Diploblasts

Definition

Diploblasts are animals that develop from two primary germ layers: the ectoderm and the endoderm. They lack a mesoderm, which is present in more complex animals called triploblasts.

5 Must Know Facts For Your Next Test

1. Diploblasts include organisms like cnidarians (jellyfish, corals) and ctenophores (comb jellies).
2. The two germ layers in diploblasts lead to simpler body structures compared to triploblasts.
3. Diploblastic organisms typically exhibit radial symmetry.
4. Because they lack a mesoderm, diploblasts do not form true organs or complex tissues.
5. The ectoderm forms the outer layer of the organism while the endoderm forms the inner layer, including the gut.

Review Questions

• Which animal groups are considered diploblasts?
• What are the two primary germ layers found in diploblastic organisms?
• Why don't diploblasts form true organs or complex tissues?

Related terms

Ectoderm: The outermost germ layer in an embryo that develops into skin and nervous tissue.

Endoderm: The innermost germ layer that develops into the lining of the digestive tract.

Triploblasts: Animals that develop from three primary germ layers—ectoderm, mesoderm, and endoderm—allowing for more complex body structures.