daily science facts

The oceans — their sea levels, temperatures and acidity all on the rise — do not read Breitbart News in the United States or the Daily Mail in the United Kingdom, which by spreading science denial put the most vulnerable at risk.
—  Cynthia Barnett’s Op-Ed in the LA Times, read here. 
Today's science fact is about octopodes.

The octopus is not only very intelligent, but has an extremely complex nervous system. So much so that its brain isn’t large enough to properly calculate the movement of its limbs. In a mammal like a human, muscle movement is coordinated in the brain or, for many involuntary movements, the spinal chord. In an octopus, the brain decides how a limb will move, but most of the actual movement is coordinated by nerve networks in the limb itself; those signals don’t come from the brain.

Today's science fact is about the spleen.

The spleen is an important but nonvital organ. It’s obvious job is to filter and recycle blood, but it also acts as a blood reservoir. The spleen holds a reserve of blood that is released to fight shock. It also houses half of the body’s monocytes (a type of white blood cell). These cells act as a reservoir to be dispatched if there’s an injury, creating a better immune response than just those patrolling the bloodstream. So in addition to being a blood filter, the spleen is an important regulatory organ in case of physical change or injury.

Today's science fact is about hand nerves.

It’s been previously mentioned that the fingers don’t contain muscles, just tendons; the muscles responsible are in the arm. In fact, the muscles that control all hand movements are controlled by just three motor nerves – the median, radial and ulnar nerves. These three nerves produce all the precise and varied hand movements and positions that we are capable of.

One easy way to differentiate the three nerves is through rock, paper, scissors. Coincidentally, each nerve is responsible for producing one of these hand forms. The clenched fist is a function of the median nerve. The spread palm is a function of the radial nerve. She scissors (actually a slight variation on the scissors is often used, where the index and middle fingers are held together and the thumb is held upward, but this is a quite difficult gesture for many people to produce) is created by the ulnar nerve. Although simpler tests are usually used by professionals, the “rock, paper, scissors” formations are one simple way to check for proper function of these nerves.
Today's science fact is about choices.

To maximise commitment to a decision, the best amount of options to give a human is three. Humans can handle about six options before the brain starts to give up; although we consciously feel better with as many choices as possible, the brain can’t really handle more than six. (This might explain why it’s harder to find something to watch on hundreds of TV channels than on just a few.) Experiments involving jam sales show that people given about six choices of jam to buy will try a couple before buying one; if given much more options, they are more likely to try many more and express appreciation of them, but less likely to actually buy any jam.

Today's daily science fact is about plaque and heart disease.

There is a causal link between tooth plaque and certain types of heart disease.

The reason is immune. The immune system identifies bacterial invaders based on proteins in their membrane (proteins the immune system reacts to are called antigens), and some bacteria that cause and live in plaque have proteins very similar to those in the cells that make up heart valves. If these bacteria get into the bloodstream through damaged gums (which is more likely to happen if they build up in plaque), there is a slight chance that the immune system will end up mounting a defense against its own heart cells, and slowly damage the heart.

Today's science fact is about viral endosymbiosis.

Awhile ago we talked about the cell organelles mitochondria (for energy creation) and chloroplasts (for photosynthesis) being bacteria that invaded or were eaten by early eukaryotic cells and became symbiotes. Well this is also one hypothesis for the origin of our DNA – that it used to be a virus.

DNA in eukaryotic cells (like plants and animals) is very different to DNA in prokaryotic cells (like bacteria). Eukaryotic DNA is linear, like a virus, and packed and read similarly to large DNA viruses. This hypothesis is quite contentious, though. (Since DNA viruses hijack our cells to make more of them, it would also make perfect sense for them to evolve to be more similar to our DNA.)

Today's science fact is about wolbachia.

Wolbachia are bacteria that infect mostly insects. Wolbachia are extremely interesting to evolutionary biologists, because they infect the ovaries and testes of their hosts and are passed down to offspring through the female line. They can have several effects on the reproduction of host species to ensure they end up in as many children as possible. Common results of a wolbachia infection are:

- Death of infected male larva. Males are “dead ends” to wolbachia. They’re inherited from the mother, so by killing off all the male larva, the infected females have a better chance to survive and pass them on.

- Stop infected males from being able to fertilise uninfected females. This can cause speciation events in the host species.

- Feminisation of males. In the most successful cases, male carriers will become female instead, allowing them to pass on wolbachia to their children.

- Parthenogenesis (asexual reproduction). Some strains of wolbachia make their female hosts able to reproduce asexually, ensuring they end up in all the (female) children. Wolbachia has killed nearly all the males of one species of wasp and enables the females to reproduce without them.

today's science fact is about an animal/plant fusion: Elysia chlorotica!

E. chlorotica is a sea slug that literally sucks the chloroplasts out of algae and preserves them to use for photosynthesis. Once a baby slug ingests enough chloroplasts it can potentially never have to eat again, relying on the sun for its energy needs. Recent studies have found that the slug encodes and expresses plant genes encoding chlorophyll- the green pigment used in photosynthesis- which needs to be continuously replaced in chloroplasts.

Today's science fact is about bacteria and scent cues.

