Reproduction 101110032348-phpapp02


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Reproduction 101110032348-phpapp02

  1. 1. Reproduction in some forms of life<br />
  2. 2. Reproduction <br />Forms the next generation of species<br />The means to continue life (perpetuation of species)<br />May be sexual or asexual<br />
  3. 3. Asexual reproduction<br />Sexual reproduction<br />Does not involve gametes or sex cells<br />Occurs in many forms and is performed by many lower forms of organsims, including plants<br />No genetic variation in organisms<br />Involves sex cells<br />The sperm and the egg unite to form a zygote<br />Characteristic of many organisms, including plants, animals and humans<br />Increases genetic variation among organisms<br />
  4. 4. Examples of Asexual reproduction<br />Fission – one cell divides into two either longitudinally, transversely or even diagonally<br />E.g. Algae Volvox and Ulothrix, paramecia, amoeba, bacteria and corals<br />Fragmentation – pieces of an organism may break off and develop into whole organisms<br />Colonies of algae, sea anemone, comb jelly, flatworms<br />
  5. 5. Paramecium<br />
  6. 6. Examples of Asexual reproduction<br />Budding – cells in some areas of an organism’s body organize themselves to form new individuals or buds<br />Hydra (freshwater polyp)<br />Parthenogenesis (virgin birth) – an egg possessing diploid chromosomes develops into an adult without being fertilized<br />Daphnia, rotifers, snails, honeybees and sea urchins<br />
  7. 7. Budding in Hydra<br />
  8. 8. Examples of Asexual reproduction<br />Paedogenesis – smaller larvae develop from bigger larvae and grow up to become adults<br />Flukes, taperworm, ascaris<br />Regeneration – demonstrated by sea stars; when a sea star is cut into pieces, such that each arm has aportion of the central disk, each piece grows the rest of the central disk and the for other arms<br />
  9. 9. Sea stars<br />
  10. 10. Conjugation <br />Sexual reproduction in lower forms of life<br />Genetic material (not necessarily gametes) is transferred between two individuals through a protoplasmic bridge before allowing autotomy (voluntary separation of a body part) to take place<br />Paramecium, bacteria and cyanobacteria, fungi<br />
  11. 11. Examples of Asexual reproduction<br />Common bread mold (amag) – reproduces through spores encased inside a capsule-like container called sporangium<br />Mosses and ferns – spore-producing plants<br />Spores – primary structures responsible for asexual reproduction in mosses and ferns<br />
  12. 12.
  13. 13. Asexual or Vegetative Reproduction in Flowering Plants<br />
  14. 14. Natural Vegetative Reproduction<br />Runners – grow along the ground from the parent plant; forms adventitious roots and shoots at the tips<br />Strawberry<br />Tip layering – allows their aerial stems to arch downwards so that their tips touch the ground<br />Blackberry, raspberry and spider plant<br />Leaf reproduction – new plants develop along the margins of their leaves<br />katakataka<br />
  15. 15. Artificial Vegetative Reproduction<br />Cutting – portions of stems and roots are removed and transferred to loose, damp soil or sand<br />Herbaceous and woody plants such as rose<br />Layering – stimulates the growth of roots on a stem; a stem is buried in the ground then cut when roots are formed<br />Grafting and budding – splicing together of two stems or the union of their two cambium layers (from the stock and scion)<br />
  16. 16. Sexual Reproduction in Flowering Plants: Floral Parts<br />Calyx – collection of sepals<br />Corolla – collection of petals<br />Stamen – male reproductive part<br />Filament – slender stalk<br />Anther – produces colored grains called pollen, which contains sperm nuclei<br />
  17. 17. Pistil/Carpel – female reproductive part<br />Stigma – sticky topmost part<br />Style – slender stalk that supports the stigma<br />Ovary – swollen base<br />Ovules – found inside the ovary <br />
  18. 18.
  19. 19. Stages of Sexual Reproduction in Plants<br />Formation of Gametes<br />Megasporogenesis – formation of female gametophyte<br />Microsporogenesis – formation of male gametophyte<br />Sporogenesis – involves a reduction division process that produces haploid gametes: egg in embyo sac and sperm in the pollen grain<br />
  20. 20. b. Pollination – transfer of the pollen grain from the anther to a stigma of a flower<br />Self-pollination – pollen is transferred from the anther to the stigma of the same flower <br />Cross-pollination – pollen is transferred from the anther to the stigma of another plant<br />
  21. 21. c. Double-fertilization <br />Pollen grain with two nuclei (generative and tube nucleus)<br />generative nucleus  moves into the pollen tube and forms two sperm nuclei<br />tube nucleus  grows through the stigma, style and into the ovule, clearing the way for the entry of sperm nuclei<br />1 sperm nuclei (N) + 1 egg (N) = zygote (2N)<br />1 sperm nuclei (N) + 2 polar nuclei = endosperm (3N)<br />Embryo + endosperm + covering layers of the ovule  seed<br />
  22. 22. d. Fruit and seed development<br />ovary  fruit<br /> ovule  seed<br /> Seed  embryo, stored food and seed coat/testa<br /> Embryo  cotyledon, hypocotyl and epicotyl<br />
  23. 23. e. Seed Germination<br />Viability – ability of the seed to germinate<br />Conditions:<br /> a. Suitable temperature ( between 16C and 27  C)<br /> b. Plenty of moisture<br /> c. Sufficient oxygen <br />Seedling  young plant that develops out of a plant embryo from a seed<br /> radicle – root<br /> hypocotyl – shoot<br /> cotyledons – seed leaves<br />