1. Animal Reproduction
Chapter 46

2. What you need to know!
The role of meiosis and fertilization in sexually reproducing organisms
The hormonal control of the menstrual cycle.
How oogenesis and spermatogenesis differ.

3. Asexual Reproduction Oldest form of reproduction Adv: Easy and fast
Mostly lower order organisms
Adv: Easy and fast
DisAdv: No genetic variation
Types:
Binary fission - bacteria
Vegetative propagation - plants
Budding - anemones
Fragmentation - starfish
Sporulation - fungi

4. Sexual Reproduction
Evolutionarily novel process of meiosis (evolved from mitosis)
Virtually all higher order organisms engage in sexual reproduction
Many can alternate sex depending on resources
Adv: near infinite # of new genotypes
DisAdv: complicated, time-consuming, dangerous, costly
Types:
Fusion of gametes
Parthenogenesis: development of females from unfertilized eggs (bees and ants)

5. Spermatogenesis Creation of sperm
Diploid germ cells undergo meiosis I, II, and maturation
Onset/duration: puberty/death
Meiosis I to maturity: 70 days
Location: seminiferous tubules in testes
Quantity: 100 million per day

6. Sperm Development
During meiosis cells migrate from outside the seminiferous tubule wall to the inside
The seminiferous tubule leads to the epididymis
The epididymis is a 6m coiled duct where sperm mature

7. Sperm Structure
Acrosomes are digestive enzymes that dissolve the protective layer around the egg
The nucleus is haploid
Mitochondria in the midpiece power the sperm on its 2 day journey

8. Ejaculation
Delivers 30ml of semen containing approximately 100 million sperm
Many sperm die in the acidic environment of the vaginal canal
Semen contains antacids to help some survive
Many sperm have defects
Age, stress, and environment contribute to sperm count

9. Spermatogenesis Animation

10. Oogenesis Creation of eggs
A Female embryo produces approximately 450 primary oocytes
Primary oocytes are germ cells hibernating in Prophase I
Onset: puberty
One primary oocyte per month completes M1
Creation of a secondary oocyte and a polar body
M2 begins upon the secondary oocyte’s release from the ovary
M2 is not complete until fertilization

11. Oogenesis Location: Ovaries and Fallopian Tubes
Oocytes do an unequal division of the cytoplasm during cytokinesis
One ovum gets the maximum amount of nutrition and organelles
Yields 1 ovum and 2 polar bodies

12. Menopause Women run out of primary oocytes between 40-50 years of age
Coincides with a drop in sex hormones
Leads to the stop of menstruation by the mid 50’s (on average)

13. Oogenesis Animation

14. Stages of Meiosis in Humans

15. Menstrual Cycle