Question

The space between body wall and alimentary canal lined by mesoderm is called as
A. Acoelom
B. Pseudocoelom
C. Coelom
D. None of the above

Answer 1

Hint: Animals that are triploblastic organisms, that is there are three germ layers of cells. They are known as ectoderm, mesoderm and endoderm from outside to inside. These three layers are responsible for the formation of organs and tissues of vertebrates. There may or may not be a space in between the germ layers.

Complete answer:
The germ layers are developed during the gastrulation stage of embryogenesis.
Body cavity or coelom is present in many organisms. It is located in between the body wall and the alimentary canal. The coelom is lined by the mesoderm or the middle of the three germ layers of the body. Coelom is formed during the embryonic development during a stage called gastrulation. Coelom is filled with a fluid called the coelomic fluid. It functions as a shock absorber and provides a hydrostatic skeleton to the body. It is also known to increase space for organs to develop and function properly.
Acoelomate animals are the animals that lack a coelom. They are triploblastic animals, but their mesoderm is filled with tissue. Acoelomate animals are flatworms that belong to the phylum Platyhelminthes.
Pseudocoelomate animals are the ones that possess a pseudocoelom or false body cavity. The cavity is filled with fluid and holds the organs in place, but loosely. The pseudocoelom is far from being as organized as a coelom. Pseudocoelom is seen in roundworms.
Therefore, it can be concluded that the space between the body wall and alimentary canal lined with mesodermal cells is known as the coelom.

Hence, option (C) is correct.

Note: Triploblastic animals are the animals that have three germ layers namely, ectoderm, mesoderm and endoderm. If there is a space ectoderm and endoderm, the animals are called coelomate. If the space is absent, they are called acoelomate. The body cavity is lined by mesodermal cells and encloses the digestive organs. It increases the space for organs to grow properly and acts as a shock absorber.