1. Evolution of multicellular plants

2. Fig 16.27 Evolution of a multicellular organism from a unicellular protist

3. Going from unicellular to multicellular Advantages Disadvantages Challenges Going from unicellular to multicellular “Communication” between cells The development of tissue systems Loss of mobility – evolution of specialized plant parts is essential for nutrition and reproduction Organization and specialization of plant parts Reduction in individual plant growth rate Permanent colonization of land becomes possible

4. Photos of slime moulds http://www.hiddenforest.co.nz/slime/intro.htm Photos of slime moulds by Clive Shirley Organisms with both unicellular and multicellular stages

5. Slime moulds have structural adaptations Slime moulds have structural adaptations and life cycles that enhance their ecological role as decomposers Two main groups. 1 - Plasmodial slime moulds or true slime moulds, are a large single-celled mass with thousands of nuclei called a plasmodium formed when individual flagellated cells swarm together and fuse into one large bag of cytoplasm with many diploid nuclei. 2 - Cellular slime moulds spend most of their lives as separate single-celled amoeboid protists, but upon the release of a chemical signal, individual cells aggregate into a great swarm, known as a pseudoplasmodia and eventually muticellular slugs. http://www.wvonline.com/myxo/intro.htm

6. The life cycle of a cellular slime mold, Dictyostelium

7. Film of Dictyostelium

10. Dictyostelium amoebae grow as separate, independent cells but interact to form multicellular structures when challenged by adverse conditions such as starvation. Up to 100,000 cells signal each other by releasing a chemo- attractant and aggregate to form a mound. Subsequent processes depend on cell-cell communication. Many of the underlying molecular and cellular processes appear to have arisen in primitive precursor cells and to have remained fundamentally unchanged throughout evolution. Basic processes of development such as differential cell sorting, pattern formation, stimulus-induced gene expression, and cell- type regulation are common to Dictyostelium and metazoans. A model organism for bio-medical research. Characteristics of Dictyostelium

11. Alternation of Generations

12. Origin of alternation of generations?

13. Sizes and morphology of generations Relative sizes and general morphology of gametophyte and sporophyte generations in bryophytes, ferns and seed plants

14. The life cycle of Ulva Fig 16.26C The life cycle of Ulva

16. Fig 16.27 Evolution of a multicellular organism from a unicellular protist

17. Sections you need to have read 16.21 16.22 16.23 16.24 16.25 16.26 16.27 16.28 Courses that deal with this topic MICROM 435 Microbial Ecology