Chapter 22 Lecture Outline See PowerPoint Image Slides

1. Chapter 22 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

2. What is a plant? • Eukaryotic • Multicellular • Contains chlorophyll a and b • Carries on photosynthesis • Has cellulose cell walls • Lives in a variety of terrestrial habitats • And a few shallow aquatic habits • Exhibits alternation of generations

3. Plant Diversity

4. Alternation of Generations • A life cycle that involves two generations • Sporophyte generation • Diploid • Undergoes meiosis to generate haploid spores • Spores germinate and divide by mitosis to give rise to the gametophyte generation. • Gametophyte generation • Multicellular haploid generation • Undergoes mitosis to produce haploid gametes • Gametes unite to form a zygote. • Zygote divides by mitosis to form the sporophyte generation.

5. Alternation of Generations

6. The Evolution of Plants • Photosynthetic algae are thought to be the ancestors of plants. • Green algae have the same types of chlorophyll. • There is extensive DNA homology between plants and green algae. • The evolution of plants shows two trends. • Toward greater specialization for living in a dry environment • Toward a more prominent sporophyte generation

7. The Evolution of Plants • Primitive plants • Lack vascular tissue to carry water • Have flagellated sperm; no seeds • Have to live in moist habitats • Have dominant gametophyte generation • More advanced plants • Have specialized cells that transport water • Have seeds that do not require water for distribution • Have dominant sporophyte generation

8. The Taxonomy of Plants

9. Nonvascular Plants • Include • Mosses, hornworts, liverworts • Known as the bryophytes • Common features • Lack vascular tissue • Use diffusion and osmosis to obtain water and nutrients • Do not have true roots or leaves • Gametophyte is dominant • Sperm swim to egg • Must have water to reproduce sexually • Are small and confined to moist habitats

10. Moss Life Cycle

11. http://www.youtube.com/watch?v=jcWYAnmm-QE

12. Kinds of Nonvascular Plants • Mosses • Grow as a carpet of many individual gametophyte plants • Each individual is less than 5 cm tall. • Liverworts and hornworts • Form flat sheets only a few cells thick • Each cell contains one large chloroplast.

13. Non-vascular plants • http://www.youtube.com/watch?v=kBPLKUTtXBM

14. The Significance of Vascular Tissue • Vascular tissue is an adaptation to living in dry environments. • Allows plants to transport water and nutrients throughout the plant • Associated with the development of • Leaves for photosynthesis • Roots for absorbing water and minerals • Vascular tissue allowed for an increase in plant size • Accompanied by the appearance of a waterproof coating on the plant surfaces • Two types of vascular tissue • Xylem • Phloem

15. Xylem • A series of dead, hollow cells that form tubes • Vessel elements • Form long tubes with cells end-to-end • Tracheids • Tapered cells with holes • Overlap to form a sieve-like tube • The walls of these cells are strengthened by cellulose and lignin. • Transports water and minerals from the soil to the leaves

16. Xylem

17. Phloem • Carries organic molecules produced in the leaves to the rest of the plant • Sugar • Amino acids • Consists of two types of cells • Sieve-tube elements • Lack a nucleus and organelles, but have cytoplasm • Have holes in the end walls for the transport of material • Companion cells • Actively transport sugars and amino acids out of the leaf cells and into the sieve-tube elements

18. Phloem

19. Video Xylem and phloem • http://www.youtube.com/watch?v=J1PqUB7Tu3Y

20. The Development of Roots, Stems, and Leaves • The appearance of vascular tissue allowed for the development of specialized plant parts. • Roots are specialized for absorption. • Stems are specialized for transport. • Leaves are specialized for photosynthesis.

21. Roots • Underground parts of a plant that • Anchor in the soil • Absorb water and nutrients • Move the nutrients into the vascular system • Grow from the tips • Explore new areas of soil for water and nutrients • Root tips have root hairs that increase their absorptive surface. • Can be important storage sites • Many plants store carbohydrates in their roots during growing season to be used during the winter. • Carrots, turnips, radishes, maple trees, rhubarb, grasses

22. Kinds of Roots

23. Stems • Above-ground structures that • Support the leaves • Transport raw material from the roots to the leaves • Transport manufactured material from the leaves to other parts of the plant • Vary greatly in diameter and length • Tree trunks are large and support branches. • Dandelion stems are short. • Some stems are underground.

