Planaria and tapeworms are examples of which group?

Planaria and tapeworms are examples of which group?

• A. Flatworms
• B. Roundworms
• C. Nematodes
• D. Annelids

Answer: (A)

Planaria and tapeworms are flatworms, a phylum known as Platyhelminthes. Their bodies are ribbon-like and flattened top-to-bottom, which gives a large surface area relative to volume and allows diffusion to meet their metabolic needs. They are acoelomates, lacking a true body cavity. Planaria are free-living flatworms with a simple, branching gut, while tapeworms are parasitic and lack a digestive system entirely, absorbing nutrients directly through their surface and attaching to hosts with a specialized scolex, with reproductive units called proglottids along their length. This combination of body shape, absence of a true body cavity, and these digestive/attachment traits distinguishes them from roundworms (cylindrical, pseudocoelomate with a complete digestive tract) and annelids (segmented, true coelomates).