BIOL 371 Lecture Notes - Lecture 3: Protostome, Gastrulation, Sponge
Document Summary
Embryonic tissue folds in to form two layers, the inner is called the endoderm, outer=ectoderm. Diploblastic (radial) have ecto/endoderm= only has two layers (ex: cnidarian) Tripoblastic (bilateral) have ecto/meso/endoderm= has middle layer (mess) Bilateral species have cephalization ( a clear head end with function concentrated at one end) Sponges, assymetrical and have no true tissues, called porifera bc they are porous. Within the biletaria there is a fundamental distinction into two big lineages: the protostomia and the deuterostomia. The most diverse lineage is insects names= how the organism develops. Protostomia go into the ecdysoza (these most, they have a rigid cuticle they need to shed to grow) The deuterstomia split into chordata (humans) and ambulacra (sea urchins etc) Hox genes: master control switch, turn genes on and off. Acoelomate have no spaces in the mesoderm, they have a solid body well.
