Evolution of Kingdom Plantae: From Algae to Angiosperms

1. Chapter 19: Kingdom Plantae

2. 19.1 Land plants evolved from green algae • Multicellular • Usually photosynthetic • Mostly terrestrial • Plant: multicellular autotroph, embryo develops in female parent

3. Origins of Plants from Algae • Closest ancestors = multicellular green algae • Charophytes • Some shallows dried out – plants adapted

4. Challenges of Life on Land • 4 challenges • 1. obtaining resources • 2. staying upright • 3. maintaining moisture • 4. reproducing

5. 1. Resources • Air – light, carbon dioxide (photosynthesis) • Shoots, leaves • Soil – water, mineral nutrients • Roots • Vascular tissue • System of tube-shaped cells that branches throughout the plant • Materials – roots/shoots

6. 2. Staying Upright • Water - buoyancy • Air – rigid support tissue • Lignin – hardens plants’ cell walls

7. 3. Moisture • Internal watery environment for cell processes • Adaptations: • Waxy cuticle – retain water, slow exchange gases between air and leaves • Stomata – pores in leaf’s surface • Gas exchange • Guard cells

8. 4. Reproduction • Gametes / offspring – moist • Sperm – pollen grain • Egg – female tissues • Dispersal • Sperm – wind / animals • Embryo develops in female parents  seeds

9. Overview of Plant Diversity • 4 major periods plant evolution • 1. Bryophytes – mosses • No seeds, no lignin • 2. Pteridophytes – ferns • Lignin – vascular tissue • 3. Gymnosperms – naked seeds, conifers • 4. Angiosperms – flowering plants

10. Figure 19-5Fossil evidence indicates that bryophytes are the oldest and angiosperms the youngest of the four major plant groups. Fig. 19-5

11. Alternation of Generations • Diploid (Sporophyte) / haploid (Gametophyte) • Multicellular • Fig. 19-6

12. Figure 19-6A plant's life cycle alternates between the gametophyte and sporophyte generations

13. Spores vs. Gametes

14. 19.2 Mosses and Bryophytes • Damp habitats • Lack rigid support tissues  grow close to ground

15. Bryophyte Adaptations • Dominant generation = gametophyte (1n) • Nonvascular – no lignin • Fig. 19-7 – overhead

16. Separate male/female gametophytes • Flagellated sperm swim to eggs • Fertilization – zygote grows from female gametophyte into sporophyte • Sporophyte (2n) = stalklike, capsule at top • Capsule produces/releases spores  new gametophytes

17. Diversity of Bryophytes • Hornworts – hornlike sporophytes

18. Mosses • Moss mat = many gametophytes in tight pack • Stalks = sporophytes • Spongy – absorb / retain water

19. Liverworts – liver-shaped gametophytes

20. 19.3 Pteridophytes: Ferns / other seedless vascular plants • Pteridophyte adaptations: • Fig. 19-10 - overhead • Vascular tissue – lignin – water, sugar • Carboniferous period – fossil fuel • Dominant generation = sporophyte • Underside of fronds – spore capsules • Haploid spores, gametophytes • Underside of gametophyte • Produce sperm / egg • Sperm swim to egg  zygote  new sporophyte

22. Diversity of Pteridophytes • Ferns – most diverse • Leaves = fronds • Shady forests

23. Club “mosses” – little pine tree • Vascular tissue, no seeds, forest floors

26. Horsetails • Marshy, sandy areas • Outer layer = silica – gritty • Scrub pots/pans • “scouring rushes”

29. 19.4 Pollen and Seeds Evolved in Gymnosperms • Gymnosperm adaptations • Gymnosperms = plants that bear seeds that are “naked” • Not enclosed in an ovary • Most common - conifers

30. 3 more adaptations than ferns: • 1. Smaller gametophyte • Dominant generation = diploid sporophyte = pine tree • Tiny gametophytes are in cones- protection • 2. Pollen • Reduced male gametophyte • Contain cells that become sperm • Wind – pollen from male to female- no water needed • 3. Seeds • Plant embryo with a food supply in a protective coat

31. Life Cycle of Gymnosperms • Male pollen cone - spore sacs with haploid spores become pollen grains (male gametophyte) • Female gametophytes develop within ovules • On scale of cone – 2 ovules • Large spore cell – meiosis • 4 haploid cells – 1 survives female gametophyte

32. Wind – blows pollen between trees • Pollen lands in female cone • Sperm matures and fertilizes egg in female gametophyte • 2 eggs fertilized often – still only 1 zygote into embryo (seed) = new sporophyte

33. Diversity of Gymnosperms • 4 phyla today • Gingkos • Gingko biloba • Fan-like leaves • Shed in autumn • Cities- • Tolerates • pollution

34. Gnetophytes • Mormon tea, desert shrub

35. Cycads – large, palm-like leaves • Not true palms which are flowering plants

36. Conifers • Spruce, pine, fir, junipers, cedar, redwood • evergreen

37. 19.5/20.1 Flowers and fruits evolved in angiosperms • Angiosperm Adaptations • Gametophytes develop in flowers of sporophyte • Flower = specialized type of plant shoot that functions in reproduction, only in angiosperms • Attract animal pollinators – variety • Insects transfer pollen between flowers • Grasses – wind pollinated – small flowers

38. Flower Anatomy • Flower – specialized shoot • 4 rings modified leaves • Sepals – protect flower bud • Petals – color – insects • Stamens – male, many • Carpels (pistils) – female,1+

39. Stamen – produces male gametophytes • Filament + anther • Filament – supports anther • Anther – pollen • meiosis – spores – pollen grains = male haploid gametophytes • Each pollen grain – 2 cells with thick protective wall • Fig 20-2 in packet

40. Carpels – female gametophytes • stigma – style – ovary • Stigma – sticky – pollen • Style – supports stigma – pollen tube • Ovary - ovules

41. Angiosperm Life Cycle • Pollen on stigma - pollination • Pollen tube to ovule in ovary - style • 2 sperm cells in pollen grain in tube • In ovules – diploid cell – • meiosis • 4 haploid spores – ¾ die • survivor enlarges – 3 cycles mitosis  embryo sac – 7 cells (1 egg cell + 1 large cell with 2 haploid nuclei)

43. Water lilies

44. Star Anise

45. 1st sperm fertilizes 1 egg = zygote  embryo • 2nd sperm fuses with nucleus in larger center cell  triploid cell = endosperm (nutrient storage) • “double fertilization” – zygote and endosperm develop into seed

46. Many ovules, many seeds • Seeds develop, ovary wall thickens fruit • Fruit = ripened ovary of a flower • Protects, disperses seeds • Colorful, attract animals, eat, digest, waste

47. Monocots – day lilies, orchids, irises, palms, grasses • Flower petals – multiples of 3 • Dicots – poppies, roses, peas, sunflowers, oaks, maples • Flower petals – multiples of 4 or 5

48. Human Dependence on Angiosperms • Food – human, domestic animals • Corn, rice, wheat, fruit, vegetables • Furniture, medicines, perfumes, decorations, clothing fibers • Threat – tropical rain forest

49. 20.1 Reproductive Adaptations contribute to angiosperm success

50. Seed Development and Dispersal • Seed parts • Seed coat – outer layer – protects embryo and endosperm • Mini root and shoot • Cotyledon – food storage • Monocot, dicot