Posts tagged science
Posts tagged science
Neil DeGrasse Tyson, an anomaly in American science
the Water Cycle
I want to reblog this every day for the rest of my life.
This requires a link back to the original on the artist’s website. For biology nerds like me, her site is awesome!
I’m a little worried about the scare quotes around “smell”. Lots of birders are under the bizarre impression that most birds can’t smell… but there’s a huge amount of information in the peer-reviewed literature indicating that, yeah, they can all totally smell, and it seems to be a pretty important sense. And it appears they can recognize kin by smell:
Krause, E. et al. (2012) Olfactory kin recognition in a songbird. Biol. Lett. 8(3) 327–329.
I doubt parents would reject a suddenly human-smelling chick, but it could still be interesting to test.
Avian sensory perception research has primarily been focused on visual and auditory cues, so olfactory perception among birds is still a misunderstood (but developing) area. Certain birds - like the Kiwi (Apteryx spp.) who sniff out their earthworm prey- seem to have a more developed sense of smell than others.(x) Yet, the size of the olfactory bulb is not the only correlate to a developed sense of smell. (x) Passeriformes, for example, were thought to lack a sense of smell due to their small OR bulb, yet this has been disproved… at least in some passerines. (x)
What “smell” might be referring to, is that birds may not smell humans. Not that we are invisible to their sense of smell, but more that a bird is (probably) unlikely to identify any olfactory cues from humans on their offspring as being distinctly human.
Well first off we bathe quite a lot, so we’re often washing off our own natural sent and oils. Secondly, we have a lovely tendency to slather ourselves in the sent of lotions, deodorants, perfumes, detergents, and other chemicals. If a bird does smell “human” (like any two people smell exactly the same) on their babies, it would most likely be categorized as “other” or “not my kin” or something along those lines before it would be categorized as “human”. Of course, this kind of research would involve brain imaging (kind of like what they’re doing with dogs right now!), but it’s an exciting prospect!
Regardless of how well particular bird species’ has developed a sense of smell, there is something stronger at play here. Parental instinct. There is a very strong drive here to take care of their offspring, even if they happen to smell a little funky. As long as the potential threat (that means you, well meaning human) is gone, Mom and/or Dad will swoop in and continue doing their best for their baby. At least, that is what the literature, and my friends, colleagues, and own combined experience on this in the field and in captivity.
tl;dr. Yes birds can smell, but they’ll stay away because you are a scary potential predator… not because you made the babies stink like human.
References: (all open access)
Clark, L., K. V. Avilova, and N. J. Bean. “Odor thresholds in passerines.”Comparative Biochemistry and Physiology Part A: Physiology 104.2 (1993): 305-312. (x)
Steiger, Silke. Evolution of avian olfaction. Diss. lmu, 2008. (x)
Steiger et al. Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds? Proceedings of The Royal Society B Biological Sciences, 2008; 1 (-1): -1 DOI: 10.1098/rspb.2008.0607 (x)
There were some experiments dealing with neophobia of odors in birds, but the results seem to be rather ambiguous. It’s reviewed in Roper (1999 — partially accessible, sadly). But yeah… even if parents were for some reason afraid of a new smell, it seems really unlikely they’d abandon their chick.
Also interesting is that rollers can barf up a scent indicating they’ve been stressed, so even if they’re covered in an unfamiliar smell, they’ll just make a new one for their parents to react to.
Parejo, D. et al. (2012) Rollers smell the fear of nestlings. Biol. Lett. 8(4_ 502–504
"im writing a research paper so reblog if—"
no youre not
A thing I noticed this week.
Do a snarl. No, not a full-blown all-teeth bared one: just curl one side of your lip and show us a canine. Good.
Now try doing it with the other side of your face.
If you’re anything like me or the other folks I’ve tried this on, not so easy, is it?
I’m right-handed and I curl the left side of my lip, but the right side just… doesn’t do. I wonder if there have been any studies of lateralization of lip-curling during snarls? :o
Butterflies can’t see their wings. They can’t see how truly beautiful they are, but everyone else can. People are like that as well.
