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: