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13. radiate animals
The document summarizes key information about radiate animals in the phyla Cnidaria and Ctenophora. It describes their radial symmetry, diploblastic structure, and characteristics like cnidocytes. It provides details on the classes within Cnidaria, including Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa. It also discusses coral reef ecology and threats to corals from factors such as warming oceans, acidification, and pollution.
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13. radiate animals
- 1.
- 2. Radiate Animals Phylum Cnidaria& Phylum Ctenophora Radial Symmetry Diploblastic – 2 embryonic tissue layers
- 3. Phylum Cnidaria All animalsexcept sponges belong to the clade Eumetazoa, the animals with true tissues.
- 4. Phylum Cnidaria Phylum Cnidariais one of the oldest groups in this clade. Fossil history back 700 MY.
- 5. Phylum Cnidaria Cnidarians have: Radialsymmetry Gastrovascular cavity – extracellular digestion Tissues – derived from two embryonic germ layers Cnidocytes – special cells with stinging organelles called nematocysts.
- 6. Phylum Cnidaria Cnidarians have diversifiedinto a wide range of both sessile and floating forms including jellies, corals, and hydras. Polymorphism – some species exist as both polyps and medusae during their life cycles.
- 7. Phylum Cnidaria The basicbody plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity. A single opening functions as both mouth and anus.
- 8. Phylum Cnidaria In colonialforms that share a gastrovascular cavity, polyps may be specialized for feeding, reproduction, or defense.
- 9. Body Wall Cnidarians havean outer tissue layer, the epidermis, derived from ectoderm, and an inner gastrodermis, derived from endoderm, with jellylike mesoglea in between.
- 10. Body Wall The epidermallayer contains several types of cells organized into tissues.
- 11. Reproduction Polyps can reproduceasexually by budding, fission, or pedal laceration.
- 12. Reproduction Cnidarians, typically medusae,can also reproduce sexually. A zygote usually develops into a motile planula larva. Some species only exist as polyps, others only as medusae, others alternate between the two.
- 13. Feeding Cnidarians are carnivoresthat use tentacles to capture prey. The tentacles are armed with cnidocytes – unique cells that function in defense and the capture of prey. Nematocysts contain toxins used for prey capture and defense.
- 14. Feeding Nematocysts are used toinject a toxin. Variable in form. May be used for prey capture or defense.
- 15. Feeding Extracellular digestion beginsin the gastrovascular cavity, but is completed within the cells of the gastrodermis. Some cnidarians supplement their diet with nutrients collected from algal symbionts (zooxanthellae).
- 16. Nerve Net Cnidarians havea diffuse nervous system. Nerve cells forming two interconnected nerve nets in the epidermis and gastrodermis. No concentrated grouping of nerve cells forming a central nervous system. CNS does not provide advantage for radially symmetrical animals where stimuli approach from all sides.
- 17. Classification The phylum Cnidariais divided into four major classes: Class Hydrozoa Class Scyphozoa Class Cubozoa Class Anthozoa
- 18. Classification A fifth class,Staurozoa, has been proposed. No medusae in life cycle but polyp topped by medusa-like region.
- 19. Phylum Cnidaria Class Staurozoa Commonly called stauromedusans No medusa stage. Solitary polyp body that is stalked. Uses adhesive disk to attach to seaweeds, and objects on sea bottom. Polyp top resembles a medusa with eight extensions (“arms”) ending in tentacle clusters surrounding mouth. Reproduce sexually.
- 20. Class Hydrozoa Hydrozoans are variablein form. Mostly marine. Usually colonial, sometimes solitary. http://youtu.be/MpSPdeTN74I
- 21. Class Hydrozoa –Typical Life Cycle Most hydrozoans alternate between polyp and medusa forms. Some have only polyps. Some have only medusae.
- 22. Class Hydrozoa -Polyps Typical hydroids have a base, a stalk, and one or more terminal zooids (individual polyp animals). Thecate – presence of a protective cup around the polyp. Obelia Athecate – no such protection. Ectopleura
- 23. Class Hydrozoa -Medusae Hydroid medusae are usually smaller than those in the class Scyphozoa. Gastrovascular cavity is continuous from mouth to tentacles and is lined by gastrodermis. Velum, inward projection of the bell, is present. Specialized organs: Statocysts – equilibrium Ocelli – light sensitive
- 25. Class Hydrozoa Members ofthe order Siphonophora, such as the Portuguese man-of- war, are actually colonies of polyp individuals. One polyp may be gas filled and used as a float. Feeding polyps each with one long tentacle Reproductive polyps
- 26.
- 27. Class Scyphozoa In theclass Scyphozoa, jellies (medusae) are the prevalent form of the life cycle. No velum present. Rhopalium – sense organ containing statocysts and sometimes ocelli.
- 28. Class Scyphozoa Tentacles around theperiphery of the bell contain nematocysts used to paralyze prey animals. In the center are four frilly oral arms used to capture and ingest prey. http://youtu.be/aJUuotjE3u8
- 29. Class Scyphozoa –Typical Life Cycle Planula larvae develop into a polyp-like form. Saucer-like buds called ephyrae are produced by strobilation.
