Question

Discuss the evolution of the coelom and pseudocoelom. What advantages do coelomate animals have over acoelomates?

Answer 1

In cnidarians, the space which is present between the ectoderm and endoderm of the limbs is filled with some acellular mesoglea. In the platyhelminthese mesoderm fills the space between the mesoderm and endoderm:
the benefits of Coelom
1. Hydrostatic skeleton- a fluid-filled artery produces a more durable structure than mesoderm muscle pull-out and consequently a more efficient skeletal support system.

2. Circulatory system:
Inorganic nutrients can be distributed throughout the body and metabolic waste can be transported more efficiently to the body of the host rather than the solid mesoderm.

II. Result - Faster locomotion and greater body size are possible.

Two types of Cavities:
Pseudocoelom
Coelom of course

Pseudocoelom:
A pseudocoelm is a blastocoel stored in adulthood.
In addition to having a cavity of the body, creatures with pseudocoeloms also have a complete digestive tract - an open separation of food and penetration into the unaffected food. This makes digestion and nutrition more effective because an animal can eat it without finishing its previous digestion.

Living organisms with pseudocoeloms are not a monophyletic group.

Psuedocoelomates contain various small oganisms, including

Nematodes (roundworms):
Gastrotrichs
Rotifers
and, Kinorhynchs
Two types of true Coeloms
1. Schizocoelom
2. Enterocoelom
The true coelom is tied to all sides by a mesoderm that provides muscle around the intestines and is below the body wall. This allows for efficient digestion because food can be absorbed by the digestive tract.

- The advantage of coelom over pseudocoleom is:
It allows the digestive tract and digestive system to be more complex.
Coelomic fluid acts as a hydrostatic spray and aids the body's processes.
It is the skeletal muscle within the mesoderm, while the pseudocoelum is the line between the mesoderm and endoderm that wash the internal organs

Pseudocoel is an extension of the blastocoel.
The veisceral organs of eucoelomates have muscle and move independently Ex: peristalsis.
Regional focus of the alimentary canal in the stomach, gizzard, esophagus occurs in eucoelomates due to mesodermal and endoderm interactions. It's called primary induction.
Regional diagnosis is not possible because the endoderm does not associate with the mesoderm in pseudocoelomates.
Gametes and excretory products are released from the coelom to other coelomates.