SCI-ART LAB
Science Simplified!
JAI VIGNAN
All about Science - to remove misconceptions and encourage scientific temper
Communicating science to the common people
'To make them see the world differently through the beautiful lense of science'
Ah! Another evolution episode before your own eyes!
Earlier I wrote about convergent evolution that took very little time(1). Now we have another story of rapid one to show the deniers!
Deniers? ! Yes! Watch this video on how creationists confront the scientists asking them to show evidence of evolution over and over again :
The times have changed. And we are getting more and more evidence of evolution.
This discussion is added because scientists, science writers and communicators can confront creationists with evidence now.
Creationists don't accept DNA markers' proof because they cannot see it with their unaided eyes! This is my second discussion on such evidences.
Darwin would have loved to hear this!
Evolution is normally described as the consequence of freak mutations winding up helping a species adapt and change.
Florida lizards evolve rapidly, within 15 years and 20 generations!
Evolution is often thought of as being such a slow process that it can’t be observed. That’s not true, but to happen quickly, there usually has to be some sort of strong pressure on a population to drive any sort of fast evolution.
Scientists working on islands in Florida have documented the rapid evolution of a native lizard species — in as little as 15 years — as a result of pressure from an invading lizard species, introduced from Cuba.
After contact with the invasive species, the native lizards began perching higher in trees, and, generation after generation, their feet evolved to become better at gripping the thinner, smoother branches found higher up.
The change occurred at an astonishing pace: Within a few months, native lizards had begun shifting to higher perches, and over the course of 15 years and 20 generations, their toe pads had become larger, with more sticky scales on their feet.
The native lizards studied, known as Carolina anoles or green anoles, are common in the southeastern U.S. The invasive species, Cuban anoles or brown anoles, are native to Cuba and the Bahamas. Brown anoles first appeared in South Florida in the 1950s, possibly as stowaways in agricultural shipments from Cuba, and have since spread across the southeastern U.S. and have even jumped to Hawaii.
This latest study is one of only a few well-documented examples of what evolutionary biologists call "character displacement," in which similar species competing with each other evolve differences to take advantage of different ecological niches. A classic example comes from the finches studied by Charles Darwin. Two species of finch in the Galápagos Islands diverged in beak shape as they adapted to different food sources.
The researchers speculate that the competition between brown and green anoles for the same food and space may be driving the adaptations of the green anoles. Stuart also noted that the adults of both species are known to eat the hatchlings of the other species.
So it may be that if you're a hatchling, you need to move up into the trees quickly or you'll get eaten. Maybe if you have bigger toe pads, you'll do that better than if you don't.
There lies the stress and pressure to evolve as fast as you can! And it is happening!
Sources:
http://www.eurekalert.org/pub_releases/2014-10/uota-fle102214.php
https://www.sciencenews.org/blog/wild-things/invasion-drives-quick-...
References:
1. http://kkartlab.in/group/some-science/forum/topics/macro-evolution-...
Questions people asked about Evolution and replies by scientists:
Q: Why have basic life forms not evolved more?
Reply by scientists: 1. All life forms are continually evolving in response to the pressure of Natural selection . A very complex animal that evolved from a very basic life-form is, in fact, occupying the exact space as you are right now!
The reason there are still bacteria, and they never became people - is three-fold:
1. Evolution is parsimonious. It only goes as far as it has to. We don't develop super brains because we can function quite well with the brains we have. Bacteria don't change into plants because, actually, archaea (which includes bacteria) is the most successful life group on the planet - in number of species, in number of individuals and in total mass.
2. Evolution is driven by a change in the environment. If the environment doesn't change, genetic changes almost never confer advantages, so no "evolution" occurs. But if some members of a fish species mutate to be able to keep their gills wet out of water, and the environment gets drier, so that their lakes dry up, those members will survive to crawl to other lakes, continue to live and reproduce - and we have amphibians. That's called selection pressure.
