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Page 518, Figure 25.9
Photosynthesis
by
Purple Bacteria
Protists:
•Domain Eukarya
•Some Autotrophic (photosynthetic), some not
•Aquatic
•Greater part of life cycle as Haploid
Bryophytes
Sporophyte
↑
Liverwort
Moss →
Gametophyte
Ferns & Fern Allies:
Fossil
230 million years old
China
Horsetail
The Seed Plants
All plants that produce seeds are either
Gymnosperm = “naked seed”
or
Angiosperm = “covered seed”
Most gymnosperms occur in areas that are:
very cold (like the forests of Canada or Alaska)
or
very dry (like deserts).
There aren’t many gymnosperms in tropical regions
(which have warm temperatures,
and plenty of moisture).
Gymnosperm
leaves
are usually
tough and
leathery and
shaped like:
Needles
or
Scales
or
Fronds
But there are some exceptions!
Gnetum
Ginkgo
Gymnosperms are usually perennials
(live many years)…so are trees or shrubs.
Gymnosperms tend to be evergreen.
Although the leaves (be they needles, scales, etc.)
do fall off, they do so continuously
instead of on any set schedule
like you see with many deciduous (Angiosperm)
trees and shrubs.
In Gymnosperms, the reproductive structures
are not called “flowers”
They are “cones”
Cones are usually unisex....
Either male or female
Cones are often tough,
and not very colorful,
and can be:
papery
or
woody
or
berry-like
Most gymnosperms are wind-pollinated
(and can cause allergies for some people).
…females produce a “pollination droplet”
which catches pollen grains
to increase odds of fertilization.
Insect pollinators are not required.
Gymnosperms are generally considered to be
more ancient than Angiosperms
...this primarily comes from fossil evidence
Gymnosperms were the most common plants
during the “Age of the Dinosaurs”
(65 to 250 million years ago)
....although there were some Angiosperms
during this period
they didn’t become real abundant until about
60 million years ago.
Mostly Cycads at that time
What advantage
do Angiosperms
have that
Gymnosperms
don’t have?
Angiosperms often have shorter life spans so
they can grow faster, and reproduce more
(before being eaten by animals).
This shorter life cycle would allow faster
evolution, because there are more generations.
Plus, when insect pollination came on the scene
there was more opportunity for plants to evolve
different mechanisms for attracting insects
…..not only to pollinate them,
but also to eat and disseminate the fruit
This may help explain why there
are only 760 species of Gymnosperms
while
there are about 250,000 species of Angiosperms
currently on the planet.
There are 4 phyla of Gymnosperm:
1) the Conifers
2) the Cycads
3) Ginkgo biloba (a single species)
4) the Gnetophytes
CONIFERS:
Juniper
Cypress
Fir
Cedar
Sequoia
Redwood
Pine
Hemlock
Larch
Arborvitae
Yew
CYCADS:
the palm-like gymnosperms
Ginkgo biloba
Gnetophytes:
Ephedra
Welwitschia
Gnetum
Only 1 species...it grows
only in the desert of
Namibia...can live 1000
years...gets its water mostly
from fog
Welwitschia mirabilis
Durio zibethinus
An Angiosperm
Native to Borneo