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SEXUAL REPRODUCTION. SEXUAL REPRODUCTION AND DEVELOPMENT. SEXUAL REPRODUCTION. Sexual reproduction requires two different parent cells from two separate organisms or from two sexually different parts of a single organism.

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  2. SEXUAL REPRODUCTION Sexual reproduction requires two different parent cells from two separate organisms or from two sexually different parts of a single organism. Sexual reproduction produces off springs that are genetically different from either parent. In simple organisms, sexual reproduction involves transport of genetic material from one organism to another. In more complex organisms, two special sex cells, called gametes are needed. (pg: 417)

  3. TYPES OF GAMETES l) ISOGAMY It is a condition in which the sexual cells (gametes) are of the same form and size. Many algae and some fungi have isogamous gametes. Ex: Ulotrix

  4. TYPES OF GAMETES ll) HETEROGAMY It is a condition of having differently sized male and female gametes. A) ANISOGAMY The union of morphologically unlike motile gametes. Oedogonium sp.(green algae)

  5. TYPES OF GAMETES B) OOGAMY The union of unlike gametes, usually a large non-motile female gamete and a small motile male gamete.

  6. EXCEPTIONAL CASES IN SEXUAL REPRODUCTION A)Conjugation The type of sexual process most commonly found among simple organisms is called conjugation. In conjugation, a cytoplasmic bridge forms between two cells, and an exchange or transfer of nuclear material takes place through the bridge. Ex: Paramecium, bacteria


  8. B) Hermaphroditism In some animals sexes are not separate. Instead, each individual has both testes and ovaries. These organisms are called hermaphrodite. Hermaphroditism is usually found among animals that move slowly or those that are attached to surface. Ex: earthworms, flatworms, snails, hydras, sponges and some flowering plants.

  9. B) Hermaphroditism Even though hermaphroditic organisms can produce both eggs and sperm, self-fertilization is rare. Instead, these organisms exchange sperm with another individual of the same species.

  10. B) Hermaphroditism ! Self fertilization is seen in flatworms but not in earth worms. ! Reproductive organs of sponges are not found at a particular site of the organism. Some cells found in different places of the organism produce eggs and sperms.

  11. C) Parthenogenesis mitosis worker (2n) Sterile female honey Male bee(n) Sperm cells (n) fertilization royal jelly (2n) female Queen (2n) meiosis Egg cells (n) Queen (2n) meiosis No fertilization Drone (n) parthenogenesis

  12. C) Parthenogenesis The development of an unfertilized egg into adult animal without fusion with sperm is called parthenogenesis. In nature it takes place in many insects, including bees, wasps and certain ants. For example, in bees, the queen bee mates only once. She can then produce either unfertilized eggs or fertilized eggs. The unfertilized eggs become male drones while the fertilized eggs become female workers or queen.

  13. SEXUAL REPRODUCTION IN ANIMALS External Fertilization Internal Fertilization The gametes fuse outside of the body The gametes fuse inside the body of female


  15. EXTERNAL FERTILIZATION In external fertilization, the eggs are in the environment outside the body of the female. Takes place in animals that live in water. Ex: Fish (but not sharks), many amphibians To overcome the hazards of external fertilization, large numbers of eggs and sperm are released. Embryo inside the fertilized egg develops in aquatic environment.



  18. INTERNAL FERTILIZATION Fertilization within the body of the female is called internal fertilization. It is found most often in animals that reproduce on land and also found in some aquatic animals, such as sharks. Internal fertilization requires a specialized sex organ to carry sperm from the body of the male into the body of the female. Less number of eggs are produced After fertilization, either the zygote is enclosed in a protective shell and released by the female, or it remains and develops within a special part of the female’s body.

  19. Metamorphosis In some animals that produce large number of eggs, embryo hatches into nymph or larvae before it completes its development. Nymphs or larvae complete their development at the outside and become adults. This series of changes is called metamorphosis.

  20. Metamorphosis

  21. REPRODUCTION IN FISH AND AMPHIBIANS Eggs are not covered with a hard shell, instead they are surrounded by a jellylike substance. Eggs that are produced in the ovaries of females pass to the Müller’s duct through the ciliated funnel (kirpikli huni) and then released out of the body from the cloaca(kloak). Wolf’s ductcarries both sperms and excretory materials to the cloaca in males.

  22. REPRODUCTION IN FISH AND AMPHIBIANS Egg Kidney Testes Ciliated funnel Ovary Muller’s duct Kidney Wolf’s duct Urinary bladder Ureter Urinary bladder Cloaca Cloaca Male fish and amphibian urogenital system Female fish and amphibian urogenital system

  23. REPRODUCTION IN REPTILES AND BIRDS • Internal fertilization is mostly seen in reptiles and birds. • Embryo found in the fertilized egg completes its development inside the egg. • In females, eggs are transferred to the cloaca through the Muller’s duct. Inside the Muller’s duct egg white and shell are formed. • Wolf’s duct carries only sperms in males. Egg shells of birds are harder than reptiles. Fertilization occurs in Muller’s duct. • Excretory substances are transported from a separate duct to the cloaca.

