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Plant Diversity

Plant Diversity. What Is A Plant?. Multicellular eukaryotes Cell walls with cellulose P hotosynthesis using green pigments chlorophyll a and b Autotrophs Some are parasites or saprobes. What Plants Need To Survive. Sunlight Water and minerals Gas exchange

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Plant Diversity

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  1. Plant Diversity

  2. What Is A Plant? • Multicellular eukaryotes • Cell walls with cellulose • Photosynthesis using green pigments • chlorophyll a and b • Autotrophs • Some are parasites or saprobes

  3. What Plants Need To Survive • Sunlight • Water and minerals • Gas exchange • Movement of water and nutrients

  4. Early Plants • For most of Earth’s history plants did not exist • Origins in the water • Green algae: the first plants evolved from an organism much like the multicellular green algae living today • Depended on water to complete their life cycles

  5. The First Plants • Life on land favored the evolution of plants: • More resistant to the drying rays of the sun • More capable at conserving water • More capable of reproducing on dry land

  6. The First Plants • Four groups based on: • Water-conducting tissues • Seeds • Flowers • Today scientists can classify plants more precisely by comparing DNA sequences of various species • Like today’s mosses • Gave rise to the plants of today! • Non-vascular Plants • Seedless Vascular Plants • Gymnosperms • Angiosperms

  7. The Plant Life Cycle: Alternation of Generations • Haploid gametophyte (N): gamete-producing phase of an organism • Diploid sporophyte (2N): spore-producing phase of an organism

  8. SEEDLESS PLANTS

  9. Green Algae • First plants • Mostly aquatic • Fresh and salt water, some moist areas on land • Absorb water and nutrients from surroundings • Life Cycle: switch between haploid and diploid • No specialized cells

  10. Bryophytes • Mosses, liverworts, hornworts • Depend on water • Sperm swim through water to reach eggs of other plants • No vascular tissue • Can draw up water by osmosis only a few cm above the ground

  11. Mosses • The most common bryophytes • Well adapted to wet habitats and nutrient-poor soils • Gametophyte dominant • Reproduce  produce thin stalks with sporophyte • Rhizoids: long, thin cells that anchor them in the ground and absorb water and minerals from the surrounding soil • No true roots

  12. Life Cycle of A Moss • Archegonia: produces eggs • Antheridia: produces sperm • Sperm of the bryophyte must swim to an egg for fertilization to occur • A diploid zygote results from fertilization • Sporophyte: the zygote • Grows out of the gametophyte and depends on it for water and nutrients • When ready, haploid spores are released to start the cycle again

  13. VASCULAR PLANTS

  14. Vascular Plants: Tracheophytes • Vascular tissue: a type of tissue that is specialized to conduct water and nutrients through the body of the plant • Tracheid: hollow plant cell in xylem tissue with thick cell walls that resist pressure • One of the great evolutionary innovations of the plant kingdom!

  15. Vascular Plants • Xylem and Phloem: • move fluids throughout the plant body • even against the force of gravity • Allow vascular plants to: • grow upright • reach great heights

  16. Structure of Vascular Tissue • Xylem: vascular tissue that carries water upward from the roots to every part of the plant • Phloem: vascular tissue responsible for the transport of nutrients & carbohydrates produced by photosynthesis

  17. Vascular Plants • Roots: absorb water and minerals • Leaves: photosynthetic organisms that contain one or more bundles of vascular tissue • Stems: supporting structures that connect roots and leaves, carrying water and nutrients between them

  18. SEEDLESS VASCULAR PLANTS

  19. Seedless Vascular Plants • Club mosses, horsetails, and ferns • Ferns have survived Earth’s long history in numbers greater than any other group of spore-bearing vascular plants • More than 11,000 species live today • Strong roots • Rhizomes: creeping or underground stems • Fronds: large leaves • Can thrive in areas with little light • Most abundant in wet or seasonably wet habitats

  20. Life Cycle of Ferns • Sporophyte = Dominant • Produce haploid spores on the underside of their fronds in sporangia • Spores are released • Spores germinate into haploid gametophytes • Diploid zygote is produced from fertilization • Sporophyte grows and the gametophyte withers away

