plants - PowerPoint PPT Presentation

plants n.
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  1. plants

  2. Plants are multicellular, eukaryotic, autotrophic with cell walls made of cellulose.

  3. Land plants evolved from green algae, based on 3 key traits: • both contain chlorophyll a and b • Both store excess carbohydrates as starch • Both have cellulose in their cell walls

  4. Derived traits of plants: 1. Apical meristems-localized regions of cell division at the tips of stems and roots

  5. 2. Alternation of generations-life cycle consists of two distinct stages called the sporophyte and the gametophyte

  6. Diversity of plants: 1. Bryophytes-nonvascular plants • Examples: liverworts, hornworts and mosses

  7. Habitat: moist and cool environments • Size: most are under 15 cm • Importance: • Peat moss preserves corpses • Source of fuel in Europe and Asia • Used as packing around plants that are shipped

  8. 2. Seedless vascular plants a. examples: -lycophytes-includes epiphytes -whisk ferns-lack true roots, stems and leaves, known as a living fossil

  9. -horsetails-less common today, found in marshy areas -ferns-most widespread of the group, they are mainly tropical

  10. b. Importance: Coal deposits

  11. 3. Seed plants • They develop unique structures: • An ovule which produces 1 or more eggs • Pollen grain which contains the sperm • The seed develops from joining egg and sperm. It is multicellular.

  12. The advantage of seeds: • Dispersal is more successful • They resist harsh environments • They can remain dormant for years

  13. Gymnosperms • Name means naked seed • Seeds form on cones • Examples: • Cycads-has large cones with palm shaped leaves

  14. Ginkgo: only 1 species left on earth, ornamental in large cities because it is tolerant of air pollution.

  15. Gnetophyta includes: • Welwitschia-1 species in Africa • Gnetum-tropical trees and shrubs • Ephedra-desert shrubs (Mormon tea)

  16. Conifers-largest group • Yews, firs, pines, junipers, spruces

  17. Angiosperms • Means covered seed, these are the flowering plants • Includes: • Monocots (about 1/3) • Eudicots (about 2/3)

  18. Monocots • 1 cotyledon (seed leaf) • Leaves have parallel veins • Vascular tissue in the stem is scattered • Roots are fibrous • 1 opening on the pollen grain • Petals are in multiples of 3

  19. Eudicots • 2 cotyledons • Leaves have branching veins • Vascular tissue in a ring • Roots are taproots • 3 openings on pollen grains • Petals in multiples of 4 or 5

  20. Flowers • Are specialized for sexual reproduction • Sepals-small leaves that protect the bud • Petals-attract insects and other animals

  21. Stamens are the male structures • Anther-top, makes the pollen • Filament-stalk that holds the pollen up high • Carpel is the female structure (also called a pistil) • Stigma-top, sticky to hold pollen • Style-tube carrying sperm down • Ovary-produces the eggs

  22. Fruits • Fruit is a mature ovary • Fleshy fruits ripen to be soft and sweet • Dry fruits include beans, nuts, grains

  23. Dispersal adaptations • Wind-seeds must be lightweight and have attachments to float in air

  24. Water-seeds are hollow to float

  25. Animal fur-seeds have attachments to hook onto fur and drop off later

  26. Animal digestion-fleshy fruits are eaten and seeds pass through the digestive tract unharmed and land in new places

  27. Many plants and animals coevolved in order to pollinate and disperse the seeds

  28. Plant tissues 1. Vascular tissue a. xylem-conducts water and nutrients Tracheids Vessels

  29. b. Phloem conducts sugars to where they are needed. Sieve tubes Companion cells serve the sieve tubes.

  30. 2. Parenchyma tissue -makes up soft moist primary growth of roots, stems, leaves and flowers -thin walled cells, pliable, many sided -functions in photosynthesis in the leaf, starch storage in the root, makes up the fleshy part of fruits, repairs wounds

  31. 3. Collenchyma tissue -stretchable, grouped in strands or cylinders -provides support for rapidly growing parts, found in young stems and petioles -wall is thick and rich in pectin

  32. 4. Schlerenchyma tissue -functions in support, found in cells that have stopped growing in length -dead at maturity -includes fibers (long tapered cells that flex and twist and schlereids (stubby branched cells that make seed coats, hard nut shells and makes pear gritty

  33. Plant organs • Leaves-carry on photosynthesis • Blade-wide and flat to increase surface area • Petiole-attaches leaf to stem • Simple leaves have one blade • Compound leaves have several leaflets

  34. Epidermis-outer layer of cells • Stomata –openings in the epidermis for gas exchange • Guard cells-2 bean shaped cells that control the stomata

  35. Mesophyll-middle layer, does most of the photosynthesis • Cuticle-waxy covering on epidermis to prevent water loss

  36. Roots • Anchor plant, absorb water and nutrients • Primary root-first structure to pass through seed

  37. Taproot-one main long root • Fibrous roots-many small branching roots • Root hairs-small extensions that increase the surface area of the root

  38. Stems • Allows greater height for maximum sun exposure • Bark-made of dead tissue (cork) and a living inner layer • Heartwood-dry core, no longer transports water, stores wastes such as resins, oils and gums making it darker and aromatic • Sapwood-outer layers that still carry water, pale and wet

  39. Growth rings-light ring made in the spring, has large cells with thin walls and dark ring made in the summer has smaller cells with thick walls

  40. Hardwood-dicots such as oak, maple, ash • Softwoods-conifers

  41. Importance: • Domestication of crops changed human society • Food staples-3 crops make up 80% of human calories • Non-staples-spices, coffee, chocolate

  42. Lumber, building • Paper • Medicine • Perfumes • Flowers • Landscaping

  43. Nutrition and Transport 1. Soil a. humus-decomposing organic matter (fallen leaves, animal feces, etc.) b. particles-sand, silt, clay (biggest to smallest)

  44. c. topsoil-most essential for growth Deserts have only a few cm