Envisionary Universe

April 2, 2012

Most animals share a set of derived traits not found in other groups of organisms. These traits make animals unique out of every other organism on the planet.  One such trait is specialization.  In specialization, cells start out as un undetermined or undifferentiated lump and “grow up” into different types of cells, like skin cells, bone cells, blood cells and nerve cells.   However, some animals like sponges lack specialized cells.  Advanced multicellular animals have specialized tissues that perform unique functions.   Jellyfish, for example (though they are not in the strictest sense “fish”) have specialized stinging cells called cnidocytes that release a deadly poison when other organisms get too close.   The process of specialization requires a highly-specific set of genes to regulate an animal’s growth and development.  Scientists on Earth have discovered that all animals on Earth share this same set of genes, from organisms as simple as tapeworms to incredibly large and complicated organisms like the blue whale.

This development of animals is controlled by the so-called Hox genes.  These Hox genes are responsible for assigning a location and identity to our cells in order to build body parts.  Hox genes contain within them a DNA sequence known as the homeobox. The homeobox is a DNA sequence found in Hox genes and other genes that code for transcription factors, which is are proteins that bind to specific DNA sequences in order to activate the transcription of DNA into mRNA.  The sequence of amino acids encoded by the homeobox is called the homeodomain.  Our so-called Hox genes are a shared set of programs that determine how all complex animals develop. These genes are so important to the development of all complex animals that just about any mutation in this set of instructions is all but assured to result in the death of the organism.  This means that there are only a few highly specific ways that these genes could be rearranged without killing the organisms during development.  One example of researchers messing with Hox genes resulted with antennapedia, a fruit fly with legs on its head where its antennas ought to be.  It provides evidence that evolution is a ongoing process and that natural selection can explain the evolution of all life on Earth.  If there is a mutation in the hox genes, it would likely cause a deleterious effect (like building a human with feet where their ears ought to be), and that is the reason why organisms seem to be intelligently designed when in reality they are not.  Anything less-than-perfect design that comes by natural selection would get weeded out quickly, leaving only the most exquisitely-designed forms still around. Because of this, virtually every animal on Earth shares the same gene sequence responsible for development. Such genes are astoundingly preserved, maintaining the exact same sequence universally across all deuterostomes over half a billion years of evolution.

This is the single greatest piece of evidence that supports the idea that all animal life on Earth is related through evolution by natural selection.  Only random mutation can explain why our Hox genes work just like the set found in every other animal on Earth. And only hox genes can explain why humans develop gills and a tail as a pharyngula just as fish do.  During our development, however, the hox genes eventually eliminate the gills and tail.  Why would an intelligent designer start to create developing humans as though we were a developing fish, only to remove those fish characteristics anyway later on in development?  The only reasonable explanation is that the genes that are responsible for creating all vertebrates during development were preserved  by natural selection and that these genes are so fundamental to the success of an individual that we’ve relied on the same set of Hox genes, essentially unchanged since the first vertebrates flopped around in the sea.

The Hox genes that all animal life share on Earth reminds me of something poignant that I learned in biology class as a freshman in college.  We are connected in an unbroken lineage to the very earliest lifeforms on Earth.  All life shares a last universal common ancestor and it is by the virtue of our ancestors’ integrity that we all can be alive today.  And I mean not just our human ancestors, either, but our primate ancestors, our mammalian ancestors, and even our chordate ancestors from 350 million years ago.  I marvel sometimes at this fact that on a planet that is over four billion years old, I am alive for at best 100 years, roughly 1-forty-millionth of the history of the planet.  And that the human race being around for at most two million years has only been around one-two-thousandth of the history of the planet Earth.  Any yet my ancestors carried on in an unbroken chain of creation for over four billion years before I came along.  It makes me feel a sense of awe in a way that no religion ever has been able to instill upon me.  I am part of a much larger and much older biological community almost as old as the planet itself.

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Envisioned Universe

March 5, 2012

Animals that breathe oxygen use a process called oxidative respiration to get their energy from the food they eat and respire or breathe out water vapor and carbon dioxide.  Oxidative respiration is a hallmark for all complex animal life, but there are many evolutionary steps between the advent of the first life form that breathes oxygen, which was singe-celled and the first true animal life, which might have millions or even trillions of cells.  Before the first animals could appear on Earth, a highly organized and complex system responsible for governing an organism’s growth and development was needed to make sure that all of an animal’s cells were arranged in the proper place.  Imagine a fruit fly with feet on its head, and this should give one some perspective about the importance of the genes that regulate growth and development in animals.  The growth and development of organisms is controlled wholly by a specific set of genes and how these genes are activated is a process called gene expression.  Gene expression is of paramount important for eukaryotic organisms because of the sheer complexity involved in the development process.  Single-celled prokaryotic organisms don’t need the same tightly-regulated mechanisms that are characteristic of eukaryotes, but when trillions of cells need to be organized in a coherent way, these genes must be able to step up and complete the task.

