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Gastrulation has been celled "the most important time of
your life" (Lewis Wolpert); without it you would be flat
like a pancake! It is the process by which the simple
structure of the blastula is transformed into the complex,
3-dimensional structure of the basic body plan by a series
of cell shape changes and rearrangements. Due to basic
differences in the construction of the early embryos (e.g.
amount of yolk), the movements of gastrulation are
dramatically different in different orders of
animals.
The
movements of gastrulation have been visualized by staining
small regions of the surface. The stained groups of cells
were followed, originally manually and recently using
time-lapse microscopy. The cells of the blastula can be
divided into three groups according to which of the three
germ layersthey will
become. The cells that remain on the outside will give rise
to the ectoderm. The cells that end up in the middle
to form the gut tube and associated organ are known as the
endoderm. The cells that end up in between are the
mesoderm.
Each
group is to construct 4models
depicting sequential stages of gastrulation of a particular
organism (sea urchin, chordate, fish, amphibian, chick or
mouse) using the colored clay that is available. Use the
handouts and figures in your text as guides. In keeping with
the conventions of developmental biology, use specific
colors to represent the different layers and structures as
follows:
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