1 / 23

Plant Reproduction

Plant Reproduction. AP Biology Unit 5. Alternation of Generations. All land plants can exist in two different multicellular forms Sporophyte (2n) Gametophyte (n) In a life cycle, plant generations alternate between sporophyte and gametophyte Each form gives rise to the other form.

rose-ellison
Download Presentation

Plant Reproduction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Plant Reproduction AP Biology Unit 5

  2. Alternation of Generations • All land plants can exist in two different multicellular forms • Sporophyte (2n) • Gametophyte (n) • In a life cycle, plant generations alternate between sporophyte and gametophyte • Each form gives rise to the other form

  3. Sporophyte vs. Gametophyte • Sporophyte (2n) • Diploid, multicellular form of a plant • Forms haploid spores through meiosis • Gametophyte (n) • Haploid, multicellular form of a plant • Forms gametes through mitosis

  4. Alternation of Generation

  5. How is this different from other organisms? • In other organisms (like humans) the haploids are unicellular (sperm and egg) • In plants both forms (sporophyte and gametophyte) can be multicellular

  6. Evolution of Plant Reproduction • Each type of plant has a dominant form (sporophyte or gametophyte) • Dominant form = the “plant” we think of • As plants have evolved, there have been changes to relationship between sporophyte and gametophyte

  7. Gametophyte/Sporophyte Relationships • 3 different possibilities • Larger gametophyte, sporophyte is dependent on it • Larger sporophyte, gametophyte is independent • Larger sporophyte, gametophyte is dependent

  8. Question… • What trend do you see between the evolution of plants (from nonvascular  vascular; nonseed  seed plants) and the alternation of generations? • As plants have evolved, the gametophyte has become more reduced, sporophyte has become more dominant

  9. Reproductive Organs • Archegonium • Female sex organ  produces egg • Antheridium • Male sex organ  produces sperm

  10. Vascular Plants: Homosporous vs. Heterosporous • Vascular plants have sporophylls • modified leaves that produce sporangia (which become spores) • Homosporous plants • Most ferns • Heterosporous plants • All seed plants (angiosperms and gymnosperms) and some seedless plants

  11. Water vs. Wind • Mosses and Ferns require water to help the sperm reach the egg. • Seed plants no longer require water to reproduce • Pollen (male gametophyte) can be carried by wind, animals, etc.

  12. Gymnosperm Life Cycle • Sporophyte is the dominant form • Heterosporous • Have “naked” seeds – nothing around the seed • Cones are either male (contain pollen) or female (contain ovule)

  13. Flower Anatomy • The flower is the reproductive organ of an angiosperm • Female part = Carpel • Consists of the stigma, style, and ovary • Male part = Stamen • Consists of anther and filament

  14. Angiosperms • Dominant form is the sporophyte • Heterosporous • Male gametophyte = pollen grain • Female gametophyte = embryo sac

  15. Female Gametophyte • The megaspore will go through MITOSIS to create a series of different cells in the female gametophyte • Cells involved in fertilization are • Egg (n)– haploid • Polar nuclei (2n) – 2 nuclei in one cell

  16. When the pollen grain lands on the stigma, it will extend a pollen tube down the style to get to the egg Specific cells in the pollen tube go through mitosis to form 2 sperm Sperm will enter

  17. Double Fertilization • Angiosperm fertilization actually consists of 2 separate fertilization events = double fertilization • Both sperm in the pollen tube are used • One sperm fertilizes the egg  diploid zygote (2n) forms • The other sperm fertilizes the polar nuclei (2n)  forms triploid endosperm (3n)

  18. Double Fertilization • Double fertilization is unique to angiosperms • Through this process, resources are used most efficiently since endosperm can only develop in a fertilized ovule. • Endosperm = starchy material that serves as nutrition for the growing embryo

  19. Other Post-Fertilization events • Embryo develops (diploid) • Seed coat forms • Ovary develops into fruit around the seed

  20. Germination and Seedling Formation • Seeds are dormant until they begin germination • When conditions are right, seeds will begin to germinate to form a seedling. • Germination starts with imbibition—when water enters the seed and triggers enzymes that are needed for growth.

  21. Seed Benefits • What are the evolutionary benefits of seeds? • Dispersal- embryo can travel far from parent • Protection- seed coat protects embryo • Dormancy- can wait until conditions are favorable to germinate • Storage- food for the embryo can be stored inside seed (ex. endosperm)

  22. Monocots vs. Eudicots • Most angiosperms can be classified as either Monocots or Eudicots

More Related