BISC 1112 Lecture Notes - Lecture 4: Gonopore, Tube Feet, Arthropod
Document Summary
Bilaterians- animals that are symmetric bilaterally: blastopore- is an opening into the embryo. Protostomes- the blastopore becomes the mouth ( mouth first) Deuterostomes- the blastopore becomes the anus ( anus first) Cell division is radial: mesoderm- appears in the bastocoel between the ectoderm and endoderm. In most bilaterians, a body cavity or coelom is formed. If no coelom is formed, the animal is acoelomate. If the coelom is lines on only one side by the mesoderm, the animals is pseudocoelomate. If the coelom is lines on all sides by mesoderm, the animal has a true coelom (2 types: 1) schizocoelom- forms from splitting the mesoderm. Occurs in protostomes that have a true coelom: 2) enterocoelom- forms from pockets that form on the side of the gut. Protostomes- flatworms, molluscs, annelids, nematodes, arthropods: flatworms: phylum platyhelminthes. Gas exchange take place across the body wall (no respiratory system) Nutrients move through the body by diffusion (no circulatory system)
