Marine Biology, Chapter 9, 9.1 Cnidarians
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
