The more the merrier: comparative analysis of microarray ...
The More the Merrier?
description
Transcript of The More the Merrier?
![Page 1: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/1.jpg)
The More the
Merrier?The Evolution of
Multicellular Organisms
![Page 2: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/2.jpg)
The problem of size All animals need to
exchange substances with the environment
Diffusion› Surface area› Difference in
concentration› Distance
SURFACE AREA : VOLUME› Bacteria – 6 000
000/m› Whale – 0.06/m
Maximum size limit of single cell
All organisms larger than size limit are MULTICELLULAR
![Page 3: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/3.jpg)
As the cell gets larger, surface area to volume ratio gets smaller.
![Page 4: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/4.jpg)
Solving the SA:V problemAvoidanceGeometric solutions
Increase surface areaDecrease effective volume
Increase rate of supplyHigh concentration of nutrientsImprove nutrient transport
withinImprove efficiency to reduce
demandDivision of labor within the cellDivision of labor between cells
![Page 5: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/5.jpg)
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 Model: Volvocine series – Order Volvocales
![Page 6: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/6.jpg)
![Page 7: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/7.jpg)
Chlamydomonas Unicellular
flagellate Isogamy
![Page 8: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/8.jpg)
Gonium
Small colony (4, 8,16, or 32 cells) Flat plane, mucilage No differentiation Isogamy Intercellular communication
![Page 9: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/9.jpg)
Pandorina Colony (8, 16, or
32 cells) in 1 layer Spherical Isogamy Anterior cells
larger eyespots Coordinate
flagellar movement
Colony dies when disrupted
![Page 10: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/10.jpg)
![Page 11: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/11.jpg)
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
![Page 12: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/12.jpg)
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
![Page 13: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/13.jpg)
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
![Page 14: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/14.jpg)
![Page 15: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/15.jpg)
Summary of Evolutionary Changes Shown
Unicellular colonial life Increase in # of cells in colonies Change in shape of colony Increase in interdependence among
vegetative cells Increase in division of labor:
vegetative and reproductive cells Isogamy anisogamy oogamy Fewer female gametes are produced
![Page 16: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/16.jpg)
Advantages of multicellularity
Increase in size of the organism
Permits cell specialization
Increase in surface area to volume ratio
![Page 17: The More the Merrier?](https://reader035.fdocuments.us/reader035/viewer/2022081507/568166b4550346895ddab99b/html5/thumbnails/17.jpg)
Problems of multicellularity
Interdependence Complexity