Unit 5 animal reproduction and development

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ANIMAL REPRODUCTION.

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Unit 5 animal reproduction and development

  1. 1. UNIT 5: ANIMAL REPRODUCTION AND DEVELOPMENT Campbell & Reece, 2010: Chapters 46, 47
  2. 2. INTRODUCTION  Animal reproduction takes many forms  Animal form and function can be viewed broadly as adaptations contributing to reproductive success.  Both asexual and sexual reproduction occur in the animal kingdom.
  3. 3. Sexual reproduction Is the creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
  4. 4. Asexual reproduction Is creation of offspring without the fusion of egg and sperm.
  5. 5. ASEXUAL REPRODUCTION
  6. 6. Mechanisms of Asexual Reproduction Many invertebrates reproduce asexually. One of these is by the process of fission. FISSION: Is the separation of a parent into two or more individuals of about the same size. FISSION OF AN AMOEBA
  7. 7. Fission of a sea anemone to producer two daughter organisms
  8. 8. Second method: BUDDING In budding, new individuals arise from outgrowths of existing ones BUDDING OF A HYDRA
  9. 9. Third method: FRAGMENTATION Is breaking of the body into pieces,  some or all of which develop into adults. Fragmentation must be accompanied by regeneration - regrowth of lost body parts FRAGMENTATION AND REGENERATION OF SEA STARS
  10. 10.  Fourth method: Parthenogenesis  Is the development of a new individual from an unfertilized egg
  11. 11. SEXUAL REPRODUCTION
  12. 12. Introduction to sexual Reproduction in animals Almost all eukaryotic species reproduce sexually. Sexual reproduction results in genetic recombination – variation within species.
  13. 13. Genetic recombination provides potential advantages: 1. An increase in variation in offspring, 2. An increase in the reproductive success of parents in changing environments. 3. An increase in the rate of adaptation. 4. Elimination of harmful genes from a population.
  14. 14. REPRODUCTIVE CYCLES AND PATTERNS
  15. 15. REPRODUCTION CYCLES AND PATTERNS Ovulation is the release of mature eggs at the midpoint of a female cycle. Most animals exhibit reproductive cycles related to changing seasons. Reproductive cycles are controlled by hormones and environmental cues
  16. 16. Animals may reproduce asexually or sexually, or they may alternate these methods. Lizards reproduce only by a complex form of parthenogenesis that involves the doubling of chromosomes after meiosis Asexual whiptail lizards are descended from a sexual species, and females still exhibit mating behaviours.
  17. 17. Sexual behavior in parthenogenetic lizards
  18. 18. Sexual reproduction is a special problem for organisms that seldom encounter a mate. One solution is hermaphroditism, in which each individual has male and female reproductive systems Some hermaphrodites can self- fertilize. C. elegans makes both sperm and eggs and can reproduce by self-fertilization.
  19. 19. Individuals of some species undergo sex reversals Some species exhibit male to female reversal (for example, certain oysters), while others exhibit female to male reversal (for example, a coral reef fish)
  20. 20. HOW DO ORGANISMS ENSURE THE SURVIVAL OF THEIR OFFSPRING?
  21. 21. Ensuring the Survival of Offspring All species produce more offspring than the environment can handle. The proportion that survives is small. Species with external fertilization produce more gametes than species with internal fertilization.
  22. 22. Species with internal fertilization provide greater protection of the embryos and more parental care. The embryos of some terrestrial animals develop in amniote eggs with protective layers. Other animals retain the embryo, which develops inside the female. In many animals, parental care helps ensure survival of offspring.
  23. 23.  AMNIOTIC EGG OF A CHICKEN
  24. 24.  PARENTAL CARE OF AN INVERTEBRATE
  25. 25. GAMETE PRODUCTION AND DELIVERY
  26. 26. Gamete Production and Delivery Sexually reproducing animals have systems producing gametes. These individuals have gonads - organs producing gametes. Male gonads : Testis Female gonads: Ovaries Some gametes form from undifferentiated tissue.
