Thursday, February 26, 2015

Alien Vs. Predator Vs. Parasaurolophus

A few days ago, I sat down and, with several hours of homework to do, watched Ridley Scott's 1979 classic "Alien."  It was phenomenal, and I enjoyed it, and went on to watch Predator (great) and Prometheus (not so great).  Now, on this excellent but snowy Thursday afternoon, I'm about an hour into "Aliens," knowing that any second now an Alien xenomorph is going to appear out of nowhere and kill something.  But that's not why I paused the movie at the 54:44 minute mark.  What I've been thinking about is far more pressing: what's the purpose of that enormously distended xenomorph cranium?
If you have no idea what's going on in this picture yet, that means you're probably sane.
Usually with aliens, you can just pass off a big head as an indicator of big brains.  Ki-Adi Mundi from Star Wars, for example, has two brains in that big 'ol Cerean cranium of his, and an extra heart to boot.  If you rewatch "A New Hope" extra carefully, see if you can't spot Pons Limbic (note the brainy pun) in the Mos Eisley Cantina, the big-brained Siniteen whose head literally resembles a brain.  The Guardians of the Universe from the D.C. Comics franchise are often pretty wise, but in light of some recent events, they might not be quite as level headed and emotion spectrumless as we thought (but that's a story for another bright snowy day).  The Face of Boe from Doctor Who seems to be pretty smart, given that he's literally just a giant head in a tank and can communicate telepathically.  Then there's Zilius Zox, a Red Lantern from the D.C. universe, who also appears to be little more than a giant head.  Both Jumba (from Disney's "Lilo and Stitch") and E.T. the Extra-Terrestrial (from E.T. the Extra-Terrestrial) seem to have noggins that are larger than average in proportion to body size, and seem to have above average intelligence to match.  Marvin the Martian and Roger from American Dad?  Both smart, both big-headed.
A skull of the duck-billed hadrosaur Parasaurolophus at the American Museum of Natural History in New York, from my visit last summer with my good friend Zach Evens (who also deserves some credit listing big-brained aliens).
Now what about the aliens, or xenomorphs, from the "Alien" franchise?  Although undeniably intelligent to some degree, they aren't what you'd typically think of when the subject of brainy aliens comes up around the dinner table, at least not in terms of processing power.  But they definitely have big heads.  So what are they used for if not for thinking?  We, of course, can turn to the science of dinosaur paleontology to help us with this question.  Take a look at the dinosaur skull above.  This critter is a hadrosaur, or duck-billed dinosaur, called Parasaurolophus.  Scientists believe that it blew air through its special crest to produce a sound very similar to that of a trombone!  Many hadrosaurs had wild cranial ornamentation, as did other dinosaurs such as some of the ceratopsians and the pachycephalosaurs, just to name a few.  These wacky head-dos almost certainly had a whole lot to do with attracting a mate and sexual selection.  Essentially, the bigger your crest is, the more attractive you are.  Is it possible a similar sort of thing evolved for the Alien xenomorphs?  In "Aliens," we can see that the queen has a different head pattern than do all of the other xenomorphs that we've seen so far, indicating some sort of sexual dimorphism is potentially at work.  Interesting.  What should you take from this blog post?  Probably just that I have way too much time on my hands.

On a brief side note, I realized I've actually talked about the skull of the xenomorphs previously, before I'd even seen the movies.  Check out that post, all about otter skulls, by clicking HERE.
Alien vs. predator vs. Parasaurolophus vs. Tyrannosaurus vs. Lego Gilderoy Lockhart vs. Darth Vader vs. Polly Pocket vs. creepy frog candle vs. macaw vs. Apatosaurus vs. medieval archer vs. Boba Fett Pez Dispenser vs. Ambelodon vs. mallard vs. fisherman from an ironic fish cake vs. Jumba vs. Craire Cat Hello Thingy vs. six different types of shark vs. Taz monster truck vs. Aragorn son of Arathorn vs. Liam Payne vs. Marty from "Pirates of the Caribbean" vs. mouse cat toy vs. basilisk lizard vs. Spider-Man vs. penguins with jet packs and missile launchers vs. Themistocles vs. Terri Irwin.  And this is why it takes me so long to write a blog post.  I think we were all a little surprised about how quickly things escalated.  Yeah, I definitely have too much time on my hands.

