Individuals are either exclusively poly­ploid or medusoid or constituted by both forms in the life cycle. They are the pioneer in the tissue grade of organisation. composed of two tissue layers, an outer epidermis (ectoderm) and an inner gastro-dermis (endoderm) with several to many cell types and a less cellular mesoglea at the centre. General characteristics of Phylum Coelenterata. Characteristic Features of Phylum Platyhelminthes: 1. General Zoology, Hydras, Phylum Cnidaria, Zoology. Figure 1. Body diploblastic i.e. 1.35D), Antipathes, Meandrina (brain coral) (Fig. An example of the polyp form is Hydra spp. 1.32C), Valella (Fig. TOS4. Privacy Policy3. 1.34E). vii. Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Etymology: Cnidaria-Greek : knide, nettle. Endoparasitic with hooks and suckers for anchorage to the host body. Primarily microscopic animals. Carybdea, Chiropsalmus, Chironex, Tripedalia (Fig. - “Tissue grade” eumetazoans with a radial symmetry. - The term “Coelenterata” signifies the presence of a single internal cavity called coelenteron, or gastrovascular cavity,combining functions of both digestive and body cavities. Study of Mollusca is called Malacology. View this video animation showing two anemones engaged in a battle. They have the following characteristics: Each individual is known as zooid. The classification of Cnidarians by Parker and Haswell or as revised by Marshall and Williams, 1972 (7th edn. These coiled threads release toxins into the target and can often immobilize prey or scare away predators. Coelenteron is undivided and without stomodaeum. This group includes free living or … A spadeful of soil contains numerous Nematodes. Coelenterata was divided into Cnidaria (for coelenterates proper) and Acnidaria (for the cteno­phores). Body diploblastic i.e. Cnidarian cells exchange oxygen and carbon dioxide by diffusion between cells in the epidermis with water in the environment, and between cells in the gastrodermis with water in the gastrovascular cavity. When touched, the cells are known to fire coiled threads that can either penetrate the flesh of the prey or predators of cnidarians (see Figure 1) or ensnare it. Purestock / Getty Images. Cnidarias have an internal sac for digestion which is called the gastrovascular cavity. This anemone has tentacles and exhibits radial symmetry. v. Extending between the stomodaeum and the body-wall there are mesenteries. The classificatory scheme followed in this text is based on the scheme outlined by Ruppert and Barnes, 1994 (6th Edn.). Three other features sometimes considered to be diagnostic of Cnidaria are radial symmetry and planula and polyp stages in development, but all are problematic. Before publishing your Notes on this site, please read the following pages: 1. Habit: solitary or colonial. Welcome to NotesOnZoology.com! They are characterized and categorized in … The outer wall of the cell has hairlike projections called cnidocils, which are sensitive to touch. All the members are aquatic and with the exemption of a few, are marine. Anthozoa is a class of marine invertebrates which includes the sea anemones, stony corals and soft corals.Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton.The basic unit of the adult is the polyp; this consists of a cylindrical column topped by a disc with a central mouth surrounded by tentacles. An­tho­zoans in­clude sea anemones, a va­ri­ety of corals, sea fans, and sea pens. Our mission is to provide an online platform to help students to discuss anything and everything about Zoology. 1)Huxley (1856) proposed the name Hydrozoa. Excretion by … Body has more than two cell layers, tissues and organs. D) Know the adaptive features of the Eubacteria 3.0 MAIN BODY Animals from the phylum Cnidaria have stinging cells called cnidocytes. The nervous system is primitive, with nerve cells scattered across the body. The hydrozoans contain sessile forms and swimming colonial forms like the Portuguese Man O’ War. They are diploblastic, with two layers of cells, an outer layer called the ectoderm and the inner layer called the endoderm. The class Anthozoa includes all cnidarians that exhibit a polyp body plan only; in other words, there is no medusa stage within their life cycle. i. Polyp with eight tentacles and eight septa (mesenteries). Disclaimer Copyright, Zoology Notes | Exclusive Notes on Zoology for Students, Phylum Ctenophora: Classification and Features | Marine Animals, Ctenophora: Features and Classification | Zoology, Phylum Hemichordata: Features and Classification, Classification of the Phylum Cnidaria | Zoology, Phylum Porifera: Classification and Features | Protozoa. composed of two tissue layers, an outer epidermis (ectoderm) and an inner gastrodermis (endoderm) with several to many cell types and a less cellular mesoglea at the centre. Some cnidarians are polymorphic, that is, they have two body plans during their life cycle. Respiratory, circulatory and excretory systems are absent; gas exchange is per­formed by diffusion. viii. i. Polyps with more than eight tentacles and septa, typically in cycles of 12. ii. 2. All cnidarians show the presence of two membrane layers in the body that are derived from the endoderm and ectoderm of the embryo. PHYLUM PLATYHELMINTHES- CHARACTERISTICS The name platyhelminthes was de­rived from the Greek "platys" flat and helminthes worms. Most possesses a through straight gut with an anus. The phylum Cnidaria contains about 10,000 described species divided into four classes: Anthozoa, Scyphozoa, Cubozoa, and Hydrozoa. Diagnostic features of sponges Figure 3. Between these two membrane layers is a non-living, jelly-like mesoglea connective layer. iii. 1.35C). The first is the gastrozooid, which is adapted for capturing prey and feeding; the other type of polyp is the gonozooid, adapted for the asexual budding of medusa. They are acoelomates due to the absence of coelom. The distinguishing features are: Presence of jointed legs; Body is divided into head, thorax and abdomen; Body is bilaterally symmetrical and triploblastic. Arms bifurcated, with two pinnules. Arthropods, members of the phylum Arthropoda, are a diverse group of animals including insects, crustaceans, spiders, scorpions and centipedes. The gastrovascular cavity has only one opening that serves as both a mouth and an anus, which is termed an incomplete digestive system. Definition of Phylum Platyhelminthes: Triploblastic, acoelomate, un-segmented and bilaterally symmetrical metazoans, without anus, circulatory system, but with a mouth, protonephridial system, parenchyma tissues within the space between the body wall and the gut, and spiral cleavage development. Figure 2. They can live alone or in colonies and are the most primitive and simple of all animals. Development often involves an almost bilaterally symmetrical, ciliated ‘planula’ larva. About 9,000 species known. Gorgonia (sea fan) (Fig. There is also no circulatory system, so nutrients must move from the cells that absorb them in the lining of the gastrovascular cavity through the mesoglea to other cells. Systematic Resume. - The term “Cnidaria” indicates the presence of stinging cells (Gr., knide= nittle or stinging cells). It includes the familiar hydras, the transparent jelly fishes, the beautiful and bright coloured sea anemones, a variety of corals and about 10,000 delightful aquatic species. The phylum has the following distinguishing characteristics: These are pore-bearing multicellular animals. This nerve net may show the presence of groups of cells in the form of nerve plexi (singular plexus) or nerve cords. These cells are present around the mouth and tentacles, and serve to immobilize prey with toxins contained within the cells. Systematic Resume. The mouth of a sea ane… Cnidarians have two distinct body plans, the medusa (a) and the polyp (b). Hydra (Fig. The larva is free swimming for a while, but eventually attaches and a new colonial reproductive polyp is formed. The phy­lum Coelentarata was established by Leuckart in 1847, which also included the sponges and ctenophores. However, the members of this phylum, despite their incredible diversity and sheer numbers, share a number of important distinguishing characteristics. FAQ’s for You. Unicellular performing all metabolic functions inside a single cell. Body is distinctly flattened to form four sides. 1.34B), Corallium (red coral) (Fig. Body possesses 4 pairs of […] The lack of a circulatory system to move dissolved gases limits the thickness of the body wall and necessitates a non-living mesoglea between the layers. They have tube feet without suckers; Examples: Neometra, Antedon, Rhizocrinus, etc Phylum Echinodermata: General Characteristics and Classification ii. Phylum Cnidaria is also known as Phylum Coelenterata. 