All animals on Earth share certain key characteristics, like the ability to use oxygen in respiration mentioned earlier.  To start, because all animals are eukaryotic, the DNA is contained within the nucleus of cells so the process of replicating DNA, called transcription, occurs within the nucleus.  In addition, the process of replicating proteins, called translation, occurs mostly in ribosomes, which are organelles found in the cytoplasm.  Compared to prokaryotes where the process of translation and transcription occur in the cytoplasm, eukaryotes undergo translation and transcription separately.  This is important for eukaryotes because by segregating these two processes, both translation and transcription become more efficient.  This is especially important for eukaryotic organisms because the genome of eukaryotes can be 10 to 100 times larger than the prokaryotic genome.  The DNA of eukaryotic cells is loaded with transposons.  Transposons are repetitive sequences of genetic material that are able to move a transposase gene around within the genome.  Transposase allows the DNA to loop around itself and cut off a piece of the genome and relocate itself somewhere else within that strand of DNA.  Wherever it lands, the excised transposon disrupts the function of the gene that was occupying that stretch of the DNA.  So transposons help to regulate when and where and how which of our genes function at any given time.

Our Areiosan life uses all of the same steps for genomic expression that Earth life does, but different proteins are responsible for regulating genomic expression because our hypothetical life would have evolved on a different world and would have been subject to a completely different environment.  A typical eukaryotic protein-coding gene is surrounded on both sides by what are called a promoter and terminator sequence.  A promoter sequence is located upstream of each gene and serves as the sign that identifies that particular gene to the enzymes that will latch onto to it.  The terminator sequence appears at the very end of the gene and marks the point on the DNA were an enzyme should stop coding and signifies where a certain gene ends. DNA is made up of two different kinds of sequences; sequences that code for a certain gene and sequences and don’t code for a certain gene.   Noncoding sequences within DNA called introns.  They appear on the DNA in between segments responsible for coding proteins.  The sequences of genes that are responsible for coding proteins are called exons.

The similarities that pop up between my Areiosan gene expression and Earth gene expression are twofold. One, I don’t have an advanced degree in molecular biology, biochemistry, or genetics, so the thought of making up a brand new system of gene expression is a daunting task, and I thought it would be best to go with what I knew, which was how this works on Earth. And second, I like the idea of unifying life. Even in an imaginary world that I made up, it’s comforting to envision similarities, especially with the creatures that I designed to be so alien to begin with. One thought that has been hanging around my subconscious for a while came from a physicist Lawrence Krauss:

“Every atom in your body came from a star that exploded. And, the atoms in your left hand probably came from a different star than your right hand. It really is the most poetic thing I know about physics: You are all stardust. You couldn’t be here if stars hadn’t exploded, because the elements — the carbon, nitrogen, oxygen, iron, all the things that matter for evolution and for life — weren’t created at the beginning of time. They were created in the nuclear furnaces of stars, and the only way for them to get into your body is if those stars were kind enough to explode…The stars died so that you could be here today.”

I’m comforted by the thought that if we were to ever meet intelligent aliens out there in the universe, the first thing that I would want to convey to these aliens would be our bodies (if these aliens had bodies) could very well be comprised from atoms expelled from the same star over four billion years ago. I would express awe that on the most fundamental level, our atoms are a part of the same cosmos, inanimate and incapable of any sentient thought, but that through evolution, these atoms were arranged in such a way that in this form they had been incorporated into beings not only endowed with reason, compassion, and empathy, but that for the first time in the history of the universe, the cosmos found a way to meditate onto itself and contemplate its own existence.   

