If you look up in the night’s sky and point even a simple pair of binoculars at Jupiter, like Galileo did with a rudimentary telescope 405 years ago, you will see what he did: a reddish-pink planet with swirling masses of clouds. These clouds are beautiful in their own right, but there is one particular feature that has drawn the eyes and the fascination of people for over four centuries. The Great Red Spot.
This swirling, gurgling red super-storm could fit three earths inside of it and has been raging on the gas giant ever since we’ve been keeping records. How it has lasted for so long and why it has such a different colour has long been a mystery.
In 2000, on the way to Saturn, an ESA mission called Cassini aimed to give us some clues when it flew within 9.7 million kilometres of Jupiter and looked more closely at the spot than we had ever done before or since. 9.7 million kilometres sounds like a lot, but consider that is only about 1% of the distance between Jupiter and Saturn. (As a side note, did you know that Jupiter and Saturn are further away from each other than Jupiter and Earth? I didn’t!).
With its flyby, Cassini found out that the clouds that form the spot are up to eight kilometres higher than the surrounding clouds and started to understand the chemical composition of the clouds.
14 years later, in November 2014, NASA scientists released results that combine data from the Cassini flyby with lab experiments on Earth. They showed that the colour must come from the interaction of ultraviolet (UV) light from the sun and the ammonia and acetylene in the top layers of the storm. Once the red particles are produced, they are trapped by the circular winds of the storm. This overturns the previous theory that it was the bottom clouds which provided the colour. The NASA scientists compare the colour of the storm to a sunburn rather than a blush.
So, thanks to NASA and the Cassini mission, we have a better idea about how the spot gets its colour, but last spring the astronomy world was in a tizzy because news came that the spot has been shrinking.
Since it is so noticeable, the storm has been recorded as far back as the 1800s, when it was believed to be about 41000 km across (roughly equal to the circumference of Earth). The most recent image, from 2014, puts the size at only 16500 km (less than the length of the great wall of China). Not only is it much smaller than it used to be, but the rate of shrinkage is increasing.
If my calculations are correct, and if the storm keeps shrinking the way it has been, it will disappear entirely in about 35 years, in 2059. That means we may be among the last people to ever see the spot that Galileo spied on that fateful night in 1610.
Instead of relying on me and my calculations, however, NASA sent a spacecraft to go investigate. Juno left in 2011 and by now is more than halfway to its destination. When it arrives in July 2016, Juno will study the gas giant in a variety of ways and hopefully get the bottom of this whole shrinking storm mystery.
Unbeknownst to the rest of us, a debate has been raging in the world of biogeography. The debate stems from a simple observation made by a young Canadian scientist in 1964: island animals are weird. Sometimes they’re way bigger than normal, like the Tenerife Giant Rat, and other times they are way smaller than normal, like the Elephas falconeri, a tiny species of elephant.
J.B. Foster published a short, two-page paper in the April 1964 edition of Nature positing that rodents get bigger and lapidomorphs (rabbits), carnivores, and artiodactyls (deer/goats) get smaller on islands. This, he thought, was because small animals found the isolation of islands to be liberating. They no longer had to worry about predators and could grow to fill their new space. Larger animals, however, might be restricted by the relative paucity of resources on islands and would have immense evolutionary pressure to become smaller.
This led to Foster’s Rule, also known as the Island Rule. It states that in general, big animals get small on islands and small animals get big. They also do so very quickly (in evolutionary terms). For instance, red deer on Jersey, an island in the English Channel, were shown to have shrunk to to 1/6th their original size in only 6000 years.
There’s a problem, though. Like pretty much every rule in biology, there are lots of exceptions. Sometimes small animals get smaller (like Brookesia micra, the world’s tiniest chameleon) and relatively big animals get bigger (like Haast’s eagles).
A 2011 article by a joint Israeli-Italian-British team of researchers calls the whole theory into question, showing that the smallest species in any given group is no more likely to be from an island than would be expected by chance. Size extremes, they say, exist everywhere. Islands don’t have some sort of monopoly. They do concede that large mammals tend to get smaller, but they think the idea that small animals get bigger only seems like common sense because they are easier to notice.
A British paper from 2008 throws even more confusion into the mix, showing that depending on the kinds of statistical tests you use, you can show that the island rule either exists or doesn’t. They suggest that the island rule should be looked at in “taxonomically restricted studies” – biologist-speak for “case-by-case basis”. That seems to kind of defeat the purpose of a nice heuristic, though.
