protosomes/platyhelminthes

Protosomes

Triploblastic, spiral and determinate cleavage, the Blastopore becomes the mouth, the coelom cavity forms from the splitting of a solid block of mesoderm tissue

2 main groups of protosomes

Lophotrochozoans and ecdysozoans

Lophotrochozoa

They have an outer Skelton that expands with them as they grow and have ciliated cells

3 phyla’s within lophotrochozoa

Platyhelminthes, mollusca, annelida

Platyhelminthes

“Flatworms”, possess true organs, possess bilateral symmetry, and show some cephalization, incomplete digestion

Nerve ladder

Platyhelminthes have 2 main nerve cords that form this

Pharynx

Connects too a highly distributed internal cavity called a gastrovascular cavity

Protonephridia

Their excretory system consist of a network of tubules

Excretory pores

Body fluids travel through these tubes in the outer body wall to reabsorb valuable materials

Flame cells

Ciliated cells that establish the flow through their pores

Hemaphrodites

Most flatworms possess both sets of reproductive systems