1.34A), Alcyonium (Dead-men’s finger) (Fig. 1) Spongiaria 2) Cnidaria and 3)Ctenophora. Lamarck coined the term Molluscus. Polyp forms are sessile as adults, with a single opening to the digestive system (the mouth) facing up with tentacles surrounding it. What are the main taxonomic features of phylum cnidaria? Definition of Phylum Nematoda: Phylum Nematoda are un-segmented vermiform animals with ante­rior lateral chemosensory organs or amphids and with a persistent blastocoel or pseudocoelom; dorsal and ventral nerve cords in epidermis and excretory system of renette cells or tubules. Nearly all (about 99 percent) cnidarians are marine species. Phylum coelenterata characteristics 1. A mouth opening is surrounded by tentacles bearing cnidocytes. The term Mollusca was first applied by Aristotle to cuttle fish. xiv. 1.32D), Obelia, Millepora, Physalia (Fig. 1.32B). Diagnostic Features of Phylum Nematoda 3. Only one ventral siphonoglyph is pre­sent. The four major diagnostic features of the phylim mollusca are: visceral mass, foot, mantle, and shell. 1.35A), Fungia (mushroom coral) (Fig. xiii. ii. The body wall composed of a special type of cell called of ‘Cnidocytes’, con­taining stinging organelles called ‘nema­tocysts’. Locomotory organ- Pseudopodia, cilia or flagella. Diagnostic Features of Phylum Cnidaria: i. 1.34D), Helipora, Telesto, Tubipora (organ-pipe coral) (Fig. An example is the colonial hydroid called an Obelia. Cnidaria—Greek: knide, nettle . Answer (1 of 8): The characteristics of phylum protozoa are that they are single-celled (otherwise known as unicellular) organisms that are microscopic (three to a thousand microns). Nervous system is of primitive type consisting of diffused network of un-polarized nerve cells. Mesogloea separates these two layer i. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU. Nearly all (about 99 percent) cnidarians are marine species. The sessile form of Obelia geniculate has two types of polyps: gastrozooids, which are adapted for capturing prey, and gonozooids, which bud to produce medusae asexually. Diagnostic features : All the members and aquatic and with the exemption of a few, are marine. Coelom absent. In this article we will discuss about the Phylum Cnidaria:- 1. The sessile polyp form has, in fact, two types of polyps, shown in Figure 3. a nematocyst). Body is star shaped; Some of the forms were extinct and living forms. The male medusa makes sperm, whereas the female medusa makes eggs. iv. When the reproductive buds mature, they break off and become free-swimming medusa, which are either male or female (dioecious). The outer tissue layer, called the ectoderm or epidermis, includes cnidocytes—the distinctive diagnostic feature of the phylum. iii. They tend to be brightly col­ored. Scheme of Classification 4. The gastrovascular cavity has only one opening, a mouth, through which the animal takes in food and releases waste. vi. Classification. The endodermal gastric tentacles are present. Germ layer: diploblastic, outer ectoderm and inner endoderm. Body cavity is partially a coelom. Although many cnidarians exhibit radial symmetry, some are directionally asymmetric (Dunn & Wagner 2006), and many have a biradial or bilateral organization, Animals in this phylum display two distinct morphological body plans: polyp or “stalk” and medusa or “bell” (Figure 2). Phylum Cnidaria includes animals that show radial or biradial symmetry and are diploblastic, that is, they develop from two embryonic layers. Nematocysts contain coiled threads that may bear barbs. Dipoblastic body with two layers of cells, outer layer called ectoderm or epidermis and the inner layer known as the endoderm or gastrodermis. Examples include sea anemones (Figure 1), sea pens, and corals, with an estimated number of 6,100 described species. In terms of cellular complexity, cnidarians show the presence of differentiated cell types in each tissue layer, such as nerve cells, contractile epithelial cells, enzyme-secreting cells, and nutrient-absorbing cells, as well as the presence of intercellular connections. They cause diseases such as Ascariasis, Trichuriasis, Hookworm, Enterobiasis, Filariasis, and Angiostrongyliasis in humans. Examples: Sea-anemones (Adamsia, Edivardsia, Metridium) (Fig. 1.38), Pilema, Lucernaria, Pericolpa. When hairlike projections on the cell surface are touched, (b) the thread, barb, and a toxin are fired from the organelle. Hyman regarded ctenophora as a separate phylum. Unit 9 Phylum Cnidaria 60-62 Unit10 Phylum Platyhelminthes 63-66 ... Know the diagnostic features of the Eubacteria, C) Know the differences between the gram positive and gram negative bacteria. Short and slender tentacles encircle the mouth in one or more whorls. Sea anemones are car­niv­o­rous polyps that are quite large, rang­ing up to 200mm in length. The outer layer (from ectoderm) is called the epidermis and lines the outside of the animal, whereas the inner layer (from endoderm) is called the gastrodermis and lines the digestive cavity. 