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THE PLANT KINGDOM All Plants Evolved from Common Ancestor: Ancient Green Algae Cell walls made of cellulose Store excess carbohydrates as starch Form a cell plate during cytokinesis Have same photosynthetic pigments: Chlorophyll a and b Carotenoid – carotene and xanthophyll Adaptations to life on land: Cuticle Waxy layer on aerial portion that prevents dessication Thickness depends on how dry the environment is Adaptations to life on land: Cuticle Stomata: Pores on the surface of leaves and stems Allows for gas exchange Adaptations to life on land: Cuticle Stomata Gametangia Multicellular sex organs Covered by a layer of sterile cells – protection Embryo develops inside gametangia Plant Life Cycle Alternation of generations Gametophyte Multicellular haploid stage Produces gametes Sporophyte Multicellular diploid stage Produces spores Gametophyte generation Gives rise to haploid gametes by mitosis Sperm cells form in antheridia Egg cells form in archegonia Once sperm cell fertilizes an egg cell, a zygote is formed Sporophyte generation Begins with diploid zygote Zygote divides by mitosis and develops into embryo Grows into mature sporophyte plant Specialized cells called sporogenous cells divide by meiosis into haploid spores Four Main Groups of Plants Bryophytes Seedless vascular plants Gymnosperms Angiosperms Bryophytes Nonvascular plants Rely on diffusion and osmosis Restricted in size Generally require moist environment MOSSES, LIVERWORTS, HORNWORTS Moss Life Cycle Vascular Plants Ferns, Gymnosperms, Angiosperms Contain xylem and phloem Cell walls contain lignin Strengthening polymer Support Conduction Allows plants to grow tall Seedless Vascular Plants Ferns & club mosses Most important adaptation: Xylem – transports water Phloem – transports food Transport allows plants to grow larger Club Mosses Only group of vascular plants with microphyll Leaf with single vascular strand True Roots Rhizome & aerial stems Reproductive leaves with sporangia Ferns Rhizome w/ roots Fronds Sori found on fronds Clusters of sporangia Sporagenous cells undergo meiosis spores Fern Life Cycle Prothallus Homospory vs. Heterospory Homospory – sporophyte produces 1 kind of spore Heterospory – microspores & megaspores Dominant Stages Bryophyte – Gametophyte Seedless Vascular – Sporophyte Gymnosperms – Sporophyte Angiosperms - Sporophyte