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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
4 major periods in plant evolution1. Bryophytes – mosses – gametangia – little or
no vascular tissue2. Ferns (Pterophyta) – seedless, vascular
plants3. Gymnosperms (Coniferophyta) – the first
seed plants4. Angiosperms (anthophyta) – emergence of
the flowering plants – complex reproductive organs
Bryophytes
Mosses Cuticle and gametangium Sperm are flagellated – must swim to reach
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 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