Enveloping Unvierse

October 4, 2011

Carl Sagan wrote that if the Earth were the size of a globe our atmosphere at that scale would be about as thin as a single sheet of paper. Yet the air we breathe is so fundamental to life that even the tiniest changes in the composition of our air could cause cascading climate change on a global scale. While carbon dioxide is present in only trace amounts, scientific consensus indicates at a change from 292 parts per million today to 380 parts per million by the next century could spell disaster for human civilization through rising sea levels, changes in established wind and ocean currents, melting ice caps and desertification associated with the overall average trend of global warming. And so atmospheric regulation is essential to the continuing survival of all life; this biogeochemical process is mainly controlled by single-celled organisms.

Our atmosphere on Earth is mostly made of nitrogen, but it’s also about 20% oxygen. Oxygen is a corrosive gas that is dangerous under high concentrations because of how reactive it is with other chemicals. But this concentration of oxygen has been by no means stable over the last four-and-a-half billion years; oxygen levels in our atmosphere have been virtually non-existent until about half a billion years ago, when the so-called Great Oxidiation Event (GOE) took place. The GOE released huge plume of oxygen into the sky over the course of a few million years, radically altering the compostition of life on Earth and giving rise to the ancestors of the eukaryotes. Early life on Earth was anaerobic, meaning that it could function without oxygen. While aerobic animal life takes in oxygen and burns it during metabolism to create carbon dioxide and energy as waste, anaerobic life uses a myriad of metabolic pathways to produce energy, reducing molten iron, acetate, sulfate, hydrogen gas, or other inorganic molecules to produce their energy.

It wasn’t until the rise of cyanobacteria that any appreciable oxygen could be produced. These cyanobacteria are blue-green algae that performed photosynthesis by taking in sunlight, carbon dioxide and water to grow. One byproduct of this reaction was oxygen gas. The early Earth environment was highly reducing, meaning that it would readily absorb any oxygen and quickly oxidize something in the environment. Substrate like iron (III) dissolved in the water would readily oxidize and become iron (II) oxide, which was insoluble in water and would sink to the bottom of primordial seas. We find these banded iron deposits around the world and they are a ready source of the iron we use in modern manufacturing. The presence of banded iron formations would indicate the presence of oxygen being produced by cyanobacteria at the time, so we can reasonable assume that aerobic photosynthesis was going on around 2.1 billion years ago. In fact, cyanobacteria were so pervasive on Earth that their combined exhalations of oxygen radically altered the composition of air.

Areios’s atmosphere is mostly nitrogen, like the Earth’s atmosphere, but the outgassing of volcanoes and the rapid destruction and creation of crust means that oxygen is less abundant in the atmosphere, which has profound implications for the development of animal life. Combine this with the later start for photosynthesis, and this means that aerobic life doesn’t appear until about 12 billion years into Areios’ existence, yet this kind of more complex life persists for over 3 billion years before the surface temperature gets too hot for photosynthesis to maintain itself permanently. Fifteen billion years after creation, the planet’s atmosphere undergoes another profound change. As Hemera gets brighter, the atmosphere would start to slump off and this would alleviate some of the heat that gets trapped in the Areiosan atmosphere. Eventually the atmosphere becomes so thin with carbon dioxide that there isn’t enough CO2 to fuel photosynthesis and plants would die off en-masse. This drop in carbon dioxide would eliminate the greenhouse effect on Areios, and in turn this massive die-off would incite the next ratcheting up of carbon dioxide, which would in turn lead to a positive temperature feedback loop. Oceans would boil over until the last life left on the planet would paradoxically resemble the earliest life; a halophilic thermophile. Eventually, even this hardy creature wouldn’t be able to survive Areios would once again be a world sterile of all life. Temperature would still rise, though, and would boil the carbon dioxide out of the carbonate rocks in the crust, causing a runaway greenhouse effect like the one that we see on Venus. Sadly, this is the fate of all terrestrial planets as their parent star grows old; the same fate awaits our own planet earth in the coming eons.

Long after the Earth's atmosphere boils away, our Sun will evolve into a Red giant star.

Ensconcing Universe

July 16, 2011

Where do Eukaryotes come from? The distinguishing feature of eukaryotes is the stately nucleus that adorns every eukaryotic cell. The best theory to explain how nuclei came to be is called the endosymbiotic theory. The origin of the earliest eukaryotic cells was one of the leading mysteries in biologist, but the researcher Lynn Margulis offered a compelling solution to this enigma with her endosymbiosis theory. The theory can adequately explain many mysteries about the origin of the Eukaryotic domain. While much the process remains elusive, scientists believe they have a fairly accurate conception of how the first endosymbiosis occurred. Some archean bacteria have a rigid cell wall that keeps its shape, but at some point, this cell wall disappears in a certain archean lineage. Through either a faulty cell wall gene or a complete excision of the genes that controls cell wall production, a cell’s insides were no longer boxed in by a cell wall and the only thing keeping the contents of our cell from leaking into the outside world is a tenuous cell membrane. This underlying cell membrane is fluid and allows cells’ edges to fold in on themselves, creating bubbles called vacuoles. Rather than sucking in dissolved chemicals through the cell wall, this archean cell can engulf cell fragments and even whole smaller cells by folding itself over the cell to be eaten, and then pinching itself off to form a vacuole around it. This process is called phagocytosis and it engulfs macromolecules in vacuoles.