  27. 27. GONADS: MALE – TESTIS AND FEMALE - OVARIES
  28. 28. Complex systems contain many sets of:  accessory tubes  and glands that carry nourish, and protect gametes and developing embryos.
  29. 29. Some organisms have a cloaca: is a common opening between the external environment and the digestive, excretory, and reproductive systems Common in non-mammalian vertebrates; Mammals usually have a separate opening to the digestive tract.
  30. 30. CLOACA OF A LIZARD
  31. 31. Monogamy is relatively rare among animals. Males and/or females which have mechanisms to decrease the chance of their mate mating with another individual.
  32. 32. COURTSHIP BEHAVIOUR Courtship, in animals – behaviour that results in mating and eventual reproduction
  33. 33. Courtship behaviours can include: special calls, postures, and movements, special plumage, bright colours or other ornamentation
  34. 34. EXAMPLES The 'dancing' done by male birds of paradise.
  35. 35. Method of reproduction in which eggs are laid and embryos develop
  36. 36. Three Methods of reproduction in which eggs are laid and embryos develop Ovipary Ovovivipary Vivipary
  37. 37. OVIPARYOUS ORGANISMS Reproduction in which eggs are laid and embryos develop outside the mother's body. Each egg eventually hatching into a young animal. Little or no development occurs within the mother's body. Most invertebrates and many vertebrates reproduce in this way.
  38. 38. Ovoviviparous: Animals produce eggs, but instead of laying the eggs, the eggs develop within the mother's body. The young eat unfertilized eggs in the womb for nourishment The young are born alive without placental attachment (umbilical cord), as certain reptiles, fishes, sharks, insects.
  39. 39. VIVIPAROUS Where the embryo develops within the uterus. and is nourished through a yolk sac placenta from the mother’s blood. Young are born alive.  most mammals and some reptiles and fishes.
  40. 40. OVOVIVIPAROUS
  41. 41. ANIMAL DEVELOPMENT
  42. 42. Introduction to animal development The question of how a zygote becomes an animal? The first step is cell division (mitosis) Second step: Cell differentiation (Is the specialization of cells in structure and function) Third step: Morphogenesis (Is the process by which an animal takes shape.)
  43. 43. Fertilization
  44. 44. Fertilization Fertilization depends on mechanisms that bring together sperm and eggs of the same species. All fertilization requires:  critical timing, mediated by:  environmental cues,  pheromones, and/or  courtship behaviour.
  45. 45. Fertilization Two types of fertilizations:  External fertilization  Internal fertilization
  46. 46. External Fertilization In external fertilization, eggs shed by the female are fertilized by sperm of male in the external environment.
  47. 47. Internal Fertilization In internal fertilization, sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract
  48. 48. Internal Fertilization Internal fertilization requires:  behavioural interactions and  compatible copulatory organs. MALE COPULATORY ORGANS
  49. 49. PROCESS OF FERTILIZATION Fertilization brings the haploid nuclei of sperm and egg together, forming a diploid zygote. The sperm’s contact with the egg’s surface initiates metabolic reactions in the egg that trigger the onset of embryonic development. Metabolic reactions: Acrosomal reaction Cortical reaction
  50. 50. ACROSOMAL REACTION Triggered when the sperm meets the egg. The acrosome, at the tip of the sperm releases hydrolytic enzymes that digest material surrounding the egg. Gamete contact depolarizes the egg cell membrane and sets up a fast block to polyspermy.
  51. 51. Sperm contacts egg
  52. 52. Acrosome releases hydrolytic enzymes – digest egg jelly coat
  53. 53. Actin filaments of acrosomal process binds to the sperm binding receptors.
  54. 54. Plasma membranes of sperm and egg fuses
  55. 55. Sperm releases haploid nucleus in egg cytoplasm – fast block prevent polyspermy.
  56. 56. The Cortical Reaction Initiated by the fusion of egg and sperm. It causes a rise in Ca2+. This stimulates cortical granules to release their contents outside the egg. Cause formation of a fertilization envelope (functions as a slow block to polyspermy.)
