Thursday 18 January 2018

Staying Afloat

The group of fish which evolved with bony skeletons also evolved a way of staying afloat without the constant need to keep swimming.

They developed a swim bladder which is a bag of air that can be filled or emptied by diffusion of gases or by expelling the gases direct 

This way a fish can control its buoyancy and level in the water.


Compare a picture of a shark and a fish.


What other differences might help to make the fish such a manoeuvrable swimmer? 

Tuesday 9 January 2018

FISH FACTS - PERPETUAL MOTION



Did you know a charging shark cannot stop. It can swerve but it can't swim in reverse. If it stops beating its tail it sinks.

Rays and skates, which have skeletons made of cartilage the same as sharks, have given up on the energy consuming task of constantly beating their tails. They have become bottom, dwellers. Their tails have become thin and whip like and some have developed poisonous barbs on the end