Saturday, January 3, 2015

Snowy Palms: An Omen of Death

Recently, parts of Southern California experienced some surprisingly cold weather, as falling snow graced the tops of the palm trees around Christmas time.  A White Christmas is nothing terribly surprising for folks like myself, born and raised in Colorado, but for California natives it was definitely more of a surprise.  People had pulled over on the side of the highway for an opportunity to play in the snow, throwing snowballs and taking selfies all over the place.
Wind turbines in the foreground, and snow capped mountains in the background in the middle of the desert just outside of Palm Desert in California.
A family stopped along Interstate-15 in Temecula, California to play in the snow, a scene that could easily have been lifted out of Colorado, if not for the trees adorned with green leaves, and especially the palm tree in the background.
A snow selfie on the side of the Interstate-15 in Temecula, California.
Although the winter freeze was very exciting for many of the residents, for the native residents of Southern California's deserts, the freeze would be much less welcome.  Over millions of years, the animals that call these seemingly barren slopes home have evolved to cope with extreme environmental stress typical of those experienced in the desert.  Aridity and extreme heat of course play major roles in any desert ecosystem, and many of the adaptations of desert animals are in response to these climatic factors.
The bobcat (Lynx rufus), one of the residents of the Southern California deserts.  This particular individual was at The Living Desert in Palm Desert.
A captive desert bighorn sheep (Ovis canadensis nelsoni) at The Living Desert.  This subspecies is native to the southern United States and Mexico.
A western diamond-backed rattlesnake (Crotalus atrox), also native to the southern United States and northern Mexico.
A wild greater roadrunner (Geococcyx californianus) that I chased through a Target parking lot.  
A wild California ground squirrel (Spermophilus beecheyi) that we saw foraging around at The Living Desert.
A hummingbird, possibly an Anna's hummingbird (Calypte anna).  Hummingbirds in Colorado will fly south for the winter, in order to avoid harsh weather like that seen in Southern California last week,
Of course, environmental conditions that fall well outside the norm are arguably equally important for animals native to a specific biome or region.  Even if a population of animals thrives in the harsh, arid landscape of Southern California, if all it takes is a single night of snow to wipe out the population, unusual weather (such as that seen in the area last week) can be extremely troublesome.  Extreme weather can also help control populations, and can be what keeps other animals from colonizing an area.  For example, if a population of desert rodent attempts to colonize the mountains around Palm Desert, but is unable to cope with the occasional snow storm, then that type of rodent would be much less likely to survive and thrive there.
Part of the mountains west of La Quinta and Rancho Mirage, prior to the snowstorm.
The same mountains, following the snowstorm.
Works Cited:

Hummingbirds found in California, USA. (n.d.). Retrieved January 4, 2015, from http://beautyofbirds.com/hummingbirdscalifornia.html

Friday, December 5, 2014

Night Changes: Why Color Blind People Aren't So Strange (But Really Are at the Same Time)

