Five evolutionary stages

I enjoy creating images of life forms in different media, and it's interesting to watch them evolve.  Here are five, starting with blue-green algae and ending with quite a vicious-looking shark.  As always, the different media which I use reflect the same artistic concerns; whether using glass or fluids.

'Blue-green dream'

'Ancient forms'

'Special worm'

'Advanced pond life'

'Fierce predator'