What type of animals have no body cavity?

Animals with no body cavity are called acoelomates. This means they lack a fluid-filled space between their body wall and digestive tract.

Examples of acoelomates include:

* Flatworms (Platyhelminthes): This group includes planarians, tapeworms, and flukes. They have a flattened body shape that allows for efficient gas exchange and waste removal.

* Rotifers: These microscopic animals are found in freshwater habitats.

* Gastrotrichs: These tiny, worm-like animals are also found in freshwater habitats.

Why is a body cavity important?

A body cavity, or coelom, is a fluid-filled space that provides many advantages for animals, including:

* Support and structure: The coelom acts as a hydrostatic skeleton, allowing the animal to move and change shape.

* Organ protection: The coelom protects internal organs from damage.

* Circulation: The fluid in the coelom helps transport nutrients and waste products.

* Space for organs: The coelom allows for the development of complex organ systems.

While acoelomates lack a coelom, they have evolved other adaptations to survive without one. For example, they have a flattened body shape that allows for efficient gas exchange and waste removal.