Final Answer:
The major synapomorphies of Annelida include metamerism, chaetae (bristle-like structures), and a closed circulatory system.
Step-by-step explanation:
Annelida, commonly known as segmented worms, exhibits several synapomorphies that distinguish them within the animal kingdom. Metamerism, the segmentation of the body into repeating units called metameres, is a fundamental characteristic of annelids. This segmentation allows for a high degree of specialization and flexibility in movement. Each metamere typically contains a set of organs and structures, contributing to the overall efficiency of bodily functions.
Another key synapomorphy is the presence of chaetae, which are bristle-like structures made of chitin. These structures, often protruding from the body wall, provide support and aid in locomotion. The type and arrangement of chaetae can vary among different groups of annelids, reflecting adaptations to specific environments and lifestyles. The presence of chaetae is a defining feature that sets annelids apart from other phyla.
An additional distinctive characteristic is the closed circulatory system found in annelids. Unlike an open circulatory system where blood directly bathes the tissues, annelids have a closed system where blood is confined to vessels. This closed circulatory system enhances the efficiency of nutrient and gas exchange, facilitating a more rapid and controlled distribution of resources throughout the segmented body. In summary, metamerism, chaetae, and a closed circulatory system are major synapomorphies that collectively contribute to the unique identity of the Annelida phylum.
Full Question:
List the major synamorphies of Annelida