One thing we know for sure is that islands isolate organisms. This isolation means that evolution can work differently for the island population and might lead to all sorts of interesting changes. This type of evolutionary change is also called allopatric speciation and is responsible for the variation that Darwin saw in Galapagos finches. Whether islands always create a particular kind of change is still up for discussion, but nobody can doubt that when organisms of unusual size appear, they deserve attention.
Say goodbye to foil floating hearts on Valentines, shimmering floating shamrocks on St. Patty’s, and the prospect of tying thousands of balloons to your house and abducting a neighbourhood boy scout. The world’s Helium reserve is going to run out, and sooner than you might think.
Helium is the universe’s second most abundant element and we’ve never had real cause to worry about it before, so what has changed that we need to start hoarding Helium? The short answer: the U.S. is selling off their strategic reserve and getting out of the Helium game, meaning prices are going to skyrocket as demand outstrips supply.
The longer answer begins with the fact that Helium has always been a non-renewable resource here on Earth. It is produced underground by radioactive materials like Uranium and Thorium and then floats up into the atmosphere and out into space unless it gets trapped by natural gas in the Earth’s crust. Once the radioactive materials decay and release Helium, there is no putting it back.
When we extract this gas, we can collect the Helium and use it to fill party balloons, make our voices squeaky, pack fuel into rockets, or cool superconducting electromagnets to four degrees above absolute zero (-269C).
MRIs and the LHC capitalize on the unique properties of Helium: it is inert and has the lowest boiling point of any element, allowing it to bring the temperature of metals down enough to make them superconducting. These more scientific uses of the substance have ballooned (pun kind of intended) in the past two decades, putting real pressure on producers.
We don’t think of Helium as scarce, partially because of its perceived strategic value in the 1920s. The U.S. felt that airships were the way of the future and so set up a government-owned strategic reserve in 1925. Given that the only real demand on this stockpile was the occasional rocket test or airship, this reserve built up over 70 years.
The U.S. government has long dominated the world Helium market (in 2006, U.S. helium reserves accounted for two thirds of the world’s total) and has been gradually selling off reserves, keeping prices artificially low. Maintaining the infrastructure to keep and distribute the gas isn’t cheap though, and the government wants out.
In 1996, Congress mandated the shutdown of the world’s largest (and only) strategic helium reserve by 2013. This was delayed by a last-minute law passed by Congress which averted a dreaded “helium cliff” that would have seen MRIs go silent. The new shut-down date is 2021.
Algeria and Qatar are trying to pick up the slack in time, but prices are rising by as much as a factor of 2.5 every year. Some scientists think that before long, a simple Helium-filled party balloon will cost upwards of $100.
If Slate’s Nina Rastogi’s calculations about the number of balloons required to lift Carl’s house in Up are to be believed, that would put Carl’s Helium bill at nearly one billion dollars. If there is going to be an Up2, either someone’s going to have to be a billionaire, or they might just have to risk it with Hydrogen.
Deep in Antarctica, right on top of the geographic South Pole, there is a research station that peers back in time to the very beginning of our universe. Named the Amundsen-Scott Station, it is home to instruments such as the creatively named South Pole Telescope (SPT), the Keck Array, and the BICEP experiments.
The temperature is currently sitting at about -30C and it’s the height of summer. The sun won’t set at the station until March 23rd and once it sets, it won’t rise again until September. So why the heck (or, one might say…Keck) would we build an observatory there?
Because the temperature is so low and the altitude is so high (2743m) at the South Pole, the air is thin and dry, reducing blurriness normally caused by the atmosphere. There are no cities nearby to cause light pollution and there are months of nonstop night, allowing for continuous observation. It’s an astronomer’s dream. Except the nearly-constant -30C temperatures. And the remoteness. But otherwise, dreamlike.
So what are astronomers looking for all the way down there at the end of the world? They are searching for clues as to how the universe started. Ever heard of the Big Bang Theory? No, not these clowns, the theory about the beginnings of the universe. Although, come to think of it, the theory is actually pretty well summed up by the first line of the Barenaked Ladies’ theme song to the Big Bang Theory (yes, those clowns):
Our whole universe was in a hot dense state,
Then nearly fourteen billion years ago expansion started. Wait…
That’s really the core of the theory: everything used to be really hot and dense and now its not. What happened in between is what the astronomers at the South Pole are trying to figure out.
Astronomy is awesome because when we look up, we are actually looking back in time. The distances involved are so great that it can take years (or billions of years) for light to reach us. So, what if we just looked as far as we could, wouldn’t we be able to see the Big Bang happening? What would that even look like?
