Biology Form 5 Chapter 4 : 4.5 Reproduction in flowering plants
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Biology Form 5 Chapter 4 : 4.5 Reproduction in flowering plants
- 1. Sexual ReproductionSexual Reproduction in Flowering Plantsin Flowering Plants
- 2. Reproductive organ: Flower usually bisexual or hermaphrodite sometimes unisexual
- 3. 1. Hermaphrodite: flower has both sexes MALE PART FEMALE PART
- 4. 2. Monoecious plant: male and female flowers on the SAME tree (e.g. oak) Male flowers Female flowers (from the Greek "mono-oikos" = "a single house") UNISEXUAL
- 5. 3. Dioecious plant: male and female flowers on SEPARATE trees Male carob flowers Female carob flowers Fruit only on female trees (from the Greek "di-oikos" = " two homes") UNISEXUAL
- 6. Flower parts are organised in circles called whorls sepals petals stamens carpels
- 7. Stigma Style Ovary Ovule Petal (petals = corolla) Receptacle Sepal (sepals = calyx) Pistil (carpels = female organ) Anther Filament Stamen (stamens = male organ) Structure of a FlowerStructure of a Flower
- 9. Function of sepals: Protect flower when still a bud; May persist, but no function thereafter sepal
- 10. Function of petals: To attract insects
- 11. Insect- Pollinated flowers • Some plants take advantage of the sex drive of certain insects… • Certain orchids look like female wasps, and even smell like them!
- 12. • Males try to mate with them, and in the process they pollinate the plant • The orchid gets pollinated, but the male wasp only gets frustrated!
- 13. Reproductive floral organs: male Function of: anther: forms pollen grains filament: hold anther pollen grain: contains the male gamete
- 14. Reproductive floral organs: female Function of carpel: holds female sex cells (egg cell /ovum) Egg cell
- 15. Stigma Style Ovary/Carpels Ovule Carpels : receive pollen grains support stigma protect ovule becomes seed after fertilization Structure of a FlowerStructure of a Flower
- 16. ovary develops into a fruit ovule develops into a seed
- 18. Stigma: sticky provides nutrients to pollen grain Germination of the pollen grains on the stigma
- 19. Vertical section through carpel (attaches an ovule to the ovary wall) (the point of attachment of ovule to ovary) funicle stigma style ovary wall ovule ovary placenta
- 20. TS ovary
- 22. • The ovary may contain one or more Ovules • Each ovule bears one female egg cell • The ovule develops into a seed OVULE
- 23. THE FORMATION OF POLLEN GRAINS THE ANTHER HAS FOUR POLLEN SACS FOUR POLLEN SACS
- 24. Vascular bundle Pollen sac / Anther sac TS Anther Pollen grain (contains the male gamete) A tetrad of 4 haploid cells – separate to become pollen grains
- 25. THE FORMATION OF POLLEN GRAINS EACH POLLEN SAC HAS HUNDREDS OF MICROSPORE MOTHER CELLS OR POLLEN MOTHER CELLS WHICH ARE DIPLOID CELLS
- 26. In the pollen sac, pollen mother cells divide by meiosis to produce the pollen grains.
- 27. Structure & Development of the pollen grain
- 28. POLLEN GRAINS
- 29. Production of pollen grains HaploidHaploid HaploidHaploid Meiosis in anther 4 haploid daughter cells, also called pollen tetrads FOUR POLLEN SACS
- 30. Haploid Haploid HaploidHaploid As anther matures, 4 microspores of a tetrad separate from each other. Production of pollen grains Haploid nucleus of each microspore undergoes a single mitotic division. The 2 resulting haploid nuclei become encased in a thick, resistant wall, forming a pollen grain. Pollen Grain Mitosis
- 31. Pollen grain Pollen Wall Tube Cell Generative Cell Waterproofing prevents desiccation during pollen transfer. Recognition proteins cause allergic reactions. cytoplasm cytoplasm nucleus nucleus Digests path through stigma, style, and ovary. Locates micropyle of ovule. Penetrates into embryo sac. nucleolus nucleolus Divides by mitosis to make two sperm. Both join in syngamy events.
- 32. Dehiscing anther Pollen grains (contain a haploid nucleus)
- 33. Two male gametes inside pollen grain
- 34. Remember: Pollen grain: microspore Contents of pollen grain: MALE GAMETE Embryosac: megaspore Contents of embryosac: FEMALE GAMETE Egg Sperm
- 35. Ovules hold the female sex cells Meiosis takes place inside the ovules, resulting in the production of female spores.
