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Difference between Coelenterates and Platyhelminthes - Testbook

Last Updated on Jul 31, 2023
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The vast world of invertebrates within the Kingdom Animalia is divided into many phyla. Among these, two of the most basic ones are Phylum Coelenterata and Platyhelminthes.

The primary distinguishing characteristic between Coelenterata and Platyhelminthes is the number of germ layers in the organisms. Members of the Phylum Platyhelminthes are triploblastic invertebrates, while those of the Coelenterates Phylum are diploblastic.

A Closer Look at Coelenterates
  • Coelenterates, also known as Cnidaria, are the most basic type of invertebrate in the animal kingdom.
  • These aquatic creatures are diploblastic, meaning they have an endoderm (forming the inner lining of the body) and an ectoderm (forming the outer layer of cells).
  • They are distinguished by a digestive cavity that forms the main body, which includes entities such as corals, jellyfish, and sea anemones.
  • Coelenterates have a jelly-like, radially symmetric structure, with a nerve net and an opening surrounded by sensory tentacles. They typically have colloblasts or nematocysts for capturing planktonic prey.
  • These organisms lack a special circulatory system and rely on diffusion through tissue layers for nutrient distribution.
  • Coelenterates can regenerate and reproduce both sexually and asexually.
  • Examples include Physalia, Aurelia, and Metridium.

Delving into Platyhelminthes
  • Platyhelminthes, commonly known as flatworms, are relatively simple invertebrates with an unsegmented, bilaterian, and soft body. The body is covered with a soft layer, with or without cilia.
  • These organisms are acoelomates and lack a special circulatory or respiratory structure. This limits them to a flat shape, allowing nutrients and oxygen to pass through their bodies by diffusion.
  • The digestive cavity in Platyhelminthes has a single opening for both ingestion and egestion.
  • Generally, these are parasitic, triploblastic organisms where the ectoderm is specialized with a clear epidermis.
  • Platyhelminthes are hermaphrodites, meaning they have both male and female reproductive cells in the same body.
  • Examples include Dugesia, Fasciolopsis, and Echinococcus.

Highlighting the Differences between Coelenterates and Platyhelminthes

The following table outlines the key differences between Coelenterates and Platyhelminthes.

Coelenterates

Platyhelminthes

Nature
Primitive invertebrates, diploblastic with only endoderm and ectoderm Typically parasitic, triploblastic with a specialized ectoderm having a clear epidermis
Occurrence in Nature
Free-living, solitary, and sedentary forms Both parasitic and free-living forms
Symmetry
Radial Bilateral
Cellular Organization
Tissue level organization Organ level organization
Special Structures
Nematocysts Pro-nephridia with flame cells
Presence of Cnidocytes
Yes No
Presence of Coelom
Yes No
Fertilization Type
Both external and internal Internal
Notable Members
Physalia, Aurelia, Metridium Dugesia, Fasciolopsis, Echinococcus

This article has explored some differences between Coelenterates and Platyhelminthes. For more informative articles, continue to visit our site.

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Frequently Asked Questions

The differentiating factor between Coelenterata and Platyhelminthes is the germ layers in the entities. While members belonging to the Phylum Platyhelminthes are triploblastic invertebrates, members belonging to the Coelenterates Phylum are diploblastic.

Examples of Coelenterates include Hydra, Xenia, Rhizostoma, etc.

Examples of Platyhelminthes include Taenia solium, Planaria, Schistosoma, Fasciola.
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