto we used one of our days to go to the Zoo. It was a bit of a hassle to get there as its about 7 miles from the centre of Toronto.
We had to get the subway from Union station to Bloor-Yonge (that was the yellow line) and then change to the green line and head to Kennedy Station. This is where there is a large bus station. It was about 18 stops on the subway before we got there. The payment system is rather different to the UK and what we are used to ... you can buy tokens or they do have something similar to the Oyster card. The tokens cost around $3.25 each and one token is one way outwards, you can't come back on yourself or you need to use another token. When you move to a different transport like subway/train to bus like we did you get a transfer note so if you change again the driver can check and know you have paid. So it cost us about $6.50 each - one token out, and one token back. You can also pay cash rather than with a token but its $3.50 not $3.25 like the tokens and it has to be exact - no change. After the 18 stops on the subway, we then had to wait 10 minutes for a bus (the 86A) and then it was around 25 stops to the Zoo.
We could have got a taxi from the hotel to the Zoo - but we were told it would cost about $70 each way which is quite alot.
The Zoo was large - I think we could have spent 2 or even 3 days there to actually see/read and do everything thoroughly.
The Zoo was amazing. So much to do and lots of different restaurants and places to eat also.