Question

The middle layer in the body wall of Porifera is
A. Mesoderm
B. Mesenchyme
C. Mesogloea
D. Mesentery

Answer 1

Hint: Porifera is an aquatic invertebrate that comprises sponges. They are mostly found in marine water and have a porous outer layer by which they derive nutrition. They have a diploblastic body meaning that they have one outer and one inner layer. The middle layer has an adhesive mucus glue-like substance that entraps various types of amoebocytes.

Step by step answer:
Poriferans are the lowest multicellular animals. They are pore-bearing species and from embryological studies, they are included in the kingdom Animalia. They derive their nutrition by sucking water from surrounding through their pores and are non-motile. They stay attached to hard surfaces. The outer spore-bearing layer is called the pinacoderm and the inner layer is called the choanoderm. It is hollow from inside and the cavity is called spongocoel.

Option A, Mesoderm is the middle layer present in all of the bilaterian animals. Bilaterian means animals having bilateral symmetry including humans.
Option B, Mesenchyme is a connective tissue that is found in all bilateral triploblastic (having three layers) animals. It is majorly found during embryonic development and is composed of few cells and fibers.
Option C, Mesogloea is an adhesive mucoid jelly-like substance that acts as glue for many wandering amoebocytes. The term Mesogloea consists of two words, ‘meso’ means middle and ‘gloea’ means adhesive glue-like substance present in the middle of the two layers of Porifera. So this is the correct answer.
Option D, Mesentery is an organ that is present in humans and connects the intestine to posterior abdominal walls.
Hence, the right answer is option C

Note: Porifera is a primitive multicellular organism and thus cannot have complex layers like mesoderm. Mesenchyme is a tissue as the term mesenchymal tissue and mesentery is an organ. Sponges have diverse forms ranging from flat to volcano-shaped bodies. They depend on water currents flowing through them with the help of the three layers of its body.