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Seed Plants - Gymnosperms (Seed Ferns (Later Species Had Parenchyma, Not…
Seed Plants - Gymnosperms
Progymnosperms
Extinct Group
Evolved from Trimerophytes
Gave Rise to Conifers, Cycads, and Others
Contain a Vascular Cambium
Unlimited Growth
Secondary Xylem and Phloem
Function Indefinitely
Elongated Tracheids
Tall Rays
Little to No Axial Parenchyma
No Seeds
Aneurophytales
Relictual Gymnosperms
Examples
Anuerophyton
Proteokalon
Vary in Size
No True Leaves
Archaeopteridales
Abundant Wood
Secondary Xylem
Trees
Heterosporous Reproduction
Evolution of Seeds
Difficult to Determine Life Cycle
Chauleria
Earliest Known Species with Heterospory
390 Million Years Ago
Integument
Tissue Layer
Surrounds Megasporangium
Micropyle
Hole In Integument
Permitted Sperm Cells to Swim to Egg
Pollen Chamber
Space at Top of Megasporangium
Where Microspores Settled
Microspores Evolved into Pollen Grains
4 Types of Common Pollen by Carboniferous Period
Seed Ferns
Later Species Had Parenchyma, Not Tracheids
Evolved from Aneurophytales
Resembled Modern Tree Ferns or Vines
Bore Seeds Instead of Clori
Any Woody Plant With Fern-Like Foliage
Form a Grade, Not a Clade
Not All Closely Related
Appeared in Upper Devonian Period
Long Lived Vascular Cambium
Rays Many Cells Wide
Longer and Wider Tracheids
Manoxylic Wood
Thick Cortex
Large, Compound, and Planar Leaves
Conifers
Moderate to Large in Size
Never Vines, Herbs, or Annuals
No Bulbs or Rhizomes
Leaves
Perennial, Persist Many Years
Simple Venation
Simple Needles or Scales
Wood
Lacks Vessels
Phloem Lacks Sieve Tubes
Narrow Tracheids
Pollen Cones
Simple Cones
Single, Short Unbranched Axis
Bears Microsporophylls
Seed Cones
Complex, Compound
Cone Bracts
Bears Megasporophylls
Ovuliferous Scale
Fused Megasporophylls
Fused to Bract
Shoots
Long
Short
Eggs
Very Large
Haploid Nucleus
Nucleus Larger than Expected
Year May Pass Before Pollination and Fertilization
Suspensor
Elongated Cells
Pushes Cells Deeper into Megagametophyte
Proembryo
Develop into the Embryo
Cycads
Always Dioecious
Stems Similar to Seed Ferns
Long and Wide Tracheids
Rays are Large
Trunk Covered in Bark
Seed and Pollen Cones on Separate Plants
Larger Group Ages Ago
Modern is Less Present
Unusual Distribution
Cycadeoids
All Extinct
Features Identical to Cycads, Almost
Cones Have Micro and Megasporophylls
Each Ovule Had a Stalk
Thick, Fleshy Scales Between Each
Microsporophylls Cup-Shaped
Maidenhair Tree
Single Living Species
Ginko biloba
Unusual
Large Dicot Tree, Stout Trunk, Many Branches
Conifer-Like Wood
Broad Leaves
Short and Long Shoots
No Cones Produced
Ovules Occur in Pairs
Pollen Produced in Catkin-Like Organ
Ancestors Unknown
Gnetophyta
3 Groups
Gnetum
30 Species
Ephedra
40 Species
Welwitschia mirabilis
1 Species
Vines or Small Shrubs
Gymnosperms with Vessels in Wood
Pollen Cones are Compound and Have Small Bracts
Seed Cones are Compound with Extra Tissue Around Ovules
Distinctive Pollen