"Why does your Tyrannosaurus skull have rings on its eyes?"  "Why are reptiles and amphibians, animals often brushed aside as "less superior" to mammals, frequently very colorful?"  "By contrast, why are so many mammals so drab?"  "Does it ever drive you crazy just how fast the night changes?"  All of these questions and more are ones that I've either received or asked over the last few months, and surprisingly, they are all (sort of) tied together.
A selection of the stars of this post.  In the top row from left to right, we have a Prestosuchus skull, Micronesian kingfisher, Opthalmosaurus skull, African elephant, and a white-necked raven.  Second row, we have a male peafowl, Microraptor specimen, myself pulling a "District 9" with a T-rex arm and Stan the T-rex next to me at the Morrison Natural History Museum (now you finally know what I look like [irresistible], you can cross that off your bucket list), a Mandarin Goby, and the hand of Zach Evens descending upon a brightly colored newt.  Finally, in the bottom row, we see a pair of tiger salamanders, a coyote that ran amok on the University of Colorado campus last winter, and several bees swarming a hummingbird feeder at the MNHM.  Did I forget anything?  Oh, right, the album cover of One Direction's new album "Four."  A further bonus for all you "Natural Worlders" out there: can you find the names of twenty-one One Direction songs scattered throughout the blog post?  Try not to stay up all night searching for them, one way or another I have no doubt you can figure it out.  Just shoot me and email, and I can get back for to you about where they are.  Just one of those little things that makes reading my blog so worthwhile.
When people first walk into the Morrison Natural History Museum near Denver, Colorado, you might see a rock hammer-toting, cowboy-hat wearing, beard-wielding paleontologist talking about lizard pseudo-placentas, the anatomy of the dinos in Jurassic park, or whether said dinosaurs would taste like chicken.*  You might notice the bathroom first, which is more or less right across the room from the front entrance.  Or, like most people, you might notice our cast of Stan, one of the most complete specimens of Tyrannosaurus rex known to mankind.  We tend to get a lot of questions about this bad boy (T-rex consistently being the favorite dinosaur of pretty much everybody), and one question that we get a lot pertains to his eyes.  You might have missed it if you were looking at the fantastic picture above, but take a look at the pictures below and you should see it: it looks like we've put little rings where the eyes should be.  The question is: Why does our Tyrannosaurus skull have rings on its eyes?
Believe it or not, this was not a once in a lifetime phenomena, and it is not a trick (excuse me, an illusion) we created to make the placement of the oculars more apparent for the casual observer.  It's real, and it's called the sclerotic ring.  Without getting too technical, the sclerotic ring is a ring of several bones that actually is inside of the eye of the animal, and is usually thought to help support the eye.  What I find really interesting about the ring is that the default condition in vertebrate animals is possession of this bony ring.  Even though you might not see it in a lot of museum specimens due to display difficulties or preservation issues, a sclerotic ring is present in most/all fish, lizards, birds, and dinosaurs.**  You won't see it in modern crocodilians, though, and it seems like at least some snakes don't have them either.  What's another group that doesn't have the ring?  You guessed it: mammals.
One with the ring, one without.  My bro Masaki Kleinkopf poses next to the mounted skeleton of the pterosaur Pteranodon at the Rocky Mountain Dinosaur Resource Center (RMDRC) in Woodland Park, Colorado.  Check out dat ring doe.
A mounted skeleton of the emperor penguin (Aptenodytes forsteri) at the American Museum of Natural History (AMNH) in New York.  If you liked it, you should have put a ring on it.
Skull of the therizinosaur dinosaur Falcarius on display at the Wyoming Dinosaur Center in Wyoming.  One ring to rule them all.
At this point you might be expecting some profound, fascinating statement that explains why some animals have the ring and some animals don't.  Believe me, very few things would please me more than to be able to explain this to you.  Unfortunately, I don't know.  Even more unfortunately, nobody really knows!  Although various explanations have been put forth over the years, I can't really find a fool('s gold fire)proof, satisfactory interpretation that broadly explains this phenomenon, and in this post I don't really wish to wade any further into this debate than we have already.  We have a few more questions to answer tonight.
The small feathered dinosaur Microraptor on display at the Wyoming Dinosaur Center in Wyoming.  You can see both the impressions of feathers off the wings and legs (making this Velociraptor-cousin comparable to the Sopwith Camel British biplane active during World War I), as well as the sclerotic ring nestled within the orbital.  My preciousssss.....
The name of this ichthyosaur, Opthalmosaurus, actually means "eye lizard," the name of which refers to the big @$$ eyes and sclerotic rings of this particular genus.  Better not put it on your finger, Dumbledore, it might be a Horcrux.
The pseudosuchian Prestosuchus, on display at the AMNH in New York.  This ring just exudes fellowship, don't you think?
Why is Nagini usually more brightly colored than Crookshanks or Scabbers?  Why are Polly's pigments predominantly prettier than Pongo's or Perdita's?  Although undeniably more handsome after true love's first kiss, there's no denying than many frogs and toads out there are much more exciting to look at than Prince Charming.  There's got to be a reason why the characters in "Finding Nemo" were so much brighter (sorry Dory, but I mean in terms of color) than Remy from "Ratatouille," or why Kevin is much more conspicuous than Dug in "Up." But what is the reason?  The answer seems to be fairly simple: with few exceptions, most mammals are colorblind. Primates are one of these exceptions, which is why we humans are able to differentiate between cherry and grape Jolly Ranchers and an elephant might fail, and why the Green lantern comic books and Bionicles absolutely tanked in the feline and canine demographics.  Mammals are good at a lot of things, but one thing that they're not very good at is seeing in color.  A picture is better than words in many cases, so check out some pics below of animals that can most definitely see in color.
Here we have a white-necked raven (Corvus albicollis) correctly putting four different colored game pieces into the correct slots at a special Teen Career Day event at the Denver Zoo that I attended with my sister.  He did all eight tiles in the correct category, and it didn't take him very long, either!  Some of my friends wouldn't be able to do it with such speed and accuracy....
Male peafowl (Pavo cristatus), often referred to as peacocks, are just one of many species of bird that use brightly colored feather to attract their mate.  Maybe that's why Sauron was so angry: he knew that, no matter what he did, the giant eagles would always be able to naturally two-up him.