Human sweat is almost entirely odourless to humans. The smell arises when bacteria in the skin break it down into other, smellier compounds, which is why sweat on some parts of the body smells worse than others (different bacteria live in different places). This is also true for a lot of animals that use scent cues, from sweat, to urine, to pheremones; if you take the bacteria away, there’s practically no smell.

What makes this particularly interesting is that we know that these scent cues contain genetic information. Human sweat tells people about the secreter’s major histocompatability complex (which is genetic), and whether or not they are close biological family. This doesn’t depend on whether they live together, so it’s not a question of shared bacteria, but the secretions themselves. The precise chemical differences in these secreted fluids can affect the bacterial fermentation reliably enough that they can be used as cues, even though the secreter didn’t secrete anything that can be smelled.

Theoretically, it’s very likely that the bacterial makeup affects these cues as well, so animals who live together (and thus share bacteria) are likely to smell more similar in some respects than animals that don’t, but this hasn’t been experimentally verified to my knowledge.

It's Misconception Sunday! Today's science misconception: that touching baby birds will make their mother abandon them because they smell human.

In fact, birds not only have a fairly bad sense of smell, they won’t abandon handled babies. They will wait until you’re out of the way and then go back for them. Still, it’s a bad idea to go touching baby birds that are sitting in their nests. (Birds will often abandon eggs that have been interfered with; it suggests a predator is lurking about.)

The appropriate thing to do with baby birds depends on their age. If they’re nestlings – they have no feathers – and you find them under a nest, the best thing to do is gently put them back. If they’re fledgelings – they’re growing their early feathers – they’re probably just practising flying. Put them back in the tree if the environment is dangerous (if they’re on a road or there are predators about), but otherwise leave them alone.

It's misconception Sunday! Today's science misconception: humans have five senses

In actual fact, the number of senses humans have has never been officially quantified. Depending on your definitions, it could be a dozen of it could be a hundred, but it is definitely a lot more than five. Senses that are often forgotten about include:

Equilibrioception: sense of balance, our “gravity sense”

Proprioception: Our sense of limb position relative to each other

Pain, texture, heat/cold, pressure: These are all distinct senses, not a single sense of “touch”.

… as well as many others.

Is it herpes awareness week?

 In the past 24 hours, sixteen people have liked or reblogged the Daily Science Fact about herpes ( http://dailysciencefacts.tumblr.com/post/27104912276/todays-daily-science-fact-is-about-herpes ). Only one like and no reblogs have not been about herpes. Two new people have started following Daily Science Facts, presumably due to herpes.

Why is herpes so damn popular all of a sudden?!

Today's science fact is about human pregnancy.

Human infants are born far too early. Conventional wisdom holds that this is due to a combination of bipedalism and the exceptionally large human brain; a fully formed human skull wouldn’t fit through a birth cavity small enough to allow bipedal movement.

While this is true, recent research has shown that it might not be the primary cause of birth timing. Wider pelvises don’t result in the walking and running problems they’ve always been assumed to, and they could be a little wider still and be fine, and while some infant skulls are dangerously large the majority of them could be larger and still fit through a birth canal. (There are a lot of potential hazards in childbirth, but very few are related to skull size.) In fact, the big driver of our early births might be because human pregnancy is antagonistic in nature. A fetus is competing for resources with its carrier, and the two need to reach a delicate balance where both get what they need. It may simply be that it’s safer for both parties to terminate the conflict and carry the infant outside the body than allowing it to develop completely in the uterus. (Some other animals, such as kangaroos, deliver their offspring even earlier, possibly for similar reasons.)

Today's science fact is about plant hormones. Specifically, ethylene.

Ethylene is a chemical that plants release in response to damage or disease. It contributes to the “cut grass smell”. When nearby plants detect ethylene, they amount an immune response; it’s a warning call to its neighbours, like an animal’s scream. It also causes plant cells to age and die; this is most notable as ripening fruit. Ethylene ripens fruit and the ripening causes more ethylene to be released, creating a positive feedback effect. This is why storing some types of fruit together in airtight bags makes them ripen faster. It’s also how producers artificially ripen fruit.

Today's science fact is about scabies.

Scabies is a skin infection. It is caused by tiny, invisible mites that burrow under the skin and breed. While it’s most common in countries with poor sanitation, it can occur anywhere in the world and is spread by skin-skin contact. Often the burrows made by these mites can be seen, which look like a little row of flea bites.

Scabies causes intense itching, usually with a rash. For a first infection, these symptoms don’t usually appear until after six weeks of infection; they appear much sooner in people who have had scabies before. Normally, the immune system will eliminate scabies eventually, but for immunocompromised people, the disease can progress into “crusted scabies”, there the infection gets so intense that the rashes become thick, crusty skin filled with thousands of mites. The tough skin flakes protects the mites, making crusted scabies very difficult to treat.

Scabies can infect any part of the body except the face, but the most common areas are where the skin naturally folds, such as the feet, the webs of the hands, and the genitals.

Today's science fact is about bird milk.

Generally, the mammalian class is defined by the presence of mammary glands, and thus the ability to produce milk. But pigeons, doves and flamingos (which are, of course, not mammals) also produce milk, and it’s remarkably similar to mammalian milk. This is produced in throat pouches.

Male emperor penguins, who hatch eggs and keep watch over their young while the mothers hunt, will also produce milk if the mother takes too long returning with meat.