Mutualism and Cells

[foodchain]

Is there any attempt to describe organisms as patterns of mutualistic evolution among eukaryotic cell lines that developed multicellular behavior? Or would it be possible that multicellular is a possibility of mutualistic behavior of course in a selection sense?

[lucaspa]

It appears that you are equating apples and oranges.

 

Mutualism = interaction of individual(s) of one species with an individual of another. This interaction is dependent and is either a) beneficial or b) at least not harmful

 

Multicellularity = interaction between individual cells of the same species to make an organism.

 

They both have cooperation in common, but otherwise are very different. That cooperation between cells in multicellularity has been extensively studied. For instance, many (most) bacteria form loose coalitions of cells at various times that assist one another in identifying sources of food or other tasks.

 

The amoeba Dictolystelium exists most of the time as a single-celled organism that reproduces asexually but in times of food shortage many single-celled Dictolystelium aggregate to form a multicellular organism that not only reproduces sexually but can form specialized "organs". C Zimmer, The slime alternative. Discover 19: 86-93, 1998 (Sept) http://www.sanger.ac.uk/Info/Press/2005/050505.shtml

 

For further reading on the mechanisms of multicellularity, you can read DL Kirk Molecular-Genetic Origins of Multicellularity and Cellular Differentiation.

 

A bit about mutualism and how it evolves can be found at http://blog.lib.umn.edu/denis036/thisweekinevolution/2007/05/

[Mr Skeptic]

What about the theories of the origins of various cells or cell types (eg mitochrondria, chloroplasts, white blood cells) as a separate species that got assimilated? Would that have been mutualism before they joined into a single species?

[lucaspa]

What about the theories of the origins of various cells or cell types (eg mitochrondria, chloroplasts, white blood cells) as a separate species that got assimilated? Would that have been mutualism before they joined into a single species?

 

The incorporation of organelles into single-celled organisms (mitochondria, chloroplasts) are examples of mutualism. You have a bacteria that was once a parasite in another organism and then became a mutualistic organism.

 

White blood cells are a form of differentiated cell within a multicellular organism. You can trace the lineage of a white blood cell back thru the hematopoietic stem cell to the mesodermal stem cell to the embryonic stem cell to the fertilized ovum.

 

The key difference is that mutualistic organisms have different DNA and means for replicating that DNA from each other while multicellularity has the same genome. Both mitochondria and chloroplasts have their own genome (much reduced since many of the genes got moved to the nuclear DNA) and ribosomes while white blood cells have the same genome and DNA and ribosomes as any other cell in the body.