Evolution of cycads gymnosperms and ferns
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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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Div progymnospermophyta l.jpg

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


Div pteridospermophyta seed ferns l.jpg

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”


Div pteridospermophyta seed ferns4 l.jpg

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”


Div cycadophyta cycads l.jpg

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”


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Div: Cycadophyta “Cycads”

  • All are dioecious: Micro and Megasporangia (strobili) on separate plants.

  • Cycas


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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.


Div cycadophyta cycads8 l.jpg
Div: Cycadophyta “Cycads”

  • Two motile sperms produced by each pollen tube --> archegonial chamber.

  • Cycads & Ginkgos are

  • only seed plants with

  • motile sperm


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Div: Cycadophyta “Cycads”

  • No fixed period of dormancy in cycads.



Evolution of seed plants gymnosperms l.jpg
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 - ?


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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.



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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


Div ginkgophyta l.jpg

1. Large stems; small simple leaves; deciduous.

2. Dioecious (female more shrubby)

Div: Ginkgophyta


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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


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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


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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


Div ginkgophyta reproduction fertilization the 2nd year l.jpg

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


Div ginkgophyta reproduction development l.jpg

seed

Div: GinkgophytaReproduction: Development


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Outer fleshy layer of the integument emits foul order!

However, inner part of the seed is edible!

Div: GinkgophytaReproduction: Development


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Evolved during the Carboniferous Period 325 mya

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


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Div: Coniferophyta“Pines, Spruces and Firs”


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Div: Coniferophyta“Pines, Spruces and Firs”


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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”


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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”


Div coniferophyta pines spruces and firs27 l.jpg

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”


Div coniferophyta pines spruces and firs28 l.jpg
Div: Coniferophyta“Pines”, “Spruces” and “Firs”


Div coniferophyta pines spruces and firs29 l.jpg

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”


Div coniferophyta pines spruces and firs30 l.jpg
Div: Coniferophyta“Pines”, “Spruces” and “Firs”


Div coniferophyta l.jpg

Pollen or Staminate Cone

Seed or Ovulate Cone

Div: Coniferophyta


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Div: Coniferophyta

  • Pine Pollen


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Div: Coniferophyta

  • Ovulate Pine Cones:


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Div: Coniferophyta

  • Mature Pine Ovule with Two Archegonia:


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Div: Coniferophyta

  • Ovules at Fertilization and with Embryo:


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Div: Coniferophyta

  • Pine Seedling:



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