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:
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.
Development Mechanisms of cellular differentiation Fertilization Cleavage Blastulation Gastrulation Neurulation Direct development and indirect development
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.
Fertilization and activation Prevention of polyspermy Fast block Change in membrane potential. Slow block Cortical reaction causes vitelline membrane to separate from cell membrane.
The Zygote Gray crescent Shows orientation of embryo within zygote Polarity Animal and vegetal poles Yolk Provides nutrition for developing embryo
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
Figure 8-7 From: Hickman et al (13th ed.)
Blastulation Blastula made up of blastomeres Inner cavity is called “blastocoel”
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
Figure From Hickman et al (13th ed.)
Extraembryonic membranes Present in amniotic vertebrates Reptiles, birds, mammals Help embryo conserve water Amnion, chorion, allantois
Neurulation Nervous system forms from ectoderm Induction by adjacent cells
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