Chapter 46 Animal Reproduction

Overview of sexual reproduction

 Both asexual and sexual reproduction occur in the animal kingdom sexual reproduction : fusion of haploid gametes to form a zygote, fertilized eggs Female gamete: ovum Male : spermatozoon

 Diverse mechanisms of asexual reproduction enable animals to produce identical offspring invertebrate: fission budding fragmentation and regeneration

Figure 46.0x1 Utethesia ornatrix mating

Figure 46.0x2 Red beetles mating

Figure 46.1 Two from one: asexual reproduction of a sea anemone (Anthopleura elegantissima)

Figure 46.x1 Aphid giving live birth

 reproductive cycle and pattern vary extensively among animals 1.Most animals shows definite cycles in reproductive activity 2. Controlled by hormonal and environmental cues (temperature, rainfall, day length and lunar cycle) parthenogenesis: eggs develop without fertilization fig 46.2

Figure 46.2 Sexual behavior in parthenogenetic lizards (a)

3. Reproduction may alternate between sexual and asexual hermaphrodite: individuals has both male and female reproductive system( for sessile and burrowing animals) sequential hermaphrodite protogenous : female first protandrous: male first figure 46.3

Figure 46.3 Sex reversal in a sequential hermaphrodite

Mechanisms of sexual reproduction fertilization: Internal fertilization External fertilization

 Internal and External fertilization both depend on mechanisms ensuring that mature sperm encounter mechanisms ensuring that mature sperm encounter fertile eggs of the same species fertile eggs of the same species 1.Internal fertilization a. require cooperative behavior,lading to copulation b. require sophisticated reproductive system 2. External fertilization a. an environment where eggs can develop without desiccation or heat stress

Figure 46.0 Frogs mating

Figure 46.4 The release of eggs and external fertilization

 Species with internal fertilization usually produce fewer zygotes but provide more parental protection than species with external fertilization a. External fertilization less protection for eggs and fertilized zygotes b. Internal fertilization protection by: egg shells develop within reproductive tract pouches for marsupials

Figure 46.x2 Sea urchin sperm fertilizing an egg

Figure 46.5 Parental care in an invertebrate

 Complex reproductive systems have evolved in animal phyla( phylum Annelida) 1.Polychaete( 多毛綱 )  separate sex, but no distinct gonads  eggs and sperms develop from undifferentiated linings of the coelom  gametes release from body wall and fill the coelom as they mature

2. Flat worm ( Phylum Platyhelminthes)  hermaphroditic  sperms may ejected to female reproductive system of another individual

Figure 46.6 Reproductive anatomy of a parasitic flatworm

2.Insects  separate sex with complex reproductive system  sperm develop in a pair of testes and stored in the seminal vesicles  eggs develop in a pair of ovaries  female may store sperms in spermatheca

Figure 46.7 Insect reproductive anatomy

Mammalian reproductive system

Figure 46.8 Reproductive anatomy of the human male 尿囊 貯精囊 輸精管 尿道球腺 睪丸 副睪 陰囊 包皮 龜頭 尿道 前列腺

Figure 46.8 Reproductive anatomy of the human male 尿道 陰囊 尿囊 睪丸 副睪 輸精管 龜頭 前列腺 尿道球腺 貯精囊

Spermatogenesis  The production of mature sperm cells  a ejaculation of human male contain million sperms

Figure Spermatogenesis

Figure 46.11x Spermatogenesis: Seminiferous tubules (left), sperm in semen (right)

Figure Structure of a human sperm cell

Figure 46.9 Reproductive anatomy of the human female 輸卵管 卵巢 子宮 尿囊 尿道 陰蒂 大 ( 小 ) 陰唇 陰道 尿道球腺 子宮頸

Figure 46.9 Reproductive anatomy of the human female

Oogenesis  The development of ova( mature, unfertilized egg cells)  Egg cells stays at prophase of meiosis I until puberty

Figure 46.13a Oogenesis Birth to puberty Stimulation of FSH

Figure 46.9x Ovary (left) and follicle (right)

Figure Ovulation

Figure 46.13b Oogenesis

Figure The reproductive cycle of the human female shedding of endothelium lining 雌激素 黃體激素

Differences of Oogenesis and spermatogenesis 1.Cytokinessis of meiotic division in oogenesis is unequal ( polar body degenerate) 2. Mitosis continues thought the male’s life 3. Oogenesis has long ‘resting period’

A complex interplay of hormone regulates reproduction

The male pattern  Androgen ( 雄激素 )---- testosterone  Produced by ledig cells of testes  Responsible for 1 st and 2 nd sex characteristics  development of vas deferentia, development of external reproductive structure, sperm production  The aggressiveness of male behavior is enhanced by androgen

Figure Hormonal control of the testes 下視丘 腦下垂體 濾泡刺激激素

The female pattern  Ovulation occurs during menstrual cycle( shedding of endothelium lining of uterus) or estrous(endothelium lining cycle  More pronounced behavior change for estrous cycle than menstrual cycle  Average of 28 days for menstrual cycle  Ovaries lose their response to FSH and LH during menopause (age 46-54)

Embryonic and fetal development occur during pregnancy in human and other placental animals

Figure Formation of the zygote and early postfertilization events

Reproductive Immunology Interference of immune response by trophoblast: 1. Produce chemical signal induce suppressor T cell which prevent other T cell from foreign tissue 2. Secret enzyme that break down tryptophan that is necessary for T cell survival 3. A mouse protein produced by trophoblast protect embryo from been attacked by complement

Figure Placental circulation

Figure Human fetal development 5 weeks14 weeks20 weeks

Figure Hormonal induction of labor

Figure The three stages of labor

Contraception: prevention of pregnancy 1.Prevent release of mature eggs and sperm from gonads 2.Prevent fertilization by keeping eggs and sperms apart 3.Prevent implantation 4.Abortion

Birth control pill 1. Combination of synthetic estrogen and progestin  negative feedback to inhibit release of GnRH  prevent ovulation 2.Minipill ( progestin)  alter cervical mucus to block sperm from entering

Figure Mechanisms of some contraceptive methods

Figure Ultrasound imaging

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