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Phylum Cnidaria

Many animals with brilliant colours and unusual shapes, with most species only living in the sea.

Hanna Valente

on 3 June 2011

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Transcript of Phylum Cnidaria

Phylum Cnidaria 1. Key defining characteristics of Cnidarians:
The phylum Cnidaria includes many animals with brilliant colours and unusual shapes. Cnidarians are soft-bodied animals with stinging tentacles arranged in cicrcles around their mouth. 2. Is Cnidarians the first at something evolutionarily-speaking?
They were also among the first multicellular life to evolve on earth, having arisen at least 650 mil ears ago. Their most obvious unique feature is their highly specialized stinging cells (nematocysts). Anemones - Solitary Gorgonian Coral Polyps - Colonial 3. How many living species of Cnidarians are there?
The phylum contains over 9,000 species of animals found in mainly aquatic and marine environments. 4.What are the important subgroups of Cnidarians? How are they defined?
Kingdom: Animalia
Phylum: Cnidaria
The Phylum Cnidaria contains the following subgroups:
Class: Scyphozoa (Members of the class Scyphozoa have only the medusa stage in their life cycle. They are the most large and complex members of this phylum: Examples include the common jellyfish)
Class: Anthozoa (Anthozoa have only the polyp stage in their life cycle. They are slightly more complex than hydrozoans: Examples include sea anemones)
Class: Hydrozoa (Hydrozoa have both the polyp and medusa stage in their life cycle: Examples include the Portuguese man-o-war) 5. Familiar examples of animals that belong to Cnidarians?
Familiar animals that belong to the Phylum Cnidaria are: Jellyfish, corals, sea anemones, and hydras.
Class: Scyphozoa (cup animals and common jellyfish)
Class: Anthozoa (anemones and corals)
Class: Hydrozoa (hydrazoans, Portuguese man-o-war) Polypoid (left) and Medusoid (Right) 7. Do they take in nutrients (feed)?
To feed, Cnidarians use Symbiosis, a process consisting of tiny photosynthetic protists gorwing right inside the living cells of the gastroderm. This relationship between autotrophic protist and heterotrophic animal works very efficently. The photosynthetic protists use the carbon diozide and other metabolic waste produced by the cnidarians cells to manudacture proteins. The potist use some of the oxygen and organic compounds themselved and release the rest into the tissues of their cnidarian hosts. Many Cnidarians depend on symbiosis to such an extent that they can only live in bright sunlight; therefore, they will slowely starve if keptin a adarkened laboratory tank even if they are feed pieces of shrimp or fish. 6. What is the generalized body plan of an Cnidaria?
Both polyp and medusae have a body wall that surrounds an internal space called the gasstrocvascular caivty.There symmerty is radial, there cephalization consitis of a head where there mouth is, and they have no segmentation. They also are supported by the pressure of water, hydrostatic. 8.How do they take in oxygen (breathe)?
They have cell layers that absorb oxygen and expel carbon dioxide through the water because they have no respiratory organs. 9.How do they move materials (food, oxygen, wastes) around inside them (internal transport/circulation)?
Some have long tube shaped branching gastro vascular cavities that carry partially digested food through their bodies. But, they have no organized internal transport network or excretory system. 10.How do they get rid of (excrete) waste?
They have no anus so Cnidarians have to excrete their waste through their mouth. 11.How do they move, and/or respond to their environment (nervous system)?
They have no central nervous system and no brain. Info about the environment is sent to the rest of its body (nervous system) by specialized sensory cells. Many can also change shape when responding to the nervous system. The can move by relaxing and contracting; and the contraction moves them forwards by jet propulsion. 12.How do they reproduce? (sexually/asexually)
Cnidarians can produce both sexually and asexually. Some can produce asexually by budding. Many can also produce asexually by budding off tiny medusa (motile bell shaped cnidarians) and then when the medusa mature they can reproduce sexually by releasing gametes into the water. Also, depending on the species, fertilization can happen in open water or inside an egg carrying medusa. 13.How do they fit into the world/what is their ecological role or significance?
Cnidarians create many symbiotic relationships with other animals. For example: sea anemone’s protect and provide food for symbionts and in return they help clean and protect it from certain predators too. Corals and coral reefs are also very important because they are habitats for many marine species. Coral reefs also protect land from wave erosion. They also give many clues to geologists about locations of oil deposits and are used to build houses and filter drinking water. Humans also use coral to make decorations and jewelry. Some also play a major role in medical research; they provide us with anti cancer drugs and help us learn more about cancer all together. 14.Interesting Facts
Jellyfishes: have no brain, no blood and no nervous system and are made up of more than 95% water.
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