Cnidarea

Two major sensory structures found in hydroid medusae are the , which are responsible for maintaining equilibrium within the water column, and the ocelli, which function in the reception of .

Blank 1: statocysts Blank 2: light

Coral reefs are composed of what substance that has been deposited by living organisms over thousands of years?

Calcium carbonate

Members of what cnidarian class are characterized by a dominant medusa form, with the bell being almost square in transverse section and tentacles or groups of tentacles situated at each corner of the square?

Cubozoa

Recent molecular studies confirm that myxozoans are highly reduced

Blank 1: cnidarians

The margin of the scyphozoan medusa bell is scalloped, with each notch bearing a pair of lobe-like projections called ______ Between these lies a sense organ called a ______

Blank 1: lappets Blank 2: rhopalium or rhopalia

In this diagram of a cnidarian polyp, the letter B corresponds to the Blank 1Blank 1 gastrodermis , Incorrect Unavailable, the letter D corresponds to the Blank 2Blank 2 gastrovascular cavity , Incorrect Unavailable cavity, and the letter E corresponds to the Blank 3Blank 3 mouth , Correct Unavailable.

Blank 1: mesoglea Blank 2: gastrovascular Blank 3: mouth or oral cavity

In a typical cnidarian life cycle, a newly formed zygote develops into a motile

Blank 1: planula Blank 2: polyp

Cnidarians are dimorphic; the larval or Blank 1Blank 1 c , Incorrect Unavailable form is sessile and attached to the substrate with tentacles extended into the water column, and the adult or Blank 2Blank 2 c , Incorrect Unavailable form is umbrella-shaped and adapted for a floating, free-swimming lifestyle.

Blank 1: polyp or hydroid Blank 2: medusa or jellyfish

The phylum Cnidaria includes what classes (both traditionally and recently proposed)?

Cubozoa Anthozoa Hydrozoa Staurozoa Scyphozoa

Select all of the characteristics of members of the cnidarian class Cubozoa.

Each rhopalium contains six eyes. The edge of the subumbrella turns inward to form a velarium. The base of a tentacle is differentiated into a flattened, tough blade called a pedalium.

A diploblastic organism develops from what embryonic cell layers?

Endoderm and ectoderm

What type of cells serve a similar function as true mesoderm-derived muscle cells in the diploblastic cnidarian body?

Epitheliomuscular cells

Select all of the habitats where cnidarians may occur.

Freshwater ponds and lakes At great depths in the ocean Attached to shells of marine animals On rocks and wharves in marine environments

What cnidarian class is characterized by an asexual polyp stage with a sexual medusa stage, and often occurs in marine habitats and in a colonial form?

Hydrozoa

Select all of the characteristics of members of class Anthozoa.

Many forms produce a skeleton for support. The gastrovascular cavity is partitioned by septa. They can be solitary or colonial.

Select all of the characteristics of members belonging to class Hydrozoa.

Most are colonial in form. The polyp stage is usually asexual. Some lack a medusa stage in the life cycle.

The diffuse nervous system of cnidarians can best be described as a

Nerve net

Select all the components of the cellular neuromuscular system of cnidarians.

Nerve net Epitheliomuscular cells Sensory cells

Select all of the following that describe the cnidarian nervous system

Networks of nerve cells occur at the bases of both the epidermis and gastrodermis Nerve net

Select all of the following that are contained in the rhopalia of scyphomedusae and cubozoan medusae.

Ocelli Chemoreceptors Statocysts

Which of the following statements are TRUE regarding cnidarian feeding and digestion?

Polyps are usually carnivorous. Some forms, such as corals, are able to supplement their diet with the products of photosynthesis. The mouths of both hydromedusae and scyphomedusae are found at the end of a manubrium.

The medusa of members of what cnidarian class has a scalloped margin, with each notch bearing a pair of lappets and between them a rhopalium with statocysts, sensory epithelium, and possibly ocelli?

Scyphozoa

Select all of the members of Phylum Cnidaria.

Sea anemones Corals Sea whips Jellyfishes

What are cnidocytes?

Specialized stinging cells found in cnidarians that are used in prey capture and defense

Which of the following statements are true about sponges?

