Modern Biology in a Monastery Garden 

If a river has a chance, it will meander, winding over the land in a series of loops. Geologists even call these loops "meanders."

You can see meanders on a map--along the lower Mississippi, the Alabama River near Selma, The Arkansas near Tulsa, the Ohio near Evansville, and on thousands of smaller streams--wherever there's a steady flow of water over nearly flat land of fine-textured soils.

Rivers meander because any small bend in a river tends to grow.

Water flowing around a bend in a river is a little like a car speeding around a bend in a road. The water is thrown toward the outside of the turn. That fast-moving water erodes the riverbank on the outside of the bend.

Meanwhile, on the inside of the bend, the water flows more slowly. Sediment held by the water can settle out and accumulate along the inside bank.

So the water eats away the outside of the bend while it builds up the inside of the bend. The bend in the river grows into a big loop.

When the loop gets big enough, the water cuts across the narrowest part of the loop and starts the meandering process all over again. The cut-off loop becomes an oxbow lake.

A meandering river often alters its course. Mark Twain, in his book Life on the Mississippi, says that steamboat pilots of his day traveled up and down the river even when they weren't working, just to keep track of the latest changes in the course of the water.

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Hummingbirds have a voracious appetite for nectar, the sugary fluid secreted by flowers. To survive, they usually drink between five and fourteen times their weight in nectar every day. Finding all that nectar isn’t easy. Some flowers may have already been emptied of nectar by other visitors, or might be occupied by dangerous insects such as ants.

Biologists want to understand how hummingbirds use their senses to find the right flowers to feed at. They have long known that these tiny birds can locate flowers by vision. Although vultures are known to use the sense of smell to detect the corpses of dead animals, smell didn’t seem to play a role in the foraging behavior of hummingbirds. Earlier studies, for example, found no evidence that hummingbirds could use smell to tell whether or not a flower contained nectar.

In 2021 a team of researchers from California published the first evidence that hummingbirds do use smell to avoid danger. The researchers showed that hummingbirds could detect and avoid the smell of a chemical secreted by Argentine ants to attract other ants, and the smell of a defensive chemical released by some other ant species. 

The researchers allowed more than one hundred hummingbirds to choose between two feeders. One contained sugar water alone, and the other contained sugar water scented with one of the ant chemicals. The hummingbirds specifically avoided the chemicals secreted by dangerous ants, but didn’t avoid harmless smells. They ignored the scent of a common food additive not found in nature, and the smell of European honeybees.

The finding helps biologists better understand how animals use their senses during the complex task of foraging for food.

Reviewer: Danielle J. Whittaker, Michigan State University

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Have you ever wondered why some cuisines, like Indian and Thai, are so spicy and others, like English, are so bland?

India and Thailand are very hot countries, while England is cold and damp. The answer does have something to do with the climate associated with each cuisine, but maybe not in the way that you'd first think.

You might wonder why would you want to eat spicy food when it's hot outside in the first place. Does it cool you off by making you sweat more? While that's an interesting theory, there are a few better explanations. 

The first one is that spices mask spoilage, and in a country with a hot climate and without refrigeration, that can come in handy.

For the second theory, some scientists suggest that the spices in hot cuisines help protect humans from certain kinds of bacteria found in food. In fact, the hotter the country, the more likely it is that its recipes will use the kind of spices that slow down the growth of bacteria.

For example, onion, garlic, oregano, and allspice alone all kill or inhibit up to twenty-nine different kinds food-borne bacteria. In fact, most spices inhibit bacteria to some extent. And if you think about it, this makes sense. As plants evolved, they had to learn to fight off parasites and bacteria in order to survive. That's how they got their distinctive flavoring in the first place.

All this talk about food is making me hungry.

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• Why Files - The Spice of Life

What legendary creatures of the deep fill you with wonder? The squid-like kraken, able to tear ships pirate apart with its tentacles? Or the megalodon, an enormous shark from millions of years ago? Or sirens, mermaids who lure sailors to their death?

These monsters haunt old stories of the ocean. We’re fascinated by their supernatural mystery. And perhaps no epic animal of lore enchants, inspires, and awes like the mighty dragon.  

Science hasn’t discovered any giant, flying, fire-breathing lizards quite yet. But if we look very carefully off Australia’s southern coast, we can find a creature straight from a maritime fairy tale: the leafy seadragon.

Of course, it might take a good long look to actually find any leafy seadragons. While not mythical like their namesakes, these foot-long fish are masters of camouflage, able to blend in with the kelp and other seaweed of their habitat.

