What is the evolutionary history of porifera?

What is the evolutionary history of porifera?

Sponges have evolved little since their first appearance in the fossil record some 800 million years ago. They appear to be an evolutionary blind alley and outside the main streams of animal evolution. In spite of this, their simple body plan has allowed the group to develop a wide range of body shapes and sizes.

What is significant about sponges phylum porifera in the evolution of animals?

Sponges (phylum Porifera) are a diverse taxon of benthic aquatic animals of great ecological, commercial, and biopharmaceutical importance. They are arguably the earliest-branching metazoan taxon, and therefore, they have great significance in the reconstruction of early metazoan evolution.

What are the characteristics of phylum porifera and Cnidaria?

Porifera Cnidaria
1. Animals are asymmetrical. 1. Animals are radially symmetrical.
2. Water canal system is well-developed. 2. Water canal system is absent.
3. They show the presence of choanocytes or collar cells. 3. They show the presence of cnidoblasts or nematocytes.

Why are sponges evolutionary important?

Sponges, ctenophores, placozoans, and cnidarians have key evolutionary significance in that they bracket the time interval during which organized animal tissues were first assembled, fundamental cell types originated (e.g., neurons and myocytes), and developmental patterning mechanisms evolved.

Why are sponges still classified as metazoans?

Sponges constitute the phylum Porifera, and have been defined as sessile metazoans (multicelled immobile animals) that have water intake and outlet openings connected by chambers lined with choanocytes, cells with whip-like flagella.

Why Porifera phylum is kept under the separate phylum?

Based on the embryological studies, sponges are proved as animals and are classified into a separate Phylum in animals. This phylum includes about 5000 species. The poriferans have a spongy appearance and are therefore called sponges. They are attached to the substratum and do not move.

Why do sponges phylum Porifera represent a separate lineage distinct from all other animal phyla?

Why do sponges represent a separate lineage distinct from all other animal phyla? They lack true tissues. radial symmetry, two phylum Cnidaria and Ctenophora.

Why are members of the phylum Cnidaria considered to be more advanced than members of the phylum porifera?

Members of the phyla Cnidaria and Ctenophora are considered to be more “advanced” than poriferans for two major reasons. 1. they show true tissue-level organization of body cells. Most other animal phyla are triploblastic (derived from three distinct embryonic germ layers).

Why are cnidarians considered more advanced than sponges?

Cnidarians (ni DER ee uhnz) belong to the phylum cnidaria. All of these have stinging cells. They are more complex than sponges because they have complex tissue, a gut, and a nervous system. They reproduce the same way as a sponge.

How does method of digestion differ between porifera and Cnidaria?

Digestion of the food particle takes place inside the cell. The difference between this and the mechanisms of other animals is that digestion takes place within cells rather than outside of cells. Because of this difference, poriferans do not have a nerve net or muscle cells for locomotion, which cnidarians have.