Unfortunately, because everything was so hot and dense right at the start of the universe, nothing could stick together so the universe was just a soup of energetic particles. Any light that was emitted was bounced around like the light from a flashlight in thick fog. About 380 000 years after the Big Bang , the universe had cooled and expanded enough to let atoms form and collect electrons. Atoms are mostly empty space, which means that unless they are packed very close together like in a solid or liquid, they are transparent. What resulted was light spreading pretty evenly throughout the universe, starting 13.7996 billion years ago. This is what is called the Cosmic Microwave Background Radiation (CMBR). Cosmic because it comes from space, Microwave because it has lost a lot of energy since the Big Bang and is now only 2.7 degrees above absolute zero, Background because it is there no matter which direction you look, and Radiation because it is light.
So, no matter how far you try to look, this map is all that you see. It is all that can be seen because it is the oldest light that escaped. Sounds kind of disappointing, but astronomers think that that image (what some refer to as the baby picture of the universe) holds clues to what happened before.
If there was inflation, faster-than-light expansion of space and time (again, check out my essay on the history of the universe if you’re confused), that process should have produced gravitational waves.
“Woah, woah, woah. Hold up. I understand gravity, apples falling on heads, etc etc… How the Keck could there be gravity waves?”
One of Einstein’s key contributions to science was the understanding that space and time are linked and that they are influenced by mass. He described space-time as a fabric that could be warped by the presence of mass. All that gravity is, he said, is the curvature of space-time around mass. A simplified way to understand this is by thinking of space-time as a trampoline. If you put a mass on the trampoline, it will create a depression. The heavier the mass, the more extreme the depression. Now, if you have an extreme depression and move it very quickly back and forth, it will create waves in the same way that a moving hand in a pool will create waves. Astronomers think that inflation must have created gravity waves with a very specific signature. They also think that very heavy stars moving quickly, like binary neutrino stars, would create these gravitational waves.
If (or, once they are discovered for sure, when) gravity waves pass through you, it is space itself which is expanding and contracting. You are not moving, but as the wave passes through your arm, your arm will be closer to your body than it was before and time for it will move slower.
The thing about gravity, though, is that it is by far the weakest of the fundamental interactions (Electromagnetic, Weak, Strong being the other, stronger ones). By a factor of about a nonillion (1 with 30 zeroes after it). This makes the waves it creates very difficult to detect. While your arm is probably having a taste of timelordery as you read this, there is no way you could possibly feel it. Gravity waves are not interesting for how they make us feel, but rather for the challenge they present in detecting, for the possible confirmation of our current physical model, and for what they can tell us about the origin of the universe.
So let’s come back back to the barren, frigid wasteland of Antarctica and the astronomers freezing their buns off for science. BICEP2, the second iteration of the Background Imaging of Cosmic Extragalactic Polarization experiment, looked at the CMBR and looked for patterns in the light. These patterns, called b-mode polarization, can be produced by gravity waves, but also by interstellar dust.
In order to cancel out the effect of dust, the BICEP2 team used data from Planck, a European satellite launched in 2009 with a very similar mission: to study the early universe. Whereas BICEP2 could only look at one particular wavelength with high sensitivity, Planck could look in a few different wavelengths but didn’t have quite as much sensitivity for these b-modes. Dust doesn’t leave the same polarization patterns in light in different wavelengths, so by comparing the results from different wavelengths from Planck, the BICEP2 team was able to show that the b-modes weren’t from dust and so had to be from gravity waves from the early universe. Proof of inflation! Proof of the standard model! A possible Nobel Prize!
So, understandably excited and with a positive result in hand, there was a big announcement at the Harvard-Smithsonian in March of last year. Unfortunately, the data they used was preliminary. In September, new data was released and the effect of dust seems to have been larger than they thought. The team reduced the confidence in their findings but still stood by a significant result. Just last month, in January 2015, another set of data was released that makes the BICEP2 findings inconclusive.
It seems the team jumped the gun a little bit, were blinded by the impact of their apparent discovery, and had too much confidence in preliminary data. The result of all this is that there is still no direct evidence of inflation or of gravitational waves and the teams at Planck and BICEP are going to work together now with the strengths of their instruments. Within a few years, the effect of dust should be able to be cancelled out and we will be able to see whether we were right about the beginning of the universe. And all the frostbite will have been worth it.
The year is 1791. On a crisp autumn morning in South London, Margaret Hastwell, a blackmith’s apprentice, gives birth to her third son. With her husband, son, and daughter crowded around, she decides to name the newborn Michael. Michael Faraday.
