1. This week in 206 I. Sea urchin fertilization thru gastrulation.
Dr. Lloyd
This week in 206
I. Sea urchin fertilization thru gastrulation.
II. Chick gastrulation thru organogenesis.
III. Fungi fertilization and sporangium development.

2. Development Sea urchin Deuterostome Isolecithal Holoblastic cleavage
Chick
Deuterostome
Telolecithal
Meroblastic cleavage
Fertilization
cleavage
Blastulation & gastrulation
Organogenesis & pattern formation
Why do cells move in specific ways at specific times?
How, why, and when do cells become specialized?

3. Sea urchin body plan
© 1997 Chris Patton, Stanford University

4. Fertilization

5. Sea urchin fertilization
acrosome
Cortical granules
Fertilization membrane

6. © 1997 Chris Patton, Stanford University

7. Fertilization

8. Holoblastic--cleaves completely through cell
Isolecithal--evenly dispursed yolk.

9. Sea Urchin Cleavage and blastulation
3 div.
8 cell
1st div.
Hatched
blastula
blastula

10. Three types of morphogenetic movements during
gastrulation.

11. Gastrulation -2 types of morphogenetic
movements.
Ingression of ~40 cells to form
Primary mesenchyme cells (PMC)
Formation of mesoderm.

12. Gastrulation
2. Invagination of cells at vegetal pole
Forms blastopore and
archenteron-primitive gut
3 germ layers
ectoderm-
skin and nervous system.
mesoderm-
bone, muscle, circ. system, internal organs.
endoderm-
stomach and guts.
archenteron

13. Together=mesoderm 2nd ingression of cells to form Secondary mesenchyme
Primary mesenchyme

14. 2nd invagination at animal pole
to form mouth
Complete gastrula
Germ layers
Ecto
Meso
Endo
archenteron

15. Sea urchin larval development.

16. Sea urchin larva

17. Chick Telolecithal-asymmetric 3rd 2nd 1st div. 4th
shell
Chick
Shell membrane
albumen
Nucleus
Cytoplasm
Yolk
Telolecithal-asymmetric
3rd
2nd
1st div.
4th
Meroblastic cleavage-part cleavage

18. ~100,000 cells when egg laid.
Epiblast - 3 germ layers
ectoderm
mesoderm
endoderm

19. Delamination

20. Ingression-
mesoderm

21. Chick gastrulation. Primitive streak -cells ingress
-induced by hypoblast
~blastopore
Notochord
-induced by Hansen’s node
Somites
-muscle, bone
Embryo lifts off surface-
3 layers-
ectoderm
mesoderm
endoderm
Becomes brain
Sacs form around embryo

22. Fresh laid egg-blastodisc
13 hour egg

23. 24 hour chick sections

24. 33 hour chick sections

25. 33 hour whole mount

26. 48 hour
72 hour