Butterflies have excellent vision. Similar to birds, butterflies are able to see in the ultraviolet spectrum; unlike birds, butterflies have the broadest spectrum of color vision known to exist in the animal kingdom. A compound eye is located on each side of the butterflies’ head and is made up of many little eyes pressed together into one. The tiny individual eyes are called facets, and are made up of six sides. Thousands of facets make up the two compound eyes. Unlike human vision, where we see one image, butterflies see thousands of small images at a time. Underneath the facets is a crystal cone that extends inwardly and forms a transparent rod. When light enters this rod, it has already been reversed twice, making its’ rays parallel so that light enters the rod in a straight line. Compound eyes aid in seeing into the UV, detecting movement, and seeing varied colors. The side location of their eyes enables them to see in different directions at one time, useful in detecting predators. However, butterflies cannot see detail from a distance and can only recognize the fine patterns of other butterflies from a few feet away. This would mean they are capable of seeing their own wings.
So basically this is one of those supposedly profound quotes that tries to make a point while being based on really shitty information and thus falls apart. Surely they could have found an analogy that doesn’t fly in the face of basic scientific observation if they wanted to send the “you’re more beautiful than you think” message..
This is the kind of shit I really love.
This is an interesting and complex question.
A fellow named Dollo says no, and in 1893 he proposed a law- Dollo’s Law, in fact- that stated that once lost, genetic traits could not be regained via evolution. We’ll discuss how well Dollo’s Law has held up a bit more further down.
A trait can absolutely appear more than once in a species. In fact, certain traits go in and out of style all the time in some species based on changing environments.
When I was 12, revealed to my mommy that I don’t believe in God. She looked at me wild-eyed and screamed, “So when you’re laying there dying on the hospital bed, who is going to save you?? SCIENTISTS?!”
And I said, “Yes, mommy, they’re called Doctors.”
reminded me of
Reminder to creature designers that “hermaphrodite” doesn’t mean what you think it means in zoology.
Gastropods, certain annelids and other animals that produce both eggs and sperm still have to pair up and mate. They often have elaborate mating rituals and either one partner becomes the “female” or both are fertilized simultaneously.
Multiplication without mating is usually parthenogenesis, which is essentially just natural cloning, and animals do this to increase the odds of their own genetic line finding a MATE.
A female aphid pops out female clones because genetically speaking they’re all still her, just in more than one body, so now there’s more of her around for a male to find and fertilize.
Think of parthenogenesis not as an alternate form of reproduction, but as one animal growing “larger” by splitting into many bodies.
If there are never any males and the parthenogenetic clones just keep cloning and cloning they start to die off because they’re not getting any new genetic information.
Cloning itself does not make the animal live forever. Its cell line ages and wears down like an individual!
There aren’t really any multi-cellular species who thrive without getting outside genetic information from somewhere, at some point.
If you’re trying to be scientifically sound, your fictional species needs at least some way of introducing genes to its offspring from another, different organism.
If you want to do this without anything resembling sexual reproduction, Bdelloid rotifers like this cutie employ horizontal gene transfer, borrowing genetic information from the environment around them.
This means they “steal” dna from protozoa, bacteria and even decomposing plant matter as they swim and feed, and have been keeping their populations genetically healthy in this fashion for millions of years.
From SMBC :)
The first bionic hand that allows an amputee to feel what they are touching will be transplanted later this year in a pioneering operation that could introduce a new generation of artificial limbs with sensory perception.
The patient is an unnamed man in his 20s living in Rome who lost the lower part of his arm following an accident, said Silvestro Micera of the Ecole Polytechnique Federale de Lausanne in Switzerland.
The wiring of his new bionic hand will be connected to the patient’s nervous system with the hope that the man will be able to control the movements of the hand as well as receiving touch signals from the hand’s skin sensors.
Dr Micera said that the hand will be attached directly to the patient’s nervous system via electrodes clipped onto two of the arm’s main nerves, the median and the ulnar nerves.
This should allow the man to control the hand by his thoughts, as well as receiving sensory signals to his brain from the hand’s sensors. It will effectively provide a fast, bidirectional flow of information between the man’s nervous system and the prosthetic hand.
“This is real progress, real hope for amputees. It will be the first prosthetic that will provide real-time sensory feedback for grasping,” Dr Micera said.
“It is clear that the more sensory feeling an amputee has, the more likely you will get full acceptance of that limb,” he told the American Association for the Advancement of Science meeting in Boston.
“We could be on the cusp of providing new and more effective clinical solutions to amputees in the next year,” he said.
DO YOU PEOPLE EVEN REALIZE HOW AWESOME THIS IS???