Margaret had a lot on her plate, what with two young children, a husband who was often sick, and quite a few bills to pay. She probably didn’t have much time or energy for idle thought or daydreaming. I doubt if she much considered what Michael might do with his life other than get by. There is no way it occurred to her that Michael would grow up to revolutionize the world of physics, make electricity a viable source of mechanical energy, and inspire countless scientists, engineers, and young people (including but not limited to Einstein, Rutherford, and this young science communicator, 223 years later). But that is exactly what he would do.
Faraday went to elementary school and learned to read and write, but by the time he turned 13, he had to start work in order to help his parents make ends meet. He was apprenticed to a local bookbinder and spent the next 7 years diligently mending books. But that wasn’t all he was doing. He was also reading. Over those 7 years, Faraday read voraciously and became interested in science, particularly the topics of Chemistry and Electricity. Luckily for him, George Riebau, the bookbinder to whom he was apprenticed, took an interest in young Faraday’s education and bought him tickets to lectures by Humphry Davy at the Royal Institution in 1812. This was only shortly after Davy had discovered calcium and chlorine through electrolysis. Davy was a big name in science at the time, comparable to today’s Stephen Hawking, Neil Degrasse-Tyson, or Jane Gooddall, so it was with wide eyes that young Faraday attended. He was so blown away by what he saw and heard that he faithfully wrote notes and drew diagrams. These meticulous notes would prove to be his ticket into Davy’s lab.
Later that year, Faraday sent a letter to Davy asking for a job and attached a few of his notes. Davy was impressed and so interviewed young Faraday, but ultimately rejected the eager young fellow, saying “Science [is] a harsh mistress, and in a pecuniary point of view but poorly rewarding those who devote themselves to her service.” Translation: “Sorry, I don’t have space for you in my lab, but just to let you know… Science really isn’t very profitable.” A few months later, one of Davy’s assistants got in a fight and was fired, so guess who got a call? That’s right, Mikey F.
Not only did Faraday get a spot in Davy’s lab, but he also got to go on a European tour with Mr. and Mrs. Davy. Pretty sweet deal, right? On the eighteen month journey, Faraday got to meet the likes of Ampère and Volta. If those names are ringing distant bells, it should be no surprise. Those eminent continental scientists give their names to standard units of electrical current (Ampere) and potential difference (Volt). Re-invigorated, 22-year-old Faraday returned to London and took up a post at the Royal Institution as Davy’s assistant.
The next two decades saw Faraday make great advances in chemistry, including discovering benzene, liquefying gases, and exploring the properties of chlorine. He didn’t get much chance to focus on electricity, however, until 1821. In that year, Faraday started experimenting with chemical batteries, copper wire, and magnets. Building on the work of Hans Christian Ørsted, Faraday’s work was some of the first to show that light, electricity, and magnetism are all inextricably linked (we now know that they are all manifestations of the electromagnetic force). He was a dedicated experimentalist and between 1821 and 1831, he effectively invented the first electric motor and, later, the first electric generator. These two inventions form the basis for much of today’s modern power system. The electric motor that opens your garage door as well as wind and hydro-electric generators work on the exact same principle that was discovered by Faraday back in 1831: electromagnetic induction.
Faraday’s insight was that when connected by conductive material, an electric current could make a magnet move. He also found that the reverse was true: a moving magnet can create a flow of electrons: an electric current. The experiment is actually quite simple and you can even try it at home. Induction enables the transformation of energy between mechanical, electrical, and magnetic states. Before Faraday, electricity was seen simply as a novelty. Since Faraday, we’ve been able to use it for all sorts of things. Like writing science blogs!
[While he was definitely a gifted scientist, Faraday knew next to nothing about mathematics. He observed, took careful notes, and had an intuition for how to design experiments, but could not formalize his theories in mathematical language. He would have to wait for James Clerk Maxwell, a young Scottish prodigy, to do the math and formalize Faraday’s Law in the 1860s.]
Faraday continued his work on electricity and gained all sorts of recognition, including medals, honorary degrees, and prestigious positions. This increased pressure may have been to blame for a nervous breakdown in 1839. He took a few years off, but by 1845 he was back at it, trying to bend light with strong magnets. He discovered little else after the 1850s, but continued to lecture and participate in the scientific community.