- 36. THE FORMATION OF THE EMBRYO SAC THE MEGASPORE MOTHER CELL IS ALSO KNOWN EMBRY SAC MOTHER CELL
- 37. 4 MEGASPORES OVULE with EMBRYO SAC MOTHER CELL(2n) 3 MEGASPORES DIE ONE FUNCTIONAL MEGASPORE ENLARGES TO MANY TIMES ITS ORIGINAL SIZE FILLING UP MOST OF THE OVULE EMBRYO SAC EMBRYO SAC MOTHER CELL (2n) Meiosis 1 & Meiosis II THE FORMATION OF THE EMBRYO SAC
- 38. Nucleus Of The Megaspore Undergoes Three Mitotic Divisions Mitosis 1 Mitosis 2 Mitosis 3 • 3 Migrate To One End Of The Cell - Antipodal Cells • 2 Nuclei Move To The Center - Polar Nuclei • 3 Nuclei Near The Micropyle - 1 Egg Cell Clamped By 2 Synergid Cells EMBRYO SAC 8 Nuclei
- 40. THE FORMATION OF THE EMBRYO SAC
- 41. Where is the egg cell? egg cell
- 42. POLLINATION is the transfer of pollen grains from an anther to a stigma
- 43. Stigma touches insect’s body that may be carrying pollen
- 44. Self-pollination: the transfer of pollen from the anther to the stigma of the: same flower, or of another flower of the same plant Self-pollination: the transfer of pollen from the anther to the stigma of the: same flower, or of another flower of the same plant Cross-pollination: the transfer of pollen to a flower on a different plant of the same species Cross-pollination: the transfer of pollen to a flower on a different plant of the same species
- 46. Plant fertilisation • When pollen sticks to the stigma it absorbs water and starts to germinate • A pollen tube will grow out of the grain and through the style towards the ovary
- 47. Plant fertilisation • The pollen tube nucleus remains close to the tip of the tube. • Digestive enzymes are secreted from the tube. • The tube is attracted by chemicals given out by the ovary.
- 48. Plant fertilisation • As the tube grows the generative nucleus divides by mitosis to form two haploid male gametes. Tube nucleus Male gamete
- 49. Plant fertilisation • The pollen tube enters the ovule through the micropyle. • Once inside the ovule the tube nucleus degenerates and the male gametes enter the embryo sac
- 51. Double fertilisation • One of the male gametes fuses with the female gamete forming a diploid zygote. • The other male gamete fuses with the 2 polar nuclei in the centre of the embryo sac forming a triploid nucleus – called the endosperm nucleus.
- 52. • The union of two male gametes with different nuclei of the embryo sac is termed double fertilization. – Double fertilization ensures that the endosperm will develop only in ovules where the egg has been fertilized. – This prevents angiosperms from squandering nutrients in eggs that lack an embryo.
- 53. Summary : Double FertilizationSummary : Double Fertilization fusion of male gamete & female gamete to form a zygote fusion of male gamete & 2 polar nuclei to form endosperm Process Pollen grain lands on a stigma and germinates Pollen tube grows down the style & ovary - secretes enzyme to digest a pathway through style Generative nucleus divides – form 2 male gametes Tube nucleus goes before male gametes & disintegrates One male gamete fuse with egg cell – zygote One male gamete fuses with 2 polar nuclei to form endosperm
- 56. After fertilization • Seed = Fertilized egg • Ovary becomes the fruit
- 57. • Egg becomes ……………….. then ….………. • Triploid endosperm become ……………... • Ovary becomes ………… • Ovule becomes ……………. • Integument becomes …………….. • Ovary wall becomes …………………….. After fertilisation… Zygote Endosperm Seed Seed coat Fruit wall / Pericarp Fruit Embryo
- 59. Fruit & Seed Dispersal
- 60. Structure of SeedStructure of Seed plumule radicle micropyle cotyledon seed coat
- 62. OVULE INSIDE OVARYOVULE INSIDE OVARY SEED INSEED IN A PODA POD TUBETUBE NUCLEUSNUCLEUS GENERATIVEGENERATIVE NUCLEUSNUCLEUS A TETRAD OF HAPLOIDA TETRAD OF HAPLOID MICROSPORES INSIDEMICROSPORES INSIDE POLLEN SACPOLLEN SAC
- 63. THE END Jatropha – monoecious
- 64. THE FORMATION OF POLLEN GRAINS POLLEN MOTHER CELL FOUR HAPLOID CELLS ( MICROSPORES) FOUR HAPLOID CELLS ( MICROSPORES) POLLEN MOTHER CELL
- 65. THE FORMATION OF POLLEN GRAINS The nucleus of the microspore undergoes MITOSIS to produce two nuclei GENERATIVE NUCLEUS TUBE NUCLEUS POLLEN GRAINS