The major evolutionary feats shared by Platyhelminthes, Nematoda, and Annelida are having an organ system level of organization, bilateral symmetry, and a triploblastic body structure. These feats indicate the evolution of distinct organ systems and specialized germ layers in these animals. Nematoda additionally exhibits a pseudocoelomate body cavity and a complete digestive system. Annelida displays segmented body structures and the presence of a circulatory system.

1. What are the major evolutionary feats shared by all 3 phyla( Platyhelminthes, Nematoda, and
Annelida)? What are the implications of these evolutionary feats? What two additional
evolutionary feats are exhibited by Nemotoda? And 2 feats by Annelida?
Solution
Answer:
The major evolutionary feats shared by Platyhelminthes, Nematoda and Annelida are:
1. Level of Organization- Organ system level of organization
The organisms possesses distinct organ systems which marks the evolution of organ systems in
animals.
2. Symmetry - Bilateral
This is often a result of moving in one direction, thus having a “head” end.
3. Triploblastic
They share common body wall organization, consisting of 3 layers. Three germ layers are
evidence of slowly adapting layers of developmental control during embryogenesis as cells
specialized for greater efficiency.
Two additional evolutionary feats exhibited by Nematoda are:
1. Coelom- Pseudocoelomate
2. Digestive system -Complete
Two feats of Annelida are:
1. Segmentation - Presented
2. Circulatory system -Present