So not only can Faraday be considered to be one of the fathers of the modern world because of his breakthroughs in electricity, but he can also be considered to be one of the fathers of modern popular science communication. In 1825, he decided to give a series of Christmas lectures at the Royal Institution, specifically aimed at children and non-specialists. He gave these lectures every year until his death in 1867 and was renowned as a charismatic, engaging speaker. He tried to explain the science behind everyday phenomena and in 1860 gave a famous lecture on the candle, something which everyone had used but which few actually understood. The Christmas lectures continue to this day and, continuing with Faraday’s legacy, the Royal Institution is one of the UK’s leading science communication organizations.
It is not simply that Faraday was a great scientist and lecturer, nor that he managed to escape poverty in 19th century England to become world-renowned. Michael Faraday’s story is so great because by all accounts, he deserved every bit of success he gained. One biographer, Thomas Martin, wrote in 1934:
He was by any sense and by any standard a good man; and yet his goodness was not of the kind that make others uncomfortable in his presence. His strong personal sense of duty did not take the gaiety out of his life. … his virtues were those of action, not of mere abstention
It’s no wonder that Einstein had a picture of him up in his office. I think I might just print one off myself.
Galileo Galilei is quite a famous astronomer but many of the discoveries he’s known for are just extensions of the work of others. For instance, he didn’t come up with the idea that the Sun is the centre of the Solar System, he just got in big trouble for it. He also didn’t invent the telescope (even though he is often credited). He was just one of the first people to point it up at night to look at stars instead of over the sea at enemy ships. One thing he did do, all by himself, was observe that Jupiter had some friends that followed it around the sky.
In about 1610, Galileo discovered the four largest moons of Jupiter: Io, Europa, Callisto, and Ganymede. While these celestial objects are all interesting in their own right, today I’m going to focus on Europa because it is one of the most credible candidates for extraterrestrial life.
Why might this be, and where the heck is Europa anyways? I’ll let my friends (I use the term loosely) at the NASA Jet Propulsion Laboratory explain:
While the logic there might be a bit suspect (Earth and Europa are very different systems and the rules for one don’t necessarily apply for the other), I think the infographic gives a pretty nice introduction to Europa and helps to underline that for astrobiologists, the search for life in the Universe is almost synonymous with the search for water.
And Europa certainly has a lot of water. Unfortunately, the H2O is mostly trapped under kilometres-thick sheets of ice. This has posed a serious problem for scientists because in order to sample to subsurface ocean and find out if there is indeed life on that cold, watery world, a mission would need to drill through an unknown distance of ice (but certainly on the order of kilometres) and maintain contact with Earth. Even with all of the resources available to us here on Earth, the deepest we’ve been able to go is about 12km. The technical challenges of remotely drilling through such a thick ice sheet have kept many Europa mission concepts off the table.
A recent discovery, however, has made a productive mission to Europa much more feasible. It turns out that Europa sporadically ejects plumes of water vapour. Unlike its cousins Io (another moon of Jupiter) and Enceladus (a moon of Saturn), Europa’s plumes are much less frequent, smaller, and harder to predict. We know that the polar regions have the weakest ice but for some reason plumes just don’t occur very often. They are also hard to catch on film because Europa’s relatively strong gravity means the water can’t go very high and it comes back down pretty quickly. It took the Hubble Space telescope a few tries before it finally caught the sneaky tooter in action in 2013. It’s kind of like Old Faithful, but much older and less faithful. So more like Ancient Temperamental.
While nowhere near the scale of the plumes of Enceladus, Europa’s plumes are still upwards of 200 km high. This means that in order to sample its water, all we need to do is fly through and sniff. That’s what Europa Clipper, a current mission concept, aims to do. For anybody wondering, there are also plenty of people who want to fly through the plumes of Enceladus as well.
Buzz about Europa has definitely grown a lot since it was just a dot in the telescope that Galileo pointed up (but didn’t invent). Actually, last week the White House announced $30 million in funding for developing a mission to Europa and next week NASA is hosting a workshop about Europa’s plumes.
When was the last time you ate dinosaur? I had some just the other day, next to my peas and carrots.
Shocking as it may seem, dinosaurs are all around us and we interact with them on a fairly regular basis. If you’re sitting there saying to yourself, “No, dinosaurs went extinct millions of years ago!”, let me remind you of one critical and oft-forgotten fact: all modern birds (including chickens, turkeys, toucans, and cuckoos) are dinosaurs. That’s right, the mascot for Froot Loops is a dinosaur. KFC can change it’s name to Kentucky Fried Dinosaur and still be scientifically accurate.
