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Questions and Answers
Which characteristic is NOT associated with the phylum Cnidaria?
In which body form do Cnidarians primarily exhibit polyp morphology?
What type of symmetry do Cnidarians exhibit?
Which class within the phylum Cnidaria is primarily characterized by the absence of medusae?
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What is the primary function of the gastrovascular cavity in Cnidarians?
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Cnidarian body structures are primarily surrounded by which type of tissue?
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Which of the following features is exclusive to medusae in Cnidarians?
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What type of organisms primarily exhibit colonial lifestyles within Cnidarians?
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In terms of body organization, Cnidarians are best described as being:
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Which class of Cnidarians is primarily known for their parasitic lifestyle?
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What differentiates the base of each tentacle in Cubozoa?
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What is a notable feature of Chironex fleckeri that increases its lethality?
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Which structure in the Aurelia anatomy connects the gastrovascular cavity to the radial canals?
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Which of the following statements about nematocysts is correct?
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What is a function of the velarium in Cubozoa?
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How many tentacles can Chironex fleckeri have on each corner of its bell?
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What connects the gastric pouch in Cubozoa with gastric filaments?
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In which body form is the velum present?
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What structural feature is associated with the umbrella or bell of Cubozoa?
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What role do the gastric filaments serve in Cubozoa?
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What is the primary function of dactylozooid polyps in a hydrozoan colony?
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Which type of polyp produces male or female gametes in a hydrozoan colony?
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What characteristic distinguishes free living hydromedusae from other jellyfish forms?
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Which class do organisms like Physalia physalis belong to?
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What is the role of gastrozooids in a hydrozoan colony?
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In a colony of Obelia, which term describes the polyp form that lacks tentacles and a mouth?
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What descriptions accurately apply to gonozooids in a hydrozoan colony?
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What triggers the discharge of nematocysts in cnidarians?
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What is a defining feature of the class Hydrozoa when comparing polyp and medusa stages?
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Which morphological type is responsible for the distinctive floating structure in Physalia physalis?
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Which of the following best describes the nerve net found in hydras?
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Which characteristic accurately differentiates medusae from polyp forms in hydrozoans?
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What components interact with the nerve net in cnidarians?
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What is the role of myofibrils in the cnidarian nerve net?
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Which structure is not directly involved in the discharge of a nematocyst?
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What evolutionary significance does the nerve net of cnidarians hold?
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What is the function of the operculum in a nematocyst?
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Which statement best describes a cnidocyte?
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What is NOT a component of the nerve net found in cnidarians?
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Study Notes
Phylum Cnidaria: Introduction
- Cnidarians include jellyfish, sea anemones, and corals.
- Exhibit polymorphism with two body forms: polyp and medusa.
- Possess two germ layers (ectoderm and endoderm), radial symmetry, and a gastrovascular cavity (enteron) with a single opening.
- Cnidocytes, containing cnidae (like nematocysts), are present.
Phylum Cnidaria: Body Forms and Structure
- Polyp morph is sessile, often colonial, with a mouth and tentacles at the top.
- Medusa morph is free-living, bell-shaped, with tentacles hanging down.
- Hydrozoans can be solitary or colonial, exhibiting various polyp types (gastrozooids for feeding, dactylozooids for defense, gonozooids for reproduction).
- Examples of colonial hydrozoans include Obelia and Physalia physalis (Portuguese Man-of-War). Physalia has a gas-filled float (pneumatophore).
Distinguishing Medusae Forms
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Hydrozoan medusae have a velum, a manubrium, and a gastrovascular cavity connecting to radial and ring canals.
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Scyphozoan medusae lack a velum, lack a manubrium, and have four gastric pouches connected to a complex canal system.
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Cubozoan medusae have a velarium (similar to a velum), a manubrium, gastric filaments, and radial pouches. Chironex fleckeri (sea wasp) is a highly venomous cubozoan.
Cnidae: Nematocysts
- Nematocysts are stinging organelles within cnidocytes, abundant on tentacles.
- Discharge is triggered by chemical and/or physical stimuli.
Nerve Net and Muscles
- Cnidarians possess a diffuse nerve net located at the base of the epidermis and gastrodermis, facilitating bidirectional impulse transmission.
- The nerve net connects with sensory cells, epitheliomuscular cells, and nutritive-muscular cells.
- Contraction of myofibrils allows for movement (e.g., peristalsis).
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Description
Explore the fascinating world of Cnidarians, including jellyfish, sea anemones, and corals. This quiz covers their unique body forms, structures, and distinguishing characteristics. Test your knowledge on polyp and medusa forms, as well as the various types of hydrozoans.
