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PLANT Evolution
Structural Adaptations
 Vascular system – roots and shoots
(tracheophytes)
 Mycorrhizae – fungal associations
 Stomata and cuticle
 Lignin – hardens cell walls – preventing
water loss
 Vascular tissues – xylem and phloem
Stomata
Reproductive Adaptations
 Must keep gametes from drying out.
 Gametangia – jacket surrounding moist
chamber where gametes can develop
 Sperm encased in pollen and egg in
ovule
Origin from Algae
 Charophytes – closest to plants in
molecular studies
 Natural selection favored those who
could survive when not submerged in
water
Origin of Plants
Plant Evolution
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1.
2.
3.
4.
4 major periods in plant evolution
Bryophytes – mosses – gametangia –
little or no vascular tissue
Ferns (Pterophyta) – seedless,
vascular plants
Gymnosperms (Coniferophyta) – the
first seed plants
Angiosperms (anthophyta) –
emergence of the flowering plants –
complex reproductive organs
Bryophytes
 Mosses
 Cuticle and gametangium
 Sperm are flagellated – must swim to reach
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eggs
No lignin, no vascular system
Seedless
2 generations – gametophyte (n) and
sporophyte (2n)
Alternation of Generations
Bryophytes
Moss Life Cycle
Ferns
 Have vascular tissue
 Sperm must swim through water to
reach eggs
 Seedless
 Inhabit tropical areas
Ferns
Gymnosperms
 At the end of the Carboniferous period –
climate became cold and dry.
 Provided opportunity for seed plants
 Conifers – pine, spruce, firs, redwoods
 Nearly all conifers are evergreen
 Thick cuticle – stomata in pits
Life Cycle of Conifer
 Sporophyte generation and
gametophyte generation.
 Use pollen grains to transport sperm
 Seeds can remain dormant for years
 Fire, rain, and animals can crack seeds
and cause germination.
Angiosperms
 2 types of flowering plants – Monocots and
Dicots
 Undergo double fertilization
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Pollen deposits two sperm nuclei in the female
gametophyte
One sperm fertilizes an egg- produces a zygote
and develops into an embryo
The second fertilizes another female gametophyte
cell which develops into an endosperm (nutrient
storing tissue)
 A mature ovule is a seed, a mature ovary is
the fruit
Monocots and Dicots
Monocots vs. Dicots
Monocots
 One cotyledon
(seed leaves)
 Flower parts in
multiples of 3
 Parallel leaf veins
 Ex. Corn,lily
Dicots
 2 cotyledons
 Flower parts in
multiples of five
 Netlike leaf veins
 Primrose, maple