The introduction of snakes to Guam has reverberated through the ecosystem.
Accidentally introduced to the island in the 1940s, the snake decimated the island’s native bird species in one of the most infamous ecological disasters from an invasive species.
By the 1980s, 10 of 12 native bird species had been wiped out.
Since many birds consume spiders, compete with spiders for insect prey and utilize spider webs in their nests, their loss has led to a spider explosion on the island, researchers said.
Note (for the Algebra students): The scientific article includes a nice box and whisker plot showing how many more spiderwebs there are on Guam compared to other islands.
Number of spider webs on different islands. Guam is the only island shown that has had a severe reduction in birds. Image from Rogers et al., 2012.
Changing colors of universal indicator show how blowing bubbles acidifies water (light green-second beaker) from neutral pH (dark green-third beaker) standard. For comparison, the first beaker (red) is acidified while the last beaker (blue) is made alkaline.
CO2 + H2O —-> H2CO3
This useful little reaction, where carbon dioxide reacts with water to produce carbonic acid, came up in my middle school class when we talked about respiration, it’ll come up soon in environmental science with the effects of carbon dioxide on the oceans (acidification), and it offers the opportunity to discuss pH and balancing chemical reactions in chemistry.
The middle school class did the neat little experiment where students blow bubbles in water (through a straw), and the carbon dioxide in their breath reacts with the water to slightly acidify it. A little universal pH indicator in the water (or even cabbage juice indicator) shows the acidification pretty well if you make sure to keep a standard nearby so students can see the change in color.
The fact that the CO2 in your breath is enough to acidify water begs the question — which was asked — how much of the air you exhale is carbon dioxide? According to the Oak Ridge Carbon Dioxide Information Analysis Center’s FAQ page, it’s concentration is about 3.7% by volume. Which is a lot more than the 0.04% average of the atmosphere.
Of course if you really want to talk about the pH you need to get into the acid equilibrium and the dissociation of the carbonic acid to produce H+ ions; you can get the these details here.
My students are researching the organisms they collected from the creek, and I was outlining the types of information I wanted them to find. We were talking about how many animals have seasonal reproductive cycles, and I pointed out that plants flower seasonally as well. One of my students put two and two together and came up with something close to a whole number: “You mean to say that flowers are … some sort of … creepy … sexual things?”
Microbe collected from the TFS Creek on 9/10/2012. Possibly a species of desmid.
The TFS campus has an excellent ecological gradient. It starts at the hydrologic base-level, with the small, usually permanent, creek in the valley. Then the landscape ranges up, past a narrow but dense riparian zone to the anthropomorphic campus, then up a shrub-covered hillslope that transitions abruptly into the advancing, mature, forest of the hill-top nature reserve. My environmental science class is taking advantage of our geographic proximity by doing a year-long ecological survey project.
We’ve just started, this fall, on the stream and riparian zone. I asked each of them to identify and do some research on a single organism. They all chose some type of macro-organism: spiders, crayfish, flowering herbs (note: just because it’s called an herb does not mean it’s edible), mushrooms, and more. There’s quite a bit of biodiversity down there, although, with the creek just now coming back from our particularly dry summer, the fish are few and far between.
Close-up view of the micro-organism under 1000x magnification (oil immersion lens).
Since no-one chose to look for micro-organisms — even though I did suggest they were an important part of the ecology — I decided do so myself.
I found a loosely held together patch of algae, which I collected with the hope that it would harbor its own little microscopic ecological system. And it did. There were amoebas zipping around, the filamentous algae itself, and these little organisms that I can’t quite identify yet. T
hey may be desimids, but I’m not sure. They look slightly green, but I can’t see any clear chloroplasts (like these). I’ll try staining them tomorrow to see if I can identify any organelles.
A terrible picture "showing" the patch of fillamentous algae I collected from the creek.
In his critique of research on the beneficial-bacteria storing role of the appendix, PZ Myers includes an excellent overview of the digestive system.
When you eat something, it first goes into the stomach, where it’s treated to an acid bath, some enzymes, and a lot of muscular churning to break it up. Then it’s squirted into the small intestine, where the acids are first neutralized and more enzymes are tossed onto the watery, mushy soup that the food has been rendered down into, called chyme. The primary job of the small intestine is to suck all the nutrients out of the chyme and pass them on to the circulatory system.
Once as much of the good stuff has been leeched out of the chyme as your system can do, the soup is passed on to the large intestine …. This stuff is still very watery — if you’ve ever experienced diarrhea, that’s what it is at this point. The primary job of the large intestine is to resorb water from the waste, condensing it down into the thick, pasty glop we all know and love as excrement. The large intestine is basically the sewage treatment plant here.
It has always strained credibility that the 98% of our DNA not used to code proteins would be useless. But this non-coding DNA picked up the name “junk DNA” because no-one quite knew what it did. In fact, one study (Nóbrega, 2004) found that deleting large chunks of DNA had no discernible effect on mice; the mice born without these pieces of non-coding DNA were viable.
However, a slew of papers from the Encode project indicate that the part of our genome formerly known as junk DNA, regulates the 2% that does the protein coding:
The researchers … have identified more than 10,000 new “genes” that code for components that control how the more familiar protein-coding genes work. Up to 18% of our DNA sequence is involved in regulating the less than 2% of the DNA that codes for proteins. In total, Encode scientists say, about 80% of the DNA sequence can be assigned some sort of biochemical function.
The appendix has long been supposed to be a vestigial, useless organ. But a 2007 study suggests that it might have had — and may still have in many developing countries — an important role in digestion. It may provide a refuge for helpful, commensal bacteria to repopulate our guts after we purge when we get sick (Bollinger et al., 2007):
The organs of the lower digestive system. The appendix is located in the lower left, near where the small and large intestines meet. Image from Wikipedia.
… the human appendix is well suited as a “safe house” for commensal bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon in the event that the contents of the intestinal tract are purged following exposure to a pathogen.
The shape of the appendix is perfectly suited as a sanctuary for bacteria: Its narrow opening prevents an influx of the intestinal contents, and it’s situated inaccessibly outside the main flow of the fecal stream.