3. If there's no genetic change, and that's totally random - it can be a copying error, a doubling in copying, a Hox gene turning on sooner or later, many, many things - there's nothing for selection pressure to act on - there are no different forms from which to select. (We have larger brains most likely because we went from a strictly tough vegetarian diet, which requird a fused skull almost from birth, to meat, then cooking, which ddn't require such large jaw muscles, a rigid skull [our skulls keep enlarging until about the age of 21] and someone being born with a Hox gene that did't turn on at borth, so his/her skull kept growing for a few years. Roughly - there's a lot more to it than that.)
HIV has no reason to change - its hosts (us) spread it around very nicely and it reproduces like crazy just the way it is. If it mutates to be a form that doesn't kill our immune systems, it'll be a different species of virus because it'll live longer in each host. (Mitochondria were once bacteria - now we can't live without them being part of our cells.)
2. There is a bit of a misconception about evolution that people tend to have when it comes to evolution. This assumption is that it is a constant, inevitable movement towards improvement.
In point of fact, evolution is a random process that can produce bad results just as often as good results. The reason it seems like evolution is always towards "better" forms is because the "bad" results tend to die out owing to the carriers of those evolutionary changes being more vulnerable to environmental dangers.
It also doesn't operate according to a clock. An organism may go tens or even hundreds of thousands of years without a single evolutionary change taking place, or a large number could happen within a few hundred years. The only real question with the timing is whether or not the species will be able to propagate these changes quickly enough for them to "take" or if they'll die out.
Then there's the question of these changes being able to make it for the long haul. Just because a "positive" evolutionary change has occurred in a species does not mean that it is guaranteed to last. Evolutionary changes merely shift the odds of survival and propagation a bit for the better or the worse. If a species has had a change take place only a few generations back and thus remains very localized on the coast, a single hurricane could potentially wipe that change out.
So, in essence, at any given moment, a species could randomly evolve, or not. Any given evolution could improve the survival chances of the offspring of the individual that underwent the change, or not. Any species whose evolutionary process has granted an improvement can survive long enough to spread out beyond a reasonable extinction risk, or not.
So if a species seems to have "failed to evolve" into a better form over millions, or even billions of years, it's not proof that evolution is false. It is simply proof that the species has genetics that are "good enough" to have survived and spread, and that some of the members of that species have not randomly evolved each generation since the evolutionary moment that created it in the first place.
Dr. Krishna Kumari Challa
New Zealand's kākāpō developed different feather colors to evade predatory birds, genome sequencing shows
Evolution: Aotearoa New Zealand's flightless parrot, the kākāpō, evolved two different color types to potentially help them avoid detection by a now-extinct apex predator , researchers report in the open-access journal PLOS Biology.
The kākāpō (Strigops habroptilus) is a nocturnal, flightless parrot endemic to New Zealand. It experienced severe population declines after European settlers introduced new predators. By 1995 there were just 51 individuals left, but intense conservation efforts have helped the species rebound to around 250 birds. Kākāpō come in one of two colors—green or olive—which occur in roughly equal proportions.
To understand how this color variation evolved and why it was maintained despite population declines, researchers analyzed genome sequence data for 168 individuals, representing nearly all living kākāpō at the time of sequencing. They identified two genetic variants that together explain color variation across all the kākāpō they studied.
Scanning electron microscopy showed that green and olive feathers reflect slightly different wavelengths of light because of differences in their microscopic structure. The researchers estimate that olive coloration first appeared around 1.93 million years ago, coinciding with the evolution of two predatory birds: Haast's eagle and Eyles' harrier.
Computer simulations suggest that whichever color was rarer would have been less likely to be detected by predators, explaining why both colors persisted in the kākāpō population over time.
The results suggest that kākāpō coloration evolved due to pressure from apex predators that hunted by sight. This variation has remained even after the predators went extinct, around 600 years ago.
The authors argue that understanding the origins of kākāpō coloration might have relevance to the conservation of this critically endangered species. They show that without intervention, kākāpō color variation could be lost within just 30 generations, but it would be unlikely to negatively impact the species today.
