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Non-chordates I

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Non-chordates I - Lesson Summary

Animals belonging from phylum Porifera to phylum Echinodermata are categorised as non-chordates. Non-chordates are animals without a notochord. 

The first phylum under non-chordates is Porifera. The members of this phylum are known as sponges. These are primitive, multicellular, asymmetrical, marine animals with cellular level of organisation. Sycon, Spongilla and Euplectella are some common examples of sponges. 

The second phylum is Coelenterata.

The members of this phylum are aquatic, mostly marine, sessile or free-swimming, radially symmetrical, diploblastic animals with tissue level of organisation.

Some coelenterates, like corals, have a skeletal structure made of calcium carbonate. Coelenterates have cnidoblasts on their tentacles and body, and hence, this phylum is also known as Cnidaria.

Cnidoblasts are used for anchorage, defence and to capture prey. Some common Coelenterates are Physalia, Pennatula, Gorgonia and Meandrina. 

The next phylum is Ctenophora. Ctenophores are commonly known as sea walnuts or comb jellies. These animals are marine, radially symmetrical, diploblastic with tissue level of organisation. They have eight external rows of ciliated comb plates, which help in locomotion. Pleurobrachia and Ctenoplana are some common ctenophores.

The next phylum is Platyhelminthes. They are bilaterally symmetrical, triploblastic, acoelomate animals with organ level of organisation. Flatworms are mostly endoparasites found in the digestive system of animals, including humans.The parasitic members possess hooks and suckers, and some of them use the surface of their body to absorb nutrients directly from the host. Taenia and Fasciola are some common flatworms. 

The next phylum under non-chordates is Aschelminthes. Unlike flatworms, these animals have a circular body when seen in cross-section, and hence, are called roundworms. They may be aquatic or terrestrial, free-living or parasitic in plants and animals. They are bilaterally symmetrical, triploblastic, pseudocoelomate animals with organ-system level of body organisation. Ascaris and Wuchereria are common members of this phylum. 


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