Seedless Plants: Evolution and Environmental Challenges

1. Chapter 26 The Plant Kingdom: Seedless Plants

2. Environmental challenges of living on land required evolution of adaptations • Anatomical • Physiological • Reproductive

3. Examples of adaptations • Cuticle to prevent water loss • Stomata for photosynthesis • Alternation of generations • Gametophyte • Sporophyte

4. Basicplant life cycle

5. Generalized reproductive structures of algae and plants

6. Alternation of generations, cont. • Gametophyte produces gametes by mitosis • Gametes fuse to form zygote • Zygote develops into embryo

7. Alternation of generations, cont. • Mature sporophyte develops from embryo, producing sporogenous cells • Sporogenous cells undergo meiosis to form spores

8. Examples of adaptations, cont. • Gametangia protect gametes • Antheridia • Archegonia • Xylem conducts water and sugar nutrients • Phloem conducts dissolved sugar

9. Plant gametangia

10. Plants are probably descended from charophytes • Both have similar biochemical characteristics • Same photosynthetic pigments • Same cell wall components • Same carbohydrate storage material • Similarities in fundamental processes

11. Plant evolution

12. Features distinguishing bryophytes from green algae and other plants • Bryophytes have cuticle, stomata, etc. • Bryophytes are non-vascular and do not have xylem or phloem • Bryophytes have a dominant gametophyte generation

13. The three phyla of bryophytes • Phylum Bryophyta (gametophytes grow from protonema) • Phylum Hepaticophyta (some have gametophytes that are thalli) • Phylum Anthocerotophyta (thalloid gametophytes)

14. The life cycle of mosses • Green moss gametophyte bears archegonia and/or antheridia • During fertilization, sperm cell fuses with egg cell in archegonium • Zygote develops into embryo • Embryo develops into moss sporophyte

15. Life cycle of mosses

16. The life cycle of mosses, cont. • Moss sporophyte is attached to gametophyte • Meiosis occurs in capsule of sporophyte to produce spores • When spore germinates, it germinates into a protonema that forms buds

17. Life cycle of Marchantia polymorpha

18. Features distinguishing ferns and other seedless vascular plants from algae and bryophytes • Ferns and fern allies have adaptations including • Vascular tissues • A dominant sporophyte generation

19. Evolution of microphylls and megaphylls

20. The four phyla of seedless vascular plants • Phylum Polypodiophyta • Phylum Psilotophyta • Phlylum Equisetophyta • Phylum Lycophyta

21. The life cycle of ferns • Fern sporophytes have megaphylls • Their fronds bear sporangia in clusters (sori) • Meiosis in sporangia produces haploid spores • Prothalli develop from these and bear both archegonia and antheridia

22. Life cycle of ferns

23. Generalized life cycles of homosporous and heterosporous plants • Homospory • Bryophytes, whisk ferns, horsetails, most club mosses, and most ferns • Spores give rise to gametophyte plants producing both egg and sperm cells

24. Generalized life cycles of homosporous and heterosporous plants, cont. • Heterospory • Some clubmosses, some ferns, and all seed plants • Microspores give rise to male gametophytes • Megaspores give rise to female gametophytes

25. Basic life cycle of heterosporous plants

26. Life cycle of Selaginella