Locomotion in fish-How fish moves

Fish ~ Endoskeleton

* Water provides buoyancy and support for the fish
* The fish faces the problem of water resistance as water is denser than air
* To overcome this,
i. it has streamlined and slimy body
ii. and scales which face backwards

The fish has strong myotome muscles and fins adapted for swimming.
~Contraction and relaxation of the myotome muscles causes the body and the caudal fin to move from side to side, producing a forward thrust to push the fish forward.

ESSAY ~LOCOMOTION IN A FISH ( 10 marks max)

Fish are aquatic organisms

They face resistance when moving in water

The streamlined shapes –--to overcome water resistance and enable to move quickly in the water.

The skin is covered with scales that have slimy coat---help reduce water resistance

The muscles consist of muscle blocks i.e., MYOTOMES arranged in segments on both sides of the vertebral column.

The muscles act antagonistically.

Contraction of myotomes on one side of the vertebral column and relaxation on the other side

Causes the body to bend in a direction of the contraction

Alternate contractions of the right and left myotome blocks causes body to bend side to side and the tail to bend accordingly.

This produce a forward thrust which propels the fish forward

Presence of fins i.e. dorsal and ventral fins, paired pectoral and pelvic fins.--- for stability

Suggested Answer for 3 marks: SPM Essay 2005
--Fish has endoskeleton. It is a place of muscle attachement.
-Left myotome muscles contract and right myotome muscle relax antagonistically
-and tail moves to the left and right producing forward force.