TO DO THIS MEANS WE CAN FINALLY STICHT AXONS (LONG PART OF NEURON OR NERVE CELL THAT TRANSPORTS SIGNALS FROM JUNCTIONS BACK TO THE BRAIN) BACK TOGETHER
DO YOU EVEN UNDERSTAND HOW IMPOSSIBLE THAT WAS? TO ALINE THE DAMAGED AXONS BACK TOGETHER WAS IMPOSSIBLE
WITH THIS BRAKE THROUGH YOU COULD EVENTUALLY WORK UP TO GIVING THE ABILITY TO WALK AND MOVE AGAIN TO THOSE WHO CUT THEIR SPINAL CORD IN AN ACCIDENT THIS IS BEAUTIFUL
THIS. IS. AMAZING.
via Russian Orcas:
For several years we have collaborated with a scientific group that studies behavioural lateralization. The best known example of lateralization is right- and left-handedness in humans. Also it is known that many mothers prefer to carry their babies on the left arm. As most people are right-handed, scientists suppose that mothers adapted to carrying their babies on their left arm to leave their right hand free for other work. To test this hypothesis, Karina Karenina (PhD student at St. Petersburg State University) decided to check if lateralization occurs in mother-infant contacts in animals that don’t have hands.
To study lateralization in orcas, she joined our team to observe the lateralized behavior of mothers and calves. The position of the calf on the right or left side of its mother was recorded. The research boat position (distance to whales and if it was stationary or moving) was also considered to detect its possible influence on orca behaviour.
As a result, we found that calves preferred to keep their mothers on their left side, but if the boat came too close, mother took over and moved to the calf’s right side, to keep the calf on her left side. Karina also found left-side lateralization of mother-infant contacts in other species, including beluga whales, horses, kangaroos and saiga antelopes. Probably it has something to do with the lateralization of social functions in animal (including human) brains.
The results of our joint work are published here:
This incredibly cool new study by Gossi et al, published today in PLOSone, has researched whether chickens walk differently if they have a long, heavy tail, reminiscent of the type of tail present in non-avian dinosaurs. Giving them such a tail artificially (while controlling for weight) actually changes their gait significantly, giving them more hip-driven locomotion and less knee-driven as in modern birds. Check out the paper, it’s open-access.
From the abstract:
Birds still share many traits with their dinosaur ancestors, making them the best living group to reconstruct certain aspects of non-avian theropod biology. Bipedal, digitigrade locomotion and parasagittal hindlimb movement are some of those inherited traits. Living birds, however, maintain an unusually crouched hindlimb posture and locomotion powered by knee flexion, in contrast to the inferred primitive condition of non-avian theropods: more upright posture and limb movement powered by femur retraction. Such functional differences, which are associated with a gradual, anterior shift of the centre of mass in theropods along the bird line, make the use of extant birds to study non-avian theropod locomotion problematic. Here we show that, by experimentally manipulating the location of the centre of mass in living birds, it is possible to recreate limb posture and kinematics inferred for extinct bipedal dinosaurs. Chickens raised wearing artificial tails, and consequently with more posteriorly located centre of mass, showed a more vertical orientation of the femur during standing and increased femoral displacement during locomotion. Our results support the hypothesis that gradual changes in the location of the centre of mass resulted in more crouched hindlimb postures and a shift from hip-driven to knee-driven limb movements through theropod evolution. This study suggests that, through careful experimental manipulations during the growth phase of ontogeny, extant birds can potentially be used to gain important insights into previously unexplored aspects of bipedal non-avian theropod locomotion.
It is common knowledge that large dog breeds tend to have shorter lifespans (generally around 10-13 years; for the wolfhound and the great dane, as low as 7-8 years) than smaller dog breeds (some of which can go on for as long as 15-20 years). In fact, one study found that within 74 different breeds, dogs lose about one month of life expectancy per 4.4 pounds (2 kg).
So why does this happen?
The short answer is that the answer is not definitively known. There are currently a number of theories, none perfectly satisfying, and the fact of the matter is that there are probably a number of different reasons why large dogs tend to live shorter lives than small dogs.
Let’s start with probably the most generally accepted explanation for this phenomenon in science today.
First, it should be noted that dogs are not the only species that has this trend. In general, smaller individuals within a species have a tendency to live slightly longer than the larger ones. This is even true of humans (but don’t worry if you’re very tall- remember, these data are generalizations across massive samples of people and there are plenty of other factors that affect longevity).
Dogs have some of the most extreme differences in body form within a single species (as a matter of fact, not only are all dogs in the same species, they’re a subspecies- of the wolf). It’s not a big surprise that within these different forms ages can vary so drastically.