 

An archaean cell like the one described above could flop around without a cell wall and fold over its food to eat. One of these archaean cells swallowed a living a bacterium that managed to survive in the cytoplasm of the cell that ate it. This bacterium somehow was kept from being digested by a lysosome within the host cell and lived long enough to replicate with the host cell time and time again. Eventually, this bacteria found a nice little home within the archaean cell, living sheltered from the dramatic changes in the environment that the archaean has to face. Scientists tend to think that the unlucky bacterium that got engulfed was a rickettsia bacteria; this is important because rickettsia can detoxify peroxides into water. Peroxide is a free radical inside cells, hacking apart the cellular machinery and the rickettsia is useful for the archaean cell because it takes a poisonous chemical and turns it into water. This process repeats itself on Areios, creating the first eukaryotic cells by endosymbiosis.

 

Because the engulfed cell relied on the host for maintaining homeostasis, mutations or deletions in its genome for certain biological pathways could get destroyed without impacting the cell’s ability to reproduce. For instance, lodged inside another cell meant that genes responsible for locomotion could erode without hurting the viability of the engulfed bacteria. Eventually, the engulfed cell lost much of its cellular mechanics and diminished in size until it was no smaller than an organelle. Yet unlike other organelles, like mitochondria and chloroplasts, which were created by this process of endosymbiosis differ in two unique ways. First of all, they house DNA inside of a cell yet outside of the nucleus where DNA is ordinarily kept. And two, they have a membrane that shuts them off from the rest of the cell that is wholly different from the cell membrane that separates the cell from the outside world.

 

Endosymbiosis has occurred several times in the history of eukaryotic cells as seen in euglenas and other protists that have more than one membrane surrounding their organelles. This is evidence that a proto-euglena swallowed an alga, and a secondary symbiosis had occurred in that family. This would give the euglena’s mitochondria two membranes surrounding it; the original membrane that surrounded the mitochondria of the alga, and the second cell membrane came from the alga itself that went through the same process described above, where its genome and machinery could get whittled down until just the cell membrane remained.

The earliest eukaryotes could have arisen from a symbiotic relationship with an engulfed aerobic heterotrophic prokaryote

Elevating Universe

July 11, 2011

Check out this link to Astrobiology Magazine about a three-day excursion on the Atacama desert in Chile, considered to be the driest desert on Earth. This continuing 3-part series called Islands of Life highlights Field Research Editor Henry Bortman’s trip with researchers studying Mars and its potential habitability for life. Because the Atacama Desert’s climate resembles that of early Mars, studying life in this barren region may give scientists clues about what kind of life could have survived Mars’ early environment.

Eavesdropping Universe

June 30, 2011

The Search for Extraterrestrial Intelligence (SETI) is on the brink of discovering habitable worlds in our own galaxy. With probes like the Kepler telescope already searching the stars in our galaxy and the Terrestrial Planet Finder probe soon to be launched, we have begun the search for worlds that resemble for own. While the thought of ever visiting these alien planets is still a fantasy, science fiction writers are already speculating on what we might find on these planets. Check out these links to discover more about the search for habitable worlds, the science beyond science fiction, and one curious collaboration between science and music that is truly out of this world.

 

Esoteric Universe

June 22, 2011

What did the first life on Earth look like? Research into the oldest lineages of single-celled life suggest that the first life form on Earth would likely have been an extremophile that survived in the hydrothermal vents (233) at the bottom of the ocean floor; this organisms would have lived off of the gases spewing from the vents and could have survived in near-boiling water. This cell would have been an archean life form; its cell wall would have been built out of peptidoglycan or a similar chemical meant to survive such daunting pressures and the acidity of the dissolved hydrothermal vent gases. Acidophilic cell membranes like this would be designed to pump hydrogen ions out of the cell and maintain a more neutral pH than the environment of the vents. Only an extremophile could survive the early environments on Earth and Areios.

