Question

A)List several advantages of having a body cavity as opposed to having the acoelomate condition found in the Platyhelminthes.  

B)How do rotifers react to light?

Answer 1

ANS.A) Body cavity has many different functions.

1)it prevents the internal injuries in the body.

2)the cavity allows internal organs to grow and moe independently of the outer body wall.

3)A fluid filled cavity act as hydrostatic skeleton for soft bodied animals.an animal's body is mostly made with water and water is incompressible .this means that animals with internal,water filled cavities have the capacity to resist outside pressure and the pull of gravity and so can maintain a constant bosy shape.

4)Hydrostatic skeleton not only act as help in resisting to external pressureand the pull of gravity, it can also be used to redirect the force of muscle contractions.

5)coelomates typicaly have more finer control over their movements than do psedocoleomate,much less acoelomates.

B)ANS.The rotifers are attracted by a light source . the percentage of swimming or creeping is varies with light quality in the same species under the same nutritional conditions. number of swimming females increases in going from blue to red .rotifers increase their population growth and larger number of egg production under continuous white light.rotifers were maintained in various light conditions at least for 20 generations.the response of rotifers is depends on the quality and quantity of the light.it varies with different colours of light.