Then why is increased size related to shorter lifespans*? Well, one theory states that it is because the larger animals in a species have more growing to do in the same amount of time as smaller ones do. This means that their bodies have to work harder to build that extra mass- obtain more energy, create more cells- and this leads to faster aging.
The authors of the dog study I mentioned earlier pointed out that many large breeds are more susceptible to cancer than smaller ones are. and Cancer is caused by abnormal cell growth- the rapid growth of large dogs may be what makes them more vulnerable to cancers.
However, it should be noted that this explanation isn’t perfect. There are a number of exceptions to the higher weight = shorter lifespan correlation. Case in point, some of the longest-lived dogs ever are medium-sized dogs, not small dogs.
Bella, a Labrador mix, lived to be 29 years old.
In fact, even though the trend in dogs is that lifespan decreases as weight increases, there is a great deal of variability.
Figure from Dog Longevity- site has links to citations.
Now, if you look at the list of the world’s oldest known dogs, you’ll notice something else: well over half of them are cross-breeds or mutts. This is not quite an anomaly- on average, mixed-breed dogs tend to live longer than purebred dogs. The reason may be that mixed-breed dogs are protected from genetic disorders caused by inbreeding or overbreeding.
Table from Dog Longevity.
Larger breeds of dogs may also be more susceptible to genetic disorders than smaller dogs- at least, the disorders that cause more rapid death or euthanasia.
For example, one of the major reasons owners put their dogs down is because of difficulty or inability to walk. Large dogs, with their higher weights, have a harder time with genetic disorders such as hip and elbow dysplasia, luxating patella, and arthritis.
They are also more likely to die from gastrointestinal problems and developmental disorders than small dogs, likely due to stress on organs from rapid selective breeding for size.
(On the flip side, smaller dogs are more likely to die from endocrine problems than larger dogs. It’s just that the endocrine problems tend to come up later in life than the others.)
Note that overbreeding and inbreeding can have detrimental effects on breeds of any size: just look at the English bulldog, a medium-sized dog at around 40-50 pounds with an average lifespan of 6-7 years.
And then there’s the miniature bull terrier, at 20-30 pounds, with that same painful lifespan of 6-7 years.
An interesting point of fact- while few studies have compared the lifespans of large and small mixed-breed dogs, at least one has found that large mixed dogs still have a shorter lifespan than small mixed dogs (albeit with a smaller difference than between large and small purebreds). So, again, no one factor can explain this phenomenon.
I know this is a slightly depressing topic. Here’s a fact that may cheer you up: thanks likely to modern veterinary science, overall dog lifespan is on the rise right now. Fido lives!
*Increased size WITHIN a species is correlated with shorter lifespans. Between species, however, increased size is related to longer lifespans. Compare a mouse’s lifespan to an elephant’s.
Thanks to dalektable-souffle-girl for submitting this question!
Fleming, J. M., Creevy, K. E., & Promislow, D. E. L. (2011). Mortality in North American Dogs from 1984 to 2004: An Investigation into Age‐, Size‐, and Breed‐Related Causes of Death. Journal of Veterinary Internal Medicine, 25(2), 187-198.
Kraus, C., Pavard, S., & Promislow, D. E. (2013). The Size–Life Span Trade-Off Decomposed: Why Large Dogs Die Young. The American Naturalist, 181(4), 492-505.
Patronek, G. J., Waters, D. J., & Glickman, L. T. (1997). Comparative longevity of pet dogs and humans: implications for gerontology research. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 52(3), B171-B178.
List of Oldest Dogs via Wikipedia
Dog Longevity website by Dr. Kelly M. Cassidy
Frogs and Bats Use Water Ripples to Eavesdrop on Frog Calls
by Mary Bates
Communication requires a sender, a receiver, and a message. But communication doesn’t take place in a vacuum. Often, there are unintended receivers listening in and unintentional messages getting across.
Illustrating just how complicated sending a message can be is the example of the túngara frog (Physalaemus pustulosus). Male túngara frogs, native to Central and South America, gather at night in shallow ponds and call to attract females. They space themselves out carefully, each male defending a small calling site. Competition for females is serious business, and males will fight if one horns in on another’s chosen calling site.
A new study shows how the male túngara frog’s call inadvertently creates a multisensory message that can be exploited by both rivals and predators.
In addition to the acoustic component of the male’s call, the visual of his vocal sac inflating and deflating provides an extra cue in female attraction and male competition. But the pulsating sac also creates a third signal component — ripples on the surface of the water…
(read more: Wired Science)
photo by Ryan Taylor/Salisbury University