Poisonous Frogs Evolve to Sing Louder and Longer
by Penny Sarchet
The little South American devil frog is noisy in pursuit of a partner, and doesn’t care who hears him.
The little devil frog’s fearlessness in the face of hungry predators could be down to his toxicity. The little devil, Oophaga sylvatica, is a member of the dendrobatid group of poisonous frogs. His bright colours warn predators that he is unsafe to eat, which Juan Santos of the University of British Columbia in Vancouver, Canada, believes has allowed the evolution of more flamboyant mating calls.
Santos and his colleagues examined the calls, colourings and toxicity of 170 species of frog, including the little devil. They found a strong relationship between the volume of a frog’s call and its aposematism – markings that warn of its toxicity. In general, the more toxic a frog, the brighter and more noticeable it is – and the louder and more rapidly it sings (Proceedings of the Royal Society B ).
Non-toxic frogs are camouflaged and call from less exposed perches, says Santos…
(read more: New Scientist)
photograph: Pete Oxford/NaturePL

Poisonous Frogs Evolve to Sing Louder and Longer

by Penny Sarchet

The little South American devil frog is noisy in pursuit of a partner, and doesn’t care who hears him.

The little devil frog’s fearlessness in the face of hungry predators could be down to his toxicity. The little devil, Oophaga sylvatica, is a member of the dendrobatid group of poisonous frogs. His bright colours warn predators that he is unsafe to eat, which Juan Santos of the University of British Columbia in Vancouver, Canada, believes has allowed the evolution of more flamboyant mating calls.

Santos and his colleagues examined the calls, colourings and toxicity of 170 species of frog, including the little devil. They found a strong relationship between the volume of a frog’s call and its aposematism – markings that warn of its toxicity. In general, the more toxic a frog, the brighter and more noticeable it is – and the louder and more rapidly it sings (Proceedings of the Royal Society B ).

Non-toxic frogs are camouflaged and call from less exposed perches, says Santos…

(read more: New Scientist)

photograph: Pete Oxford/NaturePL

A Life Spent Chasing Down How Whales Evolved
by Bob Holmes
The intriguing story of how whale evolution was unpicked is told in The Walking Whales, revealing what it’s like to be a globe-trotting palaeontologist
WHALES evolved from cat-sized terrestrial hoofed mammals, evolutionary biologists tell us. How could a tiny, deer-like creature morph into such a radically different leviathan? The notion has often provoked gleeful ridicule from creationists, especially because, until the 1990s, so few intermediate fossils had been discovered.
Little more than a decade later, spectacular finds had bridged that gap so convincingly that whales now stand as one of the best-documented fossil transitions – literally a textbook case of evolution in action.
Much of that change is thanks to Hans Thewissen, a palaeontologist at Northeast Ohio Medical University in Rootstown, who has made many of the key discoveries. The Walking Whales is his account of his research…
(read more: New Scientist)
image of Pakicetus, via: NHM/SPL

A Life Spent Chasing Down How Whales Evolved

by Bob Holmes

The intriguing story of how whale evolution was unpicked is told in The Walking Whales, revealing what it’s like to be a globe-trotting palaeontologist

WHALES evolved from cat-sized terrestrial hoofed mammals, evolutionary biologists tell us. How could a tiny, deer-like creature morph into such a radically different leviathan? The notion has often provoked gleeful ridicule from creationists, especially because, until the 1990s, so few intermediate fossils had been discovered.

Little more than a decade later, spectacular finds had bridged that gap so convincingly that whales now stand as one of the best-documented fossil transitions – literally a textbook case of evolution in action.

Much of that change is thanks to Hans Thewissen, a palaeontologist at Northeast Ohio Medical University in Rootstown, who has made many of the key discoveries. The Walking Whales is his account of his research…

(read more: New Scientist)

image of Pakicetus, via: NHM/SPL

What Is the Evidence for Evolution?

The evidence is voluminous, actually. Let’s start with a look at whales.

Biologists teach that all living things on Earth are related. Is there any solid evidence to back this claim? Join us as we explore the facts! We start with a close look at the origin of whales from land mammals, and then touch on the origins of several other critters, including our own species.

(via: Stated Clearly)

RNA World 2.0

Most scientists believe that ribonucleic acid played a key role in the origin of life on Earth, but the versatile molecule isn’t the whole story.

by Jef Akst (March 2014)

The ubiquity and diverse functionality of ribonucleic acid (RNA) in today’s world suggest that the information polymer could well have been the leading player early on in the establishment of life on Earth, and, in theory, it’s a logical basis for primitive life.

One can readily imagine that RNA, as a catalytic molecule capable of serving as a template for its own replication, might have reproduced itself and grown exponentially in the primordial environment. Perhaps such an RNA-based proto–life-form even replicated with an appropriate level of fidelity to allow natural selection to begin directing its evolution.

