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Chapter 48. Reproduction. Asexual reproduction A single parent endows its offspring with genes identical to its own Energy efficient Most successful in a stable environment. Means of asexual reproduction Budding Part of the parent’s body grows and separates from the rest of the body

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Chapter 48

Chapter 48

Reproduction


  • Asexual reproduction

    • A single parent endows its offspring with genes identical to its own

      • Energy efficient

      • Most successful in a stable environment


  • Means of asexual reproduction

    • Budding

      • Part of the parent’s body grows and separates from the rest of the body

    • Fragmentation

      • The parent’s body breaks into pieces

      • Each piece can grow into a new animal

    • Parthenogenesis

      • An unfertilized egg develops into an adult



  • Sexual reproduction

    • Offspring produced by fusion of two gametes

      • Ovum

      • Sperm

    • A fertilized egg (zygote) forms

    • Promotes genetic variety and is adaptive in an unstable environment


  • External fertilization

    • Mating partners typically release eggs into the water simultaneously

  • Internal fertilization

    • Male delivers sperm into the female’s body

  • Hermaphroditism

    • Single individual produces eggs and sperm


  • Human male reproductive system

    • Testes

      • Housed in the scrotum

      • Contain the seminiferous tubules, where sperm production takes place

      • Interstitial cells secrete testosterone

      • Sertoli cells produce signaling molecules and a fluid that nourishes sperm cells



  • Human male reproductive system, cont.

    • Penis

      • Three columns of erectile tissue

      • Two cavernous bodies

      • One spongy body that surrounds the urethra

    • Erectile tissue becomes engorged with blood and causes erection



  • Spermatogenesis

    • Takes place in the seminiferous tubules

    • Spermatogonia divide by mitosis

    • Head of a sperm consists of the nucleus and an acrosome, containing enzymes that help penetrate the egg

















  • Development of a human ovum

    • Oogenesis takes places in the ovaries

    • Oogonia differentiate into primary oocytes

      • Primary oocyte and granulosa cells make up a follicle



  • Development of a human ovum, cont.

    • As the follicle grows

      • Connective tissue cells form a layer of theca cells

      • Primary oocyte undergoes meitosis, giving rise to a secondary oocyte and a polar body



  • Development of a human ovum, cont.

    • During ovulation

      • The secondary oocyte is ejected and enters an oviduct to be fertilized

      • The part of the remaining follicle develops into a corpus luteum


  • Endocrine regulation of reproduction

    • Preovulatory phase

      • GnRH stimulates the pituitary to secrete FSH and LH

      • Estrogen stimulates endometrium development

      • LH stimulates final maturation of the follicle and ovulation


  • Endocrine regulation of reproduction, cont.

    • Postovulatory phase

      • LH promotes development of the corpus luteum

      • The corpus luteum secretes progesterone and estrogen

      • If fertilization does not occur, the corpus luteum degenerates, hormone levels fall, and menstruation occurs





  • Human fertilization reproduction

    • Fusion of secondary oocyte and sperm to form a zygote

    • Embryo implants in the uterus

    • hCG is the hormone that maintains the corpus luteum

    • Estrogen and progesterone

      • Secreted by corpus luteum (first trimester) and then by placenta


Fertilization reproduction



  • Human birth process reproduction

    • Several hormones, including estrogen, oxytocin, and prostaglandins regulate parturition

    • Labor

      • Divided into three stages

      • The baby is delivered during the second stage


  • Contraception reproduction

    • Hormonal methods, such as oral contraceptives

    • Intrauterine devices

    • Condoms and contraceptive diaphragms

    • Sterilization (vasectomy or tubal ligation)


Sterilization reproduction


  • Abortions reproduction

    • Spontaneous miscarriages occur without intervention

    • Induced abortions

      • Therapeutic performed to maintain the mother’s health, as birth control, or when the embryo is thought to be grossly abnormal





Major reproductionchemical groups of hormones


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