Which group of helminths has an unsegmented, round body plan and are excellent decomposers? trematodes
cestodes
annelids
nematodes
The correct answer and explanation is:
The correct answer is nematodes.
Nematodes, also known as roundworms, are a group of helminths with an unsegmented, cylindrical, or round body plan. Their body is covered by a tough outer cuticle, and they have a simple digestive system with a mouth and an anus. Nematodes can vary greatly in size and habitat, and they are found in nearly all ecological niches, from soil to aquatic environments.
One of the notable roles of nematodes is their function as decomposers. Many species of nematodes play an essential part in breaking down organic matter in the environment. They contribute to nutrient cycling by feeding on decaying plant material, microorganisms, and detritus. By doing so, they help return important nutrients to the soil, promoting the growth of plants. This decomposition process is vital for maintaining soil fertility and overall ecosystem health.
Nematodes can be free-living or parasitic. Free-living nematodes, in particular, are abundant in soil ecosystems and are key players in the decomposition of organic material. In contrast, parasitic nematodes can infect plants, animals, and humans, causing various diseases. However, their ecological role as decomposers is invaluable, as they help maintain the balance of nutrients in ecosystems.
While trematodes (flukes), cestodes (tapeworms), and annelids (segmented worms) are also types of helminths, they do not share the same characteristics as nematodes. Trematodes and cestodes typically have more complex body structures, often with segments or suckers for attachment to hosts. Annelids, such as earthworms, are segmented, which distinguishes them from the unsegmented nematodes.
In summary, nematodes are the group of helminths known for their unsegmented, round body plan and their crucial role as decomposers in ecosystems.