Nature and Technology

Sword Fern. Photo taken near middle fork snoqualmie river, WA.

Although the above sword fern may look and act almost exactly like another in nearby Oregon it has hints of once being on the track to becoming a different species. A paper by Soltis et al. (1996) looked at chloroplast DNA of the sword fern, among other plants, and found that there is a significant difference between populations in the north (Alaska to central Oregon) and populations in the south (central Oregon to northern California).

Genetic isolation of a once uniform population does not occur easily. For two populations to emerge from one there must be some sort of isolating mechanism that prevents the exchange of genetic material. Isolation allows the two populations to diverge genetically through genetic drift and selection without sharing the changes.

Soltis et al. (1996) suggested that the isolating mechanism was extensive glaciation which occurred in the Pleistocene (the famous Ice Age). Because plants have an extremely difficult time growing on moving rivers of ice the sword fern population was cleaved and left with, at least, one northern refugium and one southern refugium. The two populations were left to go about their own business and respond to their own local environment.

Today the glaciers are mostly gone and the northern and southern populations are allowed to fill the gap. Genetic material is being transferred between the two and the differences will most likely blur but there will always be the hint of what once could have been a new and noble species.

Sources

Soltis, D., Gitzendanner, M., Strenge, D., Soltis, P. (1996) Chloroplast DNA intraspecific phylogeography of plants from the Pacific Northwest of North America. Plant Systematics and Evolution (206) 353-373. http://www.springerlink.com/content/v15m72k6238462p3/

Labels: general science, photography, species

Tuesday morning people in the western hemisphere and eastern Asia will be able to view the second lunar eclipse of 2007. A lunar eclipse occurs when the Earth comes between the sun and the moon. The Earth prevents sunlight from hitting the moon so a shadow is cast.

Here's a simulation of a lunar eclipse created by E-Lad.

Labels: general science

It is often difficult to communicate scientific findings to both the scientific community and the general public. This is because journals are numerous, expensive, and often difficult to digest. In an attempt to remedy this problem SciVee has launched.

From the FAQ, "SciVee is about the free and widespread dissemination and comprehension of science." It's a video service, kind of like youtube, but smart. SciVee has the support of PloS, an online, free, peer-reviewed, journal. It works by having scientists submit their paper and accompany it with a short video presentation explaining what their paper is addressing. It's neat. It's a step towards getting science out to the masses.

Right now there seems to be a shortage of content but check it out anyways.

Labels: general science

Baby meadow vole, taken near Rochester, WA.

A paper by Pierce et al. (2005) titled Food-deprivation-induced changes in sexual behavior of meadow voles, Microtus pennsylvanicus addresses one small aspect of the complex conditions which determine vole reproduction. The research found that short-term food availability has an impact on reproduction of meadow voles.

The researches basically withheld food from male and female voles and observed the changes in sexual behavior. The females were more sensitive to brief (6-12 hr) and moderate (18-24 hr) pauses in food than the males. Females must expend more resources on carrying babies than males do with expending semen so it makes sense that females are more sensitive to a decrease in important resources such as food.

Sources

Pierce, A. Ferkin, M. Williams, T. 2005. Food-deprivation-induced changes in sexual behavior of meadow voles, Microtus pennsylvanicus. Animal behaviour 70(2): 339-348.

Labels: general science, mammals, photography, physiological biology, species

The morphology of plants is structured in such a way that repetitive patterns occur. This is termed modular organization and is a method of defining certain repetitive structures of a plant. If we consider a single instance of a leaf or a branch as a module then we can reduce a (very) simplified tree to being just a collection of these two components. If we are in need of representing a tree programmically then realizing the above makes things much easier. Even more interesting Ferra et al. (2005) states that “in some cases, the modules are arranged into compound, recursively nested, fractal-like structures, with similar patterns appearing at different scales.”

Ferra et al. mentioned that many plants have fractal-like structures. So what are they? Fractals are statistically self-similar structures, which, according to Mandelbrot (1982), is “when each piece of a shape is geometrically similar to the whole, both the shape and the cascade that generate it are called self-similar.” To see this graphically it'll help to refer to the picture of the fern. Each pinnule (the smallest 'leaf') of the fern is geometrically similar to each pinna which is geometrically similar to the entire fern. Nature repeats and beauty is a result.

Below is a flash application that I created by modifying code written by Matt Pearson (2007). The tree is composed of a 'trunk' and a 'leaf' both of which are laid down by a recursive function. Click it to randomly generate a new tree.



Sources

[1] B. B. Mandelbrot. The fractal geometry of nature. W. H. Freeman, San Francisco, 1982.
[2] Ferrao P., Godin C., Prusinkiewicz P. Toward a quantification of self-similarity in plants. Fractals, 2005. http://algorithmicbotany.org/papers/similar.fractals2005.pdf
[3] Pearson, M. Fractals in ActionScript 3 - A Flash Tutorial. zenbullets.com. 2007. http://zenbullets.com/blog/?page_id=80
[4] http://www.flickr.com/photos/roddh/156854158/

Labels: computational biology, fractals, programming