The idea that birds create magnetic maps is supported by studies like those on Australian silvereyes done by the Wiltschkos in the 1990s. They exposed the birds to a strong pulse that altered the magnetism of iron crystals in their beaks but left the eye compass unaffected. In juvenile birds that had just left the nest, this made no difference – they still tried to head in the right direction.
Birds that had migrated before, however, all headed in the wrong direction after the pulse. This suggests that the juvenile birds were relying on the compass in their eyes, whereas the experienced birds were trying to navigate based on their mental magnetic map, using the intensity receptor in their beaks.
Of course in natural situations, birds use a whole range of clues for navigation, not just magnetism. They also use the sun and stars, smells, visual landmarks and perhaps even sounds like waves breaking.
An insight into how they combine these different kinds of information came from a recent study on night-migrating thrushes. When the thrushes were exposed to artificial magnetic fields at sunset, they flew in the wrong direction during the night when released. After seeing the next sunset, however, they corrected their courses. So it appears some birds calibrate their magnetic compasses against the sun each day.
A ‘bullet’ fired by killer immune system cells has been seen in action for the first time.
The protein, called perforin, is used to punch holes in rogue cells that threaten the body.
Scientists used a powerful electron microscope to study how perforin despatches cells that have become cancerous or invaded by viruses.
The holes it blows open allow toxic enzymes to enter the cells and destroy them.
A team from The Scripps Research Institute has revealed the first-ever pictures of the formation of cells’ “protein factories.” In addition to being a major technical feat on its own, the work could open new pathways for development of antibiotics and treatments for diseases tied to errors in ribosome formation. In addition, the techniques developed in the study can now be applied to other complex challenges in the understanding of cellular processes.
Poveştile despre fantomaticul “Chupacabra” circulă în fiecare an, dar oamenii de ştiinţă au reuşit, în sfârşit, să dezlege misterul ce înconjura legendarul animal.
Wings on a flightless bird, eyes on a blind fish, and sexual organs on a flower that reproduces asexually—the casual observer might ask, what’s the point? But these vestigial organs and structures, once useful in an ancestor and now diminished in size, complexity, and/or utility, carry important information and give us clues to our evolutionary past.
Though humans often think of vestigial organs as useless little fixtures that sometimes, as in the case of the appendix, cause us extreme anguish, we wouldn’t know nearly as much about macroevolution as we do now without their presence. In On the Origin of Species, Charles Darwin used vestigial organs as evidence for evolution, and their presence has helped define and shape our phylogenetic trees.
Why the Leftovers?
Contrary to what most think, vestigial doesn’t necessarily mean useless; in some cases, we may just not yet know exactly how the organ is used in its current incarnation. (The human thymus was once thought to be vestigial). Because these structures can be traced back through the ancestors, they essentially serve as a marker of evolution; no organism can have a vestigial organ that hasn’t been found in its forefathers. For this reason, you won’t ever find feathers on a mammal or gills on a primate.
Similar in concept to vestigial structures are atavisms, which are the reappearance of a structure or trait that isn’t found in the immediate ancestors. For instance, whales and dolphins have been found in nature with hind limbs; this rare occurrence is due to the reemergence of a trait they inherited from their terrestrial ancestors.
Humans also contain structures that mark where we came from and perhaps, which structures’ evolution will take care of over time.
It’s a chicken-and-egg problem that’s concerned biologists for decades: how did the basic biochemicals of life appear before the biological catalysts needed to form them had come into existence?
But a US team believes it’s found the answer – another type of catalyst which could have jumpstarted metabolism and life itself, deep in hydrothermal ocean vents.
Perhaps he had just got tired of swimming.
James Stewart of East Tennessee State University in Johnson City and colleagues have now shown that as the skinks retain their young for longer, they reduce the thickness of the eggshell. This allows the mother to keep the embryo well fed.
However, even the live-bearers have not got rid of the shell entirely. Baby skinks that are born live come out encased in a membrane – all that is left of the eggshell. With a bit of help from their mothers, most of them break out of the membrane within 36 hours.
How did live birth evolve? One group of the egg-laying skinks retain their eggs inside their bodies for longer than the others, and it seems that the live-bearers evolved from these “intermediate” skinks.
Reptiles are more likely to develop live birth if they live in cold climates, where it is a good idea to protect their offspring in their bodies, rather than exposing them to the rigours of the environment too soon. Sarah Smith of Stony Brook University, New York, points out that this explains why it is the skinks who live in the chilly highlands that give birth to live young.
Building artificial cells will tell us much about the origins of life – and may explain how Darwinian evolution began, says Nobel laureate Jack Szostak
At a presentation on 28 July at the Ninth International Congress of Vertebrate Morphology in Punta del Este, Uruguay, Kerney reported that these algae are, in fact, commonly located inside cells all over the spotted salamander’s body. Moreover, there are signs that intracellular algae may be directly providing the products of photosynthesis — oxygen and carbohydrate — to the salamander cells that encapsulate them.
But dining with dogs was worth it. Meat is packed with lots of calories and fat. Our brain — which uses about 20 times as much energy as the equivalent amount of muscle — piped up and said, “Please, sir, I want some more.”
