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THE “EVOLUTION” OF SEED PLANTS

THE “EVOLUTION” OF SEED PLANTS. Packet #71 Chapters 29, 30 & 38. THE “EVOLUTION” OF PLANT ORGANS. “EVOLUTION” OF ROOTS. The “evolution” of roots allowed plants to become anchored and helped enable them to absorb water and nutrients from the soil

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THE “EVOLUTION” OF SEED PLANTS

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  1. THE “EVOLUTION” OF SEED PLANTS Packet #71 Chapters 29, 30 & 38

  2. THE “EVOLUTION” OF PLANT ORGANS

  3. “EVOLUTION” OF ROOTS • The “evolution” of roots allowed plants to become anchored and helped enable them to absorb water and nutrients from the soil • Roots allow the shoot system to grow taller and contain lignified vascular tissue.

  4. “EVOLUTION” OF LEAVES See Pages 584-586 Chapter 29 Figure 29.13 Page 586 • Leaves increase the surface area of vascular plants. • Leaves can be classified as microphylls or megaphylls • All lycophytes (club mosses) have small, usually spine-shaped leaves with a single vein • Microphylls • Leaves of other “modern” vascular plants are known as megaphylls • The larger sized leaves are possible due to the highly branched vascular system which supports greater photosynthetic activity.

  5. THE EVOLUTION OF SEED • The evolution of seed facilitated reproduction on land • Plants that produce seeds may be placed into two categories • Gymnosperms • Angiosperms • A seed consists of a plant embryo packaged with a food supply in a protective coat • The first vascular plant, according to the theory of evolution, originated about 360 MYBP in the Devonian Period. • Those seeds were not enclosed in any special chambers. • These plants evolved into the gymnosperms • “The Naked Seeds”

  6. THE EVOLUTION OF FLOWERS • According to the theory of evolution, flowers evolved in the Cretaceous Period about 130 MYBP • Led to further plant diversity • A flower is a complex structure that bears seeds within a protective chamber called an ovary. • Most “modern day” flowering plants are known as angiosperms.

  7. APICAL MERISTEMS • Recall, plants cannot move. • The elongation of their shoots and roots maximizes their exposure to environmental resources. • Growth occurs throughout the life of the plant via cell division in the apical meristematic tissue found at the tips of roots and shoots. • Cells produced by meristematic tissue can differentiate into various plant tissues.

  8. INTRODUCTION TO THE SEED AND SEED BEARING PLANTS

  9. INTRODUCTION TO SEED BEARING PLANTS • Seed plants are vascular plants that produce seeds. • After fertilization in seed plants, an ovule (megasporangium) and its enclosed structures develop into a seed • Earliest fossilized seeds are gymnosperms. • 360 MYBP • Seed plants dominate modern landscapes and are a large component of plant diversity. • Seed bearing plants have important reproductive adaptations: - • Continued reproduction of the gametophyte • The advent of the seed • The evolution of pollen

  10. INTRODUCTION II • The gametophytes of seed plants are even smaller than those of the seedless vascular plant and are protected in the ovules and pollen grains, • Miniature female gametophytes develop from spores that are retained within the parental sporophyte.

  11. COMPARISON OF SEEDS VS. SPORES • Seeds are the primary means of reproduction and dispersal of flowering plants. • Seeds are reproductively superior to spores. • Embryonic development is further advanced in seeds • Seeds contain an abundant food supply • Each seed has a protective coat.

  12. SEEDS, DISPERSAL & ADAPTATION • Seed dispersal becomes important in adaptations • Seed is a resistant structure that is multicellular and complex. • Seed consists of a sporophyte embryo packaged with food in a protective coat • Seeds can be dispersed by wind, water and animals.

  13. SEED BEARING PLANTS • All seed bearing plants are heterosporous • These plants have different types of sporangia that produce two types of spores. • Megasporangium • Microsporangium

  14. HETEROSPOROUS SPORE PRODUCTION Mega. vs. Micro. Diagram on Page 586 • Megasporangia • Produce megaspores • *Retained in the parent sporophyte • Formed within the megasporangium • Enveloped with tissue called integumens • *Entire structure is called the ovule • Microsporangia • Produce microspores • Develop into male (sperm containing) gametophytes. • The development of pollen reduced the need for water for fertilization.

  15. MEGASPORES • Develop into female (egg containing) gametophytes. • In the female gametophyte, there is the production of one or more egg cells • If egg is fertilized by sperm, the zygote develops into a sporophyte embryo • The ovule, that contains the fertilized egg, develops into a seed. • Seed may be viable for days, months or years.

  16. MICROSPORES • Microspores develop into pollen grains • Pollen grains mature to become the gametophytes of seed plants • The most common gymnosperms, and all angiosperms sperm, lack flagella. • Pollen can be transferred by wind and animals.

  17. POLLINATION • The transfer of pollen to ovules • Self Pollination • Cross Pollination

  18. REVIEW

  19. REVIEW • Students • List potential examination questions and/or here, and on following slides, based on the packet.

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