I worked in Inventor for quite a while, and while certainly possible, I'd advice against it. The only way I'd know how to would be making a lot of sketches in parallel planes and swiping, so basically drawing stuff on each plane in the shape it would be at that point. Furthermore, I wouldn't know how to pose it. You could of course make ball joints or something, but there would be gaps if you bend stuff. Maybe it's my lack of Inventor knowledge, but I don't know if it has surface deformation, like when you'd bend a leg or something. I'd advice you giving a try with blender. It's free and created for modelling organic objects with ease. I know it can be frustrating at first, especially coming from CAD like I did, but blender's interface is actually really easy to work with once you know how and it's the best interface I've seen so far in any software.
Just today, a peer of mine was working in Blender, and I was surprised to see what he accomplished. I'll give it a shot, and hopefully learn a thing or two. (I didn't know it was free till today) Thanks for the suggestion.
As for the inventor problem, I'd just fix the deformations with extra extrusions and fillets. (There would be work-planes everywhere. *shudder*)
I'm certain it can be done somehow, but there are certainly easier ways, and blender is really easy. Just follow along a few tutorials on boxmodelling, or instead of following along, build a pone instead, just follow the technicques. The great thing about blender you can drag and open and close tabs everywhere and put any menu in any tab and all controlls and hotkeys do the same things in any menu. Like dragging with the middle mouse button in 3D view to pan (well, in 3D view it'll rotate, and pan if you hold shift) but dragging with middle mouse button will also work to scroll text or icons or whatever, same for moving, scaling, rotating, selecting. You can do stuff by hovering over it with the mouse instead of clicking, and so much more. It's so convinient I try to do it in other software and am dissapoint that it doesn't work. And it's very powerful fav.me/d5yryps