What kind of Lens should I use?

I'm an aspiring zoologist, I often take pictures of wildlife but find my regular lens can't zoom in enough, and have a clear focused picture. I have a Nikon D70, I need a lens with a LARGE zoom, Good enough to use with Long range pictures for larger animals, but also pictures to zoom in on Insects too. Can one Lens do all that? If so, Where can i get one online?

Added (1). I guess my attachment size is 58mm? I'm not quite sure.

My lens I use is a 28-80mm Nikkor Lens.

I shoot from time to time for a local zoo.

Here are the lenses I use.

Nikkor 200-400 mm f/4 or 600 mm f/4 lens for shooting long distances. (if you do not have a grant or large budget, the Nikkor 70-300 mm will work for now.

Nikkor 105 mm macro for shooting insects or extreme closeups of animals when shooting Necropsy's

Here is a link to all the lenses Nikon makes that will work on your fine lens

http://www.nikonusa.com/...index.page

First of all, bad news, no a single lens can't do that. For insects you'd want a macro lens, preferably at least 90mm. Tamron makes one, tokina has a 100 and sigma a 105mm, all fine lenses, I prefer the tokina for it's impressive build quality. Your 28-80 could take a closeup filter like the raynox dcr-250 but it's a bit trickier to get quality shots.

For zoom as you call it nikon has a nice 70-300 VR which is good for larger animals like deer provided you can get close. Next up is a sigma 150-500 I've got a review of that here: http://wijnands.blogspot.com/2010/12/sigma-150-500mm-f5-6.html. In my opinion it's the best wildlife option below 1000 euros.

From there on it get's expensive fast. A 300mm f4 with a 1.4x teleconverter is a common option as is the sigma 50-500. Then comes the really expensive gear, nikon's 200-400 f4, nikon's 500 and 600mm and Sigma's 300-800. All really expensive. An outside option is an old 400, 500 or 600mm manual focus lens which is fine as long as you got the time to shoot, for example when you're working from a hide.
LEnses like this Can't be replaced by a screw-on attachment!

All the expensive lenses are really big and really heavy.

I've got a Nikon 60mm f2.8 Macro lens that works on that camera(same camera as mine). Takes spectacular images, especially on extreme close-up. You need a tripod for the close-ups, though.

Each lens is for specific purpose, there's no lens can do all.
If you have limited budget, Nikon 70-300mm VR is a good choice but if you can afford the Nikon 80-400mm or Nikon 200-400mm are great choice.

You should go with Nikon 28-300mm f/3.5-5.6G ED VR AF-S Nikkor Zoom Lens for Nikon Digital SLR

Versatile 10.7x zoom lens with ED glass and VR II image stabilization
Optimized for edge to edge sharpness on both FX and DX-format D-SLRs
Nikon VR II (Vibration Reduction) Image Stabilization
2 Extra-low Dispersion (ED) Elements; 3 Aspherical Lens Elements
Exclusive Nikon Silent Wave Motor (SWM)