BIO2231 - Cnidarians

Question 1

<p><strong><span>What is the Phylum Cnidaria?</span></strong></p>

<p>3 points.</p>

Answer 1

<ul><li>Anemones & Corals </li><li>Jellies (jelly fish) </li><li>Hydroids</li></ul>

<p><span>_{BIO2231 2aa}</span></p>

Question 2

<p><span>Describe</span></p>

<p><strong><span>Phylum Cnidaria -Jellies, anemones, corals</span></strong></p>

<p>5 points.</p>

Answer 2

<ul> <li>Diploblastic animals with simple tissues</li> <li>Gastrulation</li> <ul> <li>Mouth</li> <li>Gastrovascularcavity with single opening (Digestive cavity)</li> </ul> <li>Radial symmetry</li> <li>Movement</li> <ul> <li>Nervous system in the form of a nerve net </li> <li>Muscle cells </li> </ul> <li>Cnidocytes containing nematocysts </li> <li>Many classes polymorphic (polyp & medusa)</li></ul>

<p><span>_{BIO2231 2ab}</span></p>

Question 3

<p><span>Describe</span></p>

<p><strong><span>Phylum Cnidaria form</span></strong></p>

<p>4 points.</p>

Answer 3

<ul> <li>Diploblastic</li> <ul> <li>Epidermis (from extoderm)</li> <li>Gastrodermis (from endoderm)</li> </ul> <li>Separated by gelatinous Mesoglea</li> <li>Gastrovascularcavity with single opening </li> <ul> <li>Maximises surface to volume ratio (food absorption, respiration and waste disposal) </li> <li>Hydrostatic skeleton for support and movement </li> </ul> <li>Simple Tissues !!!!</li></ul>

<p><span>_{BIO2231 2ac}</span></p>

Question 4

<p><span>Phylum Cnidaria - Tissues</span></p>

<p><strong><span>Contractile elements (muscles)</span></strong></p>

<p>5 points.</p>

Answer 4

<ul><li>Epitheliomuscular cells with contractile elements </li><li>Longitudinal and circular arrangements </li><li>Body can bend and elongate/shorten </li><li>Polyp movement </li><li>Medusae swim and/or float</li></ul>

<p><span>_{BIO2231 2ad}</span></p>

Question 5

<p><span>Phylum Cnidaria - Tissues</span></p>

<p><strong><span>Nervous system (nerve net)</span></strong></p>

<p>6 points.</p>

Answer 5

<ul> <li>Nerve cells located at base of epidermis near mesoglea</li> <li>Interconnect to form two dimensional NERVE NET</li> <li>Nerve impulses conducted around body in response to local stimuli</li> <li>Sensory structures</li> <ul> <li>Perceiving touch and certain chemicals</li> <li>Specialised receptors located at specific sites e.g. Primitive eyes</li> </ul></ul>

<p><span>_{BIO2231 2ae}</span></p>

Question 6

<p><span>Phylum Cnidaria - Tissues</span></p>

<p><strong><span>Prey Capture</span></strong></p>

<p>2 points.</p>

Answer 6

<ul> <li>Specialised cells, called cnidocytes, containing nematocysts</li> <li>Nematocysts are pressurised chambers ready to fire a harpoon like poisonous thread</li></ul>

<p><span>_{BIO2231 2af}</span></p>

Question 7

<p><strong><span>Phylum Cnidaria reproduction</span></strong></p>

<p>3 points.</p>

Answer 7

<p><span>Alternation of generations </span></p>

<ul><li>Asexual polyp (sessile) and sexual medusa (mobile) </li><li>Sexual form dioecious (male and females separate) </li><li>Typically with larva (free swimming)</li></ul>

<p><span>_{BIO2231 2ag}</span></p>

Question 8

<p><span>Phylum Cnidaria - Classification</span></p>

<p><strong><span>Class Anthozoa</span></strong></p>

<p>3 points.</p>

Answer 8

<ul><li>Sea anemones</li><li>Sea pens</li><li>Corals</li></ul>

<p><span>_{BIO2231 2ah}</span></p>

Question 9

<p><span>Phylum Cnidaria - Classification</span></p>

<p><strong><span>Class Scyphozoa</span></strong></p>

Answer 9

<div>true jellyfish - <em>Aurelia</em></div>

<p><span>_{BIO2231 2ai}</span></p>

Question 10

<p><span>Phylum Cnidaria - Classification</span></p>

<p><strong><span>Class Hydrozoa</span></strong></p>

<p>3 points.</p>

Answer 10

<p><span>The hydrozoans</span></p>

<ul><li>Obelia</li><li>Physalia or Gonionemus</li><li>Hydra</li></ul>

<p><span>_{BIO2231 2aj}</span></p>

Question 11

<p><span>Class Anthozoa - taxonomy</span></p>

<p><strong><span>Sub Class Hexacorallia (Zoantharia)</span></strong></p>

<p>2 points.</p>

Answer 11

<div>Anemones and hard corals and most other corals </div>

<ul> <li>Order Actinaria sea anemones </li> <li>Order Scleractinia stony corals </li></ul>