Urban L, Santure AW, Uddstrom L, Digby A, Vercoe D, Eason D, et al. (2024) The genetic basis of the kākāpō structural color polymorphism suggests balancing selection by an extinct apex predator. PLoS Biology (2024). DOI: 10.1371/journal.pbio.3002755
Sep 11
Dr. Krishna Kumari Challa
Evolution in action: How ethnic Tibetan women thrive in thin oxygen at high altitudes
Breathing thin air at extreme altitudes presents a significant challenge—there's simply less oxygen with every lungful. Yet, for more than 10,000 years, Tibetan women living on the high Tibetan Plateau have not only survived but thrived in that environment.
A new study answers some of those questions. The research, published in the journal Proceedings of the National Academy of Sciences of the United States of America, reveals how the Tibetan women's physiological traits enhance their ability to reproduce in such an oxygen-scarce environment.
The findings not only underscore the remarkable resilience of Tibetan women but also provide valuable insights into the ways humans can adapt in extreme environments. Such research also offers clues about human development, how we might respond to future environmental challenges, and the pathobiology of people with illnesses associated with hypoxia at all altitudes.
Researchers studied 417 Tibetan women aged 46 to 86 who live between 12,000 and 14,000 feet above sea level in a location in Upper Mustang, Nepal on the southern edge of the Tibetan Plateau.
They collected data on the women's reproductive histories, physiological measurements, DNA samples and social factors. They wanted to understand how oxygen delivery traits in the face of high-altitude hypoxia (low levels of oxygen in the air and the blood) influence the number of live births—a key measure of evolutionary fitness.
They discovered that the women who had the most children had a unique set of blood and heart traits that helped their bodies deliver oxygen. Women reporting the most live births had levels of hemoglobin, the molecule that carries oxygen, near the sample's average, but their oxygen saturation was higher, allowing more efficient oxygen delivery to cells without increasing blood viscosity; the thicker the blood, the more strain on the heart.
This is a case of ongoing natural selection. Tibetan women have evolved in a way that balances the body's oxygen needs without overworking the heart.
One genetic trait they studied likely originated from the Denisovans who lived in Siberia about 50,000 years ago; their descendants later migrated onto the Tibetan Plateau.
The trait is a variant of the EPAS1 gene that is unique to populations indigenous to the Tibetan Plateau and regulates hemoglobin concentration. Other traits, such as increased blood-flow to the lungs and wider heart ventricles, further enhanced oxygen delivery.
These traits contributed to greater reproductive success, offering insight into how humans adapt to lifelong levels of low oxygen in the air and their bodies.
Beall, Cynthia M., Higher oxygen content and transport characterize high-altitude ethnic Tibetan women with the highest lifetime reproductive success, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2403309121. doi.org/10.1073/pnas.2403309121
Oct 22
Dr. Krishna Kumari Challa
Human induced evolution
A native New Zealand insect that once mimicked its toxic neighbor has changed color in deforested areas, in a striking example of human-induced evolution.
The long-tailed stonefly, Zelandoperla, had a clever strategy to avoid predation from birds: it mimicked the appearance of a uniquely toxic stonefly, Austroperla, a forest dweller that deters predators by producing cyanide.
Researchers have found that in deforested areas without Austroperla in the picture, and with fewer bird predators, some Zelandoperla have given up their guise.
The findings highlight "the possibility for populations to adapt rapidly in the wake of sudden environmental change," the team writes in their published paper.
While the long-tailed stonefly has no toxins of its own, it has managed to pull off a convincing impersonation of Austroperla using its genetic toolkit, which colored some of the insects a dark shade of ebony.
The disguise worked to deter their feathered predators, which, unable to tell the difference, steered clear of both the toxic stonefly and its mimic.
But Austroperla is a forest creature: it lives in streams where it feeds on leaves and woody debris. In deforested areas, its preferred food sources are lacking, and Austroperla has become less common.
The removal of forests since humans arrived has removed the poisonous species.
As a result, in deforested regions the mimicking species has abandoned this strategy – as there is nothing to mimic – instead evolving into a different colour.
The scientists used a combination of field observations, predation experiments, and gene map analysis to show the insect's response to human-driven change.
https://www.science.org/doi/10.1126/science.ado5331
Nov 14