Transcript Power Point over Stern`s Ch. 21

The Seedless Vascular Pants:
Ferns and Their Relatives
Outline
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Phylum Psilotophyta (Whisk Ferns)
Phylum Lycophyta (Club Mosses)
Phylum Equisetophyta (Horsetails)
Phylum Polypodiophyta (Ferns)
Fossils
Phylum Psilotophyta
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The Whisk Ferns
 Loosely resemble small, green whisk
brooms.
 Structure and Form
- Sporophytes consist almost entirely of
dichotomously forking aerial stems.
 Have neither leaves nor roots.
 Enations spirally arranged along
stems.
Life Cycle:
Phylum Lycophyta
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Ground Pines, Spike Mosses, and Quillworts
 Collectively called club mosses.
- Only two living representatives of two
major genera.
 Lycopodium
 Selaginella
 Sporophytes have microphylls.
 Have true roots and stems.
Phylum Lycophyta
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Lycopodium - Ground Pines
 Often grow on forest floors.
 Resemble little Christmas trees, complete
with cones.
 Stems are simple or branched.
- Develop from branching rhizomes.
Reproduction
Phylum Lycophyta
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Selaginella - Spike Mosses
 Especially abundant in tropics.
 Branch more freely than ground pines.
 Leaves have a ligule on upper surface.
 Produce two different kinds of spores and
gametophytes (heterospory).
Reproduction
Phylum Lycophyta
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Isoetes - Quillworts
 Most found in areas partially submerged in
water, and least part of the year.
 Microphylls are arranged in a tight spiral on
a stubby stem.
 Ligules occur towards leaf base.
 Corms have vascular cambium.
Reproduction
Phylum Equisetophyta
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The Horsetails and Scouring Rushes
 Structure and Form
- About 25 species scattered through all
continents.
- Significant silica deposits accumulate on
the inner walls of the stem’s epidermal
cells.
- Branches, when present, are normally in
whorls at regular intervals along the
jointed stems.
Phylum Equisetophyta
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Both branched and unbranched species have
tiny microphylls in whorls at the nodes.
Leaves fused at their base forming a collar.
Stems are distinctly ribbed and have obvious
nodes and internodes.
 Pith breaks down at maturity leaving a
hollow central canal.
 Aerial stems develop from horizontal
rhizomes.
Reproduction
Phylum Equisetophyta
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Human and Ecological Relevance
 Many giant horsetails used for food.
 Scouring rush stems used for scouring and
sharpening.
Phylum Polypodiophyta
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The Ferns
 Structure and Forms
- Approximately 11,000 known species of
ferns vary in size from tiny floating forms
less than 1 cm to giant tropical tree ferns
up to 25 m tall.
 Fern leaves are megaphylls that are
commonly referred to as fronds.
 Typically divided into smaller
segments.
Spore Release From a Fern Sporangium
Phylum Polypodiophyta
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Human and Ecological Relevance
 Extremely popular house plants.
- Serve as air filters.
 Cooked rhizomes serve as food.
 Folk Medicine
 Fronds used in thatching houses.
Fossils
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A fossil is generally defined as any
recognizable prehistoric organic object
preserved from past geological ages.
 Conditions of formation almost always
include quick burial in an accumulation of
sediments.
- Hard parts more likely preserved than
soft parts.
Fossils
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Molds, Casts, Compressions, and Imprints
 After being buried in sediment, the organic
material may be slowly washed away by
water percolating through the rock pores.
- If air space remains - Mold
- If silica fills space - Cast
 Compression takes place when objects are
buried by layers of sediment and greatly
compressed so that only a thin outline is
left.
Fossils
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Petrifications
 Petrifications are uncompressed rock-like
material in which the original cell structure
has been preserved.
Review
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Phylum Psilotophyta (Whisk Ferns)
Phylum Lycophyta (Club Mosses)
Phylum Equisetophyta (Horsetails)
Phylum Polypodiophyta (Ferns)
Fossils
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