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Animal Reproduction

This chapter delves into the complex processes of animal reproduction, outlining both asexual and sexual mechanisms. It begins with asexual reproduction methods such as fission, budding, and regeneration. The chapter further explores sexual reproduction, highlighting the formation and fusion of haploid gametes, including male spermatozoa and female ova. Key topics include reproductive structures, gametogenesis (spermatogenesis and oogenesis), reproductive cycles, and modern reproductive technologies. A special focus is given to mammalian reproduction in males and females, covering essential anatomy and physiological processes.

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Animal Reproduction

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  1. Animal Reproduction • Chapter 46 ~

  2. Overview • Asexual(one parent) • fission (parent separation) • budding (corals) • gemmules (porifera) • fragmentation & regeneration (inverts) • Sexual(fusion of haploid gametes) • gametes (sex cells) • zygote (fertilized egg) • ovum (unfertilized egg) • spermatozoon (male gamete)

  3. Reproductive cycles • Parthenogenesis unfertilized egg development; haploid, sterile adults (honeybees) • Hermaphroditismboth male & female reproductive systems; sessile & burrowing organisms (earthworms) • Sequential hermaphroditism reversal of gender during lifetime•protogynous(female 1st) •protandrous(male 1st)

  4. Mechanisms of sexual reproduction • Fertilization (union of sperm and egg) • external • internal • Pheromones chemical signals that influence the behavior of others (mate attractants)

  5. Mammalian reproduction, I • The Human Male • Testes~ male gonads • Seminiferous tubules~ sperm formation • Leydig cells~ hormone production • Scrotum~ outside body temp. • Epididymis~ sperm development • Vas deferens~ sperm propulsion • Seminal vesicles~ semen • Prostate gland~ anticoagulant; nutrients • Bulbourethral glands~ acid neutralizer • Penis/urethra~ semen delivery

  6. Male Reproductive Structures

  7. Mammalian reproduction, II • The Human Female • Ovaries~ female gonads • Follicle~ egg capsule • Corpus luteum~ hormone secretion • Oviduct~ fertilization • Uterus/endometrium~ womb/lining • Cervix/vagina~ sperm receptacle

  8. Female Reproductive Structures

  9. Spermatogenesis • Puberty until death! • Seminiferous tubules~ location • Primordial germ cell (2N)~ differentiate into…. • Spermatogonium (2N)~ sperm precursor • Repeated mitosis into…. • Primary spermatocyte (2N) • 1st meiotic division • Secondary spermatocyte (1N) • 2nd meiotic division • Spermatids (1N)~Sertoli cells…. • Sperm cells (1N)

  10. Oogenesis • As embryo until menopause... • Ovaries • Primordial germ cells (2N) • Oogonium (2N) • Primary oocyte (2N) • Between birth & puberty; prophase I of meiosis • Puberty; FSH; completes meiosis I • Secondary oocyte (1N); polar body • Meiosis II; stimulated by fertilization • Ovum (1N); 2nd polar body

  11. The female pattern • Estrous cycles/estrus(many mammals) • Menstrual cycle (humans and many other primates): • Ovarian/Menstrual cycles~ •follicular phase~follicle growth •ovulation~ oocyte release •luteal phase~ hormone release

  12. Ovulation

  13. Post-ovulation

  14. Embryonic & fetal development • Gestation~ pregnancy • 1st trimester: • organogenesis • fetus (week 8; all adult features) • HCG hormone (menstruation override; pregnancy test detection) • Parturition~birth • Labor~uterine contractions • Lactation~prolactin & oxytocin

  15. Modern technologies

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