All animals need to exchange All animals need to exchange substances with the substances with the environmentenvironment

SURFACE AREA : VOLUMESURFACE AREA : VOLUME› Bacteria – 6 000 000/mBacteria – 6 000 000/m› Whale – 0.06/mWhale – 0.06/m

Maximum cell size is limitedMaximum cell size is limited All organisms larger than All organisms larger than

size limit are size limit are MULTICELLULARMULTICELLULAR

Geometric solutionsGeometric solutionsIncrease surface areaIncrease surface areaDecrease effective volumeDecrease effective volume

Increase rate of supplyIncrease rate of supplyHigh concentration of nutrientsHigh concentration of nutrientsImprove nutrient transport withinImprove nutrient transport within

Improve efficiency to reduce demandImprove efficiency to reduce demandDivision of labor within the cellDivision of labor within the cellDivision of labor between cellsDivision of labor between cells

Evolved many times in eukaryotesEvolved many times in eukaryotes Three theoriesThree theories

› Symbiotic TheorySymbiotic Theory Like the endosymbiotic theoryLike the endosymbiotic theory Different species are involvedDifferent species are involved

› Syncytial TheorySyncytial Theory Ciliates and slime moldsCiliates and slime molds Commonly occur in multinucleated cellsCommonly occur in multinucleated cells

› Colonial Theory (Haeckel, 1874)Colonial Theory (Haeckel, 1874) Same species are involvedSame species are involved Green algae (Chlorophyta) > 7000 speciesGreen algae (Chlorophyta) > 7000 species

VolvoxVolvox

Unicellular flagellateUnicellular flagellate Individuals connected by

strands of cytoplasm Some individuals take on

special roles. › MovementMovement› ReproductionReproduction

If one cell dies, the rest If one cell dies, the rest survivesurvive

Volvox in Motion

Small colony (4, 8,16, or 32 cells)Small colony (4, 8,16, or 32 cells)No differentiationNo differentiation Intercellular communicationIntercellular communication

Colony (8, 16, or 32 Colony (8, 16, or 32 cells) in 1 layercells) in 1 layer

SphericalSpherical Anterior cells Anterior cells

larger eyespotslarger eyespots Coordinate flagellar Coordinate flagellar

movementmovement Colony dies when Colony dies when

disrupteddisrupted

16 or 32 cells16 or 32 cells 16 cells – no specialization16 cells – no specialization 32 – 4 for motility, the rest for reproduction32 – 4 for motility, the rest for reproduction Heterogamy – female gametes not releasedHeterogamy – female gametes not released Halves are more pronouncedHalves are more pronounced

32 to 128 cells32 to 128 cells Heterogamy – Heterogamy –

female gametes not female gametes not released, in some cases released, in some cases becoming truly non-becoming truly non-motilemotile

Division of laborDivision of labor› Anterior Anterior

vegetative cellsvegetative cells› Larger posterior Larger posterior

reproductive reproductive cellscells

Spherical colonies (500-50000 cells)Spherical colonies (500-50000 cells) Hollow sphere – coenobiumHollow sphere – coenobium Cell differentiation: somatic/vegetative Cell differentiation: somatic/vegetative

cells and gonidiacells and gonidia 2-50 scattered in the posterior 2-50 scattered in the posterior

reproductivereproductive Female reproductive cells Female reproductive cells daughter daughter

coloniescolonies Intercellular communication possibleIntercellular communication possible

Anisogamy

Anisogamy/Heterogamy

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

Amoeba Slugs Forming (About 2mm)

Life Cycle

All Cells In A Multicellular Organism Must, At Some Point…

Adhere Communicate Move Differentiate

In that order? By what mechanism?

In case you need more videos http://www.youtube.com/watch?v=OX5Yiz38fgY&feature=related http://www.youtube.com/watch?v=Ql7i_TLUurM&feature=related

http://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

What Can We Learn From Social Amoeba?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!

Increase in size of the Increase in size of the organismorganism

Permits cell specializationPermits cell specialization Increase in surface area to Increase in surface area to

volume ratiovolume ratio

InterdependenceInterdependence ComplexityComplexity

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