The Wonderful World of Green Plant Diversity and Evolution

1. The Wonderful World of Green Plant Diversity and Evolution Biol 366 Spring 2012

2. Tree of Life: The Big Picture Bacteria Archaea Eukaryotes now membrane-bound nucleus, organelles, etc. >2 bya >3.5 bya ca. 4 bya

3. Fig. 1.1 from Simpson

4. Green plants share: • Chlorophylls a (ancestral) and b • Starch storage • Stellate flagellar structure • Certain gene transfers from the chloroplast to the nucleus • And other features (see Ch. 3)

5. Green plant diversity: • Ca. 350,000 species • Two major groups: 1) chlorophytes (marine and other green algae) and 2) streptophytes [freshwater green algae and embryophytes (= land plants)] • A major branch (clade) in the eukaryotic Tree of Life

6. Fig. 3.1 from Simpson

7. Some definitions • Clade = branch on an evolutionary tree, a lineage, includes an ancestor and all its descendants. Ex.: Green plants, chlorophytes, land plants. • Paraphyletic group = a group that includes an ancestor and some (but not all) of its descendants, indicated by double quotation marks. Ex.: “Green algae”

8. Chlorophytes

9. Fig. 3.1 from Simpson

10. Spirogyra Nitella Chara (Judd et al. 2008) Basal streptophytes desmids

11. haploid body Conjugation in Spirogyra Haplontic life cycle (haploid dominant or zygotic meiosis) The only diploid cell Is the zygote zygote (2n)

12. biology.unm.edu ♀ Charales Haplontic but some have multicellular gametangia (gamete-producing structures) ♂ mason.gmu.edu

13. Embryophytes (land plants) share: • Cuticle • Alternation of generations (multicellular sporophyte and multicellular gametophyte) • Multicellular gametangia (gamete-producing structures) • Multicellular sporangium (spore-producing structure) • Embryo (young sporophyte) • Parenchyma? (more likely ancestral)

14. Generalized embryophyte life cycle: Alternation of generations

15. Bryophytes • Hornworts, liverworts, mosses • Gametophyte-dominant • No vascular tissue (except conducting cells in a few mosses) • Separate male and female gametophytes • Sperm must swim to the egg, therefore need water for fertilization and therefore must remain small

16. liverworts mosses hornworts

17. Plant Tree of Life: Embryophtes “Bryophytes” Tracheophytes (vascular plants) Mosses now Hornworts Liverworts ca. 450 mya

18. Liverwort gametophyte

19. Liverwort thallus showing air pores

20. Liverwort Multicellular gametangia (male = antheridia)

21. Liverwort Multicellular gametangia (female = archegonia) Oogamy Retention of zygote within the female gametophyte Multicellular embryo

22. G S Hornworts

23. Capsule = sporangium of the sporophyte Moss male gametangia (= antheridia)

24. Generalized embryophyte life cycle: Alternation of generations

25. Tracheophytes (vascular plants) • Vascular tissue (tracheids) present • Include lycophytes (quillworts, clubmosses, spikemosses), monilophytes (ferns, horsetails, whisk ferns), and spermatophytes (seed plants)

26. Fig. 4.1 from Simpson

27. Lycophytes & Monilophytes • Quillworts, clubmosses & spikemosses (= lycophytes); ferns, whisk-ferns, & horsetails (= monilophytes); • Independent gametophytes and sporophytes • Sperm must still swim to the egg • Most are homosporous; a few evolved heterospory • Many homosporous ferns have means of avoiding self-fertilization

28. Lycophytes Isoetes (quillwort) Lycopodium and friends (clubmosses) Selaginella (spikemoss)

29. Monilophytes (ferns, horsetails, whisk ferns) horsetails Whisk-fern (Psilotum) Ferns (Leptosporangia)

30. Nutritionally independent sporophytes and gametophytes sporophyte 2n 2n gametophyte 1n 1n spores 2n 2n

31. Fern Life Cycle, Fig. 4.32, Simpson

32. Lignophytes (woody plants) & Spermatophytes (seed plants) • Secondary xylem (wood) & bark, heterospory, seeds, eustele, pollen (also pollen tube, pollination droplet) • Includes gymnosperms and angiosperms

33. Fig. 5.1 from Simpson

34. Gymnosperms • Conifers, gingko, cycads, Gnetales • Molecular data support this group as having a single common ancestor • No obvious defining character (see characters for Lignophytes & Spermatophytes)

35. Female cone with each scale bearing usually two ovules; directly exposed to pollen Male cones with each scale bearing two or more microsporangia

36. male pine pollen biology.ualberta.edu female pine microsporangia

37. Fig. 5.7 from Simpson

38. Angiosperms • “Dicotyledons”, monocotyledons • Heterosporous (ancestral) • Sporophyte-dominant (ancestral) • Pollen = male gametophyte (ancestral) • Archegonia lost; embryo sac = female gametophyte; ovules enclosed in carpels (indirect pollination) • Double fertilization produces zygote + primary endosperm nucleus

39. Flower = a short, determinate shoot bearing highly modified leaves, some of which are fertile (i.e., bearing either microsporangia or megasporangia), with the megasporangia in carpels

40. Animal pollination syndromes

41. Wind pollination

42. A wide range of fruit types…

43. Fig. 5.7 from Simpson

44. The wonderful world of land plant diversity over 300,000 species of angiosperms