\ Visualizing Evolution: Ubiquity of Branching Structures

Friday, October 17, 2008

Ubiquity of Branching Structures

These are from an old Nature article The Phenogenetic Logic of Life, Figure 3: Ubiquity of branching structures in living organisms. (Nature Reviews Genetics 6, 36-45 (January 2005))

I can't talk about the actual article because I'm no longer a student with access to the online periodicals, and don't really want to pay the $35 to download the pdf. I'm also going to now resist the very strong temptation to digress into a rant about the cost of online journals and get on to the images. At least I have the captions!

"Multiple applications of branching logic show the logical symmetry of evolution among organisms and development within them."

In other words... visual trees can be used to demonstrate the evolution of organisms, the diversification of cells within an organism, and the resulting anatomical structures of development.

First, two on evolution and speciation:

a. "Charles Darwin's attempt to reconstruct Ernst von Baer's idea that embryos of contemporary similar species, such as vertebrates, have diverged from a common early-embryonic form."

b. "Darwin's sketch of his idea of divergence of species from a common ancestor."

See the original here. I definitely prefer to look at the aged inky version in Darwin's own pen strokes.

The next two are not about evolution, but rather the divergence of cells within a single organism. The patterns that emerge as cell types diversify are similar to those of species diversification:

c. "Divergence of the sequence of a single gene, or members of a gene family, from a common ancestor (the example of photoreceptors and olfactory receptors is shown)."
And similarly:

d. " The divergence of tissues from a single cell within an organism."

Now let's get organismal (is that a word?) and look at branching patterns found in anatomy:
e. "Schematic representation of the fractal-like mammalian bronchial (lung) tree."

And one from the world of botany:

f. "The source of the metaphor — real branches."

$35 ... seriously.


Kumah said...

Darwin's evolution trees always sort of reminded me of neurons.

Heidi Richter said...

Probably because it has multiple branches coming from each point. In modern trees, this is used to indicate when the author is uncertain of which of the two groups is more closely related.

b. in this figure ( http://palaeo.gly.bris.ac.uk/Essays/phylocode/Fig3.jpeg ) Has an example of that.