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Plant Diversity II

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  1. Plant Diversity II • The Evolution of Seed Plants

  2. SEEDS! • Seeds are plant embryos packaged with a food supply in a protective coat

  3. Evolution of Plants

  4. Five Reproductive Adaptations • Reduction of the gametophyte: • shift from haploid to diploid condition • female gametophyte and embryo depend on sporophyte • protection against drought • Protects the delicate antheridia and archegonia • Increasing reproductive success • Heterospory • Production of two types of spores • Megaspores – female gametophyte – eggs • Microspores – male gametophyte - sperm

  5. Five Reproductive Adaptations • Ovules: production of eggs • Megasporangium, megaspore plus protective tissue = ovule • Increases protection of the egg and developing zygote • Increases reproductive fitness • Evolution of pollen • Male gametophyte = pollen grain • Contain two sperm nuclei • Waterproof coat for transfer by wind • Remember before – water was required for fertilization • THIS IS A KEY ADAPTATION

  6. Five Reproductive Adaptations • Seeds • Advantages over spores • Multicellular • Layers of protective material • Supply of stored energy means seed can WAIT for good germination conditions • Stored energy supplements early growth of the embryo

  7. Gymnosperms (bare naked) • Cone-bearing plants • Lack enclosed chambers (ovaries) for seeds • Ovules and seeds develop on specialized leaves called sporophylls • Ginkgo, cycads, and conifers • All are “evergreens” • Needle-shaped leaves • Vascular tissue refinement: tracheids~ water conducting and supportive element of xylem

  8. Reproduction in Gymnosperms

  9. Reproductive Cycle

  10. Gymnosperm Life Cycle • Sporophyte • produce gametophytes inside of cones • Pollen cone (male) • produces microspore via meiosis • Ovulate cone (female) • produces megaspores via meiosis • Fertilization • pollen grains discharge sperm into egg

  11. Angiosperms – Flowers and Fruits • Seed plants that produce the reproductive structures called flowers and fruits. • 90% of all plant species • “Flowering plants” Anthophyta

  12. The Flowerdefining structure of angiosperms • Reproductive structure: pollen transfer; specialized shoot with modified leaves • Sepals: enclose flower before it opens - protection • Petals: attract pollinators • Stamens: male, produce microspores in the anther that develops the pollen grain • Carpels: female, produce megaspores - stigma, style, ovary, ovules

  13. Fruits • Fruits are the mature ovaries of the plant • The wall of the ovary thickens to become the fruit. • The purpose of fruit is to disperse the seeds

  14. Monocots and Eudicots • Angiosperms are divided into two groups • Monocots • ~70,000 species • One cotyledon in the seed • Parallel leaf veins • Flowering parts in multiples of three

  15. Monocots and Eudicots • Angiosperms are divided into two groups • Eudicots • ~170,000 species • Two cotyledon in the seed • Net leaf veins • Flowing parts in multiples of fours or fives

  16. Angiosperm life cycle