Sponges are not diploblastic. Adult sponges do not have distinct cell layers.

Members of what cnidarian class lack a medusa stage, but have a solitary stalked polyp that resembles a medusa at the top?

Staurozoa

Radiate animals have which of the following characteristics?

The process of gastrulation during development Presence of a gut cavity Two embryonic cell layers (endoderm and ectoderm)

What is the purpose of epitheliomuscular cells in the cnidarian body?

They act as muscle cells, allowing the body and tentacles to contract and expand.

True or false: Cnidarians occur in both marine and freshwater habitats.

True

Characteristics of the hydrozoan freshwater medusa Craspedacusta sowberii include

a current distribution that includes Europe, the United States, and Canada as a result of anthropogenic movement of aquatic plants. three methods of asexual reproduction.

The expulsion of zooxanthellae from coral tissues that can occur as ocean temperatures increase is called coral

bleaching

Members of the phylum Cnidaria possess cells known as ______ that produce stinging organelles called ______ for defense.

cnidocytes; cnidae

Massive formations of calcium carbonate that are deposited by living organisms in shallow tropical marine environments are called

coral reef

An organism that has only two embryonic cell layers (endoderm and ectoderm) is

diploblastic.

The stage of embryonic development known as _______ produces the cell layers of adult animals.

gastrulation

The most common type of cnida that is used to inject a toxin for prey capture and defense is a _______.

nematocyst

Some ctenophores, flatworms, and molluscs consume hydroids bearing ________ , then store and use these stinging structures for their own defense.

nematocysts or cnida

The contractile fibers of the epitheliomuscular cells and the sensory-nerve cell net in combination are known as a(n) ______ system.

neuromuscular

The sensory structures of hydroid medusae that are responsible for light reception are _____.

ocelli

Myxozoans are obligate parasites whose typical life cycle consists of _______ host(s).

two

Corals rely on their relationship with ______ for food, recycling of phosphorus and nitrogenous wastes, and assistance in the deposition of calcium carbonate.

zooxanthellae

Sea whips, Hydra, corals, and sea anemones members of which phylum?

Cnidaria

Select all of the benefits provided by zooxanthellae to corals.

Recycling of phosphorus-containing wastes Recycling of nitrogenous wastes Food through the process of photosynthesis Facilitation of calcium carbonate deposition

Identify the cnidarian organism that has the following characteristics: 1. Occurs in freshwater habitats, and likely evolved from marine ancestors in the Yangtze River in China 2. A tiny polyp stage relative to the medusa that was originally given its own species name because its relationship to the medusa was not recognized until relatively recently 3. Three methods of asexual reproduction in the polyp stage

The hydrozoan medusa Craspedacusta sowberii

What statement is true regarding the dimorphic nature of cnidarians?

The polyp stage is sessile, while the medusa stage is free-swimming/floating.

Gastrulation can be described as

a process of embryonic development in which the cell layers of animals are produced.

Widespread coral bleaching is currently occurring at an unprecedented rate and is correlated with

a rise in ocean temperature.

In some cnidarian medusae, chemoreceptors, statocysts, and often ocelli are grouped at the margin of the bell in sense organs called ________.

rhopalia

Select all of the characteristics of members of class Staurozoa.

A solitary stalked polyp body form An adhesive disc that attaches to objects on the ocean floor A polyp that resembles a medusa, with eight arms surrounding the mouth

Members of what cnidarian class are solitary or colonial marine polyps that lack a medusa stage?

Anthozoa

Match each cnidarian class to its correct description.

Anthozoa matches Choice, Largest class, which includes sea anemones, stony corals, and soft corals. Largest class, which includes sea anemones, stony corals, and soft corals. Staurozoa matches Choice, The polyp body is topped by a medusa-like region. The polyp body is topped by a medusa-like region. Scyphozoa matches Choice, The "true" jellyfishes The "true" jellyfishes Cubozoa matches Choice, Cube jellyfishes Cube jellyfishes Hydrozoa matches Choice, The most varied class, which includes hydroids, fire corals, Portuguese man-of-war. The most varied class, which includes hydroids, fire corals, Portuguese man-of-war.