pterosaur take-off

Scientists have long been perplexed by the size of pterosaurs. The largest species of the extinct flying reptiles were roughly the size of modern giraffes and weighed far more than any bird, posing the question: how did they get all that bulk into the air? Birds generally leap into flight, relying on the strength of their legs, but the muscle mass that pterosaurs would need for a similar take-off would be far too great to allow them to fly at all. Some scientists have suggested that they used cliff edges or wind patterns to launch themselves, but these would have been unreliable factors, particularly in an age replete with formidable land-bound predators like tyrannosaurs; furthermore, pterosaur fossils have been found well away from any cliffs.

Michael Habib of Johns Hopkins may have the answer. Having done analyses of bone strength in both the forelimbs and hindlimbs of pterosaurs, he has concluded that they would have been capable of a four-legged takeoff, folding up their wings while on land and walking, essentially, on their knuckles. They could have then employed a “leap-frogging” launch pattern, kicking up first with their hind legs and then with their folded wings, and been airborne in less than one second.

giant insects of the carboniferous

The Carboniferous period gets its name from the vast deposits of coal it left behind. This coal had to come from somewhere, and it did: from the enormous swamps that covered the supercontinent Pangaea, which formed over the course of the Carboniferous. These swamps were full of the most primitive land plants, like horsetails, ferns, and lycopods, but grown to a massive size in the oxygen-rich environment they created.

Estimates have placed the atmospheric oxygen content during the Carboniferous at as high as 35% (oxygen currently makes up 21% of the atmosphere). Scientists believe that this high oxygen content not only allowed plants to attain incredible stature; it also facilitated the existence of other gigantic organisms, including the dragonfly Meganeura, whose wingspan was seventy centimeters (two and a half feet).

Many different species of gigantic dragonfly existed during this period, as well as gargantuan versions of our modern mayfly and, of course, cockroach. Scientists believe that high oxygen levels compensated for the inefficiency of the insects’ respiratory systems, which, unlike humans’, are not centralized and rely on the passive diffusion of air through their tissues. In the lower-oxygen-content atmosphere of today, insects’ respiration is too inefficient to allow their bodies to grow much thicker than (in the dragonfly’s case) a pencil, and indeed, giant insects began to disappear as the Permian period dawned and oxygen levels began to decline.

prehistoric bullwhips

As you may be aware, the first human to break the sound barrier was Chuck Yeager, who did so in a rocket plane in 1947. However, scientists have also known since 1958 that the action of cracking a bullwhip also breaks the sound barrier — the thin, flexible tip of the whip surpasses the speed of sound for an instant, creating a sonic boom.

Here’s where it gets fun: according to a computer simulation created by Microsoft guru Nathan Myhrvold, sauropods, a suborder of dinosaurs that in late Jurassic and early Cretaceous set the records for the largest animals ever to live on land, could theoretically have cracked their tails like whips, creating sonic booms like cannonfire that would have resounded over prehistoric landscapes. Scientists are unsure of the purpose of such noisy displays, but have suggested that they may have played a role in male-male competition or discipline enforcement within a group.

the fluidity of perception

I always used to think of the brain’s relationship with reality as fairly concrete. If you see a house, I also see a house. Or even if I don’t — if my vision or my brain has some abnormality that prevents me from seeing the same house as you do — I still know, if you tell me, that it’s a house, and what it should look like.

Then, last fall, I took a neuroscience course, and that put paid to that.

Because there are people out there — people with perfectly normal sensory, motor, and analytical abilities — who simply don’t comprehend the same house I do. If you give them a sketch of a house and ask them to copy it, this is what they draw:

These are people with contralateral neglect syndrome, which isn’t a problem with the brain’s input or output mechanisms but rather a problem with the link between them; it’s a deficit in attention, “an inability to attend to objects, or even one’s own body, in a portion of space”. It happens when one side of a patient’s parietal lobe has suffered an injury. Since each side of the brain generally controls the opposite side of the body, someone with an injury to the right parietal lobe wouldn’t be able to pay attention to things to his or her left, as seen above.

The scientist who first described the condition (whose name, incidentally, was Brain) described several other symptoms, including the feeling that one’s limbs on one side are absent or the inability to navigate between rooms in a house due to a propensity to turn right instead of left. (Patients with this difficulty could give perfectly clear directions — they just couldn’t follow them.)

I don’t know about you, but it blows my mind just a little that I could be otherwise fully aware and in possession of my own will and still be unable to turn left.

Image and W.R. Brain quote from Purves et al.’s Neuroscience textbook, fourth edition.

acid bogs: really insanely cool.

If you’ve ever been to an acid bog and you didn’t think it was really insanely cool, you clearly don’t know enough about botany.

Acid bogs are formed when a type of moss called sphagnum (or peat moss) more or less invades a normal pond or lake. Sphagnum is special because, rather than just out-competing other species by getting the most it can out of its environment, it actually changes its environment to be less hospitable to other species. It does this through a process called cation exchange: in order to pick up its nutrients from the water it grows into, sphagnum pumps out one kind of ion, hydrogen, in order to take in the other ionic nutrients it needs (calcium, potassium, etc.). Hydrogen ions, as anyone who remembers basic chemistry should know, acidify water (the pH level is based on the concentration of hydrogen ions). A well established colony of sphagnum moss can generally lower the pH of its host lake to around 3.5.

This, of course, makes the bog rather inhospitable to normal plants, and whole new species have evolved just to fit into the ecosystem that sphagnum creates. One particularly cool adaptation is carnivory: plants like sundew and pitcher plants capture insects in order to obtain the nutrients that are missing from their acidic habitat. (A cool counter-adaptation: pitcher plant moths have learned to cut holes in the bottoms of pitcher plants, draining out the digestive juices from the cup, and then settle in to raise their young in a nice, pre-made, edible house.) Other plants that thrive in acid bogs include members of the family Ericaceae, such as blueberries and cranberries.

I should probably mention at some point the structure of an acid bog, because that’s also cool. Generally, the sphagnum grows inward from the edges, swelling as it takes in up to twenty times its dry weight in water and forming a raised mat. At some point, this mat stops being directly connected to the bottom, and if you’re walking out onto the bog, you’re literally being held up only by floating sphagnum. (This is very fun to bounce around on — ever heard of a “quaking bog”? — but not so fun if you go through.) Plants are growing up out of the sphagnum mat, including larch trees, which thrive in acidic habitats, and a number of other specially adapted species, as I mentioned before. One particularly cool member of the Ericaceae, leatherleaf, grows at the very edge of the inner ring of open water and arches out into it, putting down roots and helping provide a structure for the continued building of the sphagnum mat. Eventually, the entire lake will be filled in.

One last thing about sphagnum before I go: it blows smoke rings. No, really. A smoke ring is a pattern called a vortex ring, which is what forms when air is blowing faster through the center of an area than through its outsides (bear with me here; physics is not my strong suit). Sphagnum disperses its spores in the exact same fashion. As the capsules that produce sphagnum’s spores (see photo) dry out, they squish down steadily until finally they pop, flinging bright orange spores into the air at 30 mph — which is fast, for a plant. And all this happens in less than a thirty thousandth of a second.

If you’ve got any more questions about sphagnum or acid bogs, don’t hesitate to ask — it’s been tough keeping myself even to this length of a post!