Plant Evolution & Diversity – Ch. 22-25

1. Plant Evolution & Diversity – Ch. 22-25

2. Kingdom Protista: Algae & Protozoa • Organisms in this Kingdom don’t fit clearly into what we call plant, animal, or fungi. • Most diverse eukaryotic Kingdom (>60,000 species). • We are interested in this Kingdom because of the Chlorophytes & Charophyceans - green algae.

3. The line between Kingdom Protista and Kingdom Plantae is still being discussed…… Fig 29.4

4. Origin of Plants

5. Characteristics of Green Algae - Chlorophytes • There are unicellular and multicellular forms • Can live symbiotically with fungi as lichens

6. Fig 28.30 Volvox - freshwater Ulva – sea lettuce Caulerpa - intertidal

7. Characteristics of Green Algae - Charophyceans • fresh water ponds • They are considered to be the closest ancestors of true plants. Evidence: • . • . • . • Both form a cell plate during cell division • Genetic evidence – charophyceans share a greater % of similar DNA with true plants than any other algae

9. Plants • So how are they different from Charophyceans??

10. What challenges did plants face when they “moved” onto land?

11. Adaptation to life on Land: • . • . • . • Multicellular gametangia • Multicellular, dependent embryos

12. 1. Apical Meristems –

13. 2. Alternation of Generations

14. 2 multicellular life stages: • Sporophyte: • Diploid • Divides by meiosis to form spores • Spores – haploid cells that can grow into a new, multicellular, haploid organism (the gametophyte) without fusing to another cell. • Gametophyte: • Haploid • Divides by mitosis to form the gametes (egg and sperm) • Egg & sperm fuse to form the diploid zygote, which divides by mitosis to form the sporophyte

15. 3. Walled spores produced in sporangia • Sporopollenin protects the spore from harsh environmental conditions • Sporangia = • Sporocytes = the diploid cells within the sporangia that divide by meiosis to form the haploid spores

16. sporocytes

17. 4. Multicellular gametangia • Gametangia = • 2 types of gametangia: • Archegonia – • Antheridia – • Sperm travel to the egg, fertilizing it within the archegonia.

19. 5. Multicelluar, dependent embryos • Zygote divides by mitosis to become the sporophyte.

20. Other examples of adaptations to life on land: (not all plants have the following): • Cuticle – • Secondary compounds – • Roots – • Shoots - stems and leaves to make food. • Stomata – openings in the leaf surface to allow gas exchange for photosynthesis and to regulate water loss.

21. More Adaptations 4. . 5. A vascular system that transports food & water from roots to shoots and vice versa.

23. Fig 29.7

24. Nonvascular Land Plants: Bryophytes • Earliest land plants • 3 Phyla: • Hepatophyta – • Anthocerophyta – • Bryophyta - • . • Peat moss (sphagnum): doesn’t decay rapidly, stores 400 bil tons of carbon • Gametophyte is the dominant generation:

25. Moss life cycle Fig 29.8

26. Phylum Hepatophyta – liverworts

27. Phylum Anthocerophyta – hornworts

28. Phylum bryophyta - mosses

29. Peat bogs – sphagnum moss Fig 29.10

30. Vascular Plants • Vascular tissue: • Xylem = water & mineral transport • Phloem = food (carbohydrates) transport • . • Sporophytes branched, independent of gametophyte parent

31. Seedless Vascular Land Plants • Egg & sperm need moist environment to fertilize (similar to bryophytes)

32. Two phyla of seedless vascular plants: • Phylum Lycophyta (Club Mosses) • flammable spore clouds • were tree-like in the Carboniferous period

33. Phylum Lycophyta: clubmosses, spikemosses, quillwarts

34. 2. Phylum Pterophyta • Whisk ferns – • Horsetails – • Ferns – produce clusters (sori) of sporangia on underside of leaves (fronds)

35. Phylum Pterophyta: ferns, horsetails, whisk ferns

36. Fig 29.12 Life cycle of a fern

37. Forests of the Carboniferous period (290-360 mil years ago): • Heat + pressure + time ----> coal • Pulled lots of CO2 out of atmosphere, cooling the earth & forming glaciers • Larger species died out when climate became drier

38. Terrestrial Adaptations of Seed Plants • Seeds replace spores as main means of dispersal. • Why? • Gametophytes became reduced and retained within reproductive tissue of the sporophyte • Heterospory – • Zygote develops into an embryo packaged with a food supply within a protective seed coat. • Pollen & Pollination - freed plants from the requirement of water for fertilization.

39. 1. Seeds replace spores as main means of dispersal. • old way (ferns & mosses) = • new way: the sporophyte RETAINS its spores within the sporangia & the tiny gametophyte develops within the spore. • ovule = • after fertilization, the ovule becomes the seed • seed = sporophyte embryo + food supply (mature ovule tissues)

40. 2. Reduction of the gametophyte: Similar to Fig 30.2

41. 3. Heterospory – separate male & female gametophytes • Old way: sporangia  spores  bisexual gametophyte (antheridia  sperm, archegonia -> eggs) • New way: • Microsporangia  microspores  male gametophyte  sperm

42. 4. Ovules and seed production • Megasporangia protected by layers of tissue called integuments. • Ovule = • After fertilization, embryo develops, ovule becomes a seed

43. Fig 30.3

44. 5. Pollen & Pollination • Microsporangia  microspores  male gametophyte  sperm • Pollen = • Pollination = • Pollen tube brings sperm to egg within the ovule

45. Two types of seed plants: • 1. Gymnosperms • Evolved first • “naked seed” – • 2. Angiosperms • Evolved from gymnosperms: Sporophylls rolled together to form ovaries.

46. Gymnosperms • Four phyla: • Ginkophyta – • Cycadophyta – • Gnetophyta – • Coniferophyta – • Dominate forests of the N. hemisphere • Most are evergreen • Needle-shaped leaves to reduce water loss during drought

47. Phylum Cycadophyta

48. Phylum Ginkophyta

49. Phylum Gnetophyta

50. Phylum Coniferophyta