BIOL 305 Lecture Notes - Lecture 16: Animal, Mesoglea, Siphonophorae
7 Jun 2019
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Take notes on the fish; behaviour, anatomy, etc. Comparative embryology of metazoa the building blocks: body plans quite similar across all chordates, corals animals with no brains, generating a complex structure. Porifera: few cell types, choanoflagellates integrated together, attached to basement membranes. Epithelial tissue: not a single metazoan without epithelia, primary tissue for metazoans. Cnidaria: development of a new tissue structure: endoderm, between endoderm and ectoderm is the mesoglea, mesoglea contains muscle tissue. Muscle tissue: third primary muscle tissue in metazoans (excluding porifera) After blastula formation = gastrulation: when invagination occurs, slow pushing in of the cells, cells that are pushing in become determined as endoderm, cells attached to these are determined as mesoderm, mesoderm is where muscles are derived from. Exceptions to this kind of development: siphonophores (cnidarians) do something different after blastula formation, they have 2 growth zones, growth zones grow laterally, pushing new cells down, oldest cells are the ones at the tips of the colony.