  21. SEED PLANTS

  22. Seed Plants • Seeds include: • Acorns, pine nuts, dandelion seeds, kernels of corn, etc. • Seed plants are divided into two groups: • Gymnosperms • Angiosperms

  23. Seed Plants • Reproduction free from water • Can live just about anywhere • Adaptations to reproduce without water: • Flowers or cones • Transfer of sperm by pollination • Protection of embryos in seeds

  24. Cones and Flowers • Gametophyte of seed plants grow and mature within sporophyte structures called cones (gymnosperms) and flowers (angiosperms)

  25. Pollen • Pollen Grain: male gametophyte is contained in a tiny structure • The wind, insects, birds and small mammals may carries pollen grains • Pollination: the transfer of the pollen grain to the female gametophyte

  26. Evolution of Seed Plants • The seed was very important evolutionarily • Seed: embryo of a plant encased in a protective covering and surrounded by a food supply • Mosses and ferns underwent major adaptive radiation 300-400 mya • Land environments were much wetter than they are today • As the land became drier, it became harder for seedless plants to survive • Fossils of seed-bearing plants exist from almost 360 mya • The original seed plants resembled ferns

  27. GYMNOSPERMS

  28. Gymnosperms…Cone Bearers • The most ancient surviving seed plants • Include cycads, ginkgoes, and conifers • “Naked Seed”: these plants all reproduce with seeds that are exposed

  29. Conifers • The most common gymnosperms with more than 500 known species • Pines, spruces, firs, cedars, sequoias, redwoods, yews • Some, like the bristlecone pine tree, can live for more than 4000 years • Others, such as the giant redwood, can grow to more than 100 meters in height

  30. Ecology of Conifers • Thrive in a wide variety of habitats: on mountains, in sandy soil, and in cool, moist areas • Leaves have adaptations to dry conditions • The leaves are long and thin, like pine needles • This shape reduces the surface area from which water can be lost • Waxy layer also prevents water loss • Most are evergreens: they retain their leaves through the year

  31. Cones • Pollen Cones (male cones): produce pollen • Seed Cones (female cones): produce female gametophytes in two ovules • The complete life cycle takes 2 years to complete • The direct transfer of pollen to the female cone allows fertilization to take place without the need for gametes to swim through standing water

  32. ANGIOSPERMS

  33. Angiosperms…Flowering Plants • Flowering plants first arrived about 135 mya • Originated on land and became the dominant plant life on Earth • The majority of living plant species reproduce with flowers

  34. Flowers: An Evolutionary Advantage • Attract animals which transport pollen from flower to flower • More efficient than wind pollination of most gymnosperms • Flowers contain ovaries, which surround and protect the seeds

  35. Angiosperms…”Enclosed Seeds” • After pollination, the ovary develops into a fruit, which protects the seed and aids in its dispersal • Fruit: thick wall of tissue surrounding the seed • Adds to the success of angiosperms

  36. Monocots and Dicots Monocots Dicots Angiosperm whose seeds have two cotyledons Branched veins Floral parts often in multiples of 4-5 Stem vascular bundles are arranged in a ring Taproot • Angiosperm whose seeds have one cotyledon • Parallel veins • Floral parts often in multiples of 3 • Stem vascular bundles are scattered • Fibrous root

  37. Comparing Monocots and Dicots

  38. Woody Plants • Woody plants are made primarily of cells with thick cell walls that support the plant body • Trees • All types! • Shrubs • Blueberries, rhododendrons, roses • Vines • Grapes and ivy

  39. Herbaceous Plants • Smooth and non-woody plants that do not produce wood as they grow • Dandelions, zinnias, petunias, sunflowers

  40. Growing Season • Annuals: Flowering plants that complete a life cycle within one growing season • Garden plants, marigolds, petunias, pansies, zinnias, wheat and cucumbers too! • Biennials: Flowering plants that complete a life cycle in two years • Primrose, parsley, celery, foxglove • Perennials: Flowering plants that live for more than two years • Peonies, asparagus, grasses: herbaceous perennials • Palm trees, sagebrush, maple trees, honeysuckle: woody perennials

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