Chapter 16 Reproduction in Plants Lesson 1 - Types of reproduction in plants


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Chapter 16 Reproduction in Plants Lesson 1 - Types of reproduction in plants

  1. 1. Reproduction in plants Chapter 20 <ul><li>Content </li></ul><ul><li>• Asexual Reproduction </li></ul><ul><li>• Sexual Reproduction in Plants </li></ul>
  2. 2. Learning Objectives <ul><li>Candidates should be able to: </li></ul><ul><li>define asexual reproduction as the process resulting in the production of genetically identical offspring from one parent </li></ul><ul><li>(b) define sexual reproduction as the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspring </li></ul><ul><li>(c) identify and draw, using a hand lens if necessary, the sepals, petals, stamens and carpels of one, locally available, named, insect-pollinated, dicotyledonous flower, and examine the pollen grains under a microscope </li></ul><ul><li>(d) state the functions of the sepals, petals, anthers and carpels </li></ul>
  3. 3. Learning Objectives <ul><li>(e) use a hand lens to identify and describe the stamens and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a microscope </li></ul><ul><li>(f) outline the process of pollination and distinguish between self-pollination and cross pollination </li></ul><ul><li>(g) compare, using fresh specimens, an insect-pollinated and a wind-pollinated flower </li></ul><ul><li>(h) describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (production of endosperm and details of development are not required) </li></ul>
  4. 4. Asexual or Sexual? <ul><li>2 types of reproduction : </li></ul><ul><li>Asexual reproduction </li></ul><ul><li>Sexual reproduction </li></ul><ul><li>Difference? </li></ul><ul><li>Asexual reproduction is the formation of new individuals that does not involve fertilization ( no fusion of gametes ) </li></ul><ul><li>Sexual reproduction involves the fusion of 2 gametes . </li></ul>
  5. 5. Asexual reproduction <ul><li>Methods of asexual reproduction </li></ul><ul><li>V egetative propagation </li></ul><ul><li>S pore formation </li></ul><ul><li>B udding </li></ul><ul><li>no male and female structures (Recall: No gametes involved) </li></ul><ul><li>produces offspring that are genetically identical to parents ( clones ) </li></ul><ul><li>through mitosis (covered in Chapter 18 Cell Division) </li></ul>
  6. 6. Mitosis
  7. 7. Vegetative propagation <ul><li>Involves the growth of a new part of a plant, usually a bud or stem, which eventually becomes separated from the parent plant to form a new individual </li></ul><ul><li>e.g. by means of underground storage organ </li></ul><ul><li>1) rhizomes </li></ul><ul><li>2) bulbs </li></ul><ul><li>3) corms/tubers </li></ul><ul><li>4) runners </li></ul><ul><li>Note : Food stored in underground storage organ enables the plant to survive through unfavourable conditions </li></ul>
  8. 8. Rhizome <ul><li>Horizontal underground stem </li></ul><ul><li>Possesses dry scale leaves and buds </li></ul><ul><li>May have adventitious roots (roots arising from the nodes at the base of the plant) </li></ul><ul><li>e.g. Canna, lallang and ginger </li></ul>
  9. 9. Bulbs <ul><li>Modified shoot </li></ul><ul><li>Consists of flattened disc-like stem bearing buds, fleshy and dry scale leaves </li></ul><ul><li>e.g. onion, garlic </li></ul>
  10. 10. Corms <ul><li>Thick short underground stem swollen with food reserves (mainly starch) </li></ul><ul><li>e.g. water chestnut </li></ul>
  11. 11. Tubers <ul><li>Swollen underground stem bearing a number of reduced stem leaves and buds </li></ul><ul><li>Food reserve is mainly starch and proteins (found just beneath the skin) </li></ul><ul><li>e.g. potato </li></ul>
  12. 12. Summary
  13. 13. *** Advantages of vegetative propagation <ul><li>Does not rely on external agencies (insects/wind) for pollination & dispersal </li></ul><ul><li>Food present in vegetative structures (buds can develop rapidly into daughter plants) </li></ul><ul><li>Beneficial traits are passed on directly to daughter plants </li></ul><ul><li>Involves only one parent (no fertilization!) </li></ul><ul><li>Can colonise area quickly (already in suitable habitat) </li></ul>
  14. 14. *** Disadvantages of vegetative propagation <ul><li>Overcrowding (because there is no dispersal mechanism) </li></ul><ul><li>Less variation in offspring (less adaptable to changes in environmental conditions) </li></ul>
  15. 15. Sexual Reproduction in flowering plants
  16. 16. Facts about sexual reproduction in flowering plants <ul><li>involves fusion of gametes </li></ul><ul><li>Flowers = organs of sexual reproduction </li></ul><ul><li>Pollination + fertilisation = mechanisms to ensure the male and female gametes meet </li></ul>
  17. 17. Parts of a flower
  18. 18. Label the parts of the flower
  19. 19. Worksheet 1 2 4 pedicel 3 5 6 7 8
  20. 20. Worksheet
  21. 21. Parts of a flower - modified leaves (enclose & protect other parts of flower in bud stage) - enlarged end of flower stalk on which other parts of flower are borne pedicel - flower stalk <ul><li>modified leaves forming conspicuous part of flower </li></ul><ul><li>brightly coloured (attract insects for pollination) </li></ul><ul><li>landing platform </li></ul><ul><li>male part of flower </li></ul><ul><li>consists of filament bearing an anther (that produces pollen grains) </li></ul><ul><li>female part of flower </li></ul><ul><li>consists of carpels </li></ul><ul><li>each carpel consist of ovary + style (above the ovary) + one or more stigmas </li></ul>
  22. 22. General parts of a flower 6. 2. 3. 4. 5. 1.
  23. 23. Anther <ul><li>usually made up of two lobes </li></ul><ul><li>each lobe has 2 pollen sacs containing pollen grains (produced by meiosis -> haploid number of chromosomes) </li></ul><ul><li>each pollen grain gives rise to two haploid male gametes </li></ul><ul><li>when anther matures, the two lobes split -> setting free the pollen grains </li></ul>
  24. 24. Which structure is the stigma?
  25. 25. Stigma <ul><li>swollen structure at end of style </li></ul><ul><li>receives the pollen grains </li></ul>
  26. 26. Ovary <ul><li>consists of one or more ovules </li></ul><ul><li>within each mature ovule is a female gamete ( egg cell / ovum ) </li></ul><ul><li>region where ovules are attached in the ovary is called the placenta </li></ul>