1 / 26

The More the Merrier?

The More the Merrier?. The Evolution of Multicellular Organisms. The Problem of Size. All animals need to exchange substances with the environment SURFACE AREA : VOLUME Bacteria – 6 000 000/m Whale – 0.06/m Maximum cell size is limited All organisms larger than size limit are MULTICELLULAR.

shina
Download Presentation

The More the Merrier?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The More the Merrier? The Evolution of Multicellular Organisms

  2. The Problem of Size • All animals need to exchange substances with the environment • SURFACE AREA : VOLUME • Bacteria – 6 000 000/m • Whale – 0.06/m • Maximum cell size is limited • All organisms larger than size limit are MULTICELLULAR

  3. Solving the SA:V problem Geometric solutions • Increase surface area • Decrease effective volume Increase rate of supply • High concentration of nutrients • Improve nutrient transport within Improve efficiency to reduce demand • Division of labor within the cell • Division of labor between cells

  4. Evolution of multicellularity • Evolved many times in eukaryotes • Three theories • Symbiotic Theory • Like the endosymbiotic theory • Different species are involved • Syncytial Theory • Ciliates and slime molds • Commonly occur in multinucleated cells • Colonial Theory (Haeckel, 1874) • Same species are involved • Green algae (Chlorophyta) > 7000 species • Volvox

  5. Biofilms Unicellular prokaryotes Coordinate activity for own benefit Different species, same requirements Colony attaches to a surface Chemical communication to others Slime layer develops (Protein and polysaccharide) Diffusion between cells and fluid increases Cells regular pH and [food and wastes’ as a whole

  6. Where Are Biofilms?

  7. Chlamydomonas…or Volvox? • Unicellular flagellate • Individuals connected by strands of cytoplasm • Some individuals take on special roles. • Movement • Reproduction • If one cell dies, the rest survive • Volvox in Motion

  8. Gonium • Small colony (4, 8,16, or 32 cells) • No differentiation • Intercellular communication

  9. Pandorina • Colony (8, 16, or 32 cells) in 1 layer • Spherical • Anterior cells  larger eyespots • Coordinate flagellar movement • Colony dies when disrupted

  10. Eudorina • 16 or 32 cells • 16 cells – no specialization • 32 – 4 for motility, the rest for reproduction • Heterogamy – female gametes not released • Halves are more pronounced

  11. Pleodorina • 32 to 128 cells • Heterogamy – female gametes not released, in some cases becoming truly non-motile • Division of labor • Anterior vegetative cells • Larger posterior reproductive cells

  12. Volvox • Spherical colonies (500-50000 cells) • Hollow sphere – coenobium • Cell differentiation: somatic/vegetative cells and gonidia • 2-50 scattered in the posterior  reproductive • Female reproductive cells  daughter colonies • Intercellular communication possible

  13. Anisogamy Anisogamy/ Heterogamy

  14. Social Amoeba:Dictyosteliumdiscoideum We are the scientists in the lab Looking through a microscope Those little glass slides they never lie How can this small mind cope? I've never seen anything like it before This amoeba's got a mind of its own "Amoeba" by The Adolescents

  15. Amoeba Slugs Forming (About 2mm)

  16. Life Cycle

  17. All Cells In A Multicellular Organism Must, At Some Point… Adhere Communicate Move Differentiate In that order? By what mechanism?

  18. In case you need more videos http://www.youtube.com/watch?v=OX5Yiz38fgY&feature=related http://www.youtube.com/watch?v=Ql7i_TLUurM&feature=relatedhttp://www.youtube.com/watch?v=YoXWbr45rsQ http://www.youtube.com/watch?v=4VwFMqZ5KeY http://www.youtube.com/watch?v=R_nPFJlH1Vk http://www.youtube.com/watch?v=YoXWbr45rsQ “Homo Amoeba” is a artistic and entertaining look at cell movement: http://www.youtube.com/watch?v=7jd0QEe_WHE The BioClip “Day in the Life of Social Amoeba” deserves special mention for excellent design; you may have to contact Kota Miura (via www.bioclips.com) who was kind enough to email me a link to download the clip: http://www.bioclips.com/research.php3?id_article=56

  19. What Can We Learn From Social Amoeba? Chemotaxis: how cells move Cell-cell communication (chemical) Cell connection (membrane proteins) Behavior: Competition, altruism…and cheating Immune systems (sentinel cells) Molecular genetics & Development Evo-Devo Evolution, evolution, evolution!

  20. Advantages of multicellularity • Increase in size of the organism • Permits cell specialization • Increase in surface area to volume ratio

  21. Problems of multicellularity • Interdependence • Complexity

  22. Images • http://protist.i.hosei.ac.jp/pdb/images/Chlorophyta/Gonium/pectorale/sp_2b.jpg • http://www.rbgsyd.nsw.gov.au/__data/assets/image/48212/Gonium2.gif • http://www.ac-rennes.fr/pedagogie/svt/photo/microalg/pandorin.jpg • http://protist.i.hosei.ac.jp/PDB/images/Chlorophyta/Eudorina/elegans/sp_5.jpg • http://www.fytoplankton.cz/FytoAtlas/thm/0078.jpg

More Related