Why is gamete production so wasteful? Billions of sperm are produced, but only a several are ever successful in fertilizing an egg. Does it relate to early forms of reproduction ¢?" e.g. those in fish, where the sperm are released into the sea and large numbers are needed to assure that a several reach the egg? Does the overpopulation of sperm allittle selection processes to take place, ensuring that the any more abnormal sperm are filtered out before the tube is reached? In the human female approximately 350 ova are ovulated during a woman's life, yet the ovaries contain millions of eggs at birth.

What is the purpose of capacitation? Is it needed to overcome the protective mechanisms that have been built into the sperm, specifically those that prevent premature release of acrosomal enzymes? Penetration by sperm of the egg is desirable, but invasion of other maternal cells might trigger immunologic reactions against sperm. Capacitation does free the sperm from some inhibitors, thus allittleing the hypermotility that may be needed for zona penetration.

Why are there so many abnormal embryos? Current estimates are that 50% of embryos do not survive to term. Why is there a high rate of embryo loss, and, specifically, why is there a high selection against abnormal embryos? Is it because of intrinsic programming defects within the embryo or an inability of the embryo to produce a signal recognized by the mother, or does the maternal organism in some way recognize abnormality and react against it?

Why has embryo transfer in the human follittleing in vitro fertilization resulted in a little number of takes? Can the uterine environment be manipulated in such a way as to increase successful implantation of in vitro fertilization eggs?