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Chapter 8 Notes

Chapter 8 Notes. Plant Reproduction – 2 types Produce offspring that are genetically identical to the parent (Asexual) Produce offspring that are genetically different from the parents (Sexual). Advantages and Disadvantages (Table 9.1). Sexual Reproduction Advantage

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Chapter 8 Notes

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  1. Chapter 8 Notes • Plant Reproduction – 2 types • Produce offspring that are genetically identical to the parent (Asexual) • Produce offspring that are genetically different from the parents (Sexual)

  2. Advantages and Disadvantages(Table 9.1) • Sexual Reproduction • Advantage • Some offspring are more adapted, • New site could be different from parents site • Environment changes will affect some but not all • Disadvantage • Isolated individuals CANNOT reproduce • New site colonization is not rapid • Some offspring are less adapted

  3. Advantages and Disadvantages(Table 9.1) • Asexual Reproduction • Advantage • Can rapidly colonize new site if it is suitable • Isolated individuals CAN reproduce • Disadvantage • All may be adversely affected by minor environmental changes • All as adapted as the parent; none more or less

  4. Asexual Reproduction • Fragmentation – • parts of plant break off and form new plants. • Adventitious shoots form from roots • Examples include cacti, Airplane plant, Aspen • * a several acre grove of Aspen may be just one individual plant

  5. SEXUAL REPRODUCTION • Plant Life Cycle • Plants have 2 phases in life cycle • Sporophyte phase (2N) • Gametophyte phase (1N) • Familiar plants (trees, shrubs) are just one phase in the life cycle-Sporophytes

  6. SEXUAL REPRODUCTION • Sporophyte phase • Sporophytes have sex organs—flowers in Angiospems • Meiosis occurs in sex organs to produce spores (not gametes) • Gametes can fuse (syngamy) to produce 2N zygote • Spores cannot fuse • Spores grow into new haploid (1N) gametophyte • Megaspore is 1N and becomes megagametophye in the ovary • This produces the megagamete (egg) • Microspore is 1N and becomes microgametophyte in the Anther • This produces the microgamete (pollen) • Megagamete and microgamete fuse to produce zygote • The zygote grows to become the seed. • Seed grows into the new sporophyte

  7. SEXUAL REPRODUCTION • Gametophyte phase • Gametophyte looks nothing like the sporophyte in vascular plants. • Gametophyte has no roots, stems, leaves or vascular tissue (Fig. 9.4, p. 233) • Gametes are formed by mitosis (not meiosis) • Gametes fuse (syngamy) forming a zygote that grows into a new sporophyte • **This life cycle, with 2 generations—sporophyte and gametophyte—is called Alternation of Generations.

  8. Fertilization • Fertilization occurs when the microgamete and megagamete fuse, a.k.a., syngamy • Syngamy consists of 2 parts • Plasmogamy – the cells fuse • Karyogamy – the nuclei fuse • Results in a 2N zygote  seed sporophyte

  9. FRUIT TYPES (Table 9.5, p. 256) • Compound Fruits • Aggregate fruit—carpels of flower NOT fused but grow together during fruit maturation • Raspberry, blackberry • Multiple fruit—all the fruits grow together during maturations • pineapple

  10. Fruit Development • Ovary develops into a fruit that contains the seed(s) • Flower parts may persist (apple) or die and fall off (orange) • Fruits often have 3 distinct layers • Exocarp—outermost layer (skin or peel) • Mesocarp—middle layer (flesh) • Endocarp—inner layer (pit or stone) • Pericarp = exocarp + mesocarp + endocarp

  11. Pollination • Occurs when pollen reaches the stigma • 2 types—cross-pollination and self-pollination • Cross-pollination—pollination by a different individual • Self-pollination—pollination by the same individual • Self-pollination has similar results as asexual reproduction • Cross-pollination is similar to reproduction in mammals • insures the mixing of genetic material • insures genetic diversity

  12. Mechanisms to Insure Cross-pollination • Stamen and Style mature at different times • Stigma and pollen are incompatible—stigma prevents pollen growth if it’s from the same plant • Monoecious and Dioecious species • Monoecious—male / female flowers on the same plant • Example = corn • Dioecious—male / female flowers on different plants • Example = dates, willows

  13. Animals and Pollination • Wind pollination is inefficient and “expensive”—why? • Angiosperms and insects begin association 120 mya • Angiosperms and Insects evolved together—co-evolution • Plants developed flowers that attracted pollinators • Insects developed body parts to reach nectar • Some flowers developed bilateral symmetry to match the pollinator • Co-evolution also occurred with birds and bats • Some bizarre adaptations for pollination can be found at:http://www.life.uiuc.edu/plantbio/260/Attenborough1.pdf

  14. Some plants developed to protect the ovary from damage by animals. The bases of the stamens, petals and sepals fuse around the ovary, and the “flower” begins above the ovary. This is an “inferior ovary” • Some did not develop this way, and the ovary is above the petals, sepals and stamens. This is a “superiorovary”. • (See Figure 9.29 on p. 251)

  15. Inflorescences • Refers to how the flower is positioned on the plant. • Consult pp. 251-254 • Seed Dispersal (and examples)—the big 5! • Wind (Dandelion) • Water (Coconut palm) • Thrown from the parent plant (Poppy) • Attaches to an animal and is carried away (Beggars Lice) • Eaten by animals and deposited elsewhere (Apple)

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