Carving Up The Diet
As we got more, our guts shrank because we didn’t need a giant vegetable processor any more. Our bodies could spend more energy on other things like building a bigger brain. Sorry, vegetarians, but eating meat apparently made our ancestors smarter — smart enough to make better tools, which in turn led to other changes, says Aiello.
“If you look in your dog’s mouth and cat’s mouth, and open up your own mouth, our teeth are quite different,” she says. “What allows us to do what a cat or dog can do are tools.”
Tools meant we didn’t need big sharp teeth like other predators. Tools even made vegetable matter easier to deal with. As anthropologist Shara Bailey at New York University says, they were like “external” teeth.
Habitat: Caves in southern Europe, especially Slovenia and Croatia, and in fairy tales, sitting on piles of treasure.
A blind little amphibian with translucent skin – once thought to be an infant dragon – is providing valuable clues in the quest for the elixir of life.
The olm, also known as the “human fish” because its pale skin reminded Europeans of their own, is a small, cave-dwelling salamander weighing up to 20 grams. Spending its whole life in cave water, it is one of the few amphibians that are entirely aquatic. Like many cave-dwelling animals it has adapted to the subterranean darkness, losing its eyes and skin pigmentation.
Olms seem to reproduce whilst still in the larval stage, and unlike frogs and toads, adults are neotenous – they retain juvenile features such as gills. It was once thought that this was a result of failure to develop fully in the cave’s hostile environment. And in the 17th century the scholar Janez Vajkard Valvasor wrote that peasants believed the animals were the babies of a dragon that caused the Bella river in Romania to flood periodically.
But Yann Voituron of the University of Lyon, France, is interested in the olm for another reason: its extreme lifespan. In zoos they live for over 70 years, but Voituron thinks they could live to 102.
A species of mole has evolved special blood that helps it survive in airless tunnels underground.
The red blood cells of the Eastern mole allow it to get away with re-breathing its own expired air.
Scientists found that they are genetically adapted to carry extra carbon dioxide.
The fossils show that the primate looked very much like a modern new world monkey, such as a capuchin but it was probably slightly larger.
The researchers say the findings will fill in some crucial gaps in our understanding of the nature and timing of evolutionary events that led to human origins.
They added: ‘Saadanius provides new evidence consistent with a divergence date after 29 to 28 million years ago, and its comparative study offers a basis for recognition of the first hominoids subsequent to this event.’
Acorn worms are one of the so-called missing links in evolutionary history. Although they are worms with no backbone, they have a few features that mark them as cousins of the chordates: animals that do have backbones.
As a result, acorn worms may be able to tell us about how backbones first evolved.
Monty Priede of the University of Aberdeen, UK, one of the lead researchers, said: “There is a head end, tail end and the primitive body plan of backboned animals is established.”
The first multicelled life appeared on Earth more than 1.5 billion years earlier than previously thought, new fossil discoveries show.
A SIMPLE on-off switch may have been key to the evolution of complex life.
How colonies of single cells evolved into multicellular organisms has long been a puzzle. The process requires single cells to band together and divide the tasks of life. To do so, some cells must give up their ability to reproduce.
To investigate, Sergey Gavrilets of the University of Tennessee in Knoxville created a mathematical model describing a colony of identical cells able to survive and reproduce. He assumed trade-offs between the tasks: being better at reproducing made cells worse at survival, and vice versa. In the simplest case, the colony evolved into organisms made of cells that were mediocre at both tasks.
But that changed when Gavrilets included genes that could suppress the activity of one trait or the other. A colony of cells could now improve both traits at the same time, by making some cells exclusively reproducers and others survivors. This led cells to completely specialise in less than a million generations – an evolutionary blink of an eye
The first humans may have started walking upright because the place where they lived was so hot, new research suggests.
Scientists discovered that the Turkana Basin of Kenya, long held as the cradle of human evolution, was even hotter millions of years ago than it is now.
Daytime temperatures would have been well into the late 90s every single day.
The discovery lends weight to the so-called ‘thermal hypothesis’ of human evolution, which states that mankind first started standing upright because of the intense heat.
Giving proteins a new glow
MIT chemists have designed a way to fluorescently label proteins that could shed light on protein functions never before seen.
Since the 1990s, a green fluorescent protein known simply as GFP has revolutionized cell biology. Originally found in a Pacific Northwest jellyfish, GFP allows scientists to visualize proteins inside of cells and track them as they go about their business. Two years ago, biologists who discovered and developed the protein as a laboratory tool won a Nobel Prize for their work.
However, using GFP as a fluorescent probe has one major drawback — the protein is so bulky that it can interfere with the proteins it’s labeling, preventing them from doing their normal tasks or reaching their intended destinations.
“You need enzymes to make ATP and you need ATP to make enzymes,” explained Dr Kee. “The question is: where did energy come from before either of these two things existed? We think that the answer may lie in simple molecules such as pyrophosphite which is chemically very similar to ATP, but has the potential to transfer energy without enzymes.”
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