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SEEDLESS VASCULAR PLANTS
Psilotophyta
Lycophyta
Equisetopsida
Pteridophyta —>
• [Homospory; heterospory]
• [leptosporangia; eusporangia]
leptsporangia - developmental patterning
eusporangia- simple—> single apical initial
complex —> multiple initials

• There are a lot of themes that underlie these plants and most of them are to
do with the ability to transport water [extant]
...

• In ferns [pteridophyta] you see a couple of different types of themes that exist
...
One of the themes is how they produce their
spores
...
Get a
homospore or a heterospore
...
Can get either sterile or fertile plants
...
Complexity is spore —>
sporangia —> sori
...

The 2 subdivisions are the leptsporangia - developmental patterning
and eusporangia- simple—> single apical initial; complex —>
multiple initials
...
Has to do with cells inside the plant
having different functions in terms of roles each cell plays in order to
create a developmental pattern
...

These patterns can be said to be either simple or complex
...

• single initial- Can think about a set of cells that exist on the underside of the
leaf
...
The actual mechanism is
unknown
...
These selected cells will then undergo a
series of divisions in order to create the final structure
...
Finally you get
the final sporangio structure that will release the final spores that are
haploid
...

• Multiple initial- Have to think of how the cell actually knows to become and
how it can actually encounter other cells
...
You end up
getting multiple initials then
...
This will form the sporangio structure
...
Whats interesting
is that in the final form you’re going to have an outer layer of cells and on
the inside will have spores
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This is a land
plant and still has a motile sperm gametophyte and thus needs water
...

Can use the annulus to identify because its quite different
...
However as conditions get
dryer and dryer it starts to tighten and starts to shrink a little and so is
under tension
...
Whole idea is to get them away from the parental plant and into
the air so they’re able to move away as far as possible
...

• With the C-ferns - think about it as having alteration of generations
...
The sporophyte starts to develop sporangia
spore or sori
...
then you get
the germination of the gametophyte which is the haploid multicellular
structure and usually they’re relatively small
...
Then you
get the motile sperm and fertilization occurs and the subsequent
generation of the sporophyte generation
...
Why are there no females? Don’t want a female
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There is a survival aspect associated with this
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However if
you’re a female and no sperm comes along to fertilize, you cannot self
fertilize yourself and the female then ends up dying
...
If an archegonium doesn’t get

fertilized by a male, it will then self fertilize since its a hermaphrodite and
this then maximizes the progeny of the sporophyte generation
...
It all has to do with survival and maximizing
progeny
...

• Fossil related stuff based on Ferns and Bryophytes
...
Ferns can get pretty tall
...
People realized that these organisms existed in a broader
way and have a lot of types
...

Gymnosperms/ Angiosperms
• The gymnosperms and the angiosperms did something in terms of surviving
on land
...
This
is a fairly large evolutionary shift between the extants and the
gymnosperms
...
In
order to do that involves the formation of the seed
...
Seeds take this to an additional level
...
Can store progeny and wait for conditions are right to
then engage in successful fertilization
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Start with a sporophytic tissue which is diploid
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The mega-gametophyte never leaves the parental
sporophyte and never germinates outside the sporophyte
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Have an archegonia structure associated with it
...
Think about evolution in terms of surviving on dry land
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They are both protected by the parental sporophyte
...


• Some of the groups that are important here within the gymnosperms start with
groups that are relatively primitive in terms of the structures that they
have
...
You have a couple such as
cycadales, Ginkgo and Gymnosperm (conifers)
Cycadales*
• Can live in some tropical island in the middle of the pacific ocean
...
Look very much like a fern
...
Have a relatively defined root system and
the leaves that develop at the top in a cluster at the top of a single stem
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Within the
leaves at the top you will have the sexual structure basically a cone-like
sexual structure
...
In terms of fertilization you will
have male microspores landing on a female creating a diploid embryo
...
The
toxin is present in the seeds and cause parkinson disease like
symptoms
...

• All of them are males in York University
...
Tend to have division between
males and females
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With ginkgo only
males present
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Have a
drupe which has the female structure inside it
...
They release an
extremely bad odour [female drupe]
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