Evolution of Cycads, Gymnosperms and Ferns

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

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

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

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

Evolution of Seed Plants Derived Trait

Evolution of Seed Plants Gymnosperms 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 - ?

Evolution of Seed Plants Gymnosperms 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.

Evolution of Seed Plants Gymnosperms

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

Div: Ginkgophyta 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 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 Reproduction: Dioecious 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: Ginkgophyta Reproduction: Fertilization the 2nd Year generative cell --> 2 flagellated sperms (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: Ginkgophyta Reproduction: Development seed

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

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

Div: Coniferophyta “Pines, Spruces and Firs”

Div: Coniferophyta “Pines, Spruces and Firs”

Div: Coniferophyta “Pines”, “Spruces” and “Firs” 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” 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” 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 “Firs” 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 Seed or Ovulate Cone Pollen or Staminate Cone

Div: Coniferophyta Pine Pollen

Div: Coniferophyta Ovulate Pine Cones:

Div: Coniferophyta Mature Pine Ovule with Two Archegonia:

Div: Coniferophyta Ovules at Fertilization and with Embryo:

Div: Coniferophyta Pine Seedling:

Div: Coniferophyta