CSB #6: We're Hurting our Clean-up System

We knew that more diverse streams and rivers are less polluted. What we didn't know, though, is why. The answer goes back again to Darwin's famous theory, and one point in particular. Darwin stated that, because every organism is unique, it has its own distinct habitat or "niche." In a river, there are different habitats depending on the water's speed and factors like ripples, pools, and eddies. If there are more species living in the river, they cover more "niches," and therefore can clean more of the river.

Specifically, Bradley Cardinale of the University of Michigan was testing how efficiently algae can remove nitrate, a common chemical in fertilizers, from the water. He used over 150 model streams, looking at a single habitat in one model and multiple habitats in another. Cardinale found that the more species of algae he put into the model stream, the more efficient the water filtration became. The 8-species mix, the one with the most species of algae and diatoms (small algae-like creatures) filtered nitrate 4.5 times faster than any single species. His main object in the experiment was to demonstrate that niches are responsible for the greater efficiency in water filtration that biodiversity presents to streams and rivers. To remove all doubt, he checked different numbers and combinations of algae species in a model stream with just one habitat; here, there was no advantage. This proved that more species "filled" more niches, and filtered more nitrate out of the water.

I love how evolution connects so many different issues. Here, though, it isn't just about evolution, although the niches are certainly vital to understanding why biodiversity is essential. Diverse species can clean up the mess we make by filtering nitrate and other chemicals out of the water, but how long can the diversity remain? Many species are going extinct because they have lost their habitat, are being hunted, cannot find food, or are overridden by species that have been introduced to the environment. However, without the diverse species, the water would be much more polluted and pose greater problems for humans. Basically, by not watching out for how what we do affects other species, we are moving towards another environmental difficulty, a greater number of over-polluted rivers. It's clear that humans have to start consciously trying to preserve biodiversity.

Why don't we already preserve biodiversity because of its other advantages? I'm sure that people already try, but not enough people are trying or their efforts are not sufficient. Using fewer resources, thereby saving habitats, would help some species survive. Polluting less by using clean energy or driving less or buying local goods to decrease pollution created by shipping would help. In effect, the same things that would help solve other environmental issues. Funny, isn't it, how they're so interconnected? Anyway, biodiversity is good for cleaner water, but we need to keep our clean-up system in good condition.

Resources:

University of Michigan. "Biodiversity Improves Water Quality in Streams Through
a Division of Labor." ScienceDaily. N.p., 6 Apr. 2011. Web. 6 Apr. 2011.

The picture is from the article and is of algae species that might be found in a stream.

CSB #5: Swimming Eyeballs

Brachiopods, or "lamp shells," are, in effect, marine worms that live in shells. A long-standing scientific question has been whether or not they can see; recently, it seemed as though some dark spots on the larvae were light sensors. Under closer examination, it was revealed that they were primitive "eyes," or the model of eye that is a "swimming eyeball." Basically, this means that it could sense light or dark, but could not do much beyond that.

Above: brachiopods

This is the first step towards the evolution of an organ as complex as the eye. Darwin himself did not feel as though something like the eye, which is, at first glance, perfect, could be explained by his ground-breaking theory of evolution. However, he did come up with steps in the evolution of such an organ, and his theory had the backing of real, living organisms with that kind of eye. This is the really phenomenal part of the theory: there is incontestable

evidence for large parts of it. The first step of his theory in the evolution of the eye, though, was unsupported until the work with the brachiopods.

Scientists also checked to see if the photoreceptor, or light receiving, genes were active at any other stage of development. Surprisingly, more of the undeveloped embryos moved towards a light source than expected, the expected being that none would move. At this point, the brachiopod embryos have no brains, no eye-like organ, or anything.

Right: eye spots on brachiopod larva

It was absolutely fascinating that our eyes, such intricate, elaborate organs, could have started out as nothing more than a bunch of photoreceptor cells. Aside from this, the fact that the undeveloped embryos could sense light is truly unexpected. Scientists hypothesize that the yolk blocks light from some directions, and this allows the brachiopod-to-be to sense the light. How this would work is not exactly clear to me, especially if it has no neurons at all and can react to its environment. Not only can it sense the light, the embryo also moves towards it.

In regards to Darwin's theory of evolution, it seems even more fantastic because proof is still being sought for it, one of the most controversial theories. The new discoveries made today, confirming his ideas, show how truly ahead of his time he was and in what accurate detail he surmised about the development.

Resources:

Article:

Zimmer, Carl. "In a Marine Worm's Eyes, the Theory of Evolution." The New York
Times. N.p., 1 Mar. 2011. Web. 6 Mar. 2011. .

Picture:

http://www.treasuresofthesea.org.nz/uploads/images/147_image_main.jpg (brachiopod)

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicyQ-gEozz_kvpVA6eIALX9_2ZGl6BMLwc1tvk2oj-ocTyXcHNNh9grpOtxnIFCd5Ke796tJqaHg431nhIDH9Gd_nroOFULRlQtDDA1TCdjImGIwGGX2BXaNh15NN-ThOCyPneW_LtsMw/s200/
BrachiopodLarva.jpg (larva)