Worms are a diverse group of animals that are generally characterized by their long, cylindrical, tube-like bodies, lack of limbs, and usually no eyes. They are invertebrates, meaning they do not have a backbone, and exhibit bilateral symmetry, meaning their body can be divided into two mirror-image halves
. There are many different types of worms, which belong to several unrelated animal groups. The main categories include:
- Flatworms (Platyhelminthes): These have soft, flat bodies and can be found in freshwater, marine, and damp terrestrial environments. Many flatworms are parasitic, such as flukes and tapeworms
- Roundworms (Nematodes): These have tubular bodies with openings at both ends and are more advanced than flatworms. They live in various environments and many are parasitic, causing diseases in humans and animals
- Segmented worms (Annelids): These worms have bodies divided into segments and possess organ systems like circulatory, digestive, and nervous systems. Examples include earthworms, leeches, and marine bristle worms. They are often found in wet environments like soil and oceans
Worms vary greatly in size, from microscopic species to some marine worms that can exceed 30 meters in length. They inhabit a wide range of habitats, including marine, freshwater, terrestrial soil, and as parasites inside other animals
. Some worms are free-living and play important ecological roles, such as earthworms that condition soil, while others are parasitic and can infect humans, animals, and plants, sometimes causing diseases
. In summary, "worms" is a general term for many unrelated groups of legless, elongated invertebrates with simple body structures, found worldwide in diverse environments, and including both free-living and parasitic species
