1. Plant Diversity II The evolution of seed plants By Selam Ahmed, Megan Foley, and Anahis Kechejian

2. Gametophyte and Sporophyte Relationships 1.Gametophyte Dominated Life Cycle o Sporophytes are dependent on gametophytes for nutrition o Examples: mosses and bryophytes 2.Sporophyte Dominated Life Cycle o There are large sporophytes which are the dominant generation. Gametephotyes are independent and small. o Examples: ferns and seedless vascular plants 3. Reduced Gametophyte Dependent on Sporophyte o Gametophytes are microscopic. They are dependent on sporophytes for nutrition o Examples: Gymnosperms and Angiosperms

3. Seedless Plants vs. Seed Plants Seedless Plants Homosporous: 1 kind of spore. All gametophytes are bisexual Adaptations of Seedless Plants o Spores serve as protection from the outside world o Spores allow dispersal First 100 million years of plant life Seed Plants Heterosporous o Female gametophytes  1 megaspore produced by megasporangia o Male gametophytes  multiple microspores produced by microsporangia Evolutionary Advantages of Seeds o *gametophytes evolved to be smaller → greater success 1.food supply in the seed 2.seeds can be dispersed 3.more resistance and protection from the outside environment

4. Reproduction in Seed Plants Ovules- where the female gametophyte develops, produces egg cells Made of megaprorangium, megaspore, integuments (protective sporophyte tissue) Pollen Grains- male gametophytes, can be carried away by the plant Pollination- the transfer of pollen to the ovules

5. Gymnosperms Gymnosperms have seeds that are not protected in an ovule (naked seeds) Progymnosperms may be the evolutionary link between seedless plants and seed plants Example: flagellated sperm cells

6. Four out of Ten Plant Phyla are Gymnosperms 1.Phylum Cycadophyta 2.Phylum Ginkgophyta 3.Phylum Gnetophyta 4.Phylum Coniferophyta

7. Gymnosperm Reproductive Cycle Note: Gametophyte generation smaller and more dependent on sporophyte generation Heteroporous: There are both male and female gametes

8. Angiosperms The most diverse phylum Includes 90% of all modern species (approximately 250,000)

9. The Angiosperm Life Cycle 1. The flower of the sporophyte produces: Microspores (forms male gametophyte) o Are in the pollen grains, each pollen grain has TWO haploid cells:  1 Cell=Generative cell that divides (mitosis) forming two cells  1 Cell= Tube cell that produces a pollen tube Megaspores (forms female gametophyte) o AKA embryo sac o Contained in an ovule o Ovule develops in ovary

10. The Angiosperm Life Cycle (continued) 2. Pollen is released from the anther 3. Pollen is carried to the stigma (located at top of carpel) Usually of another plant (cross pollination) but some plants to self-pollinate Cross pollination enhances genetic variation Mechanisms to ensure cross pollination Development of stamen and carpels at different times making self pollination impossible

11. Mechanisms for Seed Dispersal Wings- to be carried by the wind Barbs- to attach to animals Fruits are edible- digested by animals Seeds are dispersed in feces

12. 4. Pollen Grain sticks to the stigma of the carpel and germinates 5. Matured male gametophyte (tube cell) extends a pollen tube that grows down within the style of the carpel 6. When it finally reaches the ovary, the pollen tube penetrates through the micropyle (a pore or opening on the surface of the ovary) The Angiosperm Life Cycle (continued)

13. The Angiosperm Lifecycle (continued) 7. Two sperm cells are discharged into the female gametophyte (embryo sac) One sperm fertilizes the egg forming a diploid zygote The other sperm cell fuses with the two nuclei in the large central cell of female gametophyte This is known as double fertilization- a process unique to angiosperms!

14. The Angiosperm Lifecycle (continued) 8. Ovule matures into a seed, and then the zygote develops into a sporophyte embryo (alternating generations) with rudimentary roots and one or two seed leafs know as cotelydons. 9. Nucleus of the central cell of female gametophyte divides repeatedly and develops into endosperms (tissue rich in strarch and other food reserves)

15. The Angiosperm Lifecycle (continued)

16. Double Fertilization Evolved independently in Angiosperms and Gymnosperms Gymnosperm Double Fertilization fives rise to 2 embryos whereas Angiosperm Double fertilization gives rise to 1 embryo and 1 endosperm Hypothesis' on the function of double fertilization: Adaptation to prevent plants from squandering the nutrients in fertile ovules o Synchronizes development of embryo with development of food storage

17. The Evolution of Angiosperms 125 million year old angiosperm fossils Archaefructus lioaningensis and Archaefructus sinensis Archaefructus: most closely realted known fossil to all living angiosperm Suggests that ancestors of Angiosperms were herbaceous rather than woody Discovered along with fish fossils suggesting angiosperms originated as aquatic plants

18. "Mostly Male" Hypothesis Asserts that the flower evolved mainly from the pollen- producing (male) reproductive structure of a gymnosperm ancestor Proposed by Michael Frohlich “Evo-Devo” approach: synthesis of evolutionary and developmental biology Botanists test evo-devo models for origin of flowers by comparing angiosperm and gymnosperm genes

19. Biological Diversity Cotyledon: seed leaves Monocots: species with one cotyledon Dicots: Species with two cotyledons Eudicots: “true” or “modern” dicots

20. 30.4 Human Welfare Humans depend on seed plants food Herbal remedies

21. Angiosperm-Animal Co-evolution Selective pressure on both plants and animals Co-evolution results in diversity Example: Plant-pollinator relationships

22. Threats to Plant Diversity Diversity is NOT a renewable source Destruction of Habitat Fast rate extinctions

23. Works Cited http://www.google.com/imgres?q=tree+seeds+with+wings&hl=en&gbv=2&tbm=isch&tbnid=N3v2JlMCqyw4cM:&imgrefurl=http://ww w.sciencephoto.com/media/33789/enlarge&docid=nvftpw2LENxvBM&imgurl=http://www.sciencephoto.com/image/33789/large/B78 70346-Sycamore_tree_seeds- SPL.jpg&w=415&h=530&ei=oO66ToTIEcrq0gHm7aXeCQ&zoom=1&iact=hc&vpx=700&vpy=118&dur=4&hovh=254&hovw=199&tx= 89&ty=120&sig=102685288777232855691&page=1&tbnh=132&tbnw=103&start=0&ndsp=61&ved=1t:429,r:3,s:0&biw=1826&bih=1 024 http://wps.aw.com/bc_campbell_biology.html http://www.rbgsyd.nsw.gov.au http://brp-journal.blogspot.com/2008/11/traveling-seeds-or-how-seeds-get-to-new.html http://mrswolfgang.wikispaces.com/Monocots+and+Dicots+team+twix http://mshallarvadahs.pbworks.com/w/page/38617351/Coevolution%20and%20Pollinators http://health.howstuffworks.com/wellness/natural-medicine/herbal-remedies/slippery-elm-herbal-remedies.htm http://www.fsd2010.org/program/muller-landau.htm