A Micronesian kingfisher (Todiramphus cinnamominus) sittin' purty at the Denver Zoo.  Return of the King(fisher), am I right?
A clown fish (subfamily: Amphiprioninae) taking refuge amongst the stinging tentacles of a sea anemone at the Denver Zoo. 
The Mandarin goby (Synchiropus splendidus), a particularly beautiful fish, and very brightly colored as well. 
One of my two betta fish (Betta splendens), Juan Priestly.  Bright bodies with frilly fins?  Glad I'm not a betta fish, this one would steal my girl right out from under me.
Just like the default condition for vertebrates is to possess a sclerotic ring, so too does it seem that the default condition for vision is color.  So if mammals are supposedly so superior, why do so many of us lack this colorful condition?  Many paleontologists have been looking back to the Mesozoic Era, the age of the dinosaurs, to try and solve this colorful conundrum.  Just as mammals have been the dominant terrestrial vertebrates for the last 65 million years, so too did the dinosaurs rule the land during the Mesozoic, suppressing all other forms of life and filling most of the major terrestrial niches.  One of those life forms that was consistently suppressed from the Triassic through the Cretaceous was mammals.  Mostly small, shrew-like animals, Mesozoic mammals are usually thought to have been small, nocturnal creatures, pittering and pattering around the bodies of the sleeping dinos, ready to run at a moments notice.  Key word in that last sentence: nocturnal.
Can you see the little mouse-looking animal hiding underneath the box in the middle of the photograph?  That's Hufflepuff (Huffle to his friends), a small meadow vole (Microtus pennsylvanicus) that tried to hide underneath my legs when a red fox (Vulpes vulpes) happily tried to make a meal out of him last year on CU campus!  Knowing he probably had had the vole equivalent of a heart attack and taking pity on him, I said "I'll save you tonight!" and let him recover for a few days in my room before letting him go to let him live while he was young (which isn't long, I don't think most voles live longer than a year or so, but I could be wrong).  A nocturnal critter, he would have very little use for color vision, and has relatively drab coloration.
More wildlife from CU campus!  This coyote (Canis latrans) caused a bit of a stir last winter when it decided to crash on Farrand Field for a few hours, right in the middle of CU campus.  Although not exclusively nocturnal, coyotes are often active at night, but are quite adaptable, as was evidenced by this particular coyote's behavior, alive and well in the middle of campus!  Note the relatively drab coloration.
I have a friend who is partially colorblind, about as colorblind as an elephant according to some recent studies.  If you see him outside, he's going to be wearing sunglasses (unless he's done something to piss off Poseidon).***  Is he doing it just to look cool?  Well, yes, I suppose that's at least partially the case.  But for him, and for many other people who suffer from color blindness, it seems like they make up for it with above average night vision.  Essentially, an imbalance of rods (a photoreceptor that is not sensitive to color but is sensitive to light and dark conditions and aids in night vision) and cones (a photoreceptor that is sensitive to color and less sensitive to light/dark conditions) leads to many who are color blind reporting better than average ability to see what's going on in low-lighting conditions.
An African elephant drinking some water at the Cheyenne Mountain Zoo in Colorado Springs.  Drab colors?  You betcha!
When all of these seemingly disparate ideas are regarded holistically, it seems to make sense.  By default, most vertebrates enjoy a wide range of color vision (sometimes even a wider range than humans!).  However, during the Mesozoic dinosaurian domination, some groups of vertebrates such as the mammals were forced to take up residence during the night.  For millions of years, these little creatures lived a nocturnal existence, and it seems like being able to see in color no longer proved to be a competitive advantage for them.  Following the extinction of the dinosaurs and the subsequent radiation of mammals, it appears that the possession of color vision was unnecessary for them to survive and thrive.  Many mammals are still largely nocturnal today (think of your kitty at home and all of her midnight memories), which might have something to do with this disparity between their rods and cones.  All in all, it would appear that changes of the night can have some pretty profound effects on your ability to see across the color spectrum.


*You will probably come across them doing some serious work as well, but dinosaur taste-testing can be pretty important.
**I thought that Dr. Bakker, who I talked to a lot about this, mentioned that most or all frogs had the sclerotic ring, but I have been unable to confirm or deny this with a quick search through the resources I have at my disposal.
***Twice.

