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diagnostic features of phylum cnidaria

日期:2020-12-13 来源: 浏览:0

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