The five major similarities of Porifera are:

1. Porous structure

2. Filter feeding

3. Asexual reproduction

4. Cellular specialization

5. Aquatic habitat

Specialized cells of Porifera and their functions:

• Choanocytes : Absorb nutrients

• Pinacocytes : Provide shape

• Amoebocytes : Perform various tasks

• Porocytes : Form pores (ostia)

• Sclerocytes : Secrete spicules

• Myocytes : Aid in movement

Spicules are made of silica or calcium carbonate.

The various tasks of Amoebocytes:

• Distribute nutrient

• Secrete the skeleton

• Help in regeneration of tissue

Choanocytes absorb nutrients through a process called intracellular digestion.

Choanocytes, with their flagellum and collar of microvilli, create water currents that draw water and small food particles into the sponge. Choanocytes are called the digestive system of the sponges.

Pinacocytes are flat cells that line the outer surface and canals, creating the pinacoderm.

There are 3 types of pinacocytes:

1. Basipinacocytes → attached surface

2. Exopinacocytes → surface

3. Endopinacocytes → canal

3 main functions of amoebocytes:

1. Nutrient transportation

2. Gamete production

3. Sperm delivery

There are more functions. They have pseudopodia, limb-like protein extensions that protrude out from the cell cytoplasm. Amoebocytes interact with other cells called trophocytes to form both the egg and sperm.

Sponges use tiny pores (ostia) to draw water, oxygen, and food particles. Larger opening (oscula) expel water and waste products.

Two types of Sclerocytes:

1. Calcoblast → Calcium carbonate

2. Silicoblast → Silic-based

Myocytes are like the muscle cells.