Works Cited:

Sunday, September 21, 2014

Taima the Seattle Seahawk and the Genus Buteo

For those of you who watching the Broncos/Seahawks game right now, you might have noticed clips of a random bird of prey flying around which, if you're anything like me, that was the highlight of the entire game.  Named Taima, the bird is the mascot for the Seattle Seahawks football team, an augur hawk (Buteo rufofuscus).  Although sometimes referred to as the augur buzzard, I prefer the name augur hawk, as buzzard is sometimes a bit of a confusing name.*  According to the Seahawks website, Taima has been the "first one out of the tunnel" prior to every game.**  The augur hawk is one of the most common hawks in Africa, and inhabits an enormous portion of the eastern and central part of the continent.  Open plains, grasslands, and forests are the augur's preferred habitat, fairly similar to its close North American cousin, the red-tailed hawk (Buteo jaimaicensis).
Taime the Seattle Seahawk!  Photo Credit: www.seahawks.com
The broad-winged hawk (Buteo platypterus) is one of the smallest members of the genus, and a hawk that's involved in a very interesting new project, the aptly named "Broad-Winged Hawk Project."  Similar in many ways to the OCEARCH shark tracking project, the BWHP is using satellite telemetry technology to track broad-winged hawks on their migration from Pennsylvania, all the way down to Central and South America.  You can join in the tracking fun by clicking on the link HERE!  Several of the nestling broad-wings were from pretty close to where my friend Zach Evens's cabin in Pennsylvania was that we visited in August!
A broad-winged hawk.  Photo Credit: Julie Waters
There are a ton of other hawks in the genus Buteo besides the red-tail, augur, and broad-wing, several of which we've talked about here on the blog, such as the red-shouldered hawk (B. lineatus), rough-legged hawk (B. lagopus), and the Swainson's hawk (B. swainsoni).
A rough-legged hawk on the hand of Anne Price, the Curator of Raptors for the Raptor Education Foundation at one of the raptor shows at the Best Western Denver Southwest!
*In the Americas, a buzzard typically refers to a vulture, while in the Old World, buzzard is often attributed to members of the genus Buteo, of which the augur hawk is a member.  We Americans tend to refer to buteos simply as hawks, which is part of what can lead to this confusion.

**For those of you not in the know, the tunnel is not a metaphorical tunnel, and instead refers to a legit tunnel that leads from the locker room onto the stadium.

Works Cited:

Wednesday, September 10, 2014

Anoxic Conditions From Everest to Europa: Swamps, Fossils, Naked Mole Rats, and the Hunt for Extraterrestrial Life

