Class 9 Biology Diversity In Living Organisms Platyhelminthes


The organisms belonging to this group are complexly designed.

The body of these organisms has bilaterally symmetrical shape. This means that the design of the left and the right halves of the body are alike.

These organisms have three layers of cells that makes up differentiated tissues due to which such animals are called triploblastic.

These organisms have no true internal body cavity or coelom.

The body of these organisms is flattened dorsiventrally which means from top to bottom due to which these animals are also called flatworms.

These organisms are either freely existing or parasitic.

Examples of animals belonging to this group are planarians, or parasitic animals like liverflukes.

Fig. Planaria (left) and Liverflukes (right)

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