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Kingdom: Plants Domain Eukarya Domain Bacteria Domain Archaea Common ancestor Domain Eukarya Plant evolution It is thought that life evolved in the seas – 1st photosynthetic organisms were aquatic green algae • 500 mya land plants evolved – special adaptations for life on dry land >protection from drying = desiccation >waxy cuticle >gas exchange (through cuticle) -stomates >water & nutrient conducting systems -xylem & phloem >protection for embryo -seeds Plant Diversity Bryophytes non-vascular land plants Pteridophytes seedless vascular plants Gymnosperm pollen & “naked” seeds conifers mosses Angiosperm flowers & fruit flowering plants flowers ferns pollen & seeds vascular system = water conduction Tracheophytes colonization of land Ancestral Protist xylem cells = tracheids Animal vs. Plant life cycle Animal Plant diploid multicellular individual 2n diploid multicellular sporophyte mitosis 2n zygote 2n mitosis meiosis zygote 2n fertilization haploid unicellular gametes 1n no multicellular haploid fertilization meiosis gametes 1n spores 1n mitosis mitosis haploid multicellular gametophyte 1n alternation of generations First land plants • Bryophytes: mosses & liverworts – non-vascular • no water transport system • no true roots – swimming sperm • flagellated sperm – lifecycle dominated by haploid gametophyte stage Where must • mosses live? fuzzy moss plant you are familiar with is haploid – spores for reproduction • haploid cells which sprout to form gametophyte haploid diploid First vascular plants • Pteridophytes: ferns – vascular • water transport system • xylem, phloem, roots, leaves – swimming sperm Where must • ferns live? flagellated sperm – life cycle dominated by sporophyte stage • leafy fern plant you are familiar with is diploid • fragile independent haploid diploid Alternation of generations diploid produces male & female gametes archegonia antheridia haploid First seed plants – Gymnosperm: conifers • vascular • seeds – naked seeds (no fruit) • pollen – contain male gametophyte • life cycle dominated by sporophyte stage – coniferous trees are diploid – reduction of gametophyte protects delicate egg & embryo in protective cones » protected from drought & UV radiation Early Gymnosperm: ginkgo & Cycad Cones & naked seeds Why is pollen important? • Pollen eliminated need for water fertilization – spreads through wind & animals • Why does it irritate noses? – See the spikes? First flowering plants • Angiosperm: flowering plants – vascular – flower • specialized structure for sexual reproduction – seeds within fruit-protection & nourishment for seed! – pollen – life cycle dominated by sporophyte stage • trees & bushes are diploid • microscopic gametophyte Flower • Modified shoot with 4 rings of modified leaves Anther – sepals – petals – stamens Stamen Stigma Style Ovary Filament • male – carpel Petal • female Ovule sepals petals stamens Sepal carpel Carpel Identify the flower structures… Angiosperms: fruiting plants • Have fruits in many forms endosperm (3n) • Seeds contain plant embryo • Embryo consists of cotyledons cotyledons, endosperm, hypocotyl & epicotyl embryo (2n) • Seed offers… – protection for embryo – stored nutrients for growth of embryo cotyledons = “seed” leaves, first leaves of new plant seed coat Monocots & dicots • Angiosperm are divide into 2 classes – dicots (eudicot) • 2 cotyledons (seed leaves) • leaves with network of veins • woody plants, trees, shrubs, beans – monocots • 1 cotyledon • leaves with parallel veins • grasses, palms, lilies Comparison of Monocots & Dicots Acknowledgements • With thanks to • Kim Foglia & her website “Explore Biology” – Specifically the power point from which this was drawn – 13 Ch29Plants2008.ppt Also: http://www.daylilies.org/ahs_dictionary/monocot seedlingnew.jpg
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