<div>Body plan in six or multiples of six ( hexamerous ) or other</div>

<p><span>_{BIO2231 2ak}</span></p>

Question 12

<p><span>Class Anthozoa - taxonomy</span></p>

<p><strong><span>Sub class Octocorallia (Alcyonaria)</span></strong></p>

<p>2 points.</p>

Answer 12

<ul> <li>Soft and horny corals</li> <li>Sea pens</li></ul>

<div>Body plan strictly in eight parts (octamerous)</div>

<p><span>_{BIO2231 2al}</span></p>

Question 13

<p><span>Describe</span></p>

<p><strong><span>Hexacorallia</span></strong></p>

<div>Sea anemones & corals</div>

Answer 13

<ul> <li>Colonial or solitary lack medusae</li> <li>Polyps differ from hydrozoan</li> <ul> <li>mouth leads to pharynx (invagination of the body wall) then into gastrovascular cavity</li> <li>Partitioned by septa (mesenteries)</li> <li>Pedal disc attaches to substrate</li> </ul> <li>Asexual & sexual ( monoecious & dioecious)</li></ul>

<p><span>_{BIO2231 2am}</span></p>

Question 14

<p><span>Hexacorallia</span></p>

<p><strong><span>Sea anemones (Order Actiniaria)</span></strong></p>

<p>4 points.</p>

Answer 14

<ul><li>Larger and heavier </li><li>Well developed muscles </li><li>Solitary </li><li>Can be mobile!</li></ul>

<p><span>_{BIO2231 2an}</span></p>

Question 15

<p><span>Hexacorallia</span></p>

<p><strong><span>Stony Corals (Order Scleractinia)</span></strong></p>

<p>4 points.</p>

Answer 15

<ul> <li>Form coral reefs</li> <li>Similar to sea anemones but no pedal disc</li> <li>Epithelial cells secrete cuplike calcium carbonate exoskeleton around base and lower portion of column</li> <li>Sexual reproduction similar to anemones - asexual produces colony</li></ul>

<div></div>

<div><strong>Exoskeleton</strong> (and forms <strong>connections </strong>between each exoskeleton)</div>

<p><span>_{BIO2231 2ao}</span></p>

Question 16

<p><span>Define</span></p>

<p><strong><span>Zooxanthellae</span></strong></p>

<p>5 points.</p>

Answer 16

<p><span>Zooxanthellae = symbionts</span></p>

<ul><li>Endosymbiotic dinoflagellates </li><li>Inhabit cells of many cnidarians and other animals </li><li>Photosynthesis > O₂</li><li>Fix carbon > nutrients </li><li>Recycle Nitrogen & Phosphorous</li></ul>

<p><span>_{BIO2231 2ap}</span></p>

Question 17

<p><span>Hexacorallia</span></p>

<p><strong><span>Horny/Soft Corals (Octacorallia)</span></strong></p>

<p>5 points.</p>

Answer 17

<ul> <li>Always 8 tentacles each with pinnules</li> <li>individually small but organised into large colonies (all colonial)</li> <li>interconnection between polyps inside skeleton (different from Scleractinia</li> <li>mass of mesoglea ( coenenchyme ) and gastrodermal tubes unite lower half of colony</li> <li>Skeleton secreted in the coenchyme</li></ul>

<div></div>

<div><strong>Endoskeleton</strong></div>

<p><span>_{BIO2231 2aq}</span></p>

Question 18

<p><strong><span>Class Myxozoa</span></strong></p>

<p>5 points.</p>

Answer 18

<ul><li>Originally believed to be protists, then bilaterians </li><li>Economically important cause of whirling disease in farmed salmon and trout </li><li>Can be only a few cells </li><li>Smallest animal genome </li><li>Some species lack mitochondria and aerobic respiration</li></ul>

<p><span>_{BIO2231 2ar}</span></p>

Question 19

<p><strong><span>Phylum Ctenophora - comb jellies</span></strong></p>

<p>4 points.</p>

Answer 19

<ul> <li>Marine predators</li> <li>Biradial symmetry, with an oral-aboral body axis .</li> <li>Diploblastic</li> <li>Diffuse nervous system consists of a nerve net, somewhat more specialized than that found in the Cnidaria</li></ul>

<p><span>_{BIO2231 2as}</span></p>

Question 20

<p><strong><span>Why might Phylum Ctenophora be a link to bilateria?</span></strong></p>

<p>3 points.</p>

Answer 20

<p><span>Show some bilateral symmetry<br></br>"biradial" symmetry</span></p>

<ul><li>Some larvae are bilateral </li><li>Evidence of evolution of triploblastic body wall </li><li>Evidence of evolution of organ systems</li></ul>

<p><span>_{BIO2231 2at}</span></p>