Above elevations of 6500 meters (21,300 feet), most climbers tend to start using supplemental oxygen.  At altitudes higher than this, oxygen is spread so thin that humans can have a very tough time breathing.  Even people who come from sea level to my hometown of Boulder, Colorado at an elevation of 1,655 meters (5,430 feet) often get altitude sickness, and there's still a whole lot of altitude to go before you even get to Everest Base Camp.  Most birds don't fly as high as the summit of Mt. Everest, because most birds have no reason to fly that high.  However, for the bar-headed goose, the Himalayas form an unfortunate, but not impassable, barrier between their winter feeding grounds in India and their Tibetan nesting grounds.  These geese have been reported flying over some of the highest Himalayan peaks, and they're not the only ones that fly this high.  On November 29th, 1973, a Rüppell's griffon, a type of Old World vulture, collided with an airplane at an altitude of 11280 meters (37,000 feet).  By comparison, oxygen cylinders are recommended for sailplane pilots flying over 3660 meters (12,000 feet)!
Here we have a beautiful (and extraordinarily neat) size comparison and altitude chart of a number of things covered in the post, including the altitude of Denver, the summit of Mt. Everest, the upper extent of the range of the snow leopard, and the height at which the Rüppells griffon got sucked into the jet engine.  I've also thrown in some other helpful and fun things for comparison as well.
Part of what helps birds survive at altitudes that could kill a human is a series of air sacs that allow air to flow in one direction through the body of the bird.  In humans, the air we breath in and out travels back and forth along the same tubes.  In birds, as well as some of their close dinosaurian cousins, these air sacs would have have allowed the air to flow more efficiently through their bodies.  While this is simply one of many adaptations that can help birds fly at incredibly high altitudes, other animals have evolved other adaptations to assist in high altitude living.  Scientists have determined that changes in the genes EGLN1 and EPAS1 are linked with animals living in oxygen impoverished environments, such as the snow leopard, humans native to Tibet, and naked mole rats.  Naked mole rats live in underground colonies of 20-300 individuals, and are one of two species of mammal that can be classified as "eusocial," meaning that their colonies display a caste system (similar to the social structure seen in ant and termite colonies).  These underground colonies are poorly ventilated, which means that as the mole rats inhale oxygen and exhale carbon dioxide, CO2 concentrations can increase to levels that would be unsafe for humans.  Fortunately, naked mole rats are well adapted to breathing very little oxygen, and their brains seem incapable of registering pain upon contact with acids, which is thought to help them in these CO2 rich confines.  They also demonstrate similar changes in the aforementioned genes as snow leopards and the Tibetan people, indicating another adaptation to these low oxygen (or hypoxic) conditions.
A group of naked mole rats all huddled together at the Cheyenne Mountain Zoo in Colorado Springs, Colorado.  Look at all of that eusociality!
Although hypoxic conditions can bode ill for human climbers and gregarious colonial rodents, low oxygen conditions can be great for paleontologists.  When oxygen levels drop to nearly zero, anoxic conditions prevail, and bacterial decomposition of organic material is greatly reduced.  This can be a major factor when it comes to soft-tissue preservation, such as feathers and skin.  A FEW WEEKS AGO, we talked about several famous fossil sites called Lagerstätten (a German term meaning "mother lode"), that are set apart from other fossil deposits due to the quality and/or quantity of the fossils discovered there.  One of the most famous examples is the Cambrian-aged Burgess Shale in British Columbia, Canada.  Abrupt burial of the 500 million year old organisms, coupled with the anoxic conditions that prevailed at the bottom of this body of water, ensured that these soft-bodied organisms would be preserved in exquisite detail.
A drawing of Opabinia, one of the many creatures that inhabited the Cambrian aged Burgess Shale in British Columbia, Canada.  Photo Credit: Sam Lippincott
Why do swamps often have that rotten egg smell?  Believe it or not, the answer is closely related to what we've already been talking about!  Under hypoxic or anoxic conditions, bacteria that use oxygen (O2) sometimes have to make do with sulfur (S).  If you look at a periodic table, you can see that sulfur (element #16) is directly below oxygen (element #8).  In the periodic table, each group (or column) of elements has very similar chemical properties, which means each element will react in a similar fashion.*  For the bacteria that can't get enough oxygen, they will sometimes turn to its close cousin sulfur instead.  Below is the chemical formula for cellular respiration, which is what these bacteria do, as well as some of the cells in humans.  On the left, we have the inputs: glucose (C6H12O6), and oxygen (O2).  When we breath in air, we are bringing oxygen into our lungs, and we can get glucose from the foods we eat.  On the right of the arrow, we have the outputs: water (H20), carbon dioxide (CO2), and energy.  Remember how we talked about the CO2 concentrations in naked mole rat burrows?  CO2 is one of the products of respiration, and one that can be harmful in large doses.  Energy is another product of respiration, which is the fuel that cells need to do their job.  In places where there is less oxygen input (such as at the top of Mt. Everest or in a naked mole rat burrow), the cells don't get as much energy output, and they can't do their job as well.
Now, instead of having oxygen as one of the inputs of cellular respiration, let's try sticking oxygen's close cousin, sulfur, into the equation to see what will happen.  As you can see below, the glucose on the left of the equation remains unaffected, as does the carbon dioxide output on the right of the equation.  But instead of having water (H2O) as another one of the outputs, we now see a molecule with the formula H2S.  Instead of forming water (hydrogen oxide), we have now formed a closely related molecule, hydrogen sulfide.  In swamps, large amounts of organic material leads to lots of bacteria and bacterial decomposition, which in turn can lead to lots of the oxygen being used up in the water.  That's when these bacteria start using sulfur to make their energy, producing hydrogen sulfide, with that characteristic rotten egg smell.  Even with this sulfur replacement, sometimes the bacteria just can't keep up with the amount of vegetation that is deposited in the swamp, and the organic material builds up.  If the rate at which the vegetation accumulates exceeds the rate which the bacteria can decompose the vegetation, then you have coal formation potential sometime in the future.
