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Evolution can appear to be a very complex process. How biodiversity developed over millions of years, producing thousands of various animal and plant species, is continually being studied and surprises seem to crop up with every new study. Whether piecing together the many branches and various dead ends that ultimately resulted in homo sapiens or deciphering the genetic code that determines who has a tail or who has wings, scientists are, piece by piece, assembling the puzzle that makes up nature's grand experiment in life on Earth.
And yet, from time to time, they discover within the puzzle a point of commonality - a puzzle piece that is being used over and over again - and the end result in diversity becomes simply a matter of timing. A recent study, published in the Proceedings of the National Academy of Sciences, highlights a genetic process that determines gill structures in elephant fish and sharks and its similarities with the development of limbs in lizards and mammals.
The elephant fish is a distant relative to sharks and rays, sharing the same type of cartilage-based skeletal system and also an outgrowth called a branchial ray - an appendage that extends from the skeleton and forms a supporting structure for the gills. Somewhere in the 
development process, the elephant develops one set of branchial ray while sharks develop several. To determine how or when this takes place requires studying things at the embryonic level. And for the scientists involved in the study, from Cambridge and the University of Chicago, this was a challenge as elephant fish embryos are difficult to find. Elephant fish lay their eggs in cold, muddy ocean bottoms, so the researchers spent months diving and searching possible breeding sites in Australia and New Zealand, gathering the needed embryos.
The researchers traced the impact of a genetic factor called Shh - the sonic hedgehog gene. It is common to both the elephant fish and sharks but when it expresses itself in the early developmental process determines whether there's one branchial ray set or more. This same process appears in the development of lizards and mammals, helping to determine outgrowths like limbs and number of toes for different species.
"The research highlights how evolution is extremely efficient, taking advantage of preexisting mechanisms, rather than inventing new ones," said Dr. Andrew Gillis of Cambridge University. "By simply tinkering with the timing of when or where a gene is expressed in an embryo, you can get very different anatomical outcomes in adults."
"It's basically showing that the limb story is part of a much more general narrative, which is the story of outgrowths," said Dr. Neil Shubin, University of Chicago. "There's a common development toolkit for all the outgrowths that we know in the body; they're all versions of one another in a developmental sense."While analyzing all of the minute components found within the evolutionary process might seem a little esoteric or obscure to some, one of the advantages in understanding species development is to then be able to consider how or what might change that process. What environmental factors might come into play to alter or disrupt embryonic development, producing an evolutionary course correction or a tragic mutation? How easily can an evolutionary process, millions of years in the making, be altered by pollution, climate change, or other shifts in the norm?
As we study and learn more about both the complexity and the commonality or simplicity of evolutionary development, we can begin to see nature's wondrous puzzle of life and how the pieces can possibly be rearranged for better or for worse.
Read about the study in EurekAlert!
Read more in a Cambridge University press release.
Read the entire report published in Proceedings of the National Academy of Sciences.
In the complex web of evolution, one of the pivotal moments occurred with the transition from aquatic animals to land animals - an event marked by the change from fins to limbs. While fossils have shown us evidence of this transition, the actually biological processes, what accomplished this change, has not been clear.
In a report recently published in Nature, a research team from the University of Ottawa conducted experiments that could shed some light on evolutionary change. Their studies identified a group of genes responsible for the supportive fibers found in fish fins, not found in tetrapods (land animals). These genes, known as actinodins, were found in both the researchers' primary laboratory specimen, the zebrafish, and in the elephant shark - an example of an ancient fish that has changed very little from its millions year old ancestors.
By chemically suppressing the actinodin genes in zebrafish embryos or in adults that were regenerating new fins, the resulting fins lacked the supporting fibers. What could not be tested is the causal event that might have triggered the gene change millions of years ago or whether the gene loss occurred as the instigator of change or as a reaction to some other evolutionary biological process.
"It's a very nice example of how changes in one or two genes can be responsible for a huge evolutionary transition," says Axel Meyer, a evolutionary biologist at the University of Konstanz. "We tend to think that new genes bring new functions, but this study shows that the presence of genes constrains or directs development in certain directions. Gene loss is actually a creative force in evolution."
