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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
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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 46.1 Two from one: asexual reproduction of a sea anemone (Anthopleura elegantissima)
reproductive cycle and pattern vary extensively • among animals • 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
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
Mechanisms of sexual reproduction fertilization: Internal fertilization External fertilization
Internal and External fertilization both depend on • mechanisms ensuring that mature sperm encounter • fertile eggs of the same species • 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
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
Complex reproductive systems have evolved in animal phyla( phylum Annelida) • 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
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
尿囊 貯精囊 輸精管 前列腺 尿道 尿道球腺 副睪 龜頭 睪丸 陰囊 包皮 Figure 46.8 Reproductive anatomy of the human male
尿囊 貯精囊 前列腺 尿道球腺 尿道 輸精管 陰囊 副睪 睪丸 龜頭 Figure 46.8 Reproductive anatomy of the human male
Spermatogenesis The production of mature sperm cells a ejaculation of human male contain 100-650 million sperms
Figure 46.11x Spermatogenesis: Seminiferous tubules (left), sperm in semen (right)
輸卵管 卵巢 子宮 尿囊 子宮頸 尿道 陰道 陰蒂 尿道球腺 大( 小)陰唇 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
Birth to puberty Stimulation of FSH Figure 46.13a Oogenesis
雌激素 黃體激素 Figure 46.15 The reproductive cycle of the human female shedding of endothelium lining
Differences of Oogenesis and spermatogenesis • 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’
The male pattern • Androgen ( 雄激素)---- testosterone • Produced by ledig cells of testes • Responsible for 1st and 2nd sex characteristics development of vas deferentia, development of external reproductive structure, sperm production • The aggressiveness of male behavior is enhanced by androgen
下視丘 腦下垂體 濾泡刺激激素 Figure 46.14 Hormonal control of the testes
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 46.16 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
5 weeks 14 weeks 20 weeks Figure 46.18 Human fetal development