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Plant Diversity II: The Evolution of Seed Plants

Plant Diversity II: The Evolution of Seed Plants. Chapter 30. Advantages of Seeds. Embryo and food supply within ovule, protected Multicellular tissue layers provide protection Can remain dormant for days, months or years until conditions are right Transported by wind or animals.

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Plant Diversity II: The Evolution of Seed Plants

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  1. Plant Diversity II: The Evolution of Seed Plants Chapter 30

  2. Advantages of Seeds • Embryo and food supply within ovule, protected • Multicellular tissue layers provide protection • Can remain dormant for days, months or years until conditions are right • Transported by wind or animals

  3. Spores in bryophytes and mosses resist environmental changes • Seeds replace spore’s role of dispersing the species. • Spores are retained within the sporangia- • Pollen frees sperm from water

  4. Gymnosperms • What does gymnospem mean? • Naked seeds • How are the needle shaped leaves of Coniferophyta adapted to dry conditions? • Thicker cuticle, stomata in pits

  5. AngiospermsAnthophyta • More specialized xylem evolved • Tracheids seen in gymnosperms gave rise to vessel elements • Xylem is reinforced by second cell wall, the fiber (also seen in conifers) • Flower is the reproductive structure • Coevolution is seen between flowers and animals

  6. Angiosperm Diversity • Monocots • One cotyledon • Parallel leaf veins • Scattered vascular tissue • Fibrous root system • One opening in pollen grain • Floral parts in multiples of 3 • Dicots (Eudicots) • Two cotyledons • Netlike leaf veins • Vascular tissue arranged in rings • Taproot system • Three openings in pollen grains • Floral parts in multiples of 4 or 5

  7. The Fruit • What is a fruit? • After fertilization the ovary becomes the fruit. It protects the seeds. • Name three modifications that different fruits have for seed dispersal. • Sweeten and turns colorful when ripe • Have burrs that can sticks to animal’s fur • Feathery like dandelions for wind dispersal of seeds

  8. Sporophyte/Gametophytes • The life cycle of the angiosperms shows very reduced gametophyte generations. • What is the male gametophyte? • Pollen grain • What is the female gametophyte? • Embryo • What is pollination? • Bringing pollen to the stigma.

  9. Double Fertilization • The pollen tube grows following pollination and leads to double fertilization. • What is fertilized? • Sperm + egg = zygote (2n) • Sperm + 2 polar nuclei = endosperm (3n)

  10. Human welfare and seed plants • Crops • Flowering plants provide other edible products • Source of wood • Medicine

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