Acoelomates

Definition

Acoelomates are animals that lack a body cavity or coelom between their digestive tract and outer body wall. They have a solid body with tissues filled in the space where a coelom would be.

5 Must Know Facts For Your Next Test

1. Acoelomates include flatworms such as planarians, flukes, and tapeworms.
2. They exhibit bilateral symmetry, meaning their left and right sides are mirror images.
3. Acoelomates possess three germ layers: ectoderm, mesoderm, and endoderm.
4. The lack of a body cavity affects their organ development and function.
5. They rely on diffusion for gas exchange and nutrient distribution due to the absence of circulatory systems.

Review Questions

• What is the defining characteristic of acoelomates?
• Name an example of an animal that is an acoelomate.
• How does the absence of a coelom impact the physiology of acoelomates?

Related terms

Coelomates: Animals with a true body cavity completely lined by mesodermal tissue.

Pseudocoelomates: Animals with a body cavity that is not entirely lined by mesodermal tissue.

Bilateral Symmetry: A type of symmetry where an organism can be divided into mirrored left and right halves along one plane.