Gametogenesis: Spermatogenesis and Oogenesis
Gametogenesis
• Occurs in the GONADS of males and females (ovaries/testes).
• In some organisms...called Hermaphrodites (like Earthworms) have BOTH male and female gonads.
Spermatogenesis • Production of sperm:
– Continuous and prolific (produces large numbers)• Occurs in the Testes.
What happens is … • Spermatogonia (stem cells that give rise to
sperm).
• Spermatogonia are diploid (2n).
• 4 cells result:
– Develop into “MATURE” sperm
– ALL ARE Haploid (n)
Spermatogenesis
Oogenesis • The development of ova:
– Mature, “unfertilized” eggs cells
– Happens in the ovary
• Oogonia (stem cells that give rise to ova).
Oogenesis
Occurs once a month after puberty
Major Difference #1 • Unevenness in the meiotic
division/cytokinesis of oogenesis.– 3 polar bodies which degenerate.– Spermatogenesis = four mature sperm.
Major Difference #2 • The cells that produce sperm
continue to divide by meiosisthroughout LIFE(males).
• Not the case for women*BORN with all the PRIMARYoocytes.
Major Difference #3 • Oogenesis has LONG resting
periods.
• Sperm is produced in an uninterrupted sequence.
FERTILIZATION:• the UNION or “joining” of egg and sperm. • Monoploid (n) sperm to join with monoploid
egg (n) to create a diploid (2n) number of chromosomes.
• New organism WILL NOT BE IDENTICAL TO THE PARENT (SEXUAL- REPRODUCTION).
• Fertilization CAN BE internal or external!!!• ***Internal Fertilization occurs within a female.
Female reproductive system provides the perfect environment for sperm to survive.
FERTILIZATION Continued…
• Internal fertilization occurs in most land dwelling animals…such as…
• -Reptiles• -Birds• -mammals External fertilization occurs within a
water (aqueous) environment and egg and sperm meet in the water. (ex. FISH/Frogs)
External Fertilization Example: