1. Sexual Reproduction

2. Overview of Sexual Reproduction 2 haploid sex cells (Sperm and Egg) combine to form new diploid organism *Sex cells produced via meiosis* n n 2n Fertilized Egg (Zygote) Egg CellSperm Cell

3. Why Study Sea Urchins? Eggs and sperm are the same size as in humans Fertilization in sea urchins happens outside their bodies - We can watch it happen!

4. How Do Sea Urchins Reproduce? Sea urchins expel gametes (eggs and sperm) outside their bodies We can make this happen in the lab We can then watch fertilization under a microscope

5. Life of a Zygote Zygote goes through series of cell divisions via mitosis Also has a larval stage before it reaches adulthood

6. Spawning Inject urchins with KCl to release eggs and sperm

7. Spawning Inject urchins with KCl to release eggs and sperm

8. Male or Female? Eggs are orange Sperm are white

9. Collecting the Gametes Pipette sperm from urchin to tube

10. Collecting the Gametes Let eggs fall into beaker of sea water

11. Add Eggs and Sperm to a Slide and Observe Fertilization!

13. Previously fertilized cells show additional stages of cell development…

14. …as well as larval development

15. Some of the preceding pictures, animations, and movies are from the following websites: http://www.stanford.edu/group/Urchin/ani-plus.htm http://www.bio.davidson.edu/misc/movies/spermrace.mov