Which one among the following is a free living animal ?

Among the given options, Planaria is the only free-living animal. Planarians are non-parasitic flatworms belonging to the class Turbellaria within the phylum Platyhelminthes [1]. Unlike parasites, free-living organisms like Planaria are capable of finding and digesting their own food without depending on a host [2]. In contrast, the other options are obligate parasites. Liver fluke (Fasciola) is a parasitic trematode that typically infects the livers of sheep and humans [1]. Wuchereria (specifically Wuchereria bancrofti) is a parasitic roundworm responsible for lymphatic filariasis. Plasmodium is a parasitic protozoan that requires two hosts—a vertebrate and an insect—to complete its life cycle and is the causative agent of malaria. Planaria is also widely studied in biological research for its remarkable ability to regrow from body fragments [2].

Sources

1. [1] https://uou.ac.in/sites/default/files/slm/ZO(N)-101.pdf
2. [2] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 13: Our Home: Earth, a Unique Life Sustaining Planet > Ever heard of ... Ever heard of ... > p. 221