Final answer:
Leeches are not nematodes; they belong to the phylum Annelida. Nematodes, or roundworms, are unsegmented worms classified in the phylum Nematoda. Differences in body shape and anatomy distinguish Platyhelminthes (flatworms) and Nematoda.
Step-by-step explanation:
Which of these worms are nematodes?
Leeches are not considered nematodes. Nematodes, also known as roundworms, are a group of worms characterized by their round, non-segmented bodies and are classified in the phylum Nematoda. The phylum Nematoda includes over 28,000 known species, such as hookworms, pinworms, and Ascaris which is a large intestinal roundworm. The diversity of nematodes is immense, with species inhabiting a wide range of environments. Nematodes play a key role in nutrient cycling and are used as model organisms in research.
Leeches, on the other hand, belong to the phylum Annelida and are part of the class Hirudinea. They are segmented worms, which clearly distinguishes them from the unsegmented nematodes. Therefore, it is incorrect to classify leeches as nematodes.
In terms of their contribution to the carbon cycle, free-living nematodes help decompose organic material, releasing carbon dioxide into the atmosphere. As for preventing pinworm infections, maintaining good hygiene, such as regular handwashing and cleaning surfaces, can reduce transmission. Platyhelminthes and Nematoda are different phyla due to differences in morphology, such as the flat body of platyhelminthes as opposed to the round body of nematodes, and their respective anatomies.