Plant Diversity I: How Plants Colonized LandChapter 29

Learning Targets

Plants Organization

Multicellular Energy

Autotrophs (CO2 + H2O C6H12O6 +O2) Growth and Development

Have meristematic tissues (mitosis) Reproduction

alternation of generations life cycle

Why did plants move on to land?

Remember Earth was a harsh environment!

Why did plants move on to land?

The risks: Heat Desiccation (dry out) Damage by UV rays

The rewards: Plentiful CO2

Sunlight Few competitors Few herbivores

Plant Evolution ~475mya green algae evolved into

plants

Evidence: Algae Evolved Into Plants Fossilized plant spores Morphological similarities

Cell wall, chloroplasts Genetic similarities

DNA analysis shows common ancestry

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

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

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

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

5. Apical meristems Localized regions of embryonic tissue

allows for cell division at the tips of roots and shoots

Mosses and other nonvascular plants have life cycles dominated by gametophytes29.2

Bryophytes: Mosses, hornworts, liverworts Nonvascular seedless plants Rhizoid “roots” anchor Must live in moist environments

No water transportation system Flagellated sperm

Ferns and other seed plants were the first to grow tall29.3

Pterophytes: FernsSeedless vascular

plantsVascular system:

transports water Xylem: moves water Phloem: moves sugar

Roots anchor plants (absorb nutrients)

Leaves increase S.A. (capture more light)