1. Plant Diversity I: How Plants Colonized Land Chapter 29

2. Learning Targets

3. Plants  Organization  Multicellular  Energy  Autotrophs (CO 2 + H 2 O  C 6 H 12 O 6 +O 2 )  Growth and Development  Have meristematic tissues (mitosis)  Reproduction  alternation of generations life cycle

4. Why did plants move on to land? Remember Earth was a harsh environment!

5. Why did plants move on to land?  The risks:  Heat  Desiccation (dry out)  Damage by UV rays  The rewards:  Plentiful CO 2  Sunlight  Few competitors  Few herbivores

6. Plant Evolution  ~475mya green algae evolved into plants

7. Evidence: Algae Evolved Into Plants  Fossilized plant spores  Morphological similarities  Cell wall, chloroplasts  Genetic similarities  DNA analysis shows common ancestry

8. 5 Derived Traits  1. Alternation of generations  Sporophyte  The multicellular diploid plant structure  Produces spores through meiotic (asexual) division  Gametophyte  Multicellular haploid plant structure  Formed from the spore  Gives rise to the haploid gametes

9.  2. Multicellular dependent embryos  The zygote is retained surrounded by tissues of the gametophyte  The parental tissue provides the embryo with nutrients  Placental transfer cells present in the embryo and sometimes in the gametophyte as well, enhance the transfer of nutrients

10.  3. Walled spores produced in sporangia  Haploid reproductive cells that become a multicellular haploid gametophyte by mitosis  The multicellular sporangium contains sporocytes, the cells that undergo meiosis to form spores  Sporopollenin makes the walls of the spores

11.  4. Multicellular gametangia  Gametes of land plants are produced in multicellular organs called gametangia  Algae produce their gametes in unicellular gametangia, inside a single cell

12.  5. Apical meristems  Localized regions of embryonic tissue allows for cell division at the tips of roots and shoots

13. Mosses and other nonvascular plants have life cycles dominated by gametophytes 29.2

14. Bryophytes: Mosses, hornworts, liverworts  Nonvascular seedless plants  Rhizoid “roots” anchor  Must live in moist environments  No water transportation system  Flagellated sperm

15. Ferns and other seed plants were the first to grow tall 29.3

16. Pterophytes: Ferns  Seedless vascular plants  Vascular system: transports water  Xylem: moves water  Phloem: moves sugar  Roots anchor plants (absorb nutrients)  Leaves increase S.A. (capture more light)