EVERYDAY SCIENCE

Detailed explanation-1: -Flatworms are not coelomates. They don’t have a body cavity; hence called acoelomates. They have an incomplete digestive system, with only one opening. These organisms do not have a fluid-filled cavity between the digestive tract and the body wall.

Detailed explanation-2: -Features of the Flatworms 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-3: -In acoelomates, the mesodermal cells attach to the sides of other cells, via an extracellular matrix. They are devoid of the body cavity. Thus, the organs formed are completely surrounded by the mesoderm.

Detailed explanation-4: -Flatworms (Platyhelminthes) are acoelomates i.e. they lack a coelom. Molluscs and insects (Arthropoda) are coelomates as they have a true coelom derived from the germ layer mesoderm.

Detailed explanation-5: -An acoelomate is an animal which lack a coelom, or formal body cavity. True body cavities form only in multicellular organisms with true tissues.