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Sexual Reproduction
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
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!
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
Life of a Zygote
• Zygote goes through series of cell divisions via mitosis
• Also has a larval stage before it reaches adulthood
Spawning
• Inject urchins with KCl to release eggs and sperm
Spawning
• Inject urchins with KCl to release eggs and sperm
Male or Female?
Eggs are orange
Sperm are white
Collecting the Gametes
Pipette sperm from urchin to tube
Collecting the Gametes
Let eggs fall into beaker of sea water
Add Eggs and Sperm to a Slide and Observe Fertilization!
QuickTime™ and aCinepak decompressor
are needed to see this picture.
Previously fertilized cells show additional stages of cell
development…
…as well as larval development
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