Marine Biology, Chapter 9, 9.1 Cnidarians

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Two primary characteristics of Cnidarians are

(1) a tissue level of organization (2) radial symmetry

Polyp Form (Cnidarian)

- Generally sessile( don't move, anchored). Sac-like and anchored, it has a mouth and tentacles oriented UPWARD.

How many species of Cnidarians

10,000 species almost all of which are marine

The gut of the cnidarians is

A blind cavity with only ONE opening—the mouth

tentacles

A long, slender, flexible arm-like structure found around the mouth or head of an animal. Used to capture and handle food.

Describe Cnidarian digestion

After ingestion food passes to the gut. The initial stage of digestion is extra cellular because it takes place outside cells. Intracellular digestion within cells lining the gut completes the breakdown of food.

Most cnidarian species, more than 6000 are what class

Anthozoans (class Anthozoa)

Coral reefs

Are formed by Cindinarian, Anthozoans

The medusa form of Cnidarians is best described as

Bell shaped, with the oral surface and tentacles on the bottom

Cubomedusa

Box jellyfish (Class Cuboza)

Sea anemones, jellyfish, corals and their relatives are members of what phyulum

Cnidaria

What phylum are Cnidarians

Cnidaria

Box jellyfish (Cubomedusae)

Cnidaria that have smallmouth mostly transparent cube-shaped Medusa with at least four tentacles

Phylum Cnidaria

Cnidarians

The next level of organizational complexity after sponges

Cnidarians

What do cnidarians use to capture prey?

Cnidarians capture prey by discharging their nematocysts which are unique stinging structures found within cnidocytes—specialized cells in the tentacles

What are sea anemones

Cnidarians of the Anthozoan class. Phylum Cnidaria, Class Anthozoan

Intracellular Digestion

Digestion that takes place inside the cell

Extra cellular digestion

Digestion that takes place outside the cell

Describe a nematocysts

Each nematocyst consists of a fluid-filled capsule containing a thread that can be quickly injected. The thread can be sticky or a long tube that wraps around prey. Some nematocysts contain toxins

Like the Portuguese man of war, some Hydrozoans have _______ which may be bas filled

Floats

Class Hydrozoa

Hydroids, Hydra, Portuguese man-of-war

The Portuguese man of war is an example of what

Hydrozoans

What is a sea wasp

It is a type of box jelly (cubomedusae) they are among the most dangerous marine animals giving extremely painful and sometimes fatal stings

The Medusa form of cnidarians is commonly know as a

Jellyfish or sea jelly

Describe what the development of tissues makes possible

Makes it possible for organisms to swim, respond to external stimuli, and engulf prey among other things

Hydrozoans (Cnidaria)

Many consist of feathery or busy colonies of tiny polyps. They attach to piling, shells, seaweeds, and other surfaces.

Cnidarians have a mouth is ________ located and surrounded by _______

Mouth is centrally located and surrounded by tentacles

What are Cnidarians primary weapon in capturing prey

Nematocysts (their stinging cells)

Nerve net

Neuron cells interconnected to form a net to transmit impulses in cnidarians

Do cnidarians have a brain or true nerves?

No. They do have specialized nerve cells or neurons. These cells interconnect to form a nerve net that transmits impulse in all directions.

What is a tissue level of organization

Organisms whose body is organized into groups of tissue. —as compared to a sponge that has a cellular level of organization

What is the phylum and class of Hydrozoans

Phylum Cnidaria, class Hydrozoa

The flower-like appearance of many cnidarians is a consequence of what

Radial symmetry

Phylum Cnidaria, Class Anthozoa

Sea anatomies and corals

In the Life history of cnidarians

Some have both a polyp and Medusa stage and some others spend their entire life either as polyp or medusa

nemotocysts

Stinging cells on tentacles used to capture prey

Describe AnthoZOans

The Cnidaria class that are solitary or colonial polyps that lack a Medusa stage.

Compare the Medusa form of Hydrozoans to scyphozoans

The Hydrozoans Medusa are tiny. Sea jellies make up large Medusa where the Medusa phase is the dominant stage of the life cycle of the scyphozoans

Compare how a Portuguese man of war swims to how a jellyfish or sea jelly swims

The Portuguese man of war (Hydrozoan) drifts on the current using a float; the sea jelly moves by contracting the bell of its Medusa

Describe the BIG Step represented by the evolution from Sponges to Cnidarians

The evolution of multicellular animals with tissues that perform specific functions (instead of just a group of cells like sponges)

Scyphozoans

The larger jellyfishes or sea jellies common in all oceans.

What is the characteristic larva of most cnidarians

The planula

What do Cnidarians eat

They are carnivores, animals that prey on other animals. —see anemone eating fish in pic

In addition to radial symmetry, cnidarians have ________ surface where the mouth is and a ______ on the opposite side

They have an oral surface where the mouth is and an a aboral surface on the opposite side

Describe how scyphozoans swim

They swim with rhythmic contractions of the bell of the Medusa. Their swimming ability is limited and they are easily carried by currents

The presence of ____________ allows cnidarians to perform more complex functions that sponges can

Tissues

What are corals made up of

Various groups of mostly colonial Anthozoan. Many of these have calcium carbonate skeletons and in tropical water the form coral reefs

radial symmetry

body plan in which body parts repeat around the center of the body or Axis.

planula

cylindrical ciliated stage consisting of two layers of cells. After a time in the plankton, the larva settles on the bottom and metamorphoses into a polyp or developed into a Medusa.

What are the two basic forms of cnidarians

polyp and medusa


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