24. Stems • The structure of cell walls allows the stem to support the leaves. • Cell walls are made of cellulose interwoven into a box. • When cells are full of water, the cell walls will not stretch. • This makes the cells turgid, stiff and able to support weight. • Woody plants have especially thick cell walls. • These have lignin in them. • Allows woody plants to grow tall and withstand wind

25. Stems • Stems contain a lot of vascular tissue. • Stems also • Store food • Sugar cane • Yams • Potatoes • Photosynthesize • Have waterproof layers • Can be waxy or woody

26. Leaves • Specialized for photosynthesis • Have large surface area to collect sunlight • Relatively thin to allow light penetration • Have bundles of vascular tissue to transport • Water and minerals needed for photosynthesis into the leaf • The sugar that is made out of the leaf • Thick cell walls for support • Are arranged to minimize shading of lower leaves

27. The Structure of a Leaf

28. Leaves • Specialized for photosynthesis • Covered by a waxy coating to minimize water loss • Water evaporates from leaves through transpiration. • Pulls water and nutrients up from the roots • Transpiration must be regulated so plant doesn’t lose too much water. • Water and oxygen exit, and carbon dioxide enters, through stomata.

29. Stomates

30. Seedless Vascular Plants • Include • Whisk ferns • Horsetails • Club mosses • Ferns • Have vascular tissue • Are not limited to aquatic environments • Do not have seeds • Have flagellated sperm • Must have moist conditions to reproduce

31. Fern Life Cycle

32. Kinds of Seedless Vascular Plants • Ferns • Most common seedless vascular plant • Whisk ferns • Lack roots and leaves • Anchored by an underground stem • Modifications of the stem serve the functions of roots and leaves.

33. Kinds of Vascular Seedless Plants • Horsetails • Low-growing plants with jointed stems • Most photosynthesis occurs in the stems. • Have silicon dioxide in their cell walls • Called (and used as) scouring brushes by pioneers • Club mosses • Usually evergreen • Low-growing, branching plants • Some are called ground pines.

34. Seed-producing Vascular Plants • A seed is a specialized structure that contains • An embryo • Stored food • A protective outer coating (seed coat) that prevents drying • Seeds allow plants to live in dry habitats. • Aid in dispersal • Gymnosperms and angiosperms produce seeds. • Accompanied by the development of pollen • Encased sperm (male gametophyte generation) • Allows plants to reproduce without water

35. Gymnosperms • Means “naked seed” • Woody, perennial plants • Produce seeds that are not enclosed (naked) • Produce seeds in cones

36. The Pine Life Cycle

37. Kinds of Gymnosperms • Cycads • Wood plants with a ring of fern-like leaves at the top • Live in tropical regions • Ginkgo • Ginkgo biloba is the only living species • A tree with fan-shaped leaves • Used in many herbal medicines

38. Kinds of Gymnosperms • Conifers • Trees and shrubs that bear cones • Have needle-shaped leaves • Called evergreens because they do not lose their leaves • Do shed needles throughout the year • Used in the production of lumber

39. Several Gymnosperms

40. Angiosperms • Produce flowers • Have vascular tissue, seeds and pollen • Have seeds enclosed in a fruit • A modification of the ovary wall

41. Flower Structure • Composed of highly modified leaves • Petals are usually colorful. • Sepals surround petals • Petals and sepals are arranged in whorls. • Specialized for sexual reproduction • Female parts in the center • Pistil (stigma, style and ovary) • Ovary produces eggs

42. Flower Structure • Male parts surround the pistil. • Stamens (filament and anther) • Anther produces sperm. • Perfect flowers have both pistils and stamens. • Imperfect flowers have either pistils or stamens.

43. Flower Structure

44. The Life Cycle of a Flowering Plant

45. Pollination Strategies • Wind • Plants with inconspicuous flowers are usually wind-pollinated. • Produce large numbers of flowers and pollen • Many species are wind-pollinated. • Grasses and sedges • Aspens, birches and oaks • Responsible for hay fever • Some people have allergic reactions to pollen.

46. Strategies for Pollination • Animals • Plants with showy flowers are usually animal-pollinated. • These flowers usually produce nectar. • Also smell good to attract animals • Flowers attract insects, birds and small mammals. • The animals feed on the nectar and pick up the pollen. • Then move to another plant for more nectar, transferring the pollen

47. Wind- and Insect-pollinated Flowers

48. Fruit • A modification of the ovary that contains seeds • Involved in dispersal of seeds • Many fruits are nutritive to animals. • The animals eat the fruit and ingest the seeds. • The seeds pass through the digestive tract unharmed and get “planted” in the animals’ feces. • Other fruits burst open and release light seeds that are dispersed by wind. • Other fruits have sticky surfaces that cling to animals that pass by.

49. Types of Fruits

50. Angiosperm Diversity • Classified as either monocots or dicots • Refers to the number of cotyledons found in the seeds of the species • Monocots have one cotyledon (peanut). • Dicots have two cotyledons (lima bean). • Cotyledons (seed leaves) store food for the growing embryo. • They emerge as the first leaves.