AP BIOLOGY

Detailed explanation-1: -Flatworms (phylum Platyhelminthes) are simple animals that are slightly more complex than a cnidarian. Roundworms (phylum Nematoda) have a slightly more complex body plan. Segmented worms (phylum Annelida) are the most complex animals with worm-like body plans.

Detailed explanation-2: -nematode, also called roundworm, any worm of the phylum Nematoda. Nematodes are among the most abundant animals on Earth.

Detailed explanation-3: -So – “WHAT ARE NEMATODES?” They’re not insects or spiders or millipedes or anything with legs. Not earthworms or leeches or anything with segments. They belong to the Phylum Nematoda/Nemata (from the Ancient Greek “nema, ” for “thread” and “eides” for “species). They are the Roundworms.

Detailed explanation-4: -The three major worm phyla are Annelida, Nematoda, and Platyhelminthes. Worms in the Annelida phylum have bodies that are divided into sections, called segments. These worms have a closed circulatory system and muscular blood vessels that act like a heart, pumping blood throughout the body.

Detailed explanation-5: -Nematodes that commonly parasitise humans include ascarids (Ascaris), filarias, hookworms, pinworms (Enterobius), and whipworms (Trichuris trichiura).