But there’s a snag: “The odds of suddenly having a self-replicating RNA pop out of a prebiotic soup are vanishingly low,” says evolutionary biochemist Niles Lehman of Portland State University in Oregon…

(read more: The Scientist)

illustration by The Scientist staff

An Alternative Route to Oxygen in Space?
Researchers have figured out a way to break a carbon dioxide molecule with high-energy UV light and get molecular oxygen. Their results identify an unexpected pathway to oxygen which is reminiscent of the “Great Oxidation Event” that turned Earth into a living planet, and could help us understand how Earth’s atmosphere — and other planetary atmospheres — formed.
read the paper: http://scim.ag/1pQndPG 
image: NASA/Reto Stöckli

An Alternative Route to Oxygen in Space?

Researchers have figured out a way to break a carbon dioxide molecule with high-energy UV light and get molecular oxygen. Their results identify an unexpected pathway to oxygen which is reminiscent of the “Great Oxidation Event” that turned Earth into a living planet, and could help us understand how Earth’s atmosphere — and other planetary atmospheres — formed.

read the paper: http://scim.ag/1pQndPG

image: NASA/Reto Stöckli

Big History examines our past, explains our present, and imagines our future. It’s a story about us. An idea that arose from a desire to go beyond specialized and self-contained fields of study to grasp history as a whole. This growing, multi-disciplinary approach is focused on high school students, yet designed for anyone seeking answers to the big questions about the history of our Universe.

The Big History Project is a joint effort between teachers, scholars, scientists, and their supporters to bring a multi-disciplinary approach to knowledge to lifelong learners around the world…

CURRENT WORK IN HERPETOLOGY:
Study Suggests, New Poison Dart Frog Species Evolving Before Our Eyes
by James Owen
A poison dart frog from Peru that mimics its neighbors in incredible detail is evolving into a new species, scientists believe. 
The mimic frog (Ranitomeya imitator) is the first vertebrate, and only the second known animal, to suggest that mimicry can split populations into separate species, according to a study published recently in Nature Communications. The other animal is a group of Heliconius butterflies, which are also found in South America.
Separate geographic populations of R. imitator can look wildly different, depending on the frog species they’re mimicking. In north-central Peru, two R. imitator populations colorfully masquerade as two contrasting poison frog species: The splash-back poison frog (R. variabilis) or red-headed poison frog (R. fantastica)…
(read more: National Geographic)
photograph: Evan Twomey

CURRENT WORK IN HERPETOLOGY:

Study Suggests, New Poison Dart Frog Species Evolving Before Our Eyes

by James Owen

A poison dart frog from Peru that mimics its neighbors in incredible detail is evolving into a new species, scientists believe. 

The mimic frog (Ranitomeya imitator) is the first vertebrate, and only the second known animal, to suggest that mimicry can split populations into separate species, according to a study published recently in Nature Communications. The other animal is a group of Heliconius butterflies, which are also found in South America.

Separate geographic populations of R. imitator can look wildly different, depending on the frog species they’re mimicking. In north-central Peru, two R. imitator populations colorfully masquerade as two contrasting poison frog species: The splash-back poison frog (R. variabilis) or red-headed poison frog (R. fantastica)…

(read more: National Geographic)

photograph: Evan Twomey

In his fourth-floor lab at Harvard University, Michael Desai has created hundreds of identical worlds in order to watch evolution at work.

Each of his meticulously controlled environments is home to a separate strain of baker’s yeast. Every 12 hours, Desai’s robot assistants pluck out the fastest-growing yeast in each world — selecting the fittest to live on — and discard the rest. Desai then monitors the strains as they evolve over the course of 500 generations.

His experiment, which other scientists say is unprecedented in scale, seeks to gain insight into a question that has long bedeviled biologists: If we could start the world over again, would life evolve the same way? …

Evolution is often said to be “blind,” because there’s no outside force guiding natural selection. But changes in genetic material that occur at the molecular level are not entirely random, a new study suggests.

These mutations are guided by both the physical properties of the genetic code and the need to preserve the critical function of proteins, the researchers said…

An anatomical diagram of a hypothetical ancestral mollusc.
Its nervous system is hypoathroid. Throughout its unsegmented, bilaterally symmetrical body, organs occur either singly or in pairs; there is no metamerism. Its hemocoel circulatory system is filled with hemocyanin. Gametes are ejected into the pericardium before traveling through the nephridia to environment.
 Diagram illustration by K.D. Schroeder
(via: Wikipedia)

An anatomical diagram of a hypothetical ancestral mollusc.

Its nervous system is hypoathroid. Throughout its unsegmented, bilaterally symmetrical body, organs occur either singly or in pairs; there is no metamerism. Its hemocoel circulatory system is filled with hemocyanin. Gametes are ejected into the pericardium before traveling through the nephridia to environment.

Diagram illustration by K.D. Schroeder

(via: Wikipedia)

Ability to Regenerate Limbs/Digits Dates Back at Least 300 Million Years

by Ian Randall

Researchers have found the earliest evidence for limb regeneration in the fossil record. Rocks unearthed in southwestern Germany have captured 300-million-year-old amphibians that have one or more regrown limbs.

Unlike humans—who can only replace lost fingertips—salamanders are the only modern four-legged animals, or tetrapods, that maintain the ability to regenerate entire limbs throughout their lives. If tissue has been severely damaged or if the wound heals poorly, however, the regrown limb may grow back incorrectly. Such deformities can be quite common, especially if the same limb is repeatedly amputated or injured, leading to regenerated limbs with extra, missing, or fused-together digits in distinctive and unique patterns.

