Key Innovations in Animal Evolution Early biologists used

Last updated: 7/24/2022

Key Innovations in Animal Evolution Early biologists used morphology to study evolutionary trends in major animal groups. Tissue and tissue layers appeared early in animal evolution. Primary cell layers of tissue include the endoderm, ectoderm, and mesoderm. A few diploblastic animals have only two layers. Most animals exhibit either or Sponges are an exception and are Cephalization evolved in symmetrical animals. Many animals have body cavities that surround their internal organs. animals do not have a cavity muscles of the body symmetry animals have a fluid- or organ-filled space between the gut and wall animals have a fluid-filled body cavity lined by the peritoneum The fluid can serve as a hydrostatic skeleton and allows movement of the organism as well as provides support.