Bilateral symmetry,cylindrical bodies and double openings are characteristic features of

Explanation

Nematodes are bilaterally symmetrical. Bilaterally symmetrical means that an organism can be divided lengthwise into two identical halves that are mirror images of each other. Nematodes have two openings: a mouth and an anus. This is because they have a complete digestive system, also known as an alimentary canal. 

Here are some other characteristics of nematodes:

• Bilateral symmetry: Nematodes have identical right and left halves. 
• Cylindrical shape: Nematodes have a cylindrical body shape. 
• Sexually dimorphic: Most species of nematodes have both males and females. 
• No circulatory system: Nematodes don't have a circulatory system, so they transfer nutrients and oxygen to their cells through diffusion. Hydra is not bilaterally symmetrical; it exhibits radial symmetry, meaning its body can be divided into equal halves along any plane through its central axis. Protozoans are single-celled organisms that lack a true mouth and anus, instead they have a single opening that serves both the entrance and exit point for nutrients, wastes and other materials. E.g Amoeba, paramecium etc. Protists also have a single opening, though certain types of algae or protozoans with complex cell structures might have multiple openings for feeding, reproduction etc(dinoflagellates, ciliates like paramecium), but generally, protists don't have double openings in the classical sense.

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