In their new paper, published online today in the Proceedings of the Royal Society B, the researchers report identifying these same types of deformity in exceptionally well preserved fossils of the early amphibian, Micromelerpeton (pictured, with an extra, partly fused digit, second from the top)…

(read more: Science News/AAAS)

images: Ghedoghedo and Kai Nungesser

Triassic Bites and a Carnivore Conundrum

by Brian Switek

The Triassic was one of the strangest times in the history of the planet. Rebounding from the worst mass extinction of all time, life flourished into startling new varieties, including the first dinosaurs, weird marine reptiles, and croc-line critters that came in forms like “armadillodiles” and huge, jagged-toothed carnivores, to name just a few Triassic stars. But the strange nature of the Triassic extends beyond the odd anatomy of the creatures that evolved during the period.

While paleontologists are still piecing together the details of Triassic life for the early parts of the period, researchers know that the landscapes of the Late Triassic were dominated by carnivores. At many classic Late Triassic localities – such as those in Petrified Forest National Park and Ghost Ranch, New Mexico – flesh-eaters outnumber herbivores in both abundance and species diversity.

This doesn’t fit with the classic ecosystem pyramid we learn in grade school, with a greater number of herbivores providing fodder for a small number of carnivores. No, something strange was going on during the Late Triassic, and a pair of damaged leg bones may hint at why the Late Triassic held an embarrassment of predators.

The two bones, studied by paleontologists Stephanie Drumheller, Michelle Stocker, and Sterling Nesbitt, were found in different localities at different times. But they have three important features in common. They both belong to large Late Triassic carnivores called paracrocodylomorphs, both are upper leg bones called femora, and both are pocked by bitemarks from different carnivores…

(read more: Laelaps blog - National Geographic)

images: Brian Switek; Drumheller et al. 2014

palaeopedia
palaeopedia:

The trident tooth, Thrinaxodon (1894)
Phylum : ChordataClass : SynapsidaOrder : TherapsidaSuborder : CynodontiaFamily : ThrinaxodontidaeGenus : ThrinaxodonSpecies : T. liorhinus
Early Triassic (248 - 245 Ma)
50 cm long and 2 kg (size)
South Africa and Antarctica (map)
Thrinaxodon probably lived in shallow burrows dug into hillsides or riverbanks.
A low-slung, sharp-toothed carnivore, Thrinaxodon lived in burrows, and its well-differentiated teeth suggest it ate small creatures like insects, reptiles, and other small animals. Clues to its remains show that this creature was more mammal-like than its synapsid ancestors.
It had a fairly large head/skull with pits in the snout area which have suggested to some that it had whiskers, but the modern lizard Tupinambis has pits in the same area that are almost identical. An enlarged dentary bone strengthened either side of the lower jaw and contained sockets for its teeth.
Along with other cynodonts, Thrinaxodon could chew and breathe at the same time, due to the evolutionary development of the secondary palate. Its chest and lower back regions were probably separated by a diaphragm - a muscular sheet that contracted to fill lungs, and would have enabled Thrinaxodon to breathe more efficiently than its ancestors.
In response to the wide daily temperature swings of the early Triassic, it may have been eurythermic, able to function at a broad range of temperatures; this could have laid the groundwork for the development of homeothermic endothermy. Like its predecessors, Thrinaxodon laid eggs, and there were many reptilian features in its skeleton.

palaeopedia:

The trident tooth, Thrinaxodon (1894)

Phylum : Chordata
Class : Synapsida
Order : Therapsida
Suborder : Cynodontia
Family : Thrinaxodontidae
Genus : Thrinaxodon
Species : T. liorhinus

  • Early Triassic (248 - 245 Ma)
  • 50 cm long and 2 kg (size)
  • South Africa and Antarctica (map)

Thrinaxodon probably lived in shallow burrows dug into hillsides or riverbanks.

A low-slung, sharp-toothed carnivore, Thrinaxodon lived in burrows, and its well-differentiated teeth suggest it ate small creatures like insects, reptiles, and other small animals. Clues to its remains show that this creature was more mammal-like than its synapsid ancestors.

It had a fairly large head/skull with pits in the snout area which have suggested to some that it had whiskers, but the modern lizard Tupinambis has pits in the same area that are almost identical. An enlarged dentary bone strengthened either side of the lower jaw and contained sockets for its teeth.

Along with other cynodonts, Thrinaxodon could chew and breathe at the same time, due to the evolutionary development of the secondary palate. Its chest and lower back regions were probably separated by a diaphragm - a muscular sheet that contracted to fill lungs, and would have enabled Thrinaxodon to breathe more efficiently than its ancestors.

In response to the wide daily temperature swings of the early Triassic, it may have been eurythermic, able to function at a broad range of temperatures; this could have laid the groundwork for the development of homeothermic endothermy. Like its predecessors, Thrinaxodon laid eggs, and there were many reptilian features in its skeleton.