1.34C), Pennatula (Sea-pen) (Fig. In 1888, Hatschek splitted Leuckart’s Coelenterata into 3 dis­tinct phylum: Spongiaria (Porifera), Cnidaria and Coelenterata. iv. Kingdom: Animalia; Habitat: aquatic, mostly marine. Elongated round or oval in shape excepting Amoeba. Symmetry: radially symmetrical; Grade of organization: tissue grade of organization. Body wall possess a type of nematocyst called stenotale. 2)Hackle in 1891 proposed the name Scyphozoa. Content Guidelines 2. Invertebrate Zoology - Exam 1 - Phylum Cnidaria. The nerve cells show mixed characteristics of motor as well as sensory neurons. They have no germ layers, tissues or organs but they have intracellular organelles. v. There are four tentacles or tentacle clus­ters at the four corners of the margin. The cnidarians perform extracellular digestion in which the food is taken into the gastrovascular cavity, enzymes are secreted into the cavity, and the cells lining the cavity absorb nutrients. Gagenbaur 1859 coined the word platyhelminthes for the flat worms which are considered as the most primitive of all helminthes. The anthozoans, the sea anemones and corals, are all sessile species, whereas the scyphozoans (jellyfish) and cubozoans (box jellies) are swimming forms. Body monomeric. Aurelia (Fig. Body dorsoverntally flattened like like a tape. The phylum Cnidaria is a diverse group of relat i vely simple animals united by the abil ity to synthesize a highly complex cellular produc t, the cnida. In the body there is an internal space for digestion, the ‘gastro-vascular cavity’, with the mouth as the only opening. Phylum Cnidaria includes animals that show radial or biradial symmetry and are diploblastic, that is, they develop from two embryonic layers. v. Gonads are usually ectodermal in origin or if endodermal, gametes do not escape through the coelenteron and mouth. However, the development of organs or organ systems is not advanced in this phylum. The animals of this phylum are soft-bodied, non-metameric, triploblastic coelomates and fundamentally bilaterally symmetrical invertebrates with a thin fleshy envelope the mantle, around the visceral (internal organs of the body) which may secret… They come in various forms; can inject poison or attach to the prey. ), is very much similar to that of Ruppert and Barnes (1994), except that the later authors have introduced an additional class-Cubozoa, for the medusoid cnidarians with bells. Presence of velum along the margin of the medusa. Cnidarians contain specialized cells known as cnidocytes (“stinging cells”) containing organelles called nematocysts (stingers). 1.35B), Astrea (star coral) (Fig. General. Cnidarians contain specialized cells known as cnidocytes (“stinging cells”) containing organelles called nematocysts (stingers). They are characterised by the possession of radial symmetry (a primitive feature), two layers of cells, gut cavity lined by endoderm, vibratile tentacles arranged in one or more whorls around the mouth and provided with nematocysts (the stinging organ). Some of their common characteristics are: 1. Therefore, Cnidaria is the most suitable name for his phylum. xi. Medusa forms are motile, with the mouth and tentacles hanging down from an umbrella-shaped bell. Two common genera, Hydra and the green Chlorohydra resemble small sea anemones (which are also members of the Phylum Cnidaria). Classification of Phylum Cnidaria 2. They feed on the plant roots and reduce the nutrient uptake and stress tolerance of the plant. Sea anemones are usually brightly colored and can attain a size of 1.8 to 10 cm in diameter. They possess a cell called cnidocytes, which contain an organelle called a cnidocyst (e.g. Cnidocytes are confined to the epidermal layer. They exhibit holozoic nutrition. Tentacles are hollow and un-branched. 1.33). iv. Diagnostic Features of Phylum Cnidaria 3. The body has no organs. Diagnostic features – Hydrozoans (Phylum Cnidaria) are small, predatory animals, most of which are marine, but a few live in fresh water. The cnidarians are almost all marine and are either sessile or free-swimming and occur singly or in colonies. iii. Give an account of Phylum Arthropoda. These folds, along with the mouth and phar­ynx, are usu­ally arranged in a bi­ra­di­ally sym­met­ric pat­tern. Scheme of Classification 4. 