Phylum Cnidaria Overview

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Questions and Answers

Which characteristic is NOT associated with the phylum Cnidaria?

Gastrovascular cavity

Presence of cnidocytes

Triploblastic body structure (correct)

Radial symmetry

In which body form do Cnidarians primarily exhibit polyp morphology?

Cubozoa

Scyphozoa

Hydrozoa (correct)

Anthozoa (correct)

What type of symmetry do Cnidarians exhibit?

Asymmetrical

Spherical symmetry

Radial symmetry (correct)

Bilateral symmetry

Which class within the phylum Cnidaria is primarily characterized by the absence of medusae?

Anthozoa Signup and view all the answers

What is the primary function of the gastrovascular cavity in Cnidarians?

Digestion and distribution of nutrients Signup and view all the answers

Cnidarian body structures are primarily surrounded by which type of tissue?

Mesoglea Signup and view all the answers

Which of the following features is exclusive to medusae in Cnidarians?

Free-swimming locomotion Signup and view all the answers

What type of organisms primarily exhibit colonial lifestyles within Cnidarians?

Hydrozoa Signup and view all the answers

In terms of body organization, Cnidarians are best described as being:

Diploblastic with two germ layers Signup and view all the answers

Which class of Cnidarians is primarily known for their parasitic lifestyle?

Myxozoa Signup and view all the answers

What differentiates the base of each tentacle in Cubozoa?

It is differentiated into a blade-like pedalium. Signup and view all the answers

What is a notable feature of Chironex fleckeri that increases its lethality?

A minimal contact area of 3 cm can be fatal. Signup and view all the answers

Which structure in the Aurelia anatomy connects the gastrovascular cavity to the radial canals?

The ring canal Signup and view all the answers

Which of the following statements about nematocysts is correct?

They are contained within cnidocytes. Signup and view all the answers

What is a function of the velarium in Cubozoa?

It serves a role in swimming. Signup and view all the answers

How many tentacles can Chironex fleckeri have on each corner of its bell?

Up to 15 tentacles. Signup and view all the answers

What connects the gastric pouch in Cubozoa with gastric filaments?

The radial pouch Signup and view all the answers

In which body form is the velum present?

Hydrozoa. Signup and view all the answers

What structural feature is associated with the umbrella or bell of Cubozoa?

It is almost square. Signup and view all the answers

What role do the gastric filaments serve in Cubozoa?

They assist in the digestion of prey. Signup and view all the answers

What is the primary function of dactylozooid polyps in a hydrozoan colony?

Defense of the colony Signup and view all the answers

Which type of polyp produces male or female gametes in a hydrozoan colony?

Gonozooid Signup and view all the answers

What characteristic distinguishes free living hydromedusae from other jellyfish forms?

Presence of a gas-filled float Signup and view all the answers

Which class do organisms like Physalia physalis belong to?

Hydrozoa Signup and view all the answers

What is the role of gastrozooids in a hydrozoan colony?

Capturing prey and feeding Signup and view all the answers

In a colony of Obelia, which term describes the polyp form that lacks tentacles and a mouth?

Dactylozooid Signup and view all the answers

What descriptions accurately apply to gonozooids in a hydrozoan colony?

Do not possess mouths and reproduce Signup and view all the answers

What triggers the discharge of nematocysts in cnidarians?

Chemical and/or physical contact Signup and view all the answers

What is a defining feature of the class Hydrozoa when comparing polyp and medusa stages?

Polymorphism in colony forms Signup and view all the answers

Which morphological type is responsible for the distinctive floating structure in Physalia physalis?

Pneumatophore Signup and view all the answers

Which of the following best describes the nerve net found in hydras?

A diffuse nervous system allowing bidirectional impulse transmission Signup and view all the answers

Which characteristic accurately differentiates medusae from polyp forms in hydrozoans?

Medusae are free-swimming Signup and view all the answers

What components interact with the nerve net in cnidarians?

Neuro sensory and epitheliomuscular cells Signup and view all the answers

What is the role of myofibrils in the cnidarian nerve net?

To enable peristaltic movement and tentacle shortening Signup and view all the answers

Which structure is not directly involved in the discharge of a nematocyst?

Myofibril Signup and view all the answers

What evolutionary significance does the nerve net of cnidarians hold?

It is an early form of centralized nervous systems. Signup and view all the answers

What is the function of the operculum in a nematocyst?

To cover the nematocyst until activation Signup and view all the answers

Which statement best describes a cnidocyte?

A cell containing nematocysts for defense or prey capture Signup and view all the answers

What is NOT a component of the nerve net found in cnidarians?

Centralized ganglia Signup and view all the answers

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

Hydrozoan medusae have a velum, a manubrium, and a gastrovascular cavity connecting to radial and ring canals.
Scyphozoan medusae lack a velum, lack a manubrium, and have four gastric pouches connected to a complex canal system.
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.