Let's take this one step further.  In normal respiration, where oxygen is one of the inputs and water (H2O) is one of the outputs, carbon dioxide (CO2) is another one of the outputs.  If animals and bacteria keep using up oxygen and turning it into carbon dioxide, why haven't we run out of oxygen?  Will we run out one day?  Fortunately, for the time being, plants have got our back, by undergoing a process called photosynthesis.  Photosynthesis is almost the exact opposite of respiration: carbon dioxide and water are the inputs, and glucose and oxygen are the outputs.  However, unlike respiration, light is one of the inputs of photosynthesis.  In the 1700s, a man named Joseph Priestly did experiments in which he sealed a mouse in a jar, and waited to see what happened.  The mouse, as you could probably predict, suffocated and died.  It used up its oxygen to create energy (as well as carbon dioxide), and eventually ran out of oxygen.  (This is why it's important not to put animals into completely sealed jars with no airflow, as they will suffocate.)  However, if he put a plant into the same jar as the mouse, the mouse didn't suffocate.  We now know that is because, as the mouse used up the oxygen, creating carbon dioxide, the plant would use the carbon dioxide, ultimately creating more oxygen.
As you probably know, plants need light to survive, and as we mentioned before, that's because light is one of the inputs of photosynthesis.  No light, no photosynthesis.  No photosynthesis, your plant dies.  For many years, scientists assumed that all life on Earth was directly dependent on the Sun for its energy.  That is, until 1977, when scientists discovered entire communities of biological organisms living thousands of meters beneath the surface of the ocean, too far from any sunlight to undergo photosynthesis.  So what was going on?  How were these communities able to survive without access to the sunlight?
A picture of one of the hydrothermal vent communities.  Photo Credit: NOAA
Hydrothermal vents are essentially underwater hot springs that form along tectonic boundaries thousands of meters beneath the surface of the ocean.  These underwater vents spew different compounds containing sulfur into the surrounding water, just like aboveground geysers do, too.  (If you have ever been to Yellowstone National Park, then you might even remember the rotten egg smell.)  Some bacteria that surround these vents are actually able to use these sulfur-containing compounds to create the energy needed to undergo a process similar to photosynthesis, called chemosynthesis (consult the equation below).  Chemosynthesis is very similar to photosynthesis, with a few key differences, the biggest difference being the sulfur reactions vs. sunlight as one of the inputs.  You can also see that, instead of having water (H2O) as an input like in photosynthesis, chemosynthesis instead uses hydrogen sulfide (H2S) as an input.  Then, instead of producing oxygen, the chemosynthetic organisms produce water and sulfur.  You can compare it to the oxygen-poor respiration equation that we talked about with the swamps, and see that it is similar to that equation as well, simply flipped around.
But that's not all.  Scientists have taken this idea a step (or rather, one giant leap) further.  The search for life on other planets thus far has yielded nothing, but that doesn't mean it's not there.  It is now realized that some of the factors that were once thought to limit the development of life, such as sunlight, might not be as crucial as we once thought, and the hydrothermal vent communities have been crucial in the maturation of these ideas.  Some scientists suspect that life could exist on Mars by using chemosynthesis, but a new candidate has been receiving an increasing amount of attention: one of Jupiter's moons, Europa.  Icier than the planet Hoth, Europa is now thought to have an ocean of liquid water up to 160 km (100 miles) deep surrounding the solid, rocky mantle, following the discovery of a magnetic field surrounding the moon, similar to the magnetic field that surrounds the Earth.
A picture of Jupiter's moon Europa, taken by NASA.  Photo Credit: en.wikipedia.org
What keeps the liquid ocean of Europa from freezing solid?  Jupiter is pretty far from the Sun, and even Mars, which is much closer to both the Sun and the Earth than Jupiter is, has had its water frozen for millennia.  It's thought that the gravity exerted by the enormous mass of Jupiter continually pushes and pulls, or tidal stresses, on its moons, which keep the planets from becoming tectonically inactive, like Mars.  Io, another of Jupiter's moons slightly larger than our Moon, is the most geologically active body in our Solar System.  The tidal stresses from Jupiter exerted on Io apparently make Io's ground itself buckle up and down, similar to the tides we experience here on Earth, except that instead of water moving up and down 18 meters (60 feet), its solid ground moving up and down up to 100 meters (330 feet!)  It's these same tidal stresses that make Io so geologically and volcanically active that help keep Europa from freezing solid.  It has been hypothesized that the tidal flexing might also create hydrothermal vents on the bottom of Europa's oceans, and it shouldn't take too much thinking to realize what that might mean: the potential for extraterrestrial life!
Jupiter and its four Galilean Moons (from top to bottom: Io, Europa, Ganymede, and Callisto).  Photo Credit: NASA
*For example, we humans, as well as all known lifeforms, are carbon-based.  In science fiction, such as Star Trek and Transformers, you will often hear about "silicon-based lifeforms."  Why silicon, as opposed to any other element?  If you look at the periodic table, silicon is in the same group as carbon, and situated right beneath it, and therefore has very similar chemical properties as carbon.



