Porifera

Porifera Like extant Porifera, fossilized sponges are asymmetrical and have no body axes, and the walls have openings that form a canal system through which the water flows in. From: Epigenetic Mechanisms of the Cambrian Explosion, 2020 Related terms: • Cladistics • Genus • Actin • Cnidaria • Ctenophora • Mollusca • Tissues • Polychaeta Porifera possess no head and no tail; they are basal metazoans characterized by the absence of true tissues (with few exceptions), a muscular or nervous system sensu stricto, a digestive cavity, and gonads. The body architecture ( Figure 8.11) is arranged around the aquiferous system, which consists of a network of canals and chambers (in the complex, leucon-type organization of freshwater sponges) with flowing ambient water. FIGURE 8.11. The body architecture and the aquiferous system of a sponge. Figure below: modified from Boury-Esnault and Rützler (1997). An external layer of flat cells (pinacoderm), pierced with small inhalant apertures (ostia) and larger exhalant apertures (oscula), isolates the sponge internal structure (mesohyl) from the external environment ( Figure 8.11). The mesohyl includes an extracellular matrix with the consistency of jelly, collagen fibrils and fibers, skeletal structures with mineral deposits (spicules), and cells. Most body cells are totipotent, with a high degree of mobility and morpho-functional plasticity. The main sponge cell categories are cells lining outer and inner surfaces, cells secreting the ske...

Porifera Phylum Porifera are the lowest multicellular animals belonging to the kingdom Animalia. The word “Porifera” mainly refers to the pore bearers or pore bearing species. 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. Poriferans are pore-bearing first multicellular animals. The pores are known as Ostia. The poriferans have a spongy appearance and are therefore called sponges. They are attached to the substratum and do not move. They have the ability to absorb and withhold fluids. They were initially regarded as plants due to their green colour and their symbiotic relationship with algae. Later, their life cycle and feeding system were discovered, and they were included in the animal kingdom. Characteristics of Phylum Porifera Some of the important characteristics of phylum Porifera are mentioned below. • The cells of Poriferans are loosely organized. • They are mostly found in marine water. Only a few are found in freshwater. • They are either radially symmetrical or asymmetrical. • Their body is usually cylindrical. • The scleroblast secretes spicules while spongin fibres are secreted by spongioblasts. • They have no organs in their body. • They depict cellular grade of organization. • The body comprises numerous pores known as Ostia and osculum. • The central cavity is called spongocoel or atrium which opens to the outside through the osculum. • T...

4 Cell Structure • Introduction • 4.1 Studying Cells • 4.2 Prokaryotic Cells • 4.3 Eukaryotic Cells • 4.4 The Endomembrane System and Proteins • 4.5 The Cytoskeleton • 4.6 Connections between Cells and Cellular Activities • Key Terms • Chapter Summary • Visual Connection Questions • Review Questions • Critical Thinking Questions • 6 Metabolism • Introduction • 6.1 Energy and Metabolism • 6.2 Potential, Kinetic, Free, and Activation Energy • 6.3 The Laws of Thermodynamics • 6.4 ATP: Adenosine Triphosphate • 6.5 Enzymes • Key Terms • Chapter Summary • Visual Connection Questions • Review Questions • Critical Thinking Questions • 7 Cellular Respiration • Introduction • 7.1 Energy in Living Systems • 7.2 Glycolysis • 7.3 Oxidation of Pyruvate and the Citric Acid Cycle • 7.4 Oxidative Phosphorylation • 7.5 Metabolism without Oxygen • 7.6 Connections of Carbohydrate, Protein, and Lipid Metabolic Pathways • 7.7 Regulation of Cellular Respiration • Key Terms • Chapter Summary • Visual Connection Questions • Review Questions • Critical Thinking Questions • 14 DNA Structure and Function • Introduction • 14.1 Historical Basis of Modern Understanding • 14.2 DNA Structure and Sequencing • 14.3 Basics of DNA Replication • 14.4 DNA Replication in Prokaryotes • 14.5 DNA Replication in Eukaryotes • 14.6 DNA Repair • Key Terms • Chapter Summary • Visual Connection Questions • Review Questions • Critical Thinking Questions • 15 Genes and Proteins • Introduction • 15.1 The Genetic Code • 15.2...

Introduction to Porifera Poriferans are commonly referred to as sponges. An early branching event in the history of animals separated the sponges from other Sponges are characterized by the possession of a feeding system unique among animals. Poriferans don't have mouths; instead, they have tiny pores in their outer walls through which water is drawn. Cells in the sponge walls filter goodies from the water as the water is pumped through the body and out other larger openings. The flow of water through the sponge is unidirectional, driven by the beating of flagella which line the surface of chambers connected by a series of canals. Sponge cells perform a variety of bodily functions and appear to be more independent of each other than are the cells of other animals. There is an exception to the general description of sponge feeding that you just read above. Read more in the Click on the buttons below to learn more about Porifera. Sponge Note: The sponges in the image above are Clathria basilana (Levi, 1959) and Haliclona fascigera (Hentschel, 1912). Identification provided over the net by spongiologist Rob van Soest of the Institute for Systematics and Population Biology (Zoologisch Museum), University of Amsterdam. Thanks! Sponge Links: Sponge References: Bergquist, P. R. 1978. Sponges. Hutchinson and Company, London. 268 pp. Broadhead, T. W. 1983. Sponges and Spongiomorphs, Notes for a Short Course. University of Tennessee, Knoxville, Tennessee. 220 pp. De Vos, L., K. Rutz...

Sponges are a diverse group of sometimes common types, with about 5000 species known across the world. Sponges are primarily marine, but around 150 species live in fresh water. Sponges have cellular-level organization, meaning that that their cells are specialized so that different cells perform different functions, but similar cells are not organized into tissues and bodies are a sort of loose aggregation of different kinds of cells. This is the simplest kind of cellular organization found among parazoans. Other characteristics of sponges include a system of pores (also called ostia) and canals, through which water passes. Water movement is driven by the beating of flagellae, which are located on specialized cells called choanocytes (collar cells). Sponges are either radially symmetrical or asymmetrical. They are supported by a skeleton made up of the protein collagen and spicules, which may be calcareous or siliceous, depending on the group of sponges examined. Skeletal elements, choanocytes, and other cells are imbedded in a gelatinous matrix called mesohyl or mesoglea. Sponges capture food (detritus particles, plankton, bacteria) that is brought close by water currents created by the choanocytes. Food items are taken into individual cells by phagocytosis, and digestion occurs within individual cells. Reproduction by sponges is by both sexual and asexual means. Asexual reproduction is by means of external buds. Some species also form internal buds, called gemmules, whic...