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Biology
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2. 22–3 Seedless Vascular Plants
Photo Credit: ©Terry Donnelly/Dembinsky Photo Associates
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3. Evolution of Vascular Tissue
420 million years ago, moss-like plants on land were joined by taller plants.
Evidence shows that these plants had vascular tissue, which is specialized to conduct water and nutrients throughout the plant.
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Vascular Evolution
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5. Evolution of Vascular Tissue
The first vascular plants contained tracheids which are cells specialized to conduct water.
Tracheids make up xylem, a transport subsystem that carries water from the roots to every part of a plant.
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6. Evolution of Vascular Tissue
Vascular plants have a second transport subsystem composed of vascular tissue called phloem.
Phloem transports solutions of nutrients and carbohydrates produced by photosynthesis.
Minerals
H2O
CO2 O2
Sugar
Light
Xylem
Phloem
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7. Evolution of Vascular Tissue
How is vascular tissue important to ferns and their relatives?
Both xylem and phloem can move fluids through the plant body, even against the force of gravity.
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8. Ferns and Their Relatives
Seedless vascular plants include:
club mosses
horsetails
ferns
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9. Ferns and Their Relatives
The most numerous phylum is the ferns.
Ferns and their relatives have true roots, leaves, and stems.
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Life Cycle of Ferns
Ferns have vascular tissues, strong roots, underground stems called rhizomes, and leaves called fronds.
Photo credit: ©Peter Chadwick/Dorling Kindersley
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Life Cycle of Ferns
Life Cycle of Ferns
Ferns and other vascular plants have a life cycle in which the diploid sporophyte is the dominant stage.
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Life Cycle of Ferns
Fern sporophytes develop haploid spores on the underside of their fronds in structures called sporangia.
Sporangia are grouped into clusters called sori.
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Life Cycle of Ferns
The Underside of a Fern Frond
Sporangia
Photo Credit: left: ©Biophoto Associates/Photo Researchers, Inc.; right: ©Ed Reschke/Peter Arnold, Inc.
Sorus
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Life Cycle of Ferns
Fern Life Cycle
Sporangium (2N)
Frond
Young gametophyte (N)
Spores (N)
Mature sporophyte (2N)
Developing sporophyte (2N)
Mature gametophyte (N)
Antheridium
In the life cycle of a fern, the dominant and recognizable stage is the diploid sporophyte. The tiny, heart-shaped gametophyte grows close to the ground and relies on dampness for the sperm it produces to fertilize an egg. The young sporophyte grows from the gametophyte.
Sperm
Gametophyte (N)
Egg
Sporophyte embryo (2N)
Archegonium
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Fern Gametophyte
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22–3
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22–3
Plant cells specialized to conduct water are called
tracheids.
veins.
sori.
phloem.
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22–3
The presence of vascular tissue enables a plant to
carry on photosynthesis.
carry on lactic acid fermentation.
conduct water and nutrients.
make chlorophyll.
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22–3
Ferns are different from mosses because they
carry out photosynthesis using chlorophyll.
have vascular tissue to conduct water and nutrients.
help expose more of the plant’s surface area to sunlight.
exchange carbon dioxide and oxygen with the atmosphere.
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22–3
Club mosses and horsetails are similar to ferns because they have
vascular tissue.
seeds.
sori.
fronds.
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22–3
When fern spores germinate, they develop into
diploid gametophytes.
haploid gametophytes.
haploid sporophytes.
diploid sporophytes.
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22. END OF SECTION