Understanding Free-Living Animals in Biology

The question asks us to identify which of the given options represents a free-living animal. A free-living organism is one that lives independently, not in or on another organism. It finds its own food and shelter and reproduces without relying on a host.

Analyzing the Options

Let's examine each option to see if it fits the description of a free-living animal:

1. Leech

Leeches belong to the phylum Annelida. While some leech species are indeed predators that hunt other small invertebrates and can be considered free-living, many species are parasitic, feeding on the blood of vertebrates. Therefore, a leech is not exclusively free-living.

2. Tapeworm

Tapeworms (Class Cestoda) are endoparasites. This means they live *inside* the digestive tract of a host animal (like humans or other mammals) and absorb nutrients directly from the host's food. They cannot survive independently and are definitely not free-living.

3. Wuchereria

Wuchereria is a genus of parasitic nematodes (roundworms). Species like Wuchereria bancrofti cause diseases like lymphatic filariasis (elephantiasis) in humans. These worms live within the lymphatic system of their hosts. They are obligate parasites and cannot live freely.

4. Planaria

Planarians are commonly known as freshwater flatworms and belong to the class Turbellaria. Most species of Planaria are predatory and scavenge for food in aquatic environments like freshwater ponds, lakes, and streams. They live independently, find their own food, and are not dependent on a host. This makes them classic examples of free-living animals.

Conclusion

Based on the analysis:

• Leeches can be parasitic or free-living predators.
• Tapeworms are exclusively endoparasites.
• Wuchereria are exclusively endoparasites.
• Planaria are predominantly free-living predators and scavengers.

Therefore, Planaria is the best fit for the description of a free-living animal among the given choices.