1. Chapters 29-30: Evolution of Plants AP Biology Mr. Orndorff May 2004

2. Photosynthetic organisms on land Opportunities –No competition. –Greater availability of light. –Higher concentration of carbon dioxide in atmosphere –Mineral nutrients readily available. Problems –Threat of dessication. –Lower density of air vs. water requires new mechanisms to support vertical growth. –Fertilization of water- requiring gametes more difficult.

3. Adaptations of early plants Waxy cuticle secreted by epidermal cells reduced evaporation from exposed surface. Stomata provided openings in waxy cuticle for exchange of gases in photosynthesis. Sporopollenin coating of spores allowed survival during dry periods. Sterile jacket of cells in gametangia for protecting gametes and sporophyte embryo.

4. Plant life cycle (Fig. 29-2)

5. Origin of sporophyte generation (Fig. 29.5)

6. Advantages of sporophyte generation to land environment Diploid cells of sporophyte have genetic insurance against damaging mutations from increased exposure to UV radiation on land. Multicellular sporophyte able to amplify the production of dessication resistant spores since many diploid cells can divide by meiosis and not just the diploid zygote.

7. Evolution of land plants (Fig. 30.1)

8. Adaptations of seedless vascular plants Lignin supplemented cellulose in providing cell walls with the rigidity to support vertical growth in air. Evolution of vascular tissues (xylem and phloem allowed transport of water and minerals up from the ground and products of photosynthesis throughout the plant body.

9. Life cycle of fern (Fig. 29.11)

10. Seeds vs. spores Seed contains tiny sporophyte embryo enclosed with nutritive tissues in dessication resistant seed coat. Pollen is the vehicle for sperm cells in seed plants—fertilization possible without water. Spore is a single haploid cell protected from dessication by sporopollenin coat. Early development not insured by diploidy or nutritive tissues. Sperm still need water for fertilization.

11. Seed development (Fig. 30.2)

12. Pine life cycle (Fig. 30.4)

13. Gymnosperms vs. angiosperms Gymnosperm = naked seed Pollination depends on random wind currents. Seeds are unprotected and depend on wind for their dispersal. Xylem contains tracheids and fibers. Angiosperm = vessel seed Pollination enhanced by flower. Seeds are protected in ripened ovary (fruit); dispersed by animals. Xylem contains vessel elements and fibers.

14. Evolution of xylem tissue (Fig. 30.5)

15. Flower anatomy (Fig. 30.6)

16. Angiosperm life cycle (Fig. 30.

17. Evolution of Plants (Fig. 29.3)

18. Evolution of atmosphere (Fig. 30.10)