Chapter 30:
Plant Diversity II:
The Evolution of Seed Plants
Seed Plants
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Gymnosperms – naked seeds
Angiosperms – covered seeds
These two groups are the dominant plants
on Earth today.
Adaptations: Seed Plants
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Gametophytes are even more reduced.
Seeds replaced spores as the means for
dispersal.
Pollen is the vehicle for sperm cells.
Life Cycle switch
Gymnosperms - Divisions
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Coniferophyta - Conifers
Cycadophyta - Cycads
Ginkgophyta - Ginkgo
Gnetophyta - Gnetae
~700 species
Characteristics

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Seeds with multiple seed leaves.
Cones (strobili).
Xylem with tracheids only.
No flowers or fruits.
Life Cycle

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Most are heterosporous.
Male gametophyte = pollen grain.
Multi-cellular female gametophyte still
produces archegonia.
Conifers

Two types of cones


Pollen cone - male
Ovulate cone - female
Pollen Cone

Male Cones

Sporangia
Pollen Cone

Sporangia with
pollen

Male Gametophyte or Pollen
Pollination


Transfer of pollen from one individual to
another.
Usually accomplished by the wind for most
Gymnosperms.
Ovulate Cone

At time of Pollination

Ovulate Cone
Ovulate Cone


Megaspore
Mature Cones
Conifers Fertilization


Fusion of sperm and egg to produce a
zygote.
Pollination and fertilization may be separated
by 1 year.
Conifer Seeds

Embryo

Mature Seed
Importances

Coniferophyta:



Lumber
Paper
Resins
Importances



Food
Landscaping
Christmas trees
Other Examples

Cypress

Pacific Yew
Importances

Cycadophyta:


Landscaping
Food
Ginkgo

Ginkgophyta:


1 species extant
Living fossil
Ginkgo

Tree

Fall Color
Ginkgo - Male

Male cones

Sperm
Ginkgo - Female


Female cones
Mature cones
Importances

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
Landscaping
Drug
Seeds (?)
Importances

Gnetophyta:


"Mixed bag" of species
Various importances

Ephedra
Other Gnetophyta

Welwitschia

Gnetum
Angiosperms

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Division - Anthophyta
Most dominant plant group on land.
Two main classes:



Monocotyledones (Monocots)
Dicotyledones (Dicots)
~235,000 species
Characteristics

Have seeds, flowers and fruits.
Characteristics

Xylem may have
vessels.
Life History

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Male gametophyte reduced to a 2-3 celled
pollen grain.
Female gametophyte reduced to an embryo
sac.
Double fertilization.
Importances

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Food
Lumber
Medicines
Landscaping
Fibers
Importances

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Rubber
Flower Industry
Dyes
Spices
Soil Erosion Control
Angiosperms

Main group for study of plants in future
lessons.
Summary


Know the adaptations of seed plants.
Know examples, life cycles, and importances
of the gymnosperms and angiosperms.