Ch.46

1. Ch.46

3. I.Animal reproduction • A.Asexual reproduction – mitotic division, no fertilization • 1.Fission- separation of parent into two or more individuals of the same size. • 2.Budding new individual splits off original (Cnidaria). • 3.Fragmentation – breaking of the body into several pieces which will develop into new individuals.(sponges,cnidaria,annelids and tunicates). • 4.Allows for production of offspring without mates. • 5.Allows for reproduction in a short time.

5. B.Sexual reproduction – Fusion of gametes forming a diploid zygote. • C.Reproductive cycles • 1.Usually animals have seasonal cycles • a.Conservation of resources and energy • b.Allows for reproduction under favorable conditions • c.Controlled by hormones and environment • 2.Animals have various reproductive patterns – may be sexual or asexual or alternating. • a.Parthogenesis – egg develops without fertilization • b.Daphnia switches between asexual and sexual depending on conditions. • c.Male honey bees are produced by parthenogenesis, females develop from fertilized eggs. • d.Hermaphrodites – each individual has both functional male and female reproductive parts. Most mate, each producing cross-fertilized eggs. • e.Sequential hermaphroditism – reverses sex during lifetime.

7. II.Mechanisms of sexual reproduction • A.Fertilization • 1.Internal – sperm deposited in or near the female reproductive tract and fertilization occurs inside the female body. • 2.External – Eggs are shed and fertilized outside the body. • 3.Pheromones – Chemical signals between organisms of the same species. • B.Internal fertilization usually produces fewer offspring but survival through development is greater due to protection and care of offspring. • C.Complex systems • 1.Some systems do not have gonads • 2.Parasitic flatworms are have very complex reproductive systems. • 3.Believe it or not insects have testis(male) and vagina(female).

8. III.Mammalian reproduction • A.Human reproduction • 1.Male anatomy • a.Testes develop in abdomen and descend into scrotum before birth – this keeps the sperm 2 degrees below body temp. • b.Seminiferous tubules in the testes is where sperm is produced. • c.The sperm pass to the epididymus • d.At ejaculation sperm enter the vas deferens then the urethra and out. • e.Glands called the seminal vesicles secrete mucus, amino acids, fructose (energy), and prostaglandins.  Prostate secretes milky alkaline fluid which balances the acidity of the vagina.  Bulbourethral gland – secrete clear mucus right before ejaculation.

11. 2.Female anatomy • a.Ovaries – contains many follicles all formed at birth. One follicle a month will mature after puberty • b.During ovulation the egg is expelled leaving the corpus luteum which secrete progesterone and additional estrogen • c.If the egg is not fertilized the corpus luteum degenerates. • d.The egg cell travels through the oviduct to the uterus • e.Cervix – neck of the uterus, open to the vagina • f.Vagina – repository for semen and birth canal. • g.Hymen – covers vaginal opening until ruptured. • h.Clitoris – small hood of skin • i.Bartholin’s glands – secrete mucus to lubricate vagina. • j.Mammary glands – small sacs of epithelial tissue that secrete milk.

14. B.Spermatogenesis/oogenesis • 1.Spermatogenesis is continuous in adult males (100-600 million per ejaculation) • 2.Occurs in seminiferous tubules of testes • 3.Oogenesis is the development of the ova. • a.begins in embryo • b.all potential ova present at birth • c.After puberty FSH stimulates follicle to enlarge and completion of meiosis • d.LH triggers ovulation • 4.Differences • a.All four cells produced during meiosis during spermatogenesis become sperm, in oogenesis only one of the four will become a mature ova • b.Spermatogenesis is continuous throughout adult life, oogenesis happens only before birth • c.Spermatogenesis is uninterrupted oogenesis has “resting periods”

17. C.Hormone regulation • 1.Male pattern • a.Testosterone is the most important androgen which is responsible for male development. • b.GnRH from hypothalamus stimulates pituitary to release LH (for androgen production) and FSH (increases sperm production)

18. 2.Female patterns • a.Estrous cycle – non-primate mammals • i.Ovulation after the endometrium thickens • ii.No pregnancy,endometrium reabsorbed • iii.Affected by behavior and seasonal changes • iv.Estrus is the only time copulation occurs • b.Menstral cycle- primate mammals • i.Ovulation as in estrous • ii.No pregnancy, endometrium is shed- menstral flow • iii.In humans ranges from 20-40 days(menstral flow = day 1) • iv.Proliferative phase – regeneration of endometrium, 1- 2 weeks • v.Secretory phase – 2 weeks, further thickening of endometrium • vi.Ovarian cycle parallels menstral cycle • vii.Follicular phase- follicles in ovaries begin to grow, egg is expelled • viii.Luteal phase – after ovulation, left over follicular tissue becomes corpus luteum which secretes hormones

20. c.Hormones • i.GnRH from hypothalamus stimulates pituitary • ii.FSH  from pituitary stimulate the follicles to grow and produce estrogen • iii.Estrogen stimulates hypothalamus to increase production of GnRH (positive feedback) which increases FSH and LH • iv.LH stimulates final maturation of follicle and ovulation • v.Corpus luteum secretes progesterone which along with estrogen inhibits GnRH production • vi.LH declines and corpus luteum atrophies • vii.Estrogen and progesterone levels drop and GnRH is produced – process begins again • viii.Menopause – ovaries lose responsiveness to LH and FSH