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Animal development Principles of Biology, 21 April 2009 Donald Winslow References: Hickman, Cleveland P.; et al. 2008. Integrated Principles of Zoology,

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Presentation on theme: "Animal development Principles of Biology, 21 April 2009 Donald Winslow References: Hickman, Cleveland P.; et al. 2008. Integrated Principles of Zoology,"— Presentation transcript:

1 Animal development Principles of Biology, 21 April 2009 Donald Winslow References: Hickman, Cleveland P.; et al Integrated Principles of Zoology, 14 th ed., McGraw-Hill, NY., Chapter 8. Mader, Sylvia S Biology, 9 th ed., McGraw- Hill, NY., Chapter 44.

2 Development Mechanisms of cellular differentiation Fertilization Cleavage Blastulation Gastrulation Neurulation Direct development and indirect development

3 Mechanisms of cellular differentiation Cytoplasmic localization  Gradients of molecules within cells determine developmental fate of daughter cells. Induction  Adjacent cells determine the developmental fate of a cell.

4 Fertilization and activation Prevention of polyspermy  Fast block Change in membrane potential.  Slow block Cortical reaction causes vitelline membrane to separate from cell membrane.

5 The Zygote Gray crescent  Shows orientation of embryo within zygote Polarity  Animal and vegetal poles Yolk  Provides nutrition for developing embryo

6 Patterns of cleavage Superficial cleavage  Ecdysozoan protostomes (nematodes, arthropods, etc)‏ Radial cleavage—primitive deuterostomes Discoidal meroblastic cleavage  Reptiles, birds, most fishes Rotational holoblastic cleavage—mammals Mosaic vs regulative cleavage

7 Figure 8-7 From: Hickman et al (13th ed.)‏

8 Blastulation Blastula made up of blastomeres Inner cavity is called “blastocoel”

9 Gastrulation Germ layer formation Coelom formation  Schizocoely (protostomes; e.g. earthworm)‏  Enterocoely (deuterostomes; e.g. lancelet)‏ Fate of blastopore (or primitive streak)‏  Protostomes: blastopore becomes mouth  Deuterostomes: blastopore becomes anus

10 Figure From Hickman et al (13th ed.)‏

11 Extraembryonic membranes Present in amniotic vertebrates  Reptiles, birds, mammals Help embryo conserve water Amnion, chorion, allantois

12 Neurulation Nervous system forms from ectoderm Induction by adjacent cells

13 Direct and indirect development Direct development  Embryo develops into adult-like individual Indirect development  Embryo develops into larval stage  May be several intermediate stages before adult


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