First complex animals Intro to Animal Development 650 mya Soft-bodied; radial & bilateral symmetry Today’s topics: • The origin of multicellular animals • Variation in animal body plans • Intro to Development
29 March 2010
Simple Animal Phylogeny Is this your ancestor?
Colonial Choanoflagellates Individual choanoflagellate are the sister group to all other animals Choanoflagellates
OTHER EUKARYOTES Sponges Animals
Collar cell (choanocyte) Other animals Not fully multicellular organisms
Sponges Anatomy of a sponge
Fig 33.4
1 It’s what’s between cells that defines Tissue Compatibility multicellularity in animals.
Integrin http://www.scielo.br/scielo.php?pid=S1982-56762008000500007&script=sci_arttext
Fig. 32-UN1 Fig. 32-7 Common ancestor of all animals Metazoa Metazoa Sponges (basal animals)
Ctenophora Eumetazoa
Cnidaria (a) Radial symmetry Bilateria (most animals) Bilateria True Acoela (basal tissues bilaterians) Deuterostomia
Bilateral summetry Lophotrochozoa Three germ layers Ecdysozoa (b) Bilateral symmetry
Fig. 32-9 Fig. 32-11 “Porifera” Protostome development Deuterostome development Silicea (examples: molluscs, (examples: echinoderm, Metazoa annelids) chordates) Calcarea (a) Cleavage ANCESTRAL Eight-cell stage Eight-cell stage COLONIAL Ctenophora FLAGELLATE Eumetazoa Cnidaria
Acoela Deuterostomia Spiral and determinate Radial and indeterminate (b) Coelom formation Echinodermata
Key Bilateria Coelom Ectoderm Chordata Mesoderm Archenteron
Endoderm Platyhelminthes
Coelom Lophotrochozoa Rotifera Mesoderm Blastopore Blastopore Mesoderm Ectoprocta Solid masses of mesoderm Folds of archenteron split and form coelom. form coelom. Brachiopoda (c) Fate of the blastopore Anus Mouth Mollusca
Annelida Digestive tube Ecdysozoa Nematoda
Mouth Anus Arthropoda
Mouth develops from blastopore. Anus develops from blastopore.
2 Fig. 32-2 Developmental Processes Blastula and Gastrula
Blastocoel
Endoderm Cleavage Cleavage Blastula
Ectoderm
Archenteron Zygote Eight-cell stage Gastrulation Essential concepts Gastrula Blastocoel Blastopore • Cell Determination & Differentiation Cross section of blastula • Differential Rate & Timing of cell division • Programmed cell death • Tissue and Organ development
Fig. 47-UN3 The cells in the three germ layers have defined fates in the adult: Gastrulation
Sea urchin Frog Chicken
Details differ, but all result in the development of 3 tissue layers Fig 47.14
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