1. Animal Reproduction
Chapter 46

2. YOU MUST KNOW Advantages of asexual vs. sexual reproduction
Various reproductive strategies in response to energy availability
Timing and coordination of reproduction may be triggered by environmental cues as well as pheromones

3. I. Asexual v. Sexual Reproduction
Sexual reproduction – fusion of haploid gametes to form diploid zygote
Asexual reproduction – creates clones
1. Fission – parent splits in two 2. Budding – new individuals form from outgrowths from parent 3. Fragmentation – individual breaks into pieces and each one regenerates new adult 4. Parthenogenesis – females produce eggs that develop without being fertilized
Hydras, coral
Cnidarians = jellyfish
Starfish, sponges, cnidarians

5. II. Fertilization
External fertilization – eggs shed by female and meet sperm outside the body (usually in water), produce large number of gametes

6. Internal fertilization – occurs inside the female, allows sperm to reach egg even in dry environments, fewer gametes produced

7. Reproductive readiness
1. Can be triggered by day length, resource availability, etc. so that male and female gametes are produced at the same time
2. Pheromones – chemicals that are produced by individuals that influence the behavior of others (sexual attractants, trigger reproductive readiness)
3. Global climate change – has resulted in some resources emerging earlier, before some species are ready causing them to miss their best reproductive window

8. III. Gametogenesis
Spermatogenesis – production of sperm in the testes (from puberty on)
Oogenesis – development of ova in the ovaries (begins in embryonic development, pauses at prophase I, each month during reproductive years one or a few eggs finish meiosis I and begin meiosis II, pause after prophase II unless egg is fertilized)

9. Spermatogenesis
Oogenesis
Millions of sperm/day from puberty throughout life
1 secondary oocyte/month between puberty and menopause
4 gametes from each germinal cell
1 gamete from each germinal cell (+ 3 polar bodies)
Gametes are small with little cytoplasm and organelles
Gamete is large with substantial cytoplasm, organelles, and nutrients
Mitosis replaces germinal cells daily
Mitosis only replaces germinal cells in early development
Some cell growth before meiosis I
Substantial cell growth before meiosis I
Spermatids remain in seminiferous tubules until differentiation into spermatozoa occurs
Differentiation begins in the ovary but finishes after fertilization
Occurs in testes
Occurs in ovaries

10. IV. Hormones & Reproduction
GnRH – gonadotropin-releasing hormone – from hypothalamus, stimulates pituitary to release LH and FSH
FSH - along with testosterone, stimulates meiosis of spermatogonia
LH - stimulates Leydig cells in testes to produce testosterone

11. FSH & LH stimulate production of estrogen by the
FSH & LH stimulate production of estrogen by the ovary, production of Graafian follicles, lead to ovulation and creation of corpus luteum
Estrogen – increases vascularization of endometrium
Progesterone – maintains thickened endometrium
HCG – Human Chorionic Gonadotropin – secreted in early pregnancy to maintain thick endometrium, used for pregnancy tests