Question

Read the given statements and select the correct option.
Statement 1: All triploblastic animals are coelomates.
Statement 2: They have a false coelom.
A) Both statements 1 and 2 are correct.
B) Statement 1 is correct but statement 2 is incorrect.
C) Statement 2 is correct and statement 1 is incorrect.
D) Both statements 1 and 2 are incorrect.

Answer 1

Coelomates are those organisms that have a true coelom which is a true fluid filled cavity found in the body of organisms and is lined by a peritoneum that attaches the organs.

Complete answer:
Triploblastic organisms are those whose body is derived from the three embryonic layers called ectoderm, mesoderm and endoderm. Examples of triploblasts include animals that belong to phylum Plathelminthes to phylum Chordata. Another class of organisms called diploblastic organisms are those that are derived from two embryonic layers called ectoderm and endoderm. They don’t have the presence of mesoderm. Examples of diploblasts include Poriferans and Cnidarians.

Coelomates are the organisms having the true coelom. This true cavity arises from the mesoderm. The coelom is filled with coelomic fluid which is secreted by the peritoneum. It is usually in Annelids, Echinoderms and Chordates. True coelomates is of two types: schizocoelom also called schizocoel and enterocoelom which is called enterocoel. Schizocoelom develops as a split in the mesoderm sheet while enterocoelom comes from the wall of the embryonic gut.

Pseudocoelomate is an organism that is not derived from the mesoderm. Sponges, cnidarians, ctenophores, platyhelminthes, aschelminthes are examples of pseudocoelomate.

This shows that not every triploblastic organism is acoelomate and they are those who have a true cavity not those who have false cavities.

Note: Pseudocoelomates are also called blastocoelomate as the cavity in this case is derived from the blastocoel which is a cavity in the embryo. The body fluids bathe the organs in pseudocoelomates and they receive the nutrients and oxygen from the fluid in the cavity.