The Cnidaria phylum is made up of several classes of invertebrates:
- Anthozoa (sea anemones, corals);
- Cubozoa (box jellyfish);
- Hydrozoa (hydrozoans, also known as hydromedusae or hydroids);
- Scyphozoa or Scyphomedusae (jellyfish); and the
- Staurozoa (stalked jellyfish).
What are the three major classes of cnidarians?
- Gastropods. Gastropods include snails and slugs. They use their foot to crawl.
- Bivalves. Bivalves include clams, scallops, oysters, and mussels.
- Cephalopods. Cephalopods include the octopus and squid.
Which characteristic do scientists use to classify cnidarians?
Polymorphism refers to the occurrence of structurally and functionally more than two different types of individuals within the same organism. It is a characteristic feature of Cnidarians, particularly the polyp and medusa forms, or of zooids within colonial organisms like those in Hydrozoa.
What are unique characteristic common to the cnidarians?
Characteristic Features of Cnidaria: 1. Cnidarians are aquatic and radially symmetrical animals. ADVERTISEMENTS: 2. Body represents tissue grade of organization but no organs or rarely organs. 3. Embryonic cnidaria are diploblastic in nature with an outer layer of ectoderm (develops epidermis in adult) and an inner layer of endoderm (develops ...
What classes does the phylum Cnidaria contain?
The phylum Cnidaria contains about 10,000 described species divided into four classes: Anthozoa, Scyphozoa, Cubozoa, and Hydrozoa. The anthozoans, the sea anemones and corals, are all sessile species, whereas the scyphozoans (jellyfish) and cubozoans (box jellies) are swimming forms. The hydrozoans contain sessile forms and swimming colonial ...
What were cnidarians first classified as?
Cnidarians were formerly grouped with ctenophores in the phylum Coelenterata, but increasing awareness of their differences caused them to be placed in separate phyla.
What are the general characteristics of Cnidaria?
Cnidarians exhibit a specific characteristic – tentacles with stinging nematocytes which serve as small harpoons which react to stimuli by giving out tiny stinging cells which can poison and hook potential prey. Cnidarians do not show bones and a central nervous system, rather have a nerve net.
Why are cnidarians classified as animals?
Cnidaria are some of the simplest and most beautiful "animals." These creatures are flower-like and resemble plants in many respects. However, they have a mouth and a simple digestive system at the center of their tentacles. Because of these two features, these creatures are considered animals and not plants.
What are 3 characteristics that all cnidarians have in common?
What are three characteristics that all cnidarian have in common? Cnidarians have an epidermis, gastrodermis, mesoglea, gastrovascular activity and tentacles. Also, they have cnidocytes and a nervous system composed of diffuse web of interconnected nerve cells called a nerve net.
What are three classes of cnidarians?
Major Groups of Cnidarians. Cnidarians are divided into three major classes. These are the Hydrozoa (hydras and other colony-forming species), the Scyphozoa (jellyfish), and the Anthozoa (sea anemones and corals).
What are they called cnidarians?
noun. any invertebrate animal, as a hydra, jellyfish, sea anemone, or coral, considered as belonging to the phylum Cnidaria, characterized by the specialized stinging structures in the tentacles surrounding the mouth; a coelenterate. adjective.
What type of symmetry do cnidarians have?
radial symmetryThe bilateral symmetry of Cnidaria is thought to be inherited from the common ancestors of both cnidarians and triploblastic bilaterians. The secondary radial symmetry of Cnidaria evidently is a result of the adaptation to the sessile mode of life.
How do cnidarians get their name?
The phylum Cnidaria (pronounced “nih DARE ee uh”) includes soft-bodied stinging animals such as corals, sea anemones, and jellyfish (Fig. 3.23 A). The phylum's name is derived from the Greek root word cnid- meaning nettle, a stinging plant. Cnidarians are found in many aquatic environments.
What are five characteristics of cnidarians quizlet?
Cnidarian Characteristics:aquatic; majority marine.Have dipoblastic tissues.Sac-like gut (gastrovascular cavity, incomplete digestive tract)Radial symmetry.Tentacles.Two lifecycle stages.Ciliated planula larva.Nerve net, non polarized.More items...
What are two characteristics common to all cnidarians?
Two characteristics that all cnidarians share are radial symmetry and tentacles with stinging cells. Hydra and other cnidarians are radially symmetrical—able to asexually divide into identical pie-shaped segments, like a flower pot. Cnidarians also feature tentacles with stinging cells.
Which cells are characteristic of Cnidaria?
Nearly all (about 99 percent) cnidarians are marine species. Cnidarians contain specialized cells known as cnidocytes (“stinging cells”) containing organelles called nematocysts (stingers). These cells are present around the mouth and tentacles, and serve to immobilize prey with toxins contained within the cells.
Which of the following is a characteristic associated only with cnidarians?
Which of the following is a characteristic associated only with cnidarians? cnidocytes specialized for defense and capturing prey.
Radial Symmetry
The radial symmetry of these jellyfish is apparant when they are viewed top-down.
Cnidocyte Organelles
The tentacles of cnidarians have cnidocytes embedded within them. The cnidocytes of this jellyfish contain stinging nematocysts.
Diet and Eating Habits
The mouth of a cnidarian is located on the top (polyp) or under the bell (medusa) and is surrounded by tentacles.
Coral Facts and Classification
Corals belong to a group of cnidarians known as the Anthozoa. There are many types of coral and it should be noted that the term coral does not correspond to a single taxonomic class. Some groups of corals include:
Sea Anemones Facts and Classification
Sea anemones, like corals, belong to the Anthozoa. Within the Anthozoa, sea anemones are classified in the Actiniaria. Sea anemones remain polyps for their entire adult life, they never transform into the medusa form as jellyfish do.
Hydrozoa Facts and Classification
Crossota, a deep red medusa found just off the bottom of the deep sea. Alaska, Beaufort Sea, North of Point Barrow.
Scientific Name: Cinadaria
Jennifer Kennedy, M.S., is an environmental educator specializing in marine life. She serves as the executive director of the Blue Ocean Society for Marine Conservation.
Description
There are two types of cnidarians, called polypoid and medusoid. Polypoid cnidarians have tentacles and a mouth that face up (think of an anemone or coral). These animals are attached to a substrate or colony of other animals. Medusoid types are those like jellyfish—the "body" or bell is on top and tentacles and mouth hang down.
Habitat and Distribution
With thousands of species, cnidarians are diverse in their habitat and are distributed in all the world's oceans, in polar, temperate, and tropical waters. They are found in a variety of water depths and closeness to shore depending on the species, and they may live anywhere from shallow, coastal habitats to the deep sea .
Diet and Behavior
Cnidarians are carnivores and use their tentacles to feed on plankton and other small organisms in the water. They fish using their stinging cells: when a trigger at the end of the cnidocyte is activated, the thread unfurls outward, turning inside out, and then the thread wraps around or stabs into the tissue of the prey, injecting a toxin.
Reproduction and Offspring
Different cnidarians reproduce in different ways. Cnidarians can reproduce asexually by budding (another organism grows off the main organism, such as in anemones), or sexually, in which spawning occurs. Male and female organisms release sperm and eggs into the water column, and free-swimming larvae are produced.
Conservation Status
Cnidarians such as jellyfish are likely to be tolerant of climate change—in fact, some are even thriving and ominously taking over the habitats of other lifeforms—but corals (such Acropora spp) are listed as threatened by ocean acidification and environmental damage, according to the International Union for Conservation of Nature (IUCN).
Cnidarians and Humans
There are many ways cnidarians may interact with humans: They may be sought-after in recreational activities, such as scuba divers going to reefs to look at corals. Swimmers and divers may also need to beware of certain cnidarians because of their powerful stings.
