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Plant APBio


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Plant APBio

  1. 1. The Plant Kingdom
  2. 2. Key Features of Plants <ul><li>Multicellularity </li></ul><ul><li>Ability to photosynthesize (most) </li></ul><ul><li>Exhibit alternation of generations (a multicellular diploid generation alternates with a multicellular haploid generation) </li></ul>
  3. 3. Alternation of Generations <ul><li>Diploid sporophyte plant produces haploid spores through meiosis </li></ul><ul><li>Spores divide by mitosis and develop into haploid gametophyte plants </li></ul><ul><li>Haploid gametophyte plant produces haploid gametes through mitosis </li></ul><ul><li>Gametes fuse to form diploid zygotes , which divide by mitosis and develop into diploid sporophytes </li></ul>
  4. 4. Alternation of Generations in Plants Gametophytes form by meiosis Spores form by meiosis n n n Spore Mother Cell Egg Sperm Gametes meet & fuse to form zygote Zygote Embryo Sporo- phyte 2 n Spores n Gameto- phyte 2 n n n 2 n 2 n 2 n Haploid Diploid
  5. 5. Evolution of Plants <ul><li>The evolutionary origin of plants </li></ul><ul><ul><li>Division Rhodophyta—red algae </li></ul></ul><ul><ul><li>Division Phaeophyta—brown algae </li></ul></ul><ul><ul><li>Division Chlorophyta—green algae and the origin of land plants </li></ul></ul>
  6. 6. Green Algae <ul><li>Several lines of evidence support the hypothesis that green algae gave rise to plants </li></ul><ul><li>DNA comparisons show that green algae are plants’ closest living relatives </li></ul><ul><li>Both use the same type of chlorophyll and accessory pigments in photosynthesis </li></ul><ul><li>Both store food as starch </li></ul><ul><li>Both have cell walls made of cellulose </li></ul>
  7. 7. Fresh Water Ancestors <ul><li>Most green algae live in fresh water, suggesting that early plants evolved in freshwater habitats </li></ul><ul><li>Early green algae must have evolved characteristics to withstand the challenges of fresh water habitats, e.g. temperature extremes, periods of dryness </li></ul><ul><li>These adaptations provided a foundation for descendants to evolve traits for life on land </li></ul>
  8. 8. The Evolution of Land Plants <ul><li>Roots and rootlike structures (anchor & absorb) </li></ul><ul><li>Vascular tissue for transport of water & nutrients </li></ul><ul><li>Stiffening substance (lignin) for support </li></ul><ul><li>Waxy covering (cuticle) limits evaporation </li></ul><ul><li>Stomatal pores </li></ul><ul><ul><li>Mediate gas exchange </li></ul></ul><ul><ul><li>Regulate water vapor loss </li></ul></ul><ul><li>Evolutionary adaptations in plant reproduction </li></ul><ul><ul><li>Early algae relied on water currents for fertilization </li></ul></ul><ul><ul><li>Dry land adaptation include the generation of pollen, seeds, flowers, and fruit… </li></ul></ul><ul><ul><li>Adaptations in the alternation of generations… </li></ul></ul>
  9. 9. Reproduction Without Water <ul><li>Pollen </li></ul><ul><ul><li>A reduced male gametophyte that allows wind (instead of water) to carry sperm to eggs </li></ul></ul><ul><li>Seeds </li></ul><ul><ul><li>Nourish, protect, and help disperse developing embryos </li></ul></ul><ul><li>Flowers </li></ul><ul><ul><li>Attract pollinators </li></ul></ul><ul><li>Fruits </li></ul><ul><ul><li>Attract animals to disperse seeds </li></ul></ul>
  10. 10. Major Groups of Plants <ul><li>Bryophytes ( nonvascular plants ) </li></ul><ul><ul><li>Lack well-developed structures for conducting water and nutrients </li></ul></ul><ul><li>Tracheophytes ( Vascular plants ) </li></ul><ul><ul><li>Have a complex vascular system </li></ul></ul>
  11. 11. Evolutionary Tree of Major Plant Groups Ancestral Algae Liver- worts Mosses True vascular tissue & lignin appear Ferns Gymno- sperms Seeds and pollen appear Flowers & Fruits appear Angio- sperms Bryophytes Seed Plants Tracheophytes
  12. 12. The Bryophytes <ul><li>Nonvascular plants </li></ul><ul><li>No true roots, leaves, and stems </li></ul><ul><li>Still require a moist environment </li></ul><ul><li>Anchoring rhizoids absorb water & nutrients </li></ul><ul><li>Reproductive structures protect gametes </li></ul><ul><li>Still depend on water for fertilization </li></ul><ul><li>Dominant gametophyte generation </li></ul>
