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Evolution of Cycads, Gymnosperms and Ferns

Evolution of Cycads, Gymnosperms and Ferns . Gymnosperm anatomy - secondary xylem tracheids , circular bordered pits - and fern-like fronds & reproductive dispersal by spores . (no seeds) Arose in Upper Devonian 350 mya --> Pennsylvanian 290 mya All extinct

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Evolution of Cycads, Gymnosperms and Ferns

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  1. Evolution of Cycads, Gymnosperms and Ferns

  2. Gymnosperm anatomy - secondary xylem tracheids, circular bordered pits - and fern-like fronds & reproductive dispersal by spores. (no seeds) Arose in Upper Devonian 350 mya --> Pennsylvanian 290 mya All extinct Probably the immediate ancestor of all seed plants. Archaeopteris Div: Progymnospermophyta

  3. Gymnosperm anatomy and gymnosperm seed type with fern-like fronds. (seeds on fronds) Arose during Carboniferous Period 345 mya --> Permian 250 mya. All extinct Probably the immediate ancestor of the cycads. Div: Pteridospermophyta “Seed Ferns”

  4. Ovules (megasporangium with embryo after fertilization) develop into “seeds” covered with two cells layers from integument or seed coat. Naked Seed, “Gymnosperm” Monoecious Div: Pteridospermophyta “Seed Ferns”

  5. Resemble “palm trees”. Cycad foliage does not bear ovules or seeds - these are in special seed cones (strobili); pollen (with sperms) produced in pollen cones. Arose during Permian Period 280 mya --> extant A dominant form of vegetation during the Jurassic and Triassic Periods --> 135 mya. Div: Cycadophyta “Cycads”

  6. Div: Cycadophyta “Cycads” • All are dioecious: Micro and Megasporangia (strobili) on separate plants. • Cycas

  7. Div: Cycadophyta “Cycads” • Reproductive cycle in cycads wind pollination; pollen droplet • 4 - 6 months between • pollination & • fertilization • interval between pollination and fertilization: 4 - 6 months.

  8. Div: Cycadophyta “Cycads” • Two motile sperms produced by each pollen tube --> archegonial chamber. • Cycads & Ginkgos are • only seed plants with • motile sperm

  9. Div: Cycadophyta “Cycads” • No fixed period of dormancy in cycads.

  10. Evolution of Seed Plants • Derived Trait

  11. Evolution of Seed PlantsGymnosperms • Pollen - Encased male microgametophyte (n) that produces • sperms(n). • (Frees plant from the need for water in the pollination • process.) • prothallus cell(s), tube cell(s), generative cell • ---> sperms • Ovule - The female megagametophyte (n) with eggs (n) surrounded • by the old megasporangium (2n) with two layers from the • old sporophyte (2n) that will form the integument (2n). • (Frees plant from the need for water in fertilization.) • Cones - An axis bearing a tight cluster of scales or leaves for • reproduction. Scales either bear microsporangia or • meagasporangia in separate cones. (Pollen & Seed Cones) • Seed - ?

  12. Evolution of Seed PlantsGymnosperms • Seed - The matured ovule with an embryo in a resting state. • Integument - (2n) May be fleshy • Female Gametophyte - (n) nuritive; includes nucellus • Embryo - (2n) forms from zygote after fertilization.

  13. Evolution of Seed PlantsGymnosperms

  14. Div: Ginkgophyta“Ginkgos,Maidenhair Trees, Yin hing (silver apricot)” • Arose during the Permian 250 mya. • Richly branched woody plant with simple leaves. • Ginkgo biloba living fossil

  15. 1. Large stems; small simple leaves; deciduous. 2. Dioecious (female more shrubby) Div: Ginkgophyta

  16. 1. Large stems; small simple leaves; deciduous. 2. Dioecious (female more shrubby) 3. Has bud scales; dimorphism in branches. (long and spur shoots). 4. Stomates on abaxial (bottom) of leaf; two vascular bundles and 2 leaf traces per leaf. Div: Ginkgophyta

  17. 1. Large stems; small simple leaves; deciduous. 2. Dioecious (female more shrubby) 3. Has bud scales; dimorphism in branches. (long and spur shoots). 4. Stomates on abaxial (bottom) of leaf; two vascular bundles and 2 leaf traces per leaf. 5. Initiation of cambium after primary growth; growth rings. 6. Cork cambium or phellogen develops in outer cortex --> phellem (cork cells, bark) Div: Ginkgophyta

  18. Microsporangia (2n) - strobili 1 yr. --> microsporocyte (2n) --> meiosis --> microspores (n) Spring --> pollen (male gametophyte) Pollination (pollen droplet mucilaginous) --> Megasporangia - ovules 1 yr. Development of megasporocyte (2n) --> meiosis --> megaspore (n) --> female gametophyte ( with egg - n) as pollen tube grows - after 5 mos. (Aug-Oct) fertilization - development of seed - 2nd yr. Div: GinkgophytaReproduction: Dioecious

  19. generative cell --> 2 flagellatedsperms (just prior to fertilization) --> swim to end of pollen tube egg from archegonium swells and forces apart neck cells --> exposed to pollen tube and sperm for fertilization. Micropyle Div: GinkgophytaReproduction: Fertilization the 2nd Year

  20. seed Div: GinkgophytaReproduction: Development

  21. Outer fleshy layer of the integument emits foul order! However, inner part of the seed is edible! Div: GinkgophytaReproduction: Development

  22. Evolved during the Carboniferous Period 325 mya Div: Coniferophyta“Pines”, “Spruces” and “Firs”

  23. Div: Coniferophyta“Pines, Spruces and Firs”

  24. Div: Coniferophyta“Pines, Spruces and Firs”

  25. Evolved during the Carboniferous Period 325 mya 1. Leaves simple; often needle-like or scale-like. 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings). 3. Pith and cortex restricted - xylem composes most of the stem. Div: Coniferophyta“Pines”, “Spruces” and “Firs”

  26. 1. Leaves simple; often needle-like or scale-like. 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings). 3. Pith and cortex restricted - xylem composes most of the stem. Div: Coniferophyta“Pines”, “Spruces” and “Firs”

  27. 1. Leaves simple; often needle-like or scale-like. 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings). 3. Pith and cortex restricted - xylem composes most of the stem. 4. Stem may be differentiated into long and spur shoots. Div: Coniferophyta“Pines”, “Spruces” and “Firs”

  28. Div: Coniferophyta“Pines”, “Spruces” and “Firs”

  29. 1. Leaves simple; often needle-like or scale-like. 2. Xylem compact, composed mostly of tracheids (seasonal growth - rings). 3. Pith and cortex restricted - xylem composes most of the stem. 4. Stem may be differentiated into long and spur shoots. 5. Leaf traces one or few per leaf. 6. Typically evergreen; loose leaves gradually. 7. Protostelic taproot. Div: Coniferophyta“Pines”, “Spruces” and “Firs”

  30. Div: Coniferophyta“Pines”, “Spruces” and “Firs”

  31. Pollen or Staminate Cone Seed or Ovulate Cone Div: Coniferophyta

  32. Div: Coniferophyta • Pine Pollen

  33. Div: Coniferophyta • Ovulate Pine Cones:

  34. Div: Coniferophyta • Mature Pine Ovule with Two Archegonia:

  35. Div: Coniferophyta • Ovules at Fertilization and with Embryo:

  36. Div: Coniferophyta • Pine Seedling:

  37. Div: Coniferophyta

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