Hi I'm currently going through this lesson but I'll try to critique your work as best I can.

Staring with your organic dissections, I can see that you are think about how these form interact trying to achieve a believable construction, however I highly recommend you try to stick to the characteristics of simple sausages, think of them kind of like filled water balloons - they'll bend under the force of gravity (to slump and sag over the sides of the form beneath them, as shown here), but they shouldn't really be allowed to get so complex as to wobble back and forth like a worm.

Now moving onto the animal constructions, your result vary from case to case, now the thing that I would recommend the most is to take more time to observe your references, this will help you with the additional masses that could be much better done in some cases.

Also it seems that you draw way better when you occupy all the space on the paper, your most believable construction is the elephant, the bear standing on his four legs and the crocodile on my opinion.