  13. 13. Liverworts & Mosses Liverworts Female Gametophyte Archegonium (a) Mosses Female Gametophytes Sporophytes (b)
  14. 14. The Bryophytes: Reproduction <ul><li>Gametes develop within protected structures on gametophyte </li></ul><ul><ul><li>Archegonia (singular, archegonium) produce eggs </li></ul></ul><ul><ul><li>Antheridia (singular, antheridium) produce sperm </li></ul></ul><ul><ul><li>Archegonia and antheridia may be located on the same plant or on different plants </li></ul></ul>
  15. 15. Life Cycle of a Moss (a) Zygote develops into sporophyte within gametophyte Sporophyte Capsule Fertilization Meiosis Haploid spores liberated from sporophyte capsule Old Gametophyte Spores disperse and germinate Haploid 1 n Diploid 2 n
  16. 16. Life Cycle of a Moss (b) Haploid 1 n Diploid 2 n Spore germinates into gametophyte Leafy Gametophyte Archegonium produces egg Antheridium produces sperm Sperm swim to egg Fertilization
  17. 17. The Vascular Plants <ul><li>Have roots, stems, and leaves </li></ul><ul><li>Have vessels impregnated with the stiffening agent lignin </li></ul><ul><li>Sporophyte generation is dominant </li></ul><ul><li>Include the seedless vascular plants and the seed plants </li></ul>
  18. 18. Division Tracheophyta: Vascular Plants <ul><li>Adapted to life in drier conditions </li></ul><ul><ul><li>Had to generate body support </li></ul></ul><ul><ul><li>Vessels to conduct water and nutrients </li></ul></ul><ul><ul><li>A stiffening substance called lignin </li></ul></ul><ul><li>Seedless plants: club mosses, horsetails, and ferns </li></ul><ul><ul><li>Sporophyte generation more dominant </li></ul></ul><ul><ul><li>Fertilization still relies on water </li></ul></ul>
  19. 19. Life Cycle of Ferns (a) Haploid 1 n Diploid 2 n Gametophyte Sporophyte develops from gametophyte Root Stem Sporophyte Masses of Sporangia Meiosis Haploid spores liberated from sporangium Sporangium
  20. 20. Life Cycle of Ferns (b) Haploid 1 n Diploid 2 n Haploid spores liberated from sporangium Spores disperse & germinate Gametophyte Archegonium produces egg Antheridium produces sperm Sperm swim to egg Fertilization
  21. 21. Seedless Plants Club Mosses Horsetails Ferns
  22. 22. Seed Plants: General <ul><li>Dominance of the sporophyte generation </li></ul><ul><li>Reproductive adaptations </li></ul><ul><ul><li>Pollen </li></ul></ul><ul><ul><ul><li>Wind and pollinators for fertilization </li></ul></ul></ul><ul><ul><ul><li>Water not required for fertilization </li></ul></ul></ul><ul><ul><li>Seeds </li></ul></ul><ul><ul><ul><li>Stores food for embryo </li></ul></ul></ul><ul><ul><ul><li>Embryo protection for unfavorable environments </li></ul></ul></ul>
  23. 23. Seeds (a) Gymnosperm (d) Water Dispersal (c) Wind Dispersal Stored Food Embryo Seed Coat (b) Angiosperm
  24. 24. Seed Plants: Gymnosperms <ul><li>Nonflowering seed plants </li></ul><ul><li>Produce &quot;naked seeds&quot; </li></ul><ul><li>Three divisions: </li></ul><ul><ul><li>Coniferophyta </li></ul></ul><ul><ul><li>Cycadophyta </li></ul></ul><ul><ul><li>Ginkgophyta </li></ul></ul><ul><li>Conifers are adapted to dry, cold conditions </li></ul><ul><ul><li>Thin, waterproof needles to decrease evaporation </li></ul></ul><ul><ul><li>Evergreen; year-round photosynthesis </li></ul></ul><ul><ul><li>Produce an &quot;antifreeze&quot; substance in sap </li></ul></ul>
  25. 25. Two Uncommon Gymnosperms (a) Gingko (b) A Cycad – either male or female
  26. 26. Gymnosperms: Conifers <ul><li>Adapted to dry, cold conditions: </li></ul><ul><ul><li>Retain green leaves throughout the year (evergreen) </li></ul></ul><ul><ul><li>Thin, needle-like leaves covered with waterproofing material to reduce evaporation </li></ul></ul><ul><ul><li>Produce an </li></ul></ul><ul><ul><li>“antifreeze” in sap </li></ul></ul>
  27. 27. Life Cycle of the Pine (a) Haploid 1 n Diploid 2 n Mature Sporophyte Seedlings (Sporophyte) Male Cone Male Scale MEIOSIS Male gametophytes (pollen) liberated Female Cone Female Scale Ovule Spore-forming Cell MEIOSIS
  28. 28. Life Cycle of the Pine (b) Haploid 1 n Diploid 2 n MEIOSIS Pollen liberated; Dispersed by wind MEIOSIS Seedlings (Sporophyte) Egg Cell Female Gametophyte Pollen lands on female scale Pollen Tube FERTILIZATION Seed Embryo