How can this be? It all has to do with how biologists name and classify organisms (the technical term for this is taxonomy). Scientists, being very much into order and rationality, made up a few systems for naming organisms and describing their evolutionary relationships. The system I’m going to focus on today, cladistics, has only a few basic rules and is incredibly helpful for understanding the history of life on our planet. Unfortunately it can be a bit daunting because there is some pretty scary-looking jargon. Let’s unpack some of that jargon and apply it to dinosaurs in order to find out how the heck the same word can be used to (correctly) describe animals as different as stegosauruses and canaries.
Two of the most important concepts for cladistics are that:
All life on Earth evolved from a single common ancestor.
Organisms should be classified based on last common ancestors, with organisms that share recent common ancestors being interpreted to be more closely related than organisms with more distant common ancestors.
Think of your family. Everyone is descended from your grandparents (premise #1 above) and you are more closely related to your siblings (last common ancestor is your parents) than your cousins (last common ancestor is your grandparents; premise #2 above).
Those are the basic rules of cladistics. Pretty simple in theory, right? The problem is that with organisms that have been dead for millions of years and only leave behind fragments of bone, deciding where they fit in to the family tree gets difficult.
Now let’s look at some of that jargon I promised.
The first word we need to understand is monophyletic. A monophyletic group is a set of organisms that all share a common ancestor. You, your siblings, and your mum make a monophyletic group. You, your siblings, your mum, and your dad are not monophyletic because (hopefully) your mom and dad are not related. Some scientists call monophyletic groups clades and they are the bedrock of cladistics. A “proper” group must be monophyletic.
If the group you’re looking at isn’t monophyletic, it might be paraphyletic or polyphyletic. These are two types of almost-groups that can confuse a lot of people. Paraphyletic groups choose a section of the family tree, ignoring a large chunk. Polyphyletic groups choose a few individuals throughout the tree without regard for common ancestors. In the family analogy, a paraphyletic group could include your mom and two of your siblings but not you. A polyphyletic group might include you and your cousin.
Phylogenetic trees are the most common tool used by biologists to depict evolutionary relationships. Generally the root of the tree is interpreted to be the oldest and the branches are the newest. Every branching point is called a node.
So far we’ve been looking at phylogenetic trees of your hypothetical family, but now that we have a primer in cladistics under our belts, we can start to look at a dinosaur phylogenetic tree.
The way to interpret this diagram is to think of time increasing as you read up. At the bottom there are the most recent common ancestor of all crocodiles, pterosaurs, and dinosaurs: Archosaurs. Just as with all of the other terms on this diagram, everything up from any given node belongs to the group labelled at the node. This means that all dinosaurs are archosaurs (but not all archosaurs are dinosaurs).
Archosaurs evolved in the late Permian or early Triassic period, about 250 million years ago. The most familiar archosaurs from that time are probably sail-backed beasts like Ctenosauriscus koeneni.
At the next node, you see ornithodirans, a word which refers to dinosaurs and pterosaurs. The interesting part to note here is that pterosaurs (like pterodactyls and Quetzalcoatlus) aren’t dinosaurs. They are the closest relatives to dinosaurs without actually being dinosaurs.
The next node on that diagram is the one we’ve been waiting for: Dinosaurs! As you can see, dinosaurs are a monophyletic group. If you want to refer to the dinosaurs that were wiped out by an asteroid 65 million years ago, you have to make a paraphyletic group and exclude birds. You can do this by saying “non-avian dinosaurs”. Let the pedantry begin!
As the diagram shows, the dinosaur lineage splits at this point and we find one of the most important features that helps scientists classify dinosaurs. It all comes down to the hip. One group, the ornithischians, have backwards-facing pubises in line with their ischia, while saurischians have down-and-forwards facing pubises at an angle to their ischia. This will become much clearer with some labelled images:
Once you know to look for it, this difference becomes glaringly obvious whenever you look at a dinosaur skeleton. Here, have a look at a few different images of dinosaurs and see if you can tell if its ornithischian or saurischian (I often just think of these as O– and S– because even when I say them in my head I trip over the -ischi-).
You are well on your way to being a dinosaur expert!
The last node we are going to discuss in the evolution of dinosaurs is the theropods. The word itself means beast feet and it is the last taxonomic word you can use to accurately describe both T-Rex and turkey. Theropods are a terrifying group of creatures, laying claim to speedy velociraptors, vicious ceratosaurs, and of course, the King, Tyrannosaurus Rex. They evolved fairly early on (~230 million years ago) and include most carnivorous dinosaurs and their descendants.
My favourite extinct dinosaur is Ankylosaurus magniventris, an armoured tank of a creature with a club-tail that definitely meant business. On the other hand, my favourite non-extinct dinosaur is probably Meleagris gallopavo, a colourful but mean-looking dino best served with potatoes and cranberry sauce.
