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Macroevolution: seeds of diversity.

March 18, 2006

Macroevolution: Seeds of Diversity

Jul 20, 2005 Dov, in biologicalEvolution forum.

(A) From: Science, Vol 308, Issue 5729, 1752-1753 , 17 June 2005, "Macroevolution: Seeds of Diversity", Douglas H. Erwin.

" In a simple logistic growth model, the size of a population expands until further growth is limited by resource availability and the population size reaches a plateau. Robert MacArthur and E. O. Wilson extended these ideas to account for the effect of resources on species diversity in their model of island biogeography (1). Over the short term, competition for resources generates an equilibrium level of species diversity through a balance between immigration and extirpation. Over the longer term, equilibrium diversity reflects a balance between speciation and extinction, but in all cases the available resources control the equilibrium diversity".

(B) From: Science, Vol 308, Issue 5728, 1563-1565 , 10 June 2005, Immunology: "Opposites Attract in Differentiating T Cells, Mark Bix, Sunhwa Kim,Anjana Rao.

"During differentiation, precursor cells with progressively narrowed potential give rise to progeny cells that adopt one of two (or more) divergent cell fates. This choice is influenced by intricate regulatory networks acting at multiple levels (1). Early in differentiation, precursor cells show low-level activation of all progeny genetic programs. Bias toward a given lineage comes from environmental inputs that activate powerful positive- and negative- feedback loops, which work in concert to impose selective gene expression patterns".

Seems to me that (B) above is a much clearer, plainer, and a more actual description of  "Seeds of Diversity" than (A).

Dov

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