The metabolisms of all animals are very similar and involve the same metabolic pathway; oxidative respiration. But archean life has such an eclectic set of anaerobic metabolic pathways; some organisms breathe hydrogen sulfide gas that bubbles out of the hydrothermal vents at the bottom of the ocean. These organisms are cut off from the Sun and form the base of an ecosystem that is wholly independent of photosynthesis. This world relies on chemosynthesis; instead of a utilizing a photon to start the electron transport chain, these creatures harvest electrons from hydrogen sulfide to kick start the process. Organisms need not use hydrogen sulfide, though. Some creatures have been known to use molten iron, arsenate, methane, or hydrogen gas.

Areiosan life too relies on sulfur to power the electron transport chain. One flaw of this system is that it doesn’t release as much energy as oxidative respiration. Animals simply can’t function off of anaerobic respiration; only in the rarest cases can anything bigger than the simplest multicellular organisms. Yet, there are complex organisms on Earth that have found a way survive off of anerobic respiration. Tubeworms living near hydrothermal vents have chemosynthetic organisms lining their gut to thank for their providing food. These bacteria use the hydrogen sulfide from the vents to produce ATP that they feed to the tubeworms. This symbiotic relationship is exceptional on Earth, but on Areios, it all but proves to be the rule for any macroscopic life.

Giant tubeworms can thrive in these environments, stretching up to 3 meters long. These organisms are extreme even in their ability to develop and grow so rapidly. In two years, some specimens can grow almost 10 feet under ideal conditions. Few creatures on Areios are ever as big as that because rather than devoting all of that energy into growth, Areiosan life forms devote the energy from their internal bacteria into mobility and procreation, so they are on the whole much smaller than life on Earth. Not only is the climate on Areios across-the-board colder than on Earth, owing to the higher levels of sulfur dioxide, but gravity on Areios is more intense and this keeps any organisms from growing too tall because the pull of gravity would limit anything from growing too tall. Anything but the sturdiest creatures would buckle under the weight of the atmosphere. For now, life on Areios is nothing but pond scum and singular bacteria, but with the advent of oxygen, organisms can evolve into the complex forms we recognize as animals like the ones found on Earth.

Yet, the environment on Areios keeps the organisms we could identify as animals from growing to the size of some organisms we find on Earth. There are no blue whales or sequoias on Areios; the largest animal to trammel its surface is perhaps the size of a horse. Low oxygen and high sulfur levels limit the size an organisms can reach and because oxygen is so scarce, endothermic organisms like mammals and birds with such a high metabolism are unlikely to be able to survive on Areios because of how much energy they would require to maintain their high-maintenance, warm-blooded metabolisms. Yet the largest organisms on Areios are more akin to fungi or coral reefs, many-headed colonial organisms that spread out over huge geographic expanses In fact, because of this harsh environment animals don’t arrive on the scene until much later in the evolutionary history of Areios. It takes almost 10 billion years for anything complex more complex than our primordial extremophile to arise on Areios, and by then, these novel animals are only ephemeral; as soon as they arrive, they are wiped out 4 billion years later.

 

Deep under the ocean in hydrothermal vents, there is an entire ecosystem built off of chemosynthetic bacteria that feed on sulfides. This could indicate life need not rely on the light from a star, but could thrive in other extraterrestrial environments.

 

Extant Universe

June 18, 2011

Paul Gilster of Centauri Dreams reports on the 100 Year Starship Study, an initiaitve launched by The Defense Advanced Research Projects Agency (DARPA) and NASA Ames Research Center (serving as execution agent), to discuss “the practical and fantastic issues man needs to address to achieve interstellar flight one hundred years from now“. The coordinating agencies will assemble a panel to discuss the implications of this endeavor at a symposium which will lay the groundwork for an organization that will one day create a  “self-sustaining organization that will tackle all the issues and challenges inherent in long duration interstellar space flight.”