I’ve never been a cat person, myself. They just seem a bit too contemptuous as a species.
Cats, aside from being aloof, clawed, and kind of mean, also form a necessary part in the life cycle of a single-celled protozoan called Toxoplasma gondii. This sneaky parasite can only reproduce in feline intestines but also finds its way into the tissues of pretty much all warm-blooded mammals. Its reach seems almost limitless and extends to more than half of the world’s bears, birds, cattle, cats, domestic chickens, deer, dogs, domestic geese, goats, mice, pigs, rabbits, rats, sea otters, sheep, and humans. And those are only the populations that were studied. Ever heard the expression that glitter is the herpes of the craft world because it gets everywhere? More accurately, glitter is the T. gondii of the craft world.
I call it sneaky because T. gondii has been shown to alter the behaviour of its rodent hosts in order to make it more likely to be ingested. The physical mechanism for this is still under investigation and largely unknown but there are two interesting experiments worth noting. The first found that rodents infected with T. gondii are more active and more excited about new places, making them more likely to be noticed (and eaten) by cats. The second purports that rodent brain chemistry is altered so that the unfortunate rats finds the scent of cat pee sexually attractive. The scientific paper which explains this second theory is even titled “Fatal attraction in rats infected with Toxoplasma gondii”.
So we’re pretty confident that T. gondii can alter the behaviour of rodents, but what does it do to humans?
We’re not sure…
For those with weak immune systems or for the pregnant, a T. gondii infection can cause acute toxoplasmosis, a potentially fatal disease characterised by swelling lymph nodes, sore muscles, and flu-like symptoms. I wouldn’t worry about that too much because it’s about as lethal as the flu for those with regular immune systems.
For the rest of us, infection with this parasite is largely asymptomatic. There’s no way to tell whether you’re infected or not without a blood test. Unless you ask Czech researcher Jaroslav Flegr. He, along with a growing number of scientists, believes there is enough evidence to show that latent toxoplasmosis makes humans more thrill-seeking. According to a 2012 paper in the Journal of Experimental Biology, infected individuals are more likely to get into traffic accidents, score differently on personality tests than un-infected individuals, and infected men are taller on average with more masculine facial features.
Rodent and human brains are not so different, it turns out.
If your cat got infected and you happened to get exposed while cleaning out its litter box, chances are that you are infected. Your cat’s poo is likely changing your personality. If, like me, you don’t and have never owned a cat, that doesn’t mean you’re safe from infection. T. gondii is really good at getting into your body and making its way to the central nervous system, where it acts the puppetmaster and, expecting you to be a rodent, makes you excited about new environments. All this so that you can be eaten and it can reproduce.
Ever wish you could see in the dark? It would make life a bit easier. No more tripping over clutter on the ground or feeling walls for a switch. Humans rely quite heavily on their sight, but some animals can make do by illuminating their surroundings with sound.
Bats are just such an animal. They belong to a privileged group of organisms including toothed whales (like sperm whales, dolphins, and killer whales) and shrews that use sound to see the world. By listening for the reflections of their high-frequency clicks, bats are able to build up an accurate picture of the world around them. The clicks are often too high for humans to hear, sometimes reaching as high as 110 kHz (human hearing generally goes from 20Hz-20kHz). This amazing superpower is called echolocation but not all bats have it. Most microbats (usually small, insect-eating, with proportionally large ears) can echolocate using their throat to produce clicks, while megabats (larger, fruit-eating, with large eyes) usually can’t. Like most rules in biology, though, these distinctions aren’t universal. Some megabats have evolved echolocation by way of specialized nose structures and others are smaller than big microbats.
So now that you’ve been acquainted with the notion of echolocation and the bat family tree, let’s start talking about some neat things that bats can do with their special ability.
Since echolocation is dependent on a bat receiving and interpreting the reflections of sound, it is particularly susceptible to interference. The biggest source of interference is the bat itself. Bats produce some of the loudest sounds in nature and have some of the most sensitive ears to register the reflections that come back hundreds of times quieter. Imagine revving up a Harley Davidson and putting a traffic cone on your ear to hear someone whispering across the room. It would probably hurt if you did those things at the same time. You’d be too rattled by the revving to be able to listen to the whisper. Bats avoid this by temporarily disconnecting their ears as they shriek, then quickly reconnecting them in time to hear the echo.
