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PLANTS!! Food, habitats, carbon dioxide taker uppers, oxygen providers What more could we ask for??? Kingdom: Plantae • 280,000 species • Ecological, industrial and medical importance • Thought to evolve from green algae, 500 mya • Both have chlorophyll a and b, store excess carbs, cellulose in cell walls. 4 Evolutionary milestones • Nonvascular plants that nourish a multicellular embryo within the body of the female plant (different from green algae) • Vascular tissue specialized for transport (430 mya) • Production of seeds (contains embryo and stored nutrients within a protective coat) 400mya • Flower –reproductive structure 135 mya • See cladogram pg 415 Alternation of Generations • 2 multicellular individuals alternate, each produce the other 1. 2. Sporophyte – diploid generation Gametophyte – haploid generation Sporophyte generation (2n) • Sporophyte – production of spores by meiosis • Spore – haploid reproduction cell that develops a new organism without fusing with another organism. • Spores undergo mitosis and becomes a gametophyte Gametophyte generation (n) • Production of gametes • Sperm and eggs are developed by mitosis • fuse = diploid zygote • Undergoes mitosis = sporophyte Alternation of generations • Meiosis produces haploid spores (gametophyte generation) • Mitoisis occurs when • Spore becomes a gametophyte • Zygote becomes a sporophyte Alternation of Generations • In nonvascular plants – gametophyte is dominant • Vascular seedless, naked seed and flowering plants – sporophyte is dominant • Adaptation to life on land • Gameotphyte becomes microscopic Adaptations to terrestrial life • Water transport and conservation – vascular tissue • Protection from desiccation – waxy cuticle, stomata Nonvascular Plants • No means of transporting water or organic nutrients • No true roots, stems or leaves, just root like… • bryophyte – term for nonvascular plants • Gametophyte is dominant generation, the part of the plant we see. • Females produce eggs in archegonia • Males produce flagellated sperm in antheridia • need film of water for sperm to meet egg • Characteristics limits size of bryophytes • 3 phyla, hornworts, liverworts, and mosses Hornworts and liverworts • Hornworts – most live in moist shaded areas • Can reproduce asexually by fragmentation • Horns are sporophyte that grow from gametophyte • Liveworts – most terrestrial, some epiphytes • • • • Thallose – with a flattened thallus Leafy – look like mosses Lobes look like liver Phizoids – extensions that anchor in soil Mosses • Gametophyte appear as leaflike structures • Peat, true and rock mosses • Prefer damp, shaded areas, can dry up and turn brown, and be revived with rain • Can reproduce asexually by fragmentation • Moss life cycle figure 24.9 • Uses include • sphagnum – ability to absorb water, used in gardening • Peat – accumulated dead moss can be used as fuel and bandages. Vascular plants • Xylem – conducts water and minerals up from the roots • Walls of cells are strengthened by lignin • Phloem – conducts sucrose and other organic compounds down from point of photosynthesis • Seedless vascular – homosporous (1 type) • Seed plants – heterosporous (2 types, m/f), leads to evolution of pollen grain and seed Seedless vascular plants • Sporophyte dominant • Independent gametophyte, archegonium and antheridium, still need water. • Club mosses • • • • Ground pines, spike mosses and quillworts Have 1 strand of vascular tissue Rhizome – horizontal underground stem Strobili (cones) – contain sporangia Seedless vascular Ferns and allies • Horsetails • Have rhizomes and stroboli • Whisk ferns • No leaves, sporangia are yellow, look like whisk broom • Fern • • • • • first fiddleheads that unrolls into fronds Megaphylls (more than 1 vascular strand) Dominant sporophyte produces windblown spores Life cycle figure 24.16 Uses: decorative, building material, medicinal, expel intestinal parasites Seed plants • Gymnosperms (naked seed) and angiosperms (flowering plants) • Contain sporophyte embryo and stored food within a protective seed coat • Allows survival during harsh conditions • Heterosporous, 2 types of gametophytes (m/f) • Pollen grains – male gametophyte • Pollination – when pollen grain is brought to vicinity of female gametophyte by wind/pollinator, no water needed! • Female gametophyte develops within an ovule which eventually becomes a seed Gymnosperms • Conifers, cycads, ginkgoes and gnetophytes • Ovules and seeds are exposed, not enclosed by fruit (naked seed) Conifers • Conifers – evergreens, including pines, spruces, firs, cedars, redwoods…bears cones • Tallest – redwood, oldest – bristlecone pine • Life cycle of pine fig. 24.18 • Used in construction, soft due to amount of xylem tissue, resin (turpentine) • Monoecious – tree produces both pollen and seed cones Cycads • • • • Tropical, subtropical Used in landscaping, resemble palms Pollen and seed cones on separate plants Pollinated by insects Ginkgoes • • • • • • • Maidenhair tree 1 species remains, Gingko biloba Dioecious – some trees produce seeds, other pollen Female seeds produce an odor, males preferred Resistant to pollution Seeds a delicacy Extracts used medically Gnetophytes • Lack archegonia, like angiosperms, thought to be most closely related • Ephedra – shrub, ephedrine is extracted Angiosperms • • • • Flowering plants Provide clothing, food, medicines Ovules are enclosed within diploid tissues Dominance of angiosperms is related to evolution of flying insects (pollination) Monocots and Eudicots • Cotyledon – seed leaf, contains nutrients that nourish the plant embryo • Monocots – corn, tulips, poineapple, bamboo • Eudicot – cactuses, strawberries, dandelions The Flower • Common structures in all flowers • • • • • • Peduncle – flower stalk Receptacle – expanded tip, contains the following: Sepals – (calyx) – protect the flower bud before opening Petals – (corolla) – differ in color, shape and size Stamens – consists of anther (produce pollen grains) and filament Carpels – stigma (sticky knob), style (stalk) and ovary (enlarged base that encloses ovule) Flowering plant life cycle • Megaspores – in ovule within ovary of carpel, develops into egg bearing female gametophyte embryo sac • Microspore – produced in anthers, pollen grains, develop into sperm bearing male gametophytes • Fruit – derived from an ovary Diversificaiton • Wind pollinated – usually bland • Insect/bird pollinated – usually colorful • Night blooming flowers – aromatic and white • Fruits protect and aid in dispersal of seeds