What is Phylum Porifera?
A phylum is one of the second largest groups under the hierarchy system of the animal kingdom. Organisms having similar characteristics in a broader perspective are classified into different phyla.
1. Commonly known as sponges, aquatic in habitat and asymmetrical in body shape
2. Primitive multicellular animals have a cellular level of organization.
3. Food is gathered through the water transport system of the body. Water enters through the minute pores called Ostia present on the outer surface of the body and is passed on to the central cavity called spongocoel. From the cavity, the water is transported back into the environment through the osculum. Water transport also serves a purpose for the respiratory system, the excretion system.
4. Cells lining the spongocoel and the canals are called choanocytes or collar cells.
5. The body of sponges is supported by a skeleton made up of spicules or sponge fibers.
6. The digestion is intracellular.
7. Sponges are hermaphrodites (sexes are not separate).
8. Mode of reproduction is asexually by fragmentation and sexually by the formation of gametes
9. Fertilization is internal and the development of offspring is through the larval stage which is distinct from the adult stage.
10. Organisms belonging to this phylum are Sycon (Scypha), Spongilla (Freshwater sponge), and Euspongia (Bath sponge)
What is Phylum Coelenterata?
1. Aquatic in habitat, radial symmetry body shape
2. Also known as cnidoblasts or cnidocytes due to the presence of stinging capsules present on the tentacles and the body. These stinging capsules or nematocytes serve the purpose of anchorage, defense, and capturing of prey.
3. Tissue-level organization and are diploblastic
4. Presence of central gastro-vascular body cavity with a single opening called the hypostome
5. Digestion is both extracellular and intracellular
6. Some the animals like corals have a skeleton made up of calcium carbonate
7. Two different body forms are seen – polyp and Medusa. A polyp is sessile, cylindrical, and hollow shaped and Medusa is umbrella-shaped and free-swimming.
8. Organisms with polyp body shape – Hydra, Adamis, and Organisms with medusa body shape – jellyfish, Aurelia
9. Organisms belonging to this phylum such as Obelia can exhibit both Medusa and polyp shapes with alteration of generation. i.e., Polyps produce medusa asexually and medusa produces polyps sexually.
10. Examples of organisms belonging to this class – Physalia, Adamsia (Sea anemone), Pennatula (Sea-pen), Meandrina (Brain Coral)
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