NONVASCULAR

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NONVASCULAR AND SEEDLESS VASCULAR PLANTS
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The earliest plants grew in areas like the
coastal mud flats of the Devonian (410 million
years ago)The non-vascular Moss
(1)alongside vascular Cooksonia (2), Rhynia
(3),Zosterophyllum (4),Drepanophycus (5).
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The beginning of the Carboniferous had a more
uniform, tropical, and humid climate throughout
the year than exists today. Seasons, if any, were
indistinct. The number of plants during the
Carboniferous became more numerous. Vascular
plants began to dominate the landscape and
gymnosperm-like plants began to appear.
Angiosperms would appear much later.
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Early Vascular Plants a. Evolved from
Charophytes, a group of green algae b. Cooksonia
oldest vascular plant fossil Rhynia c. Late
Silurian (414 - 408 million years BP) d. No
roots or leaves e. Vascular plants dominated by
the Devonian (408 - 362 million BP)
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Plant Adaptations a. Development of a 1)
vascular system xylem and phloem, 2) ground
tissues comprise the main plant body, and 3)
dermal tissue provide protective covering to
plants b. Developed a waxy cuticle c. Upright
growth habit lignin (for structure and
conduction) and cellulose d. Stomata for gas
exchange (O2, CO2, H2O) e. Sex organs are
multicellular gametangia f.  Fertilization of egg
develops into an embryo g. Roots evolved from
underground stems
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Four Major Groups of Plants and Their
Respective Phyla Bryophytes- nonvascular
reproduce via spores, seedless plants includes
the mosses, liverworts, and hornworts Phylum
Bryophyta (Mosses) Phylum Hepaticophyta
(Liverworts) Phylum Anthocerophyta
(Hornworts) Seedless Vascular Plants- vascular
plants which are seedless, use spores in
reproduction includes the ferns and fern allies
Phylum Psilophyta (Whisk ferns) Phylum
Lycopodophyta (Club Mosses) Phylum Sphenophyta
(Horsetails) Phylum Pterophyta (Ferns) Gymnosperms
- vascular, naked seed producing plants includes
conifers, cypress, cedars, cycads, etc. Phylum
Cycadophyta (Cycads) Phylum Ginkgophyta
(Ginkgo) Phylum Coniferophyta (Conifers) Phylum
Gnetophyta (Welwitschia) Angiosperms- vascular
plants, producing protected seed includes all
flowering plants Phylum Anthophyta (Flowering
plants) Class Dicotyledones Class
Monocotyledones Class Magnoliids
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Bryophytes- nonvascular reproduce via spores,
seedless plants includes the mosses, liverworts,
and hornworts
Phylum Anthocerophyta (Hornworts) Phylum
Hepaticophyta (Liverworts) Phylum Bryophyta
(Mosses)
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It is now widely accepted (from morphological and
molecular work) that a group of green algae
called the charophytes represent the sister group
to land plants.
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Homosporous- one spore type produced and
released) Hetrosporous- two spore types produced
one developing into a male gametophyte, the other
into a female gametophyte
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All plants have alternation of generations. There
is an evolutionary trend from a dominant
autotrophic (self-feeding) gametophyte and a
nutritionally dependent sporophyte to a dependent
gametophyte and a dominant autotrophic
sporophyte. This is exemplified by exploring the
life cycles of a moss, a fern, and an angiosperm.
Sporophyte
Gametophyte
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Bryophytes- (9000 Mosses), (6000 Liverworts) and
(100 Hornworts) a. Have no conductive tissues,
thus no way to efficiently assimilate
photosynthates or minerals since they are
reliant on diffusion, they are typically very
small b. Three distinctive phyla c. Absorptive
structures called rhizoids leaflike
blades/leaves d. Typically separate male and
female gametophytic plants sperm must swim
through a thin film of water to fertilize the
egg a diploid zygote forms and grows into a
mature moss sporophyte spores will be released
from the sporophyte and will germinate to form a
protonema which further develops into the
gametophyte e. The gametophytic generation is
the dominant form of the life cycle f.
Liverworts may exhibit a leafy morphology or a
thalloid (thallus) body form some reproduce
asexually using gemmae cups containing gemma
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Life cycle of a moss. The sporophyte generation
is dependent on the photosynthetic gametophyte
for nutrition. Cells within the micro- and
megasporangia undergo meiosis to produce male and
female spores, respectively. These spores divide
mitotically to produce multicellular male and
female gametophytes. Differentiation of the
growing tip of the gametophyte produces
antheridia in males and archegonia in females.
The sperm and egg are produced in the antheridia
and archegonia, respectively. Sperm are carried
to the archegonia in water droplets. After
fertilization, the sporophyte generation develops
in the archegonium and remains attached.
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Seedless Vascular Plants (11,000 Ferns),
(Club Mosses 1,000), (Horsetails 15) and (Whisk
Ferns 12)
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Seedless Vascular Plants- plants which have
distinct tissues for conducting water and
nutrients throughout the plant use spores for
reproduction instead of seeds there are four
phyla of SVP
1. Phylum Psilophyta (Whisk ferns) 2. Phylum
Lycopodophyta (Club Mosses) 3. Phylum Sphenophyta
(Horsetails) 4. Phylum Pterophyta (Ferns)
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Whisk Ferns A. Exhibits a dichotomous branching
pattern B. Stems are the main photosynthetic
organ C. Most are extinct very primitive
vascular plant
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Club Mosses A. Once dominant plants in the
landscape, 300my ago B. Strobilus are present to
bear spores C. Some are homosporous, some are
heterosporous If heterosporous, male microspores
(n) will be produced along with female megaspores
(n) once shed, these spores will develop into
male and female gametophytes which will produce
sperm and egg respectively when the egg is
fertilized a sporophyte (2n) will form within
the strobilus spores form and the process repeats
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Horsetails A. Once dominant plants in the
landscape, 300my ago B. True roots, stems and
small leaves (reduced megaphylls) hollow jointed
stems impregnated with silica green stem main
photosynthesizing part C. Reproductive branches
bear a terminal cone-like strobilus D. Life cycle
is similar to fern life cycle also requires water
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Ferns a. Conductive tissues present xylem and
phloem!! Thus may be larger, and allowed for
true leaf evolution! b. Two Basic Leaf Types 1)
Microphyll- possess a single vascular strand and
are typically small and 2) Megaphyll- possess
more than one vascular strand and are typically
larger than microphylls webbing effect
seen c. Sporophyte is the dominant generation!
Consists of roots, rhizomes and fronds
fiddleheads are young fronds sori appear on the
fronds and house spores d. Spores (n) germinate
into a prothallus (n) which will produce eggs (n)
in the archegonium and sperm (n) in the
antheridium they combine to form a zygote (2n)
the zygote grows into a young sporophyte (2n)
the mauture sporophyte of most ferns produce only
one type of spore (homosporous- one spore type
produced and released) some are hetrosporous,
that is they produce two spore types, one
developing into a male gametophyte, the other
into a female gametophyte Water is required for
the sperm to use as a medium to swim to the egg
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Life cycle of a fern. The sporophyte generation
is photosynthetic and is independent of the
gametophyte. Meiosis of the tissue within the
sporangia yields a haploid spore that divides to
produce a heart-shaped gametophyte that
differentiates both archegonia and antheridia on
one individual. The gametophyte is photosynthetic
and independent, although it is reduced in size
relative to the sporophyte. Fertilization takes
place when water is available for sperm to swim
to the archegonia and fertilize the eggs.
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