  24. REPRODUCTION IN REPTILES AND BIRDS Testes Ovary Ciliated funnel Muller’s duct Wolf’s duct Kidney Egg Ureter Ureter Urinary bladder Urinary bladder Cloaca Cloaca Female Reptile and Bird Urogenital system Male Reptile and Bird Urogenital system

  25. Bird Reproductive System

  26. After fertilization, the development of chordates can be oviparous, ovoviviparous or viviparous. • In oviparousspecies, which include most fishes and amphibians and all birds, the eggs develop outside the mother’s body. Embryo obtains nutrients from the egg.

  27. In ovoviviparousanimals, such as sharks, the eggs develop within the mother’s body and the embryos receive nutrients from the yolk in the egg.

  28. The developing embryos of viviparousanimals, including most mammals, obtain nutrients directly from the mother’s body.

  29. EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS Embryonic membranes formed during the development of reptiles and birds are; • Chorion (serosa) • Allantois • Amnion • Yolk sac (Vitellus sac)

  30. EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS • CHORION: The outermost membrane lines the inside of the shell and surrounds the embryo and other three membranes. ***It aids in the exchange of gases between the embryoand the environment. ***In mammals, chorion is involved in the formation of placenta.

  31. EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS 2. ALLANTOIS: is a saclike structure that grows out of the digestive tract of the embryo. So that it aids in the exchange of gases and collection of waste materials. *** In mammals, waste materials pass from embryo to the mother, therefore allantois is degenerated. (körelmiştir)

  32. EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS 3. AMNION:The amniotic fluid withinthe sac acts as a cushion to protect it from shocks. *** During developmental stages of fish and frogs, amnion sac is not formed. *** In mammals, amnion sac is involved in the formation of umbilical cord (göbek bağı).

  33. EMBRİYO ZARLARI EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS 4. YOLK SAC (VITELLUS SAC): It surrounds the yolk (vitellus) and it is the source of food for the embryo. *** Yolk sac of birds and reptiles are larger than fish and frogs. *** As there is little amount of vitellus in the eggs of mammals, yolk sac is not developed as much. The mother meets the needs of the embryo.

  34. REPRODUCTION IN MAMMALS NONPLACENTAL MAMMALS Pouched mammals (Marsupials) (Keseli memelilerde) *Some internal development of the embryo takes place in the uterus, but no placenta is formed. *The young animal crawls into a pouch on the outside of the mother’s body after birth and attaches itself to a mammary gland. *Development is completed in the pouch. Ex: kangaroo, opossum (keseli ayı) Egg-laying mammals Gagalı memelilerde (platypus, ornithorenk) *The egg of egg-laying mammals contain a large amount of yolk. *The embryo completes its development outside the body of the mother and feeds upon the mother’s milk.

  35. Pouched mammals

  36. Egg-laying mammals

  37. REPRODUCTION IN MAMMALS PLACENTAL MAMMALS Most mammals, including humans, are placental mammals. (Ex:hedgehog (kirpi), bat, whale, horse, donkey, elephant, seal, sheep) In these mammals, the blood vessels of the embryo’s circulatory system are in close contact with the mother’s circulatory system. This contact takes place in a specialized structure called the placenta. The placenta allows the exchange of nutrients and wastes between the embryo and the mother.

  38. In humans, the chorion is the outermost extraembryonic membranes. Small fingerlike projections called chorionic villi form on the outer surface of the chorion and extend into the uterine lining. ( Chorionic Villus + uterus wall= Placenta)

  39. In the human, the yolk sac and the allantois develop into the umbilical cord. This rope like structure connects the developing fetus to the placenta. This structure contains blood vessels that transport waste materials out of the embryo’s body. Veins inside the umbilical cord carry oxygen and nutrients to the embryo. (Umbilical cord = vitellus sac + allantois)


  41. SPERMATOGENESIS Is the production of sperm in testes by meiotic division from immature sex cells called spermatogonia (2n). In humans, after a male matures sexually , there is a continual development of some spermatogonia into functional sperm. @

  42. 1. Spermatogonium increases in size to become a primary spermatocyte. 2. The primary spermatocyte undergoes the first meiotic division, forming secondary spermatocytes. 3. Each secondary spermatocyte undergoes second meiotic division, forming 4 haploid spermatids. 4. Each of the spermatids develops into a mature sperm with flagellum inside the epididimys.

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