2 Cnidarians are...soft-bodied, carnivorous animals that have stinging tentacles arranged in circles around their mouthsthe simplest animals to have body symmetry and specialized tissuesCnidarians get their name from the cnidocytes, or stinging cells, that are located along their tentacles. Within each cnidocyte is a nematocyst, a poison-filled, stinging structure that contains a tightly coiled up dart.Cnidarians include jellyfishes, hydras and their relatives, and sea anemones and corals.
4 Body Plan Cnidarians are radially symmetrical central mouth surrounded by many tentacles that extend outward from bodytypically have a life that includes two different-looking stages: a polyp and a medusaboth medusa and polyp have a body wall that surrounds a gastrovascular cavity, the gastroderm is the inner lining of the g.c, where digestion takes place, the epidermis is the outer layer of cells, the mesoglea is the layer that lies between these two tissues
5 Feeding & Respiration, Circulation, & Excretion After paralyzing its prey, a cnidarian pulls the prey through its mouth and into its gastrovascular cavityfood enters and leaves through this openingdigestion takes place here and is extracellular, meaning it takes places outside of cellsPartially digested food is absorbed by the gastrodermdigestion is completed intracellularly, meaning within cells in the gastrodermAny materials that can’t be digested are passed out of body through the mouthAfter digestion, nutrients are usually transported throughout body by diffusioncnidarians respire and eliminate wastes of cellular metabolism by diffusion through their bodiesTHROW BACK!!Diffusion is process by which molecules tend to move from an area where they are more concentrated to an area of low concentrationcannibalism
6 Response & MovementBoth polyp and medusa have a nerve net which is a loosely organized network of nerve cells that together allow cnidarians to detect stimuli such (ex.: the touch of a foreign object)Nerve net is usually distributed uniformly around body, but in some species it is concentrated around the mouth or in rings around the bodyCnidarians also have:statocysts, which are groups of sensory cells that help determine direction of gravity and ocelli, which are eyespots made of cells that detect lightdifferent cnidarians move in different wayssea anemones have a hydrostatic skeleton which is a layer of circular and longitudinal muscles that, with the water in the gastrovascular cavity, enable it to movemedusas, such as jellyfish, move by jet propulsionthis is when muscles contractions cause the bell-shaped body to close like an umbrella and push water out of the bell moves medusa forward
7 Reproduction Most cnidarians reproduce both sexually and asexually Polyps can reproduce by buddingone type begins with a swelling on the side of an existing polyp that breaks off and becomes a new polypanother is when polyps produce tiny medusas that separate and become newindividualsIn most cnidarians, sexual reproduction takes place with external fertilization, which the process in which the eggs are fertilized outside the female’s body
9 Hydras and their Relatives Class Hydrozoapolyps grow in branching colonies that sometimes extend more than 1 meterwithin colony, polyps are specialized to perform different functions(ex.: some digest food held by tentacles while others make eggs and sperm)most common freshwater hydrozoans are hydraslack medusa stage, instead live as solitary polypsreproduce sexually and asexuallymany get nutrient from small prey and some from symbiotic photosynthetic protists that live in their tissues
10 Sea Anemones and Corals Class Anthozoa “flower animal”only have polyp stage in their livesmany species are colonialuse nematocysts to capture prey for nutritionnew polyps produced by buddingas colony grows, they secrete underlying skeleton of calcium carbonate, or limestoneWorldwide distribution of corals determined by few factors:Temperature 2) water depth 3) light intensitylight- corals rely on mutualistic relationships with algae that capture solar energy, recycle nutrients, & help corals lay down limestoneHarmed from human activities, logging, farming, mining, etc.Coral bleaching caused by high temperatures can kill algaethat usually live in the tissues of corals, leaving behind onlytransparent cells atop ghostly white skeletonsI live an anenemone… anemonmone..
11 Vocabulary cnidocytes, or stinging cells nematocyst, a poison-filled, stinging structure that contains a tightly coiled up dart.gastrovascular cavity digestive chamber with a single opening in which cnidarians, etc., digest foodgastroderm is the inner lining of the g.c, where digestion takes placeepidermis is the outer layer of cellsmesoglea is the layer that lies between the epidermis and gastrodermextracellular, digestion takes places outside of cellsIntracellular digestion takes place inside of cellsnerve net which is a loosely organized network of nerve cells that together allow cnidarians to detect stimulistatocysts, which are groups of sensory cells that help determine direction of gravityocelli, which are eyespots made of cells that detect lighthydrostatic skeleton which is a layer of circular and longitudinal muscles that, with the water in the gastrovascular cavity, enable it to movejet propulsion this is when muscles contractions cause the bell-shaped body to close like an umbrella and push water out of the bellexternal fertilization, which the process in which the eggs are fertilized outside the female’s body
12 Soft-bodied, carnivorous, and have stinging tentacles Cnidarians are…Soft-bodied, carnivorous, and have stinging tentaclesSimplest organism with body symmetry and specialized tissuesNamed after their cnidocytes, or stinging cells, on their tentaclesWithin cnidocytes, are nematocysts, poison-filled stinging structure with a dartInclude: jellyfishes, hydras, sea anemones, and coralsBody PlanRadial symmetryTwo stages: Polyp and MedusaBoth have body wall surrounding a gastrovascular cavity which is lined with the gastroderm, where digestion takes placeEpidermis is the outer layer of cellsMesoglea is the layer between the epidermis and gastroderm
13 Feeding, Respiration, Circulation, and Excretion Feeding: paralyze the prey, pull it through the mouth, into the gastrovascular cavity, where extracelluar digestion, or outside of cells, occursfood is then absorbed by gastroderm, where digestion is completed intracellularly, or within the cellsFood not digested, leaves through the mouthOther body processes occur by diffusionResponse and MovementCnidarians have a nerve net, or a loosely organized network of nerve cells that allow the cnidarians to detect stimuliThey also have statocysts- groups of sensory cells that help determine direction of gravityAlso, they have ocelli- eyespots with cells that detect lightMovement:Sea anemones- hydrostatic skeleton, which is a layer of muscles that, with water, enables it to moveMedusas- jet propulsion, works by forcing the bell shaped body to close like an umbrella, and push water out of the bell
14 Hydras and Their Relatives Class Hydrozoa ReproductionAsexuallyPolyps reproduce by budding, either by a piece of the polyp swelling and breaking off into a new polyp, or by producing and releasing medusasSexualMale release sperm, female release eggs, and external fertilization occurs, which is the process when the eggs are fertilized outside the female’s bodyHydras and Their RelativesClass HydrozoaPolyps grow in branching colonies and each is specialized for a certain jobHydras are the most common freshwater hydrozoanslack medusa stagereproduce sexually and asexuallyget nutrients from small prey and some from symbiotic photosynthetic protists living in their tissues
15 Sea Anemones and Corals Class Anthozoa- “flower animal”Only polyp stageMany are colonialUse nematocysts to capture preyNew polyps produced by buddingAs it’s growing, it secretes a skeleton of calcium carbonate, or limestoneWhere corals grow is affected by temperature, water depth, and light intensityCorals rely on mutualistic relationships with algae that capture solar energy, recycle nutrients, and help lay down limestoneCorals are harmed by human activities, logging, farming, mining, etc.Coral bleaching caused by high temperatures kill algae in corals