AP BIOLOGY

Detailed explanation-1: -Like humans, flatworms within the phylum Platyhelminthes exhibit external bilateral symmetry, which means that their flat bodies make a near-mirror image when divided head to tail on the sagittal plane. Unlike humans, flatworms also exhibit internal bilateral symmetry.

Detailed explanation-2: -Flatworms are bilaterally symmetrical with a defined head and tail region and a centralized nervous system containing a brain and nerve cords. Clusters of light-sensitive cells make up eyespots on either side of the head.

Detailed explanation-3: -Flatworms do not have a true body cavity, but they have bilateral symmetry. Because these do not have a body cavity, they are known as acoelomates. Flatworms have an incomplete digestive system. This means that their digestive tract has just one single opening.

Detailed explanation-4: -Flatworms’ bodies are bilaterally symmetrical and they have a defined head and tail region. They have a central nervous system containing a brain and a nerve cord.

Detailed explanation-5: -Bilateral symmetry is favored in members of the phylum Platyhelminthes because it allows for cephalization. Cephalization is the characteristic of some animals in which sensory organs and more complex neural structures are located at the anterior portion of the animal. For some, this is in a structure called the head.