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Plant evolution
Plants are believed to have evolved from Green algae (Chlorophycea). Thus:
Bryophytes
e.g. Mosses
→ Pterophytes
e.g. Ferns
→ Gymnosperms
e.g. Conifers
Charophytes e.g. Chara (freshwater algae)
→ Angiosperms
(Flowering plants)
The evolution of the land plant life
Cycle New Phytologist (2010) 185: 27–
41 www.newphytologist.org
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1. Chara (Algae-Charophycea) a) Part of plant
1. Plants and Green Algae have in common:
▪ Multicellular: eukaryotic cells have walls of cellulose.
▪ Photosynthesis uses chlorophyll a and chlorophyll b inside chloroplasts.
2. Plants are most similar to the Charophycea algae such as
Chara :
For attachment only
➢ Each leaf and each stem is a chain of a single
type of cells
➢ Non-vascular and lack true organs
whorl
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1. Chara (Algae-Charophycea) b) Slide of reproductive system
Chara
Chara can be monoecious or dioecious.
Monoecious=male and female reproductive organs found on same
algae.
Dioecious=male and female reproductive organs found on separate
algae.
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1. Chara (Algae-Charophycea) b) Slide of reproductive system
Chara reproductive male organ-antheridium
stipulodes
antheridium
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1. Chara (Algae-Charophycea) b) Slide of reproductive system
Chara reproductive female organ-oogonium
Corona cells
A
(oogonium)
(stipulodes)
D
E
(antheridium)
B
F
C
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2. Mosses (Bryophytes)-Life Cycle
➢ These are nonvascular plants.
They have no vascular tissue =
parallel
tubes
transporting
water and nutrients around the
plant.
➢ They are thus very small-rise few
cms above ground.
➢ Found in wet conditions near
streams because they require
water for the sperm to swim to
the eggs.
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2. Mosses (Bryophytes)- a) Whole Plants
Mosses have a very simple structure. “Leaves” are made up of layers of identical cells
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2. Mosses (Bryophyta) b) Sporophyte Capsule
sporophyte
gametophyte
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Moss Sporophyte Capsule Longitudinal Section
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2. Mosses (Bryophyta) c) Archegonia
Female gametophyte
containing archegonia, with
single egg inside
Long thin filaments
enclosing
gametophyte
(female reproductive organ)
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2. Mosses (Bryophyta) d) Antheridia
Moss antheridia
Male gametophyte containing large
number of sperm-filled antheridia
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3. Ferns (Pterophyta)
The fern life cycle has alternation of
generations, but the long-lived plant is
the sporophyte.
Sporophytes produces spores from sori
on the underside of the leaves.
Gametophyte = a small prothallus
pressed against the ground (needs
water to transport the sperm).
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2. Ferns (Pterophyta)-Life Cycle
➢ These are
primitive
vascular plants but much
larger than mosses.
➢ Found in wet conditions
near streams because
they require water for
the sperm to swim to the
eggs.
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3. Ferns (Pterophyta) a) Whole plant
➢ Much larger and taller
than a moss due to
vascular tissue.
➢ Leaves are pinnate
(subdivided).
➢ Sporangia if present are
found on the underside of
the leaves.
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3. Ferns (Pterophyta) b) Sporangia
➢ Ring of thick-walled elongated cells surrounding the sporangium.
➢ As these circle of cells dry out, they straighten to throw out the spores.
➢ Spores inside sporangia have thick protective walls to resist dehydration.
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3. Ferns (Pterophyta) c) Prothallus
(gametophyte)
Heart-shaped gametophyte
A
➢ Gametophyte is very small in size and flat (1 layer of cells) pressed
against the soil.
➢ It is protandrous hermaphrodite, first develop as males, but can later
reproduce as females, so archegonia not visible in male slide.
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3. Ferns (Pterophyta) d) Sporophyte
B
A
Young sporophyte growing out from the archegonium
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4. Conifer (Pinus) a Gymnosperm
Junipers are found above 1500 m in the Juniper (the only Omani
western Hajar mountains (Jebel Shams + conifer) has soft cones.
Jebel Akhdar
These are female.
These are also vascular plants, but are more advanced than ferns, because:
o The sporophyte forms a large tree, but the gametophyte is no longer
independent and is a tiny parasite.
o They have seeds.
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4. Conifer (Pinus) a Gymnosperm - Life Cycle
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4. Conifer (Pinus) a Gymnosperm – a) A
male
female
mature cone
➢ A mature cone takes more than a year to
mature.
➢ It consists of hard woody scales protecting
the seeds, which may no longer be present
(fallen out).
➢ Big cones are female.
➢ Small cones are male.
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4. Conifer (Pinus) a Gymnosperm – b) Male
cones (Staminate)
➢ Male cones are much smaller than
female.
➢ The longitudinal section shows
the cone is made up of scales with
a microsporangium in between
each scale.
➢ The microsporangia are full of
pollen (the male gametophytes)
which when mature will be
released into the wind.
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4. Conifer (Pinus) a Gymnosperm – c) Female
cones (Ovulate)
➢ Female cone is also made up of scales.
➢ Between the scales are megasporangia.
➢ Each megasporangium encloses an egg.
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