Unformatted text preview: y - produced by pinching off pockets of coelom pockets coelom 4 Cell Fate Cell Developmental Patterns Regulative
(Indeterminate) = Cell fate not set at 4 cell stage separate at 4 cell stage 4 identical individuals Patterns of cell division = Cleavage Radial = regular, equal regular,
(e.g., echinoderms) Spiral = unequal, oblique unequal,
(e.g., molluscs) Mosaic
(Determinate) = Cell fate set very early separate at 4 cell stage no development of complete animal Fate of the blastopore: Correlations of Developmental Traits Protostome Blastopore becomes mouth Protostome
Schizocoely Spiral Cleavage Mosaic Development Annelida Mollusca Arthropoda Echiura Sipuncula Deuterostome
Enterocoely Radial Cleavage Regulative Development Echinodermata Hemichordata Chordata Deuterostome Blastopore does not become mouth Lophophorate Phyla Brachipoda – brachiopods, most extinct “Problem” Phyla - share synapomorphy - Lophophore Phoronida Radial Cleavage Blastopore becomes mouth Radial Cleavage Blastopore does not become mouth Radial Cleavage Blastopore does not become mouth Phoronida - phoronid worms Bryozoa - bryozoans, moss animals
important fouling species Bryozoa = Ectoprocta Brachiopoda Share protostome and deuterostome Share protostome and deuterostome characteristics 5 Morphology Difficult to measure / quantify Hard to determine homologies Hard to determine convergence Use of RNA and DNA sequences Select molecules that change at rate appropriate to level of resolution needed ?what about natural selection and convergence in these traits? Different Datasets Different trees Different Analyses on Same Dataset Different trees Many unexpected findings emerge Challenges Getting enough information for enough taxa If radiation was rapid, molecular information may not give good resolution among taxa Genes (and genomes) evolve Assume changes in sequences random Finding genes / genomes that change at an appropriate rate and others.... Protostome...
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This note was uploaded on 01/27/2010 for the course BIO 37282 taught by Professor Padilla during the Fall '10 term at SUNY Stony Brook.
- Fall '10