Enduring Universe

June 6, 2011

We encountered this concept of a shadow biosphere that suggests some organisms on Earth may be relics of a previous genesis event. Right now, this is just speculation on the part of some astrobiologists who haven’t been able to find prove of this idea yet. And if life truly did arise on Earth more than once, where is it now? What does it look like and how does it compare to life as we know it now? How would we look for evidence that this actually happened? The most straightforward way to find answers would be to test the genome of bacteria from as many different locations as possible, and the more exotic, the better. (After all, it’s unlikely that something as big as a giraffe for example could have spawned from a different origin event, but something as small and elusive as a bacteria could go unnoticed unless we found it in the backdrop and sequenced its genome.) We would want to look for places that would be cut off from the rest of the biosphere; like miles underground. Scientists found bacteria colonies that consumed hydrogen bubbling from the crust miles below the surface in an abandoned South African mine. DNA analysis showed that this germ was related to all other life on Earth, but what does that mean? How would we know if life were alien to the planet?

If life as we know it didn’t use DNA or RNA, but relied on a different molecule for storing genetic information, then we might see something wildly different from life as we know it. Peptide nucleic acid (PNA) is composed of repeating N-(2-aminoethyl)-glycine units linked by peptide bonds; the structure is more stable under high temperatures and low pH so it’s possible that it could have been incorporated into early cells and that DNA only came later because DNA is more efficient at replication. Another analogue, threose nucleic acid (TNA) is a polymer used by biochemists in studies on DNA; this analogue can function like DNA or RNA, but TNA is simpler chemically, so it could have been a precursor to RNA.

While the evidence to support a TNA or PNA-dominated biosphere isn’t readily accepted by most molecular biologists, the RNA world hypothesis has enjoyed some support by researchers over the last 30 years. Because RNA can act as an enzyme protein and an information-storing nucleic acid, this versatile chemical is thought to have preceded the advent of DNA, leading some to suspect that early life ran off of RNA and not DNA. It wasn’t until later when a genetic accident could have spawned DNA, which would have dominated the life at the time because it could more efficiently copy itself.

Areiosan life runs off of PNA, but it has a triple helix structure. This idea isn’t new to biology; Linus Pauling suggested DNA might have a triple helix structure back in the 1950’s, but the discovery of DNA’s double helix structure by Watson and Crick completely shattered that idea. Still, when molecular biologists use PNA, it latches itself onto the double helix structure and forms a totally new triple helix that stabilizes DNA under higher temperatures and lower pH. The latter is imperative for Areiosan life because of the prevalence of sulfur in the environment. Sulfur dioxide and trioxide readily form sulfuric and sulfurous acid in contact with water, so increased acid rain has lowered the pH of Areiosan bodies of water. So while the acidified oceans would warp and denature Terroan DNA, Areiosan PNA doesn’t get bent out of shape by higher acidity.

DNA undergoes mutations regularly because the process of transcribing new DNA during cell replication is imperfect. DNA can be miscopied during transcription, but DNA polymerases that add base pairs to DNA during replication can correct some of these errors during a stage called elongation in eukaryotic cells. Because this PNA’s base pairs are harder to pry apart under moderate pH, the proofreading process in Areiosan cells is shorter than in Terroan cells. Because of this, a certain type of error called a mismatch error abounds in Areiosan cells because once replication is complete; there is no proofreading mechanism to follow like with our biology. Despite radically different mechanisms to mitigate mutations to the nucleic acid, both Earth life and Areiosan life experience identical rates of mutation. Mechanisms for repairing DNA are not perfect and these imperfections that allow mutations to occur spur the creation of novel genetic material. If there were no mutations, there would be no evolution and each individual would be a carbon copy of the parent; this would be disastrous because if every individual were exactly vulnerable to the same stresses, then a single event would wipe out an entire population. Mutation causes a varying ability for survival in individuals of a population, and this diversity can provide resilience to a population. Some of those mutations will prove to be deleterious to the individual, but the heritable mutations that don’t manage to wipe the individual tend to persist or even propagate within the population. These errors in DNA replication are the basis for new genetic traits, but if this process is too imprecise, it would kill off too many individuals and prevent that material from ever being propagated. The rate of mutation is therefore fine-tuned to allow “a balance between the evolution of species and the survival and reproductive success of individual organisms.”

This diagram shows the configuration a stable triple helix used on Earth in drugs for cancer treatment.

Evaporating Universe

June 2, 2011

A new study reveals bacterial genes that influence sulfur gas flux from seawater; the research could have implications for understanding the role of ocean bacteria in cloud formation. Check out this press release posted on Astrobiology Magazine.

 

A simplified graphic shows the process by which bacterioplankton send sulfur found in decaying algae into the food web or into the atmosphere, where it leads to water droplet formation—the basis of clouds that cool the Earth. Credit: Chris Reisch, University of Georgia