Evolution is an incredibly complex process that not only provides historical insight but has the potential for unlocking secrets into the processes that impact species today in their ability to alter or adapt to changing circumstances. While some people do not subscribe to theories of evolution for religious reasons, I find that, if there is a higher power, there is no clearer evidence than in the intricacies of evolution, from single-celled organisms eons ago to the diversity of life that graces this planet today - a diversity that is being threatened by one of its most successful species.
Read more about the study in Scientific American.
When discussing conservation, the environment, or any number of global issues, there lurks in the background the 800-lb. gorilla that no one wants to talk about: human population. Not just populations in 3rd world countries, but global numbers and that includes industrialized countries as well.
If we look at this matter-of-factly, nature has over thousands of years developed methods of equilibrium, checks and balances as it were, all designed to maintain a healthy ecosystem. Whether through predation, disease, or life cycle, all plants and animals are given a chance to flourish within the boundaries of that system or face possible extinction. And humans are part of that equation. However, because of our intelligence (some cynics would say our self-importance) we have exceeded the boundaries of that natural system and are now facing many unintended consequences.
It's a touchy subject to be sure. Who wants to turn to a young child or a close family relative stricken with serious disease and say, "Sorry, it's nature's way." And who wants to consider an Orwellian future where governments control reproduction - regulations like China's one-child policy run amok like some futuristic sci-fi movie. But as long as populations increase, as long as life expectancies are increased, and mortality rates are lowered, then we have a responsibility to consider the consequences in terms of the demands we are putting on the planet as a whole.
There was a time when our ability to feed, clothe and house a growing population was accomplished through our intelligence and our ingenuity. But we are fast approaching the point where we are exceeding what the planet can provide us with in terms of food, resources, and clean air. We must act decisively to control the problems that we have brought upon ourselves and also find the compassionate means to manage a world population of 6.76 billion that has been predicted to increase by another 2+ billion in less than fifty years.
Or we can wait for nature to take care of it . . . coldly but effectively.
(Read press release from Center of Biological Diversity.)
For those of you who don't read National Geographic, here's an interesting "fun fact" from the latest March issue. . . You think the slimy villain from the Alien movies is the only creature with a second set of jaws? Well, how about the Moray Eel?
Many divers are familiar with the moray's threatening display of sharp teeth - a pose that comes about from the eel's breathing, as it doesn't have large flapping gill structures like bony fishes - and that these rear-facing teeth are designed to hold fast to its prey. But did you know that it has a second set of jaws that spring forward and assist in pulling the prey down its esophagus? This all takes place deep in the eel's throat and though it seems like something right out of a sci-fi thriller, it's actually a very efficient method of food transport for an animal that doesn't have the ability to gulp food down - like the vacuum motion you see with many other fish.
National Geographic reported that researchers from the University of California at Davis have 
studied this ability using x-ray and high-speed video (see photo) and it is apparently the first known mechanism of its kind in a vertebrate. Snakes get close, with hinged jaws that can slowly ratchet their prey down the gullet, and it's an example of evolutionary convergence - the development of a similar solution between animals facing the same problem.
As a volunteer diver at the Aquarium of the Pacific, me and my fellow team mates would feed the aquarium's eels and watch how they would grab a large sardine or squid perpendicular, turn it towards their throat and then down it would go without any help from the front teeth. A second set of jaws . . . who knew? Well, obviously somebody in Hollywood did!
Article also on online National Geographic.
Evolution can appear to be a very complex process. How biodiversity developed over millions of years, producing thousands of various animal and plant species, is continually being studied and surprises seem to crop up with every new study. Whether piecing together the many branches and various dead ends that ultimately resulted in homo sapiens or deciphering the genetic code that determines who has a tail or who has wings, scientists are, piece by piece, assembling the puzzle that makes up nature's grand experiment in life on Earth.
development process, the elephant develops one set of branchial ray while sharks develop several. To determine how or when this takes place requires studying things at the embryonic level. And for the scientists involved in the study, from Cambridge and the University of Chicago, this was a challenge as elephant fish embryos are difficult to find. Elephant fish lay their eggs in cold, muddy ocean bottoms, so the researchers spent months diving and searching possible breeding sites in Australia and New Zealand, gathering the needed embryos.
