Cnidaria Phylum Quiz

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Questions and Answers

What is the main characteristic that gives the Cnidaria phylum its name?

The display of dimorphism and polymorphism

The formation of coral reefs and islands

The presence of branching, plantlike hydroids

The possession of cells called cnidocytes (correct)

Which organism is not a part of the Cnidaria phylum?

Hydroids

Jellyfish

Ctenophores (correct)

Sea anemones

What do cnidocytes contain that is characteristic of the Cnidaria phylum?

Gland cells

Nematocysts (correct)

Tentacles

Longitudinal myofibrils

What is the function of the organelles found in cnidocytes?

Defense mechanism Signup and view all the answers

What is one of the striking aspects of the Cnidaria phylum?

Display of dimorphism and polymorphism Signup and view all the answers

Which organisms may eat hydroids bearing nematocysts and use them for their own defense?

Ctenophores Signup and view all the answers

What are the two morphological types that cnidarian forms fit into?

A polyp and a medusa Signup and view all the answers

Which cell type is responsible for efficient predation in cnidarians?

Cnidocyte Signup and view all the answers

What is the purpose of a nematocyst in cnidarians?

Injecting toxin for prey capture and defense Signup and view all the answers

What is the function of an operculum in a nematocyst?

Covering the narrowed end of the capsule Signup and view all the answers

What causes the discharge of a nematocyst in some sea anemones?

Tactile stimulation Signup and view all the answers

What is the mechanism for nematocyst discharge in cnidarians?

Combination of tensional forces and high osmotic pressure Signup and view all the answers

What is the characteristic body plan retained by both polyp and medusa forms of cnidarians?

Saclike body plan Signup and view all the answers

Which type of cell produces over 20 kinds of distinctive organelles called cnidae?

Cnidocyte Signup and view all the answers

What role does the trigger-like cnidocil play in cnidocytes?

Sensitizing to prey vibrations and causing discharge Signup and view all the answers

What causes water to rush into the capsule of a nematocyst during discharge?

High internal osmotic pressure Signup and view all the answers

What is the main function of the coelomic fluid in Phylum Annelida?

Supplying turgidity and functioning as a hydrostatic skeleton Signup and view all the answers

What is the role of chitinous setae in Phylum Annelida?

Aiding in locomotion and providing sensory feedback Signup and view all the answers

What is the characteristic nervous system structure in Phylum Annelida?

Double ventral nerve cord and a pair of ganglia with lateral nerves in each metamere Signup and view all the answers

Which respiratory pigment is often present in the circulatory system of Phylum Annelida?

Hemoglobin Signup and view all the answers

What is the primary site for excretory function in Phylum Annelida?

Nephridia Signup and view all the answers

How do earthworms and freshwater worms differ from leeches with respect to chitinous setae?

Earthworms and freshwater worms have chitinous setae, while leeches lack them. Signup and view all the answers

Which class of organisms is characterized by the presence of parapodia bearing tufts of many setae?

Class Polychaeta Signup and view all the answers

Which class of organisms has a body with conspicuous segmentation and a spacious coelom usually divided by intersegmental septa?

Class Oligochaeta Signup and view all the answers

Which class of organisms has a body with a fixed number of segments (normally 34) and oral and posterior suckers usually present?

Class Hirudinea Signup and view all the answers

Which organism is commonly used as a type in introductory courses in Zoology?

Lumbricus sp. Signup and view all the answers

What external feature distinguishes mature worms in the earthworm species?

Saddle-shaped enlargement called clitellum Signup and view all the answers

What covers the body of Lumbricus sp., protecting it from physical and chemical injury?

Thin, transparent cuticle Signup and view all the answers

What constitutes the outer tube of the earthworm's body, with the alimentary canal constituting the inner tube?

Body wall Signup and view all the answers

What lies beneath the grooves in the earthworm's body, corresponding to an internal division of the coelomic cavity into partitions?

Septa Signup and view all the answers

What part of the earthworm's digestive system lies in somites 1 to 3 and serves as a mouth cavity or buccal pouch?

Mouth cavity Signup and view all the answers

What do the setae on segment or somite 26 become in mature worms, serving reproductive purposes?

Clitellum Signup and view all the answers

Study Notes

Cnidaria Phylum

The Cnidaria phylum is named for cnidocytes, specialized cells that contain stinging organelles called nematocysts.
Sponges are not part of the Cnidaria phylum.
Nematocysts contain a capsule with a coiled thread that can be rapidly ejected.
The organelles found in cnidocytes, called nematocysts, function in defense and prey capture.
A striking aspect of the Cnidaria phylum is the diverse forms they can take, from polyps to medusas.
Organisms like nudibranchs may consume hydroids bearing nematocysts and use them for their own defense.
Cnidarian forms exist in two morphological types: polyps and medusas.
Cnidocytes are responsible for efficient predation in cnidarians.
The purpose of a nematocyst in cnidarians is to inject toxins and entrap prey.
An operculum in a nematocyst functions as a lid that keeps the coiled thread contained.
Chemical stimuli can trigger the discharge of a nematocyst in some sea anemones.
Nematocyst discharge in cnidarians occurs when the cnidocyte is stimulated, causing a rapid influx of water into the capsule, which propels the coiled thread outward.
The radial body plan is retained by both polyp and medusa forms of cnidarians.
Cnidocytes are produced by interstitial cells.
The cnidocil is a trigger-like structure that helps initiate nematocyst discharge.
During discharge, water rushes into the capsule of a nematocyst due to osmotic pressure from the sudden increase in calcium ions within the cell.

Phylum Annelida: Earthworms

The coelomic fluid in Phylum Annelida plays a role in hydrostatic skeleton and transport of nutrients and waste.
Chitinous setae in Phylum Annelida help with locomotion and anchoring.
The characteristic nervous system structure in Phylum Annelida is a ventral nerve cord with segmental ganglia.
Hemoglobin is often present in the circulatory system of Phylum Annelida.
The nephridia are the primary sites for excretory function in Phylum Annelida.
Earthworms and freshwater worms have chitinous setae on most segments, while leeches lack them or have them only near the ends of the body.

Classes in Phylum Annelida

The Polychaeta class is characterized by parapodia bearing tufts of many setae.
The Oligochaeta class has a body with conspicuous segmentation and a spacious coelom usually divided by intersegmental septa.
The Hirudinea class has a body with a fixed number of segments (normally 34) and oral and posterior suckers usually present.

Lumbricus terrestris (Earthworm)

Lumbricus terrestris, known as the common earthworm, is used as a type in introductory zoology courses.
Mature earthworms can be distinguished by the clitellum, a thickened band of segments that secretes a cocoon for eggs.
The cuticle covers the body of Lumbricus sp., protecting it from physical and chemical injury.
The body wall constitutes the outer tube of the earthworm's body, with the alimentary canal constituting the inner tube.
Septa, internal divisions of the coelomic cavity into partitions, lie beneath the grooves in the earthworm's body.
The buccal cavity is located in somites 1 to 3 and serves as a mouth cavity or buccal pouch.
In mature worms, the setae on segment or somite 26 become reproductive structures.

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Test your knowledge about the fascinating Cnidaria phylum, which includes sea anemones, jellyfish, corals, and other unique marine creatures.