Image quality will take a hit with a 2X on a 70-200/2.8....
A lot if it's on the 70-200/2.8 non-IS. Quite a bit if it's used on the 70-200/2.8 IS "Mark I".
The 70-200/2.8 IS Mark II with Canon 2X "Mark III" is the best of the bunch (but is a rather pricey pairing), though there will still be noticeable loss of IQ. Only you can say if images will be usable or not.
The weaker 1.4X teleconverters do a lot less damage to image quality, and you can get by with far less expensive combos.... Canon 1.4X II or III work pretty darned well on either 70-200/2.8 IS Mark I or II. Kenko Pro 300 1.4X DG or DGX or Kenko MC4 1.4X DGX also work well. Some say the Tamron and Sigma 1.4X work pretty darned well, too (however I don't know if there are different versions or models of these that might be better or worse).
It will be a challenge to use f5.6 in the jungle.... Even f4 might be tough. Hope it's an IS lens.
EDIT: Ahhh, I just noticed it's a 550D camera.... Good. Study Teamspeed's posts here on POTN about getting the best out of high ISO with his 7D. It's practically the same 18MP sensor in your 550D, so the same tricks will work well for you. Early examples of 70D shots suggest it might be even better, but basically the 550D and all the 18MP cameras will be among the highest ISO possible, short of going to a full frame camera model (at a much higher cost).
One suggestion... The 550D/T2i has a rather dated AF sensor array (9 points, but only the center one is the dual axis/cross type... harkening back to 20D and 30D models). I'd suggest you'll likely find your best results restricting the camera to using only the center AF point, especially in lower light situations and when using the lens + TC. If you get the 2X and end up with a combo that's effective f5.6, I think you'll be restricted to center AF point only, anyway. If you get the 1.4X, that gives you an effective f4 with that lens, which should allow the outer AF points to work, but I think you'll still get better results using only the center one.