Transcript Understanding Our Environment

Introduction to Seed Plants:
Gymnosperms
Outline
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Overview
Phylum Pinophyta
Phylum Ginkgophyta
Phylum Cycadophyta
Phylum Gnetophyta
Human Relevance of Gymnosperms
 Conifers
 Other Gymnosperms
Overview
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Gymnosperm refers to the exposed nature of
the seeds.
 Produced on the surface of sporophylls or
similar structures instead of being
enclosed within a fruit as in flowering
plants.
- Female gametophyte is produced inside
an ovule that contains a nucellus.
 Enclosed in integument.
 Four living Phyla
The Plant Ovule
Exposed versus Enclosed Seeds
Phylum Pinophyta
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The Conifers
 Pines
- Largest genus of conifers.
 Over 100 living species.
 Include world’s oldest known living
organisms (Bristlecone Pines).
Phylum Pinophyta
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Structure and Function
 Pine leaves are needlelike and are
arranged in clusters of bundles of two to
five leaves.
- Each cluster (fascicle) forms a cylindrical
rod if the leaves are held together.
 Hypodermis located below the epidermis.
 Resin canals develop in mesophyll.
- Antiseptic and Insect Deterrent.
Pine Stem Cross Section
Phylum Pinophyta
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Most wood varies considerably in hardness.
 Most gymnosperm wood consists primarily
of tracheids.
- No vessel members or fibers.
 Soft Wood
 Mycorrhizal fungi associated with the roots
of most conifers.
Fig. 22.8
Pine Life Cycle
Pine Life Cycle
Pine Ovule - Longitudinal Section
Fig. 22.9
Fig. 22.10
Phylum Ginkgophyta
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Ginkgo (Maidenhair Trees)
 Only one living species.
- Notched, broad, fan-shaped leaves.
 Leaves are produced in a spiral on
short, slow-growing spurs.
 No midrib or prominent veins.
 Hair-like veins branch dichotomously.
- Life cycle similar to pines.
 Dioecious
Fig. 22.11
Phylum Cycadophyta
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The Cycads
- Appearance of a cross between a tree
fern and a palm.
 Slow-growing plants of the tropics that
have tall unbranched trunks.
 Crown of largely pinnately divided
leaves.
- Life Cycle similar to conifers.
 Pollination is generally brought about
by beetles instead of wind.
Fig. 22.12
Phylum Gnetophyta
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The Gnetophytes
 Unique among the gymnosperms in having
vessels in the xylem.
 More than half of the 70 known species are
joint firs in the genus Ephedra.
 Most of remaining species are in genus
Gnetum.
- Occur in tropics
- Most are vine-like with broad leaves
similar to those of flowering plants.
Fig. 22.13
Fig. 22.14
Phylum Gnetophyta
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Third genus, Welwitschia, has only one
species.
- Confined to temperate deserts of
southwestern Africa.
 Average rainfall only 2.5 cm.
 Plant use CAM photosynthesis.
- Only produce two leaves throughout their
life span.
Fig. 22.15
Human Relevance of Gymnosperms
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Conifers
 Edible Seeds
 Crates, Boxes, Matchsticks, Furniture
 Telephone Poles
 Turpentine and Rosin (Resin)
 Fuel (Pitch)
 Pulpwood
 Ornamentals
 Pharmaceuticals (Taxol)
Human Relevance of Gymnosperms
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Other Gymnosperms
 Ginko Seeds - Food
 Ephedra - Mormon tea
Review
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Overview
Phylum Pinophyta
Phylum Ginkgophyta
Phylum Cycadophyta
Phylum Gnetophyta
Human Relevance of Gymnosperms
 Conifers
 Other Gymnosperms
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