Porifera - Kingdom: Animalia - SS1 Biology Lesson Note

Porifera, commonly known as sponges, are the simplest and most primitive multicellular animals belonging to the phylum Porifera within the kingdom Animalia. They are characterized by their porous body structure, lack of tissues and organs, and their ability to filter feed.

Image from shuttershock.com

Here are some key features and characteristics of Porifera:

1. Body Structure: Sponges have a simple body structure consisting of a porous outer layer called the dermis and a central cavity called the spongocoel. The body is supported by a framework of protein fibers called spongin or calcium carbonate spicules.

2. Pores and Canals: Sponges have numerous tiny openings called ostia on their outer surface. These ostia lead to a system of canals that circulate water through the sponge's body, allowing for filter feeding and gas exchange.

3. Filter Feeding: Sponges are filter feeders, meaning they extract food particles from the water that passes through their bodies. They trap and consume bacteria, plankton, and other organic matter using specialized cells called choanocytes or collar cells, which have a flagellum surrounded by a collar-like structure.

4. Lack of Tissues and Organs: Unlike other animals, sponges do not have true tissues or organs. Instead, they consist of loosely organized cell layers with different specialized cell types. These cells can perform various functions, such as feeding, reproduction, and structural support.

5. Reproduction: Sponges can reproduce both sexually and asexually. Asexual reproduction occurs through budding, where a new sponge grows from a parent sponge. Sexual reproduction involves the release of sperm and eggs into the water, allowing for fertilization and the development of larvae.

6. Habitat and Distribution: Sponges are primarily marine organisms, although some species can be found in freshwater environments. They inhabit a wide range of aquatic habitats, from shallow coastal waters to deep-sea ecosystems. Sponges can attach themselves to various substrates, such as rocks, coral reefs, or the seabed.

7. Ecological Importance: Sponges play essential roles in marine ecosystems. They filter large volumes of water, removing particles and recycling nutrients. Sponges also provide habitats and shelter for many other organisms, serving as nurseries and hiding places for small fish and invertebrates.