Phylum Cnidaria -Cnidarians Include Hydras, jellyfish, sea anemones & corals -_________________– means they are symmetrical around a central axis -_________________– lack a coelom; a coelom being a body cavity between organs and the body wall -_________________animals that have stinging tentacles arranged in circles around their mouth -they are the simplest animals to have _________________and _________________________ -they get their name from their _________________– stinging cells located along their tentacles -Two basic forms in their life cycle: -____________: a cylindrical form, they attach their base to substratum (they attach their base to rocks on the ground); usually sessile and their mouth points upward -____________: a flattened, bell-shaped version of the polyp; they move freely, and their mouth is on the bottom Activity Find a partner. One of you will research Medusae and the other will research Polyps. Create a sketch below of what you are researching and label 3-4 different structures of each. Once you are done researching, let your partner copy what you have found. You may use your phones, computer or textbook in your research. Medusae Polyps Cnidaria Basic Body Plan -Have an outer epidermis -Have an inner _________________ (a layer of cells) which forms the lining of the _________________ -the gastrovascular cavity is the primary organ of digestion and circulation in Cnidaria -Has a middle "jelly filled" layer called _________________, which functions as a hydrostatic skeleton, which is a flexible skeleton that is supported by fluid pressure Activity if your sketch above does not include the following terms (epidermis, gastrovascular cavity and mesoglea), please take a minute to add them now. Cnidocytes and Nematocysts -Cnidarians are predators -They have tentacles that possess batteries of special cells called _________________ -Cnidocytes contain special stinging capsules called _________________ -When triggered, nematocysts shoot out a discharge thread which can entangle and/or poison its intended prey and can also be used for defense -after paralyzing their prey, they pull their prey through their mouth into their gastrovascular cavity -digestion occurs in their gastrovascular cavity Activity Take a minute to find a picture of what a nematocyst looks like before AND after firing and make a quick sketch. Once done, please compare it with your neighbour’s sketch and make corrections if necessary. Nematocyst Sketch A: Before discharge B: After Discharge Class Discussion: We have discovered that fluid pressure is involved in a Cnidarian’s hydrostatic skeleton and that it could be involved in the firing of their nematocysts. What are some other functions that fluid pressure could play in the body of a jellyfish? What other organisms might use fluid pressure in their biology? What are some examples of how we use fluid pressure in society? Portuguese Man O’ War – an interesting Cnidarian -NOT a jellyfish -their tentacles can be up to 50 metres long! Respiration, Circulation and Excretion -nutrients are usually transported throughout the body by _________________; the same process is used for respiration and excretion Response -cnidarians gather information from their environment using a _________________ -a nerve net is a loosely organized network of nerve cells that together allow cnidarians to detect stimuli such as the touch of a foreign object -they also have _________________, which are groups of sensory cells that help determine the direction of gravity -they have _________________– eyespots that detect light Movement -in some cnidarians, their hydrostatic skeletons have circular and longitudinal muscles, that, together with the water in the gastrovascular cavity, allow cnidarians to move -i.e. anemones -other cnidarians, like medusa, move by _________________ Cnidaria Reproduction -Reproduction usually occurs sexually by __________________________________ -egg and sperm forming larvae -Reproduction can also occur asexually through _________________ -in budding, a new organism develops from an outgrowth or bud due to cell division at one particular site -polyps use this form of reproduction Hydra Budding: 1. Non-reproducing 2. Creating a bud 3. Daughter growing out 4. Beginning to cleave 5. Daughter broken off 6. Daughter clone of parent Class Discussion Form a group of four to read the case study and answer the questions below. Be prepared to share your answers with the class. Coral Vanishing Act The World Resources Institute, an organization that examines global environmental problems, has announced that 58 percent of the world’s coral reefs are in danger of dying. Threats to coral reefs fall into four broad categories shown in the graph. The graph indicates the percentage of reefs that are threatened by each of these categories. It also rates the threat as medium or high, based on the distance between the coral reef and the source of the threat. Use the information in the graph to answer the following questions. 1. Classifying – Place the four categories of risk in order from greatest high threat to least high threat. 2. Using Tables and Graphs – Approximately how much greater is the high threat of overexploitation than the high threat of coastal development? 3. Inferring – Based on the graph, write a generalization about the effect of human activities on the destruction of coral reefs. 4. Making Judgments – Assume that you are a legislator drafting a law to protect coral reefs. Choose one of the threats shown in the graph and outline a law that you would propose to counter the threat. There are 3 Major Classes of Cnidaria -Class Hydrozoa: i.e. Hydras -Class Scyphozoa: i.e. Jellyfish -Class Anthozoa: i.e. Anemones and corals Class Hydrozoa: The Hydras -Polyp phase is dominant -Generally microscopic -Generally, they live in freshwater Class Scyphozoa: The Jellies -Generally referred to as jellies -Medusa stage is dominant -Come in a variety of forms -Aggressive predators, can be dangerous to humans Class Anthozoa: Anemones & Corals -Appear like plants but are animals -Polyp form is dominant -Corals build calcium shells to protect themselves -Have symbiotic relationship with algae. What is a symbiotic relationship? Please write below if you know, if not please look it up and fill in below after class. Symbiotic relationship: -Can build extensive masses which can form land masses Coral Reefs: Clownfish living in an anemone: Additional Questions 1. Create a sketch of the jellyfish reproductive cycle. Be sure to include if they reproduce sexually or asexually. 2. Define zygote. 3. What is a cnidarian? 4. Is the body plan of this jellyfish a medusa or a polyp? Why?