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Thursday, August 21, 2014

'Donts and 'Apsids: Ancestral Dinos and Mammals of the Mid-Triassic

When it comes to dinosaurs and mammals, neither had quite yet evolved yet.  Most people consider animals like Herrerasaurus and Eoraptor to be among the oldest known dinosaurs, but others now consider Nyasasaurus to be the oldest, originating from 240 MY old rocks from Tanzania.  Many dinosaurs looked very similar to other, closely related archosaurs, and only extensive research and more specimens will be able to shed light on these ancient critters.
Herrerasaurus skeleton at the Field Museum in Chicago.  Photo Credit: Sharat Ganapti
Mammalian ancestors took the form of the now-extinct dicynodonts and the cynodonts, the latter of which include modern mammals, as well.  In modern mammals, you can see how the skull only has a single hole behind the eye (the space where the coronoid process sneaks in between the main part of the skull and the extruding zygomatic arch), making it a synapsid, or "one-holer."  In previous posts, we've talked about primitive, mammal-like animals such as Dimetrodon and Cotylorhynchus.  Both of these critters are synapsids.  Diapsids, or "two-holers" (remember from our recent Latin/Greek Roots post that the root "di" means "two" [click HERE to read that post]), is another large group, and includes everything from crocodiles to dinosaurs, lizards to snakes, and tuataras to birds.  It also includes the archosaurs, a subgrouping of diapsids that are characterized by an additional hole in the skull, bringing the total number of skull holes up to three.  So some diapsids are also archosaurs, such as birds, dinosaurs, and crocodiles.  There's also the anapsids, which are animals with no holes in the skull, such as amphibians and turtles.  Taxonomically, this can get a bit confusing (especially since sometimes an animals classification doesn't correspond to the number of holes that it has at that point in its evolutionary history), and maybe later we can go into greater detail about these different 'apsids, but below we have a nice picture that should help clear things up a little.
Holes in the skull.  On the top left, we have the prehistoric sea turtle Protostega, an anapsid, with no extra holes behind the eye socket.  Below Protostega, we have Prestosuchus, a type of archosaur.  Not only does Prestosuchus have the two holes in the skull behind the eye socket that characterize older diapsids, but it also has a third hole, in front of the eye socket, but behind the nose openings.  On the bottom right, we have Edaphosaurus, a primitive synapsid.  The largest hole in the skull, furthest on the right, is what will one day become the hole that the coronoid process sneaks through, between the zygomatic arch and the rest of the skull.  In the picture above Edaphosaurus, you can see what I'm talking about, with the extinct mammalian synapsid Hyaenodon.  Here, you can see the little nub of the coronoid process between the zygomatic arch and the skull.
As we talked about in that Latin/Greek post that I mentioned above, the name of the primitive, fin-backed synapsid Dimetrodon means "two measures of teeth," referring to the two different types of teeth this animal possesses.  This is a feature known as "heterodonty," a term that means "different teeth."  Most mammals are heterodonts, and most other animals like reptiles are not, but it doesn't always work that way.  Modern cetaceans such as the sperm whale, as well as orcas and dolphins, are homodonts, meaning that they only have one type of tooth in their mouth.  If you look at ancient ancestors of whales, such as Basilosaurus or Zygorhiza, you can see that they have different types of teeth in their mouth.  This condition can be traced all the way back to 50 MY old Pakicetus.
A trio of cetacean skulls.  On the top left, we have Pakicetus, a terrestrial ancestor of the cetaceans, that lived in Pakistan approximately 50 MYA.  Below Pakicetus, we have Zygorhiza, a more derived and fully aquatic cetacean.  In both Pakicetus and Zygorhiza, you can see how the front teeth and back teeth are different, with the front teeth more for gripping prey, and the back teeth perfect for slicing.  On the right, you can see the skull of the modern killer whale, or orca, which has only one type of tooth in their mouth, the conical, gripping teeth.
Then, of course, there are the heterodont reptiles and dinosaurs such as the Cretaceous crocodilian Malawisuchus, and the dinosaurs Heterodontosaurus (literally meaning "different-toothed lizard") and the oviraptorosaur Incisivosaurus.  We also talked about the primitive pterosaur Dimorphodon (two morphs of teeth) in the Latin/Greek post as well.  If you look at the skulls of any of these animals, you can clearly see the different types of teeth in their mouth.  Cynodonts were not merely an aberrant heterodont form amongst a vast sea of closely related homodonts, but instead were precursors to the default heterodont condition seen in mammals.
The skull of Heterodontosaurus, on display at the American Museum of Natural History in New York.  You can see the two different types of teeth in the skull, especially in the lower jaw.
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