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