One particular species of bat, the Mexican free-tailed bat (Tadarida brasiliensis), has been recently observed messing with its competitors’ signals. By emitting a special signal right when another bat is about to catch an insect, the bats make each other miss. It’s the bat equivalent of yelling “PSYCH!” when someone is about to shoot a free-throw. Unlike the obnoxious friend though, the bat version actually works. The bats’ success rate drops by about 80%. It’s such an effective strategy that two bats will even hang out near each other, jamming each others’ signals every time one swoops in for a bug, until someone gives up.
The same species of bat that jams also lives in close proximity to natural gas fields in New Mexico. Some of the rigs have compressors that emit a constant, loud noise that can interfere with echolocation calls. For the Mexican free-tailed bats, whose normal calls fall within the same frequency range as the compressors, the loud wells are avoided when possible. The bats have also begun to change their calls, making them longer and in a more restricted range of frequencies. This strategy would make the calls more easily distinguishable from the background din and marks the first time human-made noise has been shown to interfere with bat life.
We know that humans can’t hear a lot of what the bats are “saying” when they are building up a sonar picture because our ears aren’t sensitive to the right frequencies. This makes sense because, for the vast majority of humans, it really doesn’t matter what the bats are saying. It’s a whole other issue if you’re a moth about to be eaten. There’s a lot of (evolutionary) pressure to hear the bats coming in order to avoid getting eaten. Some noctuids, a rather large family of moths, have evolved bat-sensing ears that warn the insect of impending disaster. If the bat is far enough away, the moth will make a break for it, otherwise it will just start flying erratically in random directions to try and make the bat miss. The Pallas long-tongue bat (Glossophaga soricina) still manages to get a meal by using only ultra-high-frequency, low intensity calls to find moths and by going silent on approach. This stealth mode doesn’t trip the moth’s defences.
For more information on echolocation and bats, check out:
Imagine a creature that never grows up, can regenerate limbs without scars, and has a sort of slimy, alien-like cuteness. Sounds like a critter you’d like to meet, right? Ambystoma mexicanum, the axolotl, lives all over the world in aquaria but their only wild habitat is under severe threat. Chances are that neither of us will ever meet a wild one and that is a shame.
This fascinating amphibian, through a quirk of evolution, is neotenous. This means that it never really leaves the tadpole stage. Where most salamanders and frogs will leave behind external gills and develop lungs to breathe on land, the axolotl decides it is perfectly happy and stays put underwater with beautiful gill fans collecting the oxygen it needs.
Not only does this incredible creature never grow up, but it can also totally regenerate lost limbs. This makes it a valuable model organism for scientists to study in the lab. The exact mechanism behind this regeneration is still being investigated, in hopes that one day a technique for human regeneration will be discovered, but there are some interesting findings that have already come out.
The generally accepted theory was that when a limb was cut off, the axolotl would send a signal to the stump that would turn the cells at the end to pluripotent stem cells. These cells would be able to duplicate and grow into any tissue and are similar to the cells found in embryos. Recent research out of Germany, however, showed that the cells at the end of the stump don’t revert to a totally embryonic state. They are still able to grow into tissues, but only certain kinds of tissue. The part of the stump that was muscle remembers that it needs to grow muscle, whereas the part that was nerve remembers that it needs to grow nerve.
Lake Xochimilco in Mexico City is the only place in the world the axolotl can be found in the wild, making them critically endangered according to the IUCN. They used to live in another nearby lake named Chalco, until that was drained for fear of flooding. For hundreds of years the axolotl was abundant enough to be a staple in the diet of locals, but now they are nearly impossible to find. In a 2002-2003 survey where over 1800 nets were cast over the entirety of Lake Xochimilco, scientists could only find 42 of the little amphibians. The first thing to understand about axolotl decline is that calling Xochimilco a lake is kind of a stretch.
This small, restricted environment is a closed system, meaning it does not drain anywhere. It is also surrounded by farms which provide much of the food needed to feed Mexico City. Agricultural runoff from the farms and pollution from the nearby megacity accumulate, causing severe damage to the ecosystem and endangering the few axolotls that remain.
The axolotl is an incredible animal at severe risk of extinction in the wild. It is the Peter Pan of the animal kingdom, refusing to grow up and hiding from hooks. It’s most amazing power, regeneration, is still being studied and one day may prove the key to human limb regrowth. For all this and more, the axolotl is most definitely an interesting thing.
For more information on this beautiful creature, follow the links below
Weird Creatures with Nick Baker did a great documentary on axolotls which is available on Youtube.
The IUCN has put the axolotl on its red list of endangered animals