1.32A), Porpita{Fig. x. All the members are aquatic and with the exemption of a few, are marine. Usually two siphonoglyphs are present. Despite the simplicity of the nervous system, it coordinates the movement of tentacles, the drawing of captured prey to the mouth, the digestion of food, and the expulsion of waste. i. Medusoid form is dominant in the life cycle; polypoid form is very insignifi­cant. Introduction to Phylum Nematoda: The phylum Nematoda is one of the great success story of the animal kingdom. http://cnx.org/contents/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8. v. Almost entirely colonial, usually con­nected by coenenchyme. These animals are usually cylindrical in shape and are attached to a substrate. Reproduction is both asexual by bud­ding and sexual by ova and sperm. vi. Two different body forms may exist—a ‘medusa’ (representing sexual phase) adapted for pelagic existence and a ‘polyp’ (asexual phase) adapted for benthic existence. There is no excretory system or organs, and nitrogenous wastes simply diffuse from the cells into the water outside the animal or in the gastrovascular cavity. Anatomy - Body Forms 2. General Characteristic Features of Phylum Nematoda 3. Cnidocytes contain large organelles called (a) nematocysts that store a coiled thread and barb. iv. Study of molluscan shell is called conchology. We’d love your input. Q1. Anatomy - Cell Layers. All cnidarians have two membrane layers, with a jelly-like mesoglea between them. The predominant signaling molecules in these primitive nervous systems are chemical peptides, which perform both excitatory and inhibitory functions. xii. Class Hydrozoa (Greek: hydro, water serpent): i. After fertilization, the zygote develops into a blastula, which develops into a planula larva. ix. The Phylum Tardigrada Etymology: From the Latin Tardus for slow and Gradu a step, meaning ‘slow walker’ – which they are. These specialized cells contain organelle-like structures called cnidae or cnidocysts that aid in prey capture, defense, and, in some instances, adherence to a substrate. ; perhaps the most well-known medusoid animals are the jellies (jellyfish). The phylum Cnidaria is a diverse group with cosmopolitan distribution. Life history commonly illustrates the phenomena of metagenesis. Specific circulatory and respiratory system absent. Answer: The phylum Arthropoda (Arthro- jointed; Podos-feet) contains the animals that have jointed appendages. They are the simplest organisms (animals) with nervous system and gut. They thrive on both intracellular and extracellular type of digestion. Characteristics of the Tardigrada: Bilaterally symmetrical. Anatomy - Body Forms 1. Did you have an idea for improving this content? ( about 99 percent ) cnidarians are polymorphic, that is, they develop two. Have two membrane layers in the life cycle no germ layers, with an.. V. there are mesenteries of cnidarians by Parker and Haswell or as revised Marshall. Hookworm, Enterobiasis, Filariasis, and serve to immobilize prey or scare away predators star! Showing two anemones engaged in a battle by Leuckart in 1847, which are either exclusively poly­ploid medusoid... Perhaps the most suitable name for his phylum and become free-swimming medusa, which develops into blastula! To 200mm in length cells show mixed characteristics of motor as well as sensory neurons phylum is. Germ layer: diploblastic, that is, they have no germ,! The nervous system and gut contain large organelles called nematocysts ( stingers ) mesoglea between them Mollusca... Their incredible diversity and sheer numbers, share a number of important distinguishing characteristics by Aristotle to cuttle fish cycle., Fungia ( mushroom coral ) ( Fig small sea anemones ( which are sensitive touch... Diploblastic, that is, they break off and become free-swimming medusa, which are exclusively. Two embryonic layers '' flat and helminthes worms of polyps, shown Figure. The Portuguese Man O ’ War are chemical peptides, which also included the sponges and ctenophores Acnidaria ( the... Success story of the animal takes in food and releases waste cells, outer ectoderm and inner endoderm,. Thread and barb: radially symmetrical ; grade of organisation between these two layer 1 ) Huxley ( ). Un-Polarized nerve cells exclusively poly­ploid or medusoid or constituted by both forms in form. I. medusoid form is very insignifi­cant, Alcyonium ( Dead-men ’ s Coelenterata into 3 phylum. Singly or in colonies, Helipora, Telesto, Tubipora ( organ-pipe coral ) (.. Are derived from the endoderm or gastrodermis encircle the mouth in one or more whorls may... Stress tolerance of the phylum Cnidaria contains about 10,000 described species predominant signaling in. 1.35B ), Obelia, Millepora, Physalia ( Fig network of un-polarized cells... 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