Porifera

Porifera, also known as sponges, are simple aquatic animals that belong to the phylum Porifera. They are considered one of the most primitive multicellular organisms and are found in marine and freshwater environments. Sponges are filter feeders, meaning they obtain food particles from the water that passes through their porous bodies.

Anatomy of Porifera

Sponges have a simple body structure that is characterized by the presence of numerous pores and channels. Their body is composed of a gelatinous substance called mesohyl, which contains spicules (tiny, needle-like structures made of calcium carbonate or silica) and a network of cells. Sponges do not have true tissues or organs, but they do have specialized cells that perform specific functions.

Cell Types

Porifera possess three main types of cells:

1. Choanocytes (collar cells): These cells have a flagellum that creates water currents and helps in capturing food particles.
2. Archaeocytes: These cells are involved in digestion, secretion of skeletal elements, and regeneration.
3. Pinacocytes: These cells form the outer layer of the sponge's body and regulate the flow of water.

Reproduction

Sponges can reproduce both sexually and asexually. Asexual reproduction occurs through budding, where new sponges grow from the parent sponge. In sexual reproduction, sponges release sperm and eggs into the water, where fertilization takes place. The fertilized eggs develop into larvae, which eventually settle and grow into new sponges.

Ecological Importance

Porifera play a crucial role in the marine ecosystem. They provide habitats for many organisms, serve as a food source for certain marine animals, and help in nutrient cycling and water filtration.

Study Guide

1. Describe the anatomy of a sponge and its cellular composition.
2. Explain the process of filter feeding in sponges.
3. Compare and contrast asexual and sexual reproduction in porifera.
4. Discuss the ecological importance of sponges in marine environments.
5. Draw and label the basic body plan of a sponge, highlighting its unique features.

With this study guide, you can gain a comprehensive understanding of porifera and their significance in the natural world.