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Chapter 46 Animal Reproduction
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Overview of sexual reproduction
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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
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?Diverse mechanisms of asexual reproduction
enable animals to produce identical offspring
invertebrate fission
budding fragmentation
and regeneration
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Figure 46.0x1 Utethesia ornatrix mating
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Figure 46.0x2 Red beetles mating
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Figure 46.1 Two from one asexual reproduction
of a sea anemone (Anthopleura elegantissima)
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Figure 46.x1 Aphid giving live birth
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• ?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

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Figure 46.2 Sexual behavior in parthenogenetic
lizards
(a)
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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
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Figure 46.3 Sex reversal in a sequential
hermaphrodite
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Mechanisms of sexual reproduction
fertilization Internal fertilization
External fertilization
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• ?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

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Figure 46.0 Frogs mating
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Figure 46.4 The release of eggs and external
fertilization
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• 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

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Figure 46.x2 Sea urchin sperm fertilizing an egg
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Figure 46.5 Parental care in an invertebrate
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• Complex reproductive systems have evolved in
• animal phyla( phylum Annelida)
• Polychaete( ??? )
• ?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

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2. Flat worm ( Phylum Platyhelminthes) ?
hermaphroditic ? sperms may ejected to female
reproductive system of another individual
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Figure 46.6 Reproductive anatomy of a parasitic
flatworm
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• 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

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Figure 46.7 Insect reproductive anatomy
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Mammalian reproductive system
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Figure 46.8 Reproductive anatomy of the human
male
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Figure 46.8 Reproductive anatomy of the human
male
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Spermatogenesis ?The production of mature sperm
cells ? a ejaculation of human male contain
100-650 million sperms
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Figure 46.11 Spermatogenesis
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Figure 46.11x Spermatogenesis Seminiferous
tubules (left), sperm in semen (right)
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Figure 46.12 Structure of a human sperm cell
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Figure 46.9 Reproductive anatomy of the human
female
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Figure 46.9 Reproductive anatomy of the human
female
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Oogenesis ? The development of ova( mature,
unfertilized egg cells) ? Egg cells stays
at prophase of meiosis I until puberty
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Figure 46.13a Oogenesis
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Figure 46.9x Ovary (left) and follicle (right)
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Figure 46.10 Ovulation
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Figure 46.13b Oogenesis
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Figure 46.15 The reproductive cycle of the human
female
shedding of endothelium lining
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• Differences of Oogenesis and spermatogenesis
• Cytokinessis of meiotic division in oogenesis is
• unequal ( polar body degenerate)
• 2. Mitosis continues thought the males life
• 3. Oogenesis has long resting period

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A complex interplay of hormone regulates
reproduction
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• The male pattern
• Androgen ( ???)---- 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

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Figure 46.14 Hormonal control of the testes
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• 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)

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Embryonic and fetal development occur during
pregnancy in human and other placental animals
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Figure 46.16 Formation of the zygote and early
postfertilization events
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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
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Figure 46.17 Placental circulation
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Figure 46.18 Human fetal development
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Figure 46.19 Hormonal induction of labor
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Figure 46.20 The three stages of labor
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• Contraception prevention of pregnancy
• Prevent release of mature eggs and sperm from
  gonads
• Prevent fertilization by keeping eggs and sperms
  apart
• Prevent implantation
• Abortion

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

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Figure 46.21 Mechanisms of some contraceptive
methods
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Figure 46.22 Ultrasound imaging
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