1. Early Development • Gametes

2. Sperm

3. Egg • Lecithal = Yolk

4. Microlecithal egg Small amount of yolk Amphioxus Eutherians

5. Mesolecithal egg • Medium amount of yolk • Amphibians

6. Macrolecithal egg • Large amount of yolk • Bird and reptiles • Most fish

7. Isolecithal • Even yolk distribution • In microlecithal eggs

8. Telolecithal • Uneven yolk distribution • Macrolecithal and Mesolecithal eggs • Vegetal Pole – yolk region • Animal Pole – relatively yolk-free, high metabolic activity/embryo

9. Amniote eggs Amnion Allantoic cavity Amnionic cavity Allantois Albumin Chorion Yolk

10. Layers around egg • Vitelline membrane • Jelly • Capsule • Shell • Albumin • Corona Radiata • Zona Pellucida

11. Oviparous

12. Viviparous

13. Ovoviviparous

14. Fertilization

15. Internal Fertilization • Apodans • Urodeles • Amniotes

16. External Fertilization • Fish • Frogs

17. Zygote

18. Cleavage & BlastulaMicrolecithal Eggs Cleavage – Mitosis divisions Blastomeres Blastocoel

21. Cleavage & Blastula • Blastocyst in mammals • Inner cell mass in mammals • Trophoblast cells in mammals

24. Cleavage & BlastulaMesolecithal eggs

27. Cleavage & BlastulaMacrolecithal Eggs • Blastoderm • Blastocoel

30. Gastrulation • Germ layers form from which ALL future organs form • Notochord forms • Bilateral symmetry established

31. Gastrulation/Microlecithal eggs • Involution • Blastopore • Archenteron

33. Germ layers • Ectoderm –outer layer • Mesoderm – middle layer • Forms notochord • Splits to form coelom • Endoderm – inner layer around archenteron

34. GastrulationMesolecithal eggs • Epiboly

36. Ectoderm • Nervous System • Sensory structures • Neural crest cells that become melanocytes, adrenal gland… • Epidermis of skin • Epithelium of mouth/nose and anus

39. Endoderm • Lungs & Swim bladders • Digestive viscera

42. Mesoderm • Chordomesoderm becomes notochord

44. Mesoderm • Dorsal Mesoderm = Epimere • Segmented bands called somites • Divides into • Dermatome • Myotome • Sclerotome

48. Mesoderm • Lateral plate mesoderm = hypomere • Splits into Somatic and Splanchnic layers • Coelom between these layers

50. Hypomere • Somatic Mesoderm plus Ectoderm = • Somatopleure • Splanchnic Mesoderm plus Endoderm = • Splanchnopleure