  57. 57. Rise of calcium in egg and formation of fertilization envelope
  58. 58. Activation of the Egg The sharp rise in Ca2+ in the egg’s cytosol increases the rates of cellular respiration and protein synthesis by the egg cell. Now the egg is said to be activated. The sperm nucleus merges with the egg nucleus to form a diploid zygote and cell division begins.
  59. 59. EMBRYONIC DEVELOPMENT AFTER FERTILIZATION 3 PROCESSES OCCURE IN AN EMBRYO AFTER FERTILIZATION: 1.Cleavage 2.Gastrulation 3.Organogenesis
  60. 60. 1. CLEAVAGE A period of rapid cell division without growth. This creates a hollow ball of cells called a blastula. The blastula consists of many smaller cells called blastomeres The hollow part of the blastula is filled with fluid and called a blastocoel.
  61. 61. CELL DIVISION OF A FERTILIZED EGG FORMING A BLASTULA
  62. 62. Two types of cleavage Meroblastic cleavage, incomplete division of the egg, occurs in species with yolk-rich eggs, such as reptiles and birds. Holoblastic cleavage, complete division of the egg, occurs in species whose eggs have little or moderate amounts of yolk, such as sea urchins and frogs
  63. 63. 2. Gastrulation Gastrulation – rearranges the cells of a blastula into a three-layered embryo, called a gastrula, which has a primitive gut (archenteron)and opens in a blastopore.
  64. 64. Three embryonic germ layers of the gastrula The ectoderm forms the outer layer The endoderm lines the digestive tract. The mesoderm partly fills the space between the endoderm and ectoderm.
  65. 65. GASTRULA OF A FROG
  66. 66. 3. ORGANOGENESIS During organogenesis, various regions of the germ layers develop into organs. Early in vertebrate organogenesis, the notochord forms from mesoderm, and the neural plate forms from ectoderm.
  67. 67. ORGANOGENESIS OF A FROG
  68. 68. The neural plate soon curves inward, forming the neural tube The neural tube will become the central nervous system (brain and spinal cord).
  69. 69. THE FATE OF THE 3 GERM LAYERS Fig. 47-14 ECTODERM MESODERM ENDODERM Epidermis of skin and its derivatives (including sweat glands, hair follicles) Epithelial lining of mouth and anus Cornea and lens of eye Nervous system Sensory receptors in epidermis Adrenal medulla Tooth enamel Epithelium of pineal and pituitary glands Notochord Skeletal system Muscular system Muscular layer of stomach and intestine Excretory system Circulatory and lymphatic systems Reproductive system (except germ cells) Dermis of skin Lining of body cavity Adrenal cortex Epithelial lining of digestive tract Epithelial lining of respiratory system Lining of urethra, urinary bladder, and reproductive system Liver Pancreas Thymus Thyroid and parathyroid glands
  70. 70. AMNIOTES
  71. 71. Developmental Adaptations of Amniotes Embryos of birds, other reptiles, and mammals develop in a fluid- filled sac in a shell or the uterus Organisms with these adaptations are called amniotes.
  72. 72. During amniote development, four extraembryonic membranes form around the embryo: The chorion functions in gas exchange The amnion encloses the amniotic fluid The yolk sac encloses the yolk The allantois disposes of waste products and contributes to gas exchange.
  73. 73. EXTRAEMBRYONIC LAYERS OF BIRDS
  74. 74. PRECOCIAL AND ALTRICIAL DEVELOPMENT PRECOCIAL YOUNG ALTRICIAL YOUNG
  75. 75. At birth the young may be well-developed and able to move about at once, this is called precocial development. If at birth the young are maybe blind, hairless, and essentially helpless, it is called altricial development. In general, precocial young are born after a relatively long gestation period and in a small litter. Hares and many large grazing mammals bear precocial offspring. Rabbits, carnivores, and most rodents bear altricial young.

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