BIOL 1108 Lecture Notes - Lecture 16: Symmetry In Biology, Lophotrochozoa, Gastrulation
Document Summary
Bilaterians, including protostomes and deuterostomes, have bilateral symmetry and develop from three germ layers. Determine cleavage: cell fate is set in early embryo development. Mouth pore forms first in the gastrula. Anal pore opens first in the gastrula. Indeterminate cleavage: cell fate is set much later in the blastula (stem cells) Determinate cleavage - cell fate determined early in embryonic development. Remember, the bilateria are divided between the protostomes and deuterostomes. Lophotrochozoa and ecdysozoa make up the protostomes. Bilaterian animals have bilateral symmetry and complex organs that develop from a triploblastic embryo. This anatomical complexity makes possible types of locomotion, feeding, gas exchange, behavior, and reproduction that are unknown in earlier branching groups. Many are parasites of vertebrates, have a syncytial tegument, and have complex life cycles. Flatworms: trematodes and cestodes (tapeworms) that parasitize only animals. The life cycle includes the larvae encysting in muscle of host as well as adults living in gut.
