Animal Reproduction Chapter 46

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.

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

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)

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

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

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

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

Spermatogenesis Animation http://wps.aw.com/bc_martini_eap_4/40/10469/2680298.cw/content/index.html

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

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

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)

Oogenesis Animation http://wps.aw.com/bc_martini_eap_4/40/10469/2680298.cw/content/index.html

Stages of Meiosis in Humans

Menstrual Cycle https://www.youtube.com/watch?v=l_wX285vrrU