They are usually found living at the bottom of the sea, often attached to rocks.
Belonging to the animal kingdom, Coelenterata, or more commonly known as the Phylum Coelenterata are the simplest group of animals that fall under the category of invertebrates. They are usually found living at the bottom of the sea, often attached to rocks. Coelenterates are multicellular organisms and can be found living solitarily or also in groups. They can also be found sedentary or swimming about freely. The Phylum Coelenterata consists of marine organisms that have a body that is radially symmetrical and a mouth that has sensory tentacles that help in capturing prey easily. Other animals belonging to the Phylum Coelenterata are hydra, comb jellies, true jellies, sea pens, coral animals, sea anemones and more. Characteristics of Coelenterata Usually known to be the simplest of all animals groups, Coelenterates have true tissues and the gastrovascular cavity, which is the characteristic coelenteron. However, these organisms also have a few other characteristic features that make them highly different from other organisms in the animal kingdom, as listed below.
Common examples include Obelia, Hydra, Metridium, Rhizostoma, Xenia, Aurelia and more. Classification of Coelenterata Coelenterates can be classified into the following three categories:
Here is a more detailed explanation of the functions of each of the categories. Hydrozoa Hydrozoa belongs to Class I of the Coelenterates. It derives its name from Hydra: water and zoon: animal. These organisms have the following characteristic features.
As marine organisms, Hydrozoa exists in all three layers of the marine ecosystem. Some live on the surface and have large sail-like structures to keep them afloat above water, for example, Physalia and Velella. These also help in locomotion. Long tentacles that also have nematocysts or alternatively known as stinging cells that help Hydrozoa catch food that’s often below the surface. The second group of Hydrozoa live in the pelagic region, or more commonly known as the middle water zone. This is where organisms like Bougainvillea and Chelia exist. These organisms have long tentacles that help them jet propel themselves forward and sinking down rapidly when required. The third group of Hydrozoa exists in the bottom, that is the sea bed, where they usually anchor themselves to the rocks. A good example of these is Sea Corals. Scyphozoa Scyphozoa or Scyphomedusae belongs to Class II of the Coelenterates. These organisms have the following characteristics.
As a species, Scyphozoa can often be a source of trouble when they wash up on the beaches, or in they come in direct contact with humans. Jellyfish stings have often known to cause deaths or serious damage to humans. They are also sources of trouble when it comes to large scale fishing by often clogging the fishing nets or straying into communities. Anthozoa Anthozoa or Actinozoa belongs to Class II of the Coelenterates. These organisms have the following characteristics. These derive their name from Anthos: flower and zoios: animal.
Anthozoa can be of varying appearances. They can range anywhere from a half-inch to almost a two feet expanse of large clusters of sea pens. Colours can be as varied as red, purple, white, yellow, blue, violet and more.
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