Plant Evolution 4 major periods in plant evolution 1. Bryophytes – mosses – gametangia – little or no vascular tissue 2. Ferns (Pterophyta) – seedless, vascular plants 3. Gymnosperms (Coniferophyta) – the first seed plants 4. 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
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 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