1. The Colonization of Land by Plants and Fungi

2. Fossil Evidence
Suggests that plants colonized land in partnership with fungi
Plants may have colonized land more than 470 million years ago from Algal ancestors.
Plants have in common with algae: multicellular, eukaryotic, photosynthetic
Plants cell walls made of cellulose, like green algae, dinoflagellates and brown algae
Closest living relative to plants are Charophytes

3. Charophytes

4. Charophytes
Lack Alteration of generations and multicellular, dependent embryos.
Live by waters edges of ponds and lakes, subject to occasional drying
Natural selection may have favored those algae that could survive dry periods, enabling a move to land

5. Derived traits of plants
Alternation of generations – life cycle alternates between gametophyte (n) and sporophyte (2n) organisms. (p506)
Walled spores produced in sporangia (multicellular organs that produce spores)
Apical meristem – localized regions of cell division at the tips of roots and shoots
Additional traits that aided to terrestrial life
Cuticle
Stomata

6. Fungi played essential role in colonization of land plants
Mycorrhizae – fungi provided essential minerals and nutrients to the early rootless plants and plants provided food to fungi.

7. Fungi
Heterotrophic – absorbs nutrients from the environment outside of its body
Saprotrophic – release digestive enzymes to break down food and absorb it
Chitin in cell walls – polysaccharide
Hyphae – tiny filaments, mass of hyphae – mycelium
Asexual and sexual reproduction – through production of spores
Molecular data shows that fungi and animals are more closely related to each other than plants.

8. Evolution of Fungi
Fungi may have colonized land before plants, forming symbiotic relationships (goes back 405 mya)
Fungus still being studied today and moved within classification system based on molecular dating

9. Fungi play key role in nutrient cycling, ecological interactions and human welfare
Decomposers of organic material, breaking down cellulose and lignin
Symbiotic relationships
Mycorrhizae – plant roots
lichens (with algae), seen as a pioneer species
30% of fungi species are parasites, most plant pathogens (dutch elm, chestnut blight, rust, ergot) or animals (ringworm, athlete’s foot)
Yeasts – unicellular, used in research with Parkinson’s and Huntingtons disease

10. Plant Kingdom
280,000 species
Ecological, industrial and medical importance
Thought to evolve from green algae, 500 mya
Both have chlorophyll a and b, store excess carbs, cellulose in cell walls.

11. 4 Evolutionary Milestones
Nonvascular/Seedless plants that nourish a multicellular embryo within the body of the female plant (different from green algae)
Vascular tissue specialized for transport (430 mya)
Production of seeds (contains embryo and stored nutrients within a protective coat) 400mya
Flower –reproductive structure 135 mya

12. Cladogram

13. Traits revisited Alternation of Generations: p515
Gametophyte (n), dominant in nonvascular seedless plants
sporophyte (2n), dominant in vascular seedless, gymnosperms and angiosperms
Spores – haploid reproductive cell
Adaptation to terrestrial life: vascular system, cuticle and stomata

14. Nonvascular seedless plants
No means of transporting water or organic nutrients
No true roots, stems or leaves, just root like…
Bryophyte – term for nonvascular plants
Gametophyte is dominant generation, the part of the plant we see.
Characteristics limits size of bryophytes
3 phyla, hornworts, liverworts, and mosses

16. Vascular plants Xylem – conducts water and minerals up from the roots
Walls of cells are strengthened by lignin
Phloem – conducts sucrose and other organic compounds down from point of photosynthesis
Sporophyte dominant
Water dependent for reproduction
Club mosses, ferns and horsetails

17. Seed plants – Gymnosperms and Angiosperms
Gymnosperms (naked seed) and angiosperms (flowering plants)
Contain sporophyte embryo and stored food within a protective seed coat
Allows survival during harsh conditions
Heterosporous, 2 types of gametophytes (m/f)
Pollen grains – male gametophyte
Pollination – when pollen grain is brought to vicinity of female gametophyte by wind/pollinator, no water needed!
Female gametophyte develops within an ovule which eventually becomes a seed

18. Gymnosperms Conifers, cycads, ginkgoes and gnetophytes
Ovules and seeds are exposed, not enclosed by fruit (naked seed)

19. Angiosperms Flowering plants Provide clothing, food, medicines
Ovules are enclosed within diploid tissues, fruits are ovaries
Dominance of angiosperms is related to evolution of flying insects (pollination)

20. Diversification of flowers
Wind pollinated – usually bland
Insect/bird pollinated – usually colorful
Night blooming flowers – aromatic and white
Fruits protect and aid in dispersal of seeds