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CHAPTER 27 Reproduction and Embryonic Development

CHAPTER 27 Reproduction and Embryonic Development. Module 27.1. Mating Without Males. There are no male desert-grassland whiptail lizards The species reproduces without copulation or fertilization. The female on top behaves much like a male in other species of whiptail lizards

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CHAPTER 27 Reproduction and Embryonic Development

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  1. CHAPTER 27Reproduction and Embryonic Development Module 27.1

  2. Mating Without Males • There are no male desert-grassland whiptail lizards • The species reproduces without copulation or fertilization

  3. The female on top behaves much like a male in other species of whiptail lizards • Mating behavior seems to be an evolutionary leftover • This photo shows a ritual behavior that primes a female to lay eggs

  4. Although the reproduction method of desert-grassland whiptails is unusual, their embryonic development is similar to all other animal species • Reptiles, birds, and mammals have four embryonic membranes Chorion Embryo Amnion Allantois Yolk Yolk sac Shell

  5. Mitotic cell division • Cellular differentiation • Formation of the body and its structures • All animal species have three stages of embryonic development

  6. ASEXUAL AND SEXUAL REPRODUCTION 27.1 Sexual and asexual reproduction are both common among animals • Asexual reproduction • Budding • Fission • Fragmentation, accompanied by regeneration • Development of an unfertilized egg Figure 27.1A

  7. The fission of two haploid gametes from two parents to form a diploid zygote • Sexual reproduction Figure 27.1D

  8. “Head” Intestine Ovary • Rotifers can reproduce both asexually and sexually Eggs • Hermaphroditism • A single individual has both male and female reproductive systems Figure 27.1B, C

  9. A single individual reproduces • Many offspring are produced rapidly • Disadvantage of asexual reproduction • Little or no genetic variation • Advantages of asexual reproduction

  10. Increases genetic variation • Enhances reproductive success in changing environments • Disadvantage of sexual reproduction • Locating a mate • Advantages of sexual reproduction

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