- 30. Class Cubozoa In theclass Cubozoa, which includes box jellies and sea wasps, the medusa is box- shaped and has complex eyes. Polyps are tiny and develop directly into medusae. http://youtu.be/CCuNMIT67y8
- 31.
- 32. Class Anthozoa Class Anthozoa includesthe corals and sea anemones which occur only as polyps – no medusa stage. All marine Solitary or colonial
- 33. Sea Anemones –Order Actinaria Found in coastal waters all around the world. Attach to rocks using their pedal disc. Feed on fish or any other food of suitable size.
- 34. Sea Anemones –Order Actinaria Sea anemones usually move by gliding slowly along on their pedal discs. When a predator approaches, most withdraw. Stomphia detaches its disc and “swims” away. http://youtu.be/Dm98n3908QM
- 35. Sea Anemones –Order Actinaria Tentacles arranged around the central mouth. The gastrovascular cavity is divided into six radial chambers. Increases the surface area of the gastrodermis.
- 36. Mutualisms Sea anemones sometimesharbor zooxanthellae (photosynthetic protists) like hard corals do. Some crabs will decorate their shells with anemones.
- 37. Mutualisms Some damselfish (anemonefishes) form associations with large anemones. Fish gains protection from living in the anemone. The fish may help ventilate the anemone, or keep it free of sediment.
- 38. Hexacorallian Corals Hexacorallian corals (Order Scleractinia) arethe true or stony corals. Like tiny anemones living in calcareous cups.
- 39. Hexacorallian Corals Hexacorallians (Subclass Hexacorallia) have agastrovascular cavity subdivided by septa in multiples of six. The calcium carbonate skeleton is secreted below living tissue.
- 40. Hexacorallian Corals Polyps maybe retracted into the skeleton. Often retracted during the day. The polyps expand for feeding.
- 41. Tube Anemones andThorny Corals Members of subclass Ceriantipatharia. Have coupled but unpaired septa. Tube anemones Solitary and live in soft sediments.
- 42. Tube Anemones andThorny Corals Thorny or black corals Colonial and attach to firm substrata. Both groups have few species and live in warmer seas.
- 43. Octocorallian Corals Members ofthe Subclass Octocorallia have eight pinnate tentacles and eight septa.
- 44. Octocorallian Corals Sea fans,sea pens & sea pansies belong to this group. Often beautifully colored.
- 45. Cnidaria Medusozoa Anthozoa Staurozoa ScyphozoaCubozoa Hydrozoa Trachyline- like hydrozoaGut with septal filaments Siphonoglyph Anthozoan pharynx Hexaradial and octaradial symmetry Creeping planula without cilia Strobilation Complex eyes Velarium Boxlike medusa body Polyp lost Velum in medusae Medusae produced by lateral budding and entocodonMedusoid body form Motor nerve net Primary polyp tentacles hollow Mouth surrounded by solid tentacles Planula larva Cnidocytes Radial, polypoid body form Rhopalium Polyp reduced or lost Hydroids Man-of-war Other hydrozoa Phylum Cnidaria
- 46. Coral Reefs Coral reefsare one of the most productive and diverse ecosystems on Earth. Found in shallow tropical seas. They require warm water. Sunlight required for symbiotic zooxanthellae.
- 47. Coral Reefs The mainstructure of the reef is calcium carbonate secreted by hermatypic (reef- building) corals and coralline algae.
- 48. Coral Reefs Octocorallian coralsand some hydrozoans (those known as fire coral) also contribute calcium carbonate.
- 49. Types of Reefs Fringingreefs are close to a landmass with no lagoon or a narrow lagoon.
- 50. Types of Reefs Barrierreefs run parallel to shore and have a wide, deep lagoon.
- 51. Types of Reefs Atollsare reefs that encircle a lagoon, but not an island.
- 52. Types of Reefs Patchreefs are scattered throughout a lagoon.
- 53. Reef Zones The forereef slope, or reef front, is the side that faces the sea. Slopes into deeper water. The reef crest is the shallow or even slightly emergent top of the reef. The reef flat is the shallow back reef area that slopes into the lagoon.
- 54. Coral Reefs Nutrients fromfertilizer and sewage threaten coral reefs with excessive algal growth. Coral reefs in many areas are threatened by factors mostly of human origin. Higher atmospheric concentrations of carbon dioxide (from burning hydrocarbon fuels) tends to acidify ocean water, which makes precipitation of CaCO3 by corals more difficult metabolically. http://www.youtube.com/watch?v=QAaRJKKTOys
- 55. Coral Reefs Symbiosis between zooxanthellaeand corals is threatened by global warming. Warmer water damages the photosynthetic mechanism in zooxanthellae. Coral tissues turn white and brittle, this is called coral bleaching. Zooxanthellae die or are expelled by corals.
- 56. Phylum Ctenophora Phylum Ctenophora arethe comb jellies. No nematocysts. Tissue level of organization, like cnidarians. Mostly free swimming.
- 57. Phylum Ctenophora They usetheir ciliated comb plates for swimming. Not strong swimmers. Ctenophores are bioluminescent. Statocyst – sense organ
- 58. Phylogeny Cnidarians may haveevolved from a radially symmetrical planula-like ancestor. Trichocysts and toxicysts found in some ciliates may be precursors to nematocysts.