ANIMAL EMBRYOLOGY

1. 04 April 2011 Embryology.ppt 1 ANIMAL EMBRYOLOGY A brief essay on relationships of major animal groups.

2. 04 April 2011 Embryology.ppt 2 What IS an Animal? Petunia is a plant and Wolf spider is an animal. No trouble.

3. 04 April 2011 Embryology.ppt 3 What IS an Animal? Coral sessile (“rooted”?) stem, branches, greenish. Resembles plant; but this IS an animal! Why?

4. 04 April 2011 Embryology.ppt 4 What IS an Animal? Definition of "Animal" Multicellular (so are plants, fungi) Eukaryotic (so are plants, fungi) Diploid (usually) (sporophytes are, too) Meiosis produces gametes Sperm, egg are the only haploid cells Heterotrophic by ingestion Cells lack cell walls.

5. 04 April 2011 Embryology.ppt 5 What IS an Animal? Basic structure (not definition) = Tube-in-tube Body wall = outer tube gut (GI tract) = inside tube mouth anus

6. 04 April 2011 Embryology.ppt 6 Embryological Development in Animals Every animal begins as ZYGOTE How do animals develop tube-in-tube body form? Important in understanding relationships, classification of Phyla.

7. 04 April 2011 Embryology.ppt 7 Three fundamental processes: 1. Morphogenesis (morph- = shape, + genesis = origin) Origin of shape, form 2. Differentiation Process of cells becoming different, and specializing for different functions 3. Growth Increase in size, requires input of matter, food

8. 04 April 2011 Embryology.ppt 8 Sequence of Events: 1. Fertilization 2. Activation 3. Cleavage 4. Gastrulation 5. Mesoderm formation 6. Organogenesis

9. 04 April 2011 Embryology.ppt 9 Sequence of Events:(frog or sea urchin model) 1. Fertilization Fusion of sperm nucleus with egg nucleus Produces zygote (diploid) 2. Activation Increase in metabolism Egg metabolically inert, zygote active Movement of cytoplasm Synthesis of materials needed for cleavage

10. 04 April 2011 Embryology.ppt 10 Sequence of Events: 3. Cleavage from Zygote Division by mitosis 2 blastomeres ? 4 blastomeres ? 8 blastomeres ? 16 ? 32 ? 64 ? 128 ? 256 ? 512 ? Blastula

11. 04 April 2011 Embryology.ppt 11 Sequence of Events: 4. Gastrulation = formation of a gut; Major MORPHOGENIC event !!! Location of cells after GASTRULATION determines further development

12. 04 April 2011 Embryology.ppt 12 Sequence of Events: 4. Gastrulation Invagination & movement of cells to inside yields 2 tissue layers Ectoderm Endoderm yields Archenteron “ancient gut” = first formation of "inside tube."

13. 04 April 2011 Embryology.ppt 13 Sequence of Events: 5. Mesoderm Formation 3rd "germ layer" Ectoderm = “outside skin” Mesoderm = "middle skin" Endoderm = “inside skin”   Details of mesoderm formation vary among phyla !! to be studied with those phyla.

14. 04 April 2011 Embryology.ppt 14 Sequence of Events: 6. Organogenesis Formation of organs from three germ layers Differentiation & continued Morphogenesis

15. 04 April 2011 Embryology.ppt 15 Organogenesis Ectoderm Epidermis Lining of mouth & rectum Cornea of eye Lens of eye Nervous system

16. 04 April 2011 Embryology.ppt 16 Organogenesis Endoderm forms thin linings (mostly) linings of gut & branches lining of excretory ducts, bladder " " lungs, trachea " " reproductive ducts, uterus, vas deferens liver pancreas

17. 04 April 2011 Embryology.ppt 17 Organogenesis Mesoderm Skeleton, Muscles (skeletal, smooth, cardiac) Dermis of skin Heart, blood, blood vessels Kidneys, Ovaries/testes, etc.

18. 04 April 2011 Embryology.ppt 18 Organogenesis Ectoderm How Nervous system gets inside Dorsal surface of embryo forms Neural plate Plate sinks inward forming Neural groove Edges of groove fuse to separate Neural tube from epidermis