  29. 29. Seed Plants: Angiosperms <ul><li>Flowering seed plants </li></ul><ul><li>The dominant plant form on Earth </li></ul><ul><li>Major evolutionary adaptations </li></ul><ul><ul><li>Flowers to attract pollinators </li></ul></ul><ul><ul><li>Fruit to protect seeds and developing embryo </li></ul></ul><ul><ul><li>Broad leaves </li></ul></ul><ul><ul><ul><li>Increase photosynthesis during the growing season </li></ul></ul></ul><ul><ul><ul><li>Shed during periods of cold and drought </li></ul></ul></ul>
  30. 30. Monocot vs Dicot <ul><li>Class Monocotyledoneae (monocots): grasses, grains, corn </li></ul><ul><li>1 cotyledon </li></ul><ul><li>leave veins in parallel lines </li></ul><ul><li>Flower parts, in multiple of 3 </li></ul><ul><li>scattered vascular bundles </li></ul><ul><li>Class Dicotyledoneae (dicots): hardwood trees, shrubs, and herbs </li></ul><ul><li>2 cotyledons, web-like veins, flower petals in 4/5s, ringed vascular bundles </li></ul>
  31. 32. Flowers <ul><li>Flowers are reproductive structures in which both male and female gametophytes are formed </li></ul><ul><li>Believed to have evolved when gymnosperm ancestors formed an association with animals </li></ul><ul><ul><li>Animals benefited by eating some of the protein-rich pollen </li></ul></ul><ul><ul><li>Plants benefited by using animals as pollinators </li></ul></ul><ul><li>Most flowers are showy and attract animal pollinators (e.g. insects) </li></ul>
  32. 33. Life Cycle of a Flowering Plant (a) Fruit Seed Food Embryo Seed Coat Seedling Flower Anther MEIOSIS Ovary Ovule Spore-forming Cell Haploid 1 n Diploid 2 n
  33. 34. Life Cycle of a Flowering Plant (b) Fruit MEIOSIS MEIOSIS Spore Female Gametophyte Egg Cell Pollen (male gametophyte) Stigma Pollen Tube Sperm Nuclei FERTILIZATION Haploid 1 n Diploid 2 n
  34. 35. Fruits Encourage Seed Dispersal <ul><li>Fruits are mature ovaries that contain developing seeds </li></ul><ul><li>Various fruit adaptations help disperse seeds </li></ul><ul><ul><li>Edible fruits entice animals to eat them (seeds pass through digestive tract unharmed) </li></ul></ul><ul><ul><li>Burrs cling to animal fur </li></ul></ul><ul><ul><li>Winged fruits are carried through the air </li></ul></ul>
  35. 36. Broad Leaves <ul><li>Broad leaves of angiosperms collect more sunlight for photosynthesis than narrow leaves of gymnosperms </li></ul><ul><li>Temperate angiosperms drop leaves to conserve water when it is in short supply (fall, winter) </li></ul><ul><li>Tropical and subtropical angiosperms are evergreen </li></ul><ul><ul><li>May shed leaves during dry season </li></ul></ul>
  36. 37. Broad Leaves <ul><li>Photosynthetic advantage is offset by fact that broad, tender leaves are more appealing to herbivores than tough, waxy needles of conifers </li></ul><ul><li>Angiosperm defenses include </li></ul><ul><ul><li>Physical defenses (thorns, spines, resins) </li></ul></ul><ul><ul><li>Chemical defenses (make plant tissue poisonous or distasteful) </li></ul></ul>
  37. 38. Crucial Ecological Role <ul><li>Through photosynthesis, plants provide food, directly or indirectly, for all of the animals, fungi, and non-photosynthetic microbes on land </li></ul><ul><li>Plants produce oxygen gas as a byproduct of photosynthesis, continually replenishing oxygen in the atmosphere </li></ul>
  38. 39. Crucial Ecological Role <ul><li>Plants help create and maintain soil </li></ul><ul><ul><li>Dead plant material is decomposed by fungi, prokaryotes, and other decomposers </li></ul></ul><ul><ul><li>Decomposed plant tissue becomes part of the soil, making it more fertile </li></ul></ul><ul><ul><li>Roots of living plants help hold soil together, preventing erosion by wind and water </li></ul></ul>
  39. 40. Human Necessities and Luxuries <ul><li>Plants provide shelter </li></ul><ul><ul><li>Wood is used to construct housing </li></ul></ul><ul><li>Plants provide fuel </li></ul><ul><ul><li>Wood: important fuel for warming and cooking in many parts of the world </li></ul></ul><ul><ul><li>Coal: derived from the remains of ancient plants that have been transformed by geological processes </li></ul></ul>
  40. 41. Human Necessities and Luxuries <ul><li>Plants provide medicine </li></ul><ul><ul><li>Many medicines and drugs were originally found in and extracted from plants, e.g. aspirin, Taxol, morphine </li></ul></ul><ul><li>Plants provide pleasure </li></ul><ul><ul><li>Flowers, gardens, and lawns </li></ul></ul><ul><ul><li>Coffee, tea, and wine </li></ul></ul>
  41. 42. The End