Leafies, as they’re affectionately nicknamed, have long, undulating bodies, reminiscent of their relatives the seahorse. If you’re lucky enough to spot one, you’ll notice around twenty delicate, leaf-like appendages extending from their ribs and backbone, gently wafting in the water. As they swim, they create the illusion of floating seaweed. Shallow water leafies are often yellow or olive toned, while deep water leafies tend to be dark brown, or rich burgundy.

Their hypnotizing, magical appearance makes leafies a favorite of aquariums worldwide. In the wild, however, leafy seadragons are listed as near threatened, possibly due to over-capture and habitat loss. Will the beautiful leafy seadragon soon be reduced to myth? Conservation efforts bring together science and enchantment to save a real-life dragon.

Reviewer: Greg Rouse, the Scripps Institute of Oceanography

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If you’ve seen a grove of quaking aspen, you’ll recall trees with smooth, grey-white bark fissured with black streaks and flat leaves of green and yellow that shimmer with the lightest breeze.

A forest canopy of quaking aspen is often dense where sunlight is plentiful because they’re intolerant of shade. This growing pattern allows quaking aspen to colonize large swaths of land, with individual trees of fairly uniform arrangement, size, distribution, and health quality. We call this community of trees a “stand.”

A stand of quaking aspen may account for an extensive plot or just a minor part of a larger forest, sure to crowd out conifers or shrubs that attempt to invade its space. When one aspen tree falls, often another will quickly take its place and sprout from its roots, rather than a seed. 

Aspen grow aggressively and take advantage over shade-loving plants to repopulate their own stands. While relatively few of its seeds will become established, an aspen can regenerate individual trees by shoots along its long, lateral roots. A single root system can reproduce hundreds of individual trees in this way—each one genetically identical to the parent tree. 

A group of aspens with a single root system is called a “clone.” Clones can be less than an acre or up to 100 acres in size. These single organisms become immense and live much longer than any one tree could.

Individual aspen often don’t live beyond 150 years or so; while a clone can live for generations. The Pando Clone of Utah is one prime example, having outlasted its conifer competitors for the span of many eras.

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Many animal appendages, such as legs, tails, beaks, or ears can be used to dissipate excess body heat. Because of this cooling function, these body parts generally have a larger surface area relative to their volume for mammals and birds that live in warmer climates than for such animals that live in colder climates. This principle of animal form is called ‘Allen’s rule’ after its discoverer; the American zoologist Joel Allen.

In 2021 a team of Australian and Canadian researchers published a review summarizing evidence that many mammal and bird species are changing the shapes of their bodies over time, in accordance with Allen’s rule, to cope with the warmer climate resulting from human-caused global climate change. The evidence is particularly pronounced for several species of Australian parrots. The relative sizes of the bills of these birds have increased by four to ten percent between 1871 and the present. This increase occurred in step with increasing summer temperatures.

Similar changes were found in numerous other bird species, including the dark-eyed junco, a North American bird. The bills of birds are especially important for removing heat because they are rich in blood vessels and aren’t insulated by feathers. In mammals, legs, tails, ears, and bat wings play a similar role in heat dissipation because they are likewise rich in blood vessels and not insulated by fur.

The researchers noted corresponding increases in the relative sizes of these body parts for a variety of mammals including shrews, mice, and bats. In ongoing work, the researchers are extending their analysis to more species and habitats. The research highlights the serious ecological consequences of human-caused global climate change.

Reviewer: Ryan Long, the University of Idaho

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Today's moment of science is inspired by the plethora of crime dramas. How do the one-way mirrors we see in these shows so often actually work?

The trick is simpler than you might think. Most mirrors are made by applying a thin layer of a reflective material, aluminum in most cases, to the back of a sheet of glass. This is called back silvering, and it makes the glass opaque. When we look in a mirror, our image is reflected by the aluminum, which is made more durable by its glass covering.

So, one-way glass isn't fully silvered. The reflective material is applied less densely. This is called half-silvering. The effect is that the glass is not completely opaque like a traditional mirror. About half the light striking the glass passes through it, and the other half is reflected.

So far, people on both sides would see the same thing: fractured images of both themselves and the people on the other side.

Now for the second trick to one-way glass: the lighting. The room the suspect is in is kept bright, so that the reflective quality of the glass prevails. The room on the other side of the glass is kept dark, so that instead of their reflections, the detectives see what is illuminated on the suspect's side of the glass: the suspect.

But, if the light were to be turned up on the detective's side or turned down on the suspect's side, the magic would fizzle, and glass would become a window for both parties.

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We don’t usually think of friends in terms of what advantages they give us, although, if asked, most people would probably say that their friends add a lot to their lives.

Scientists view friendship among animals in slightly starker terms: if strong social bonds exist between animals, it probably means such ties directly benefit the animals in some way. A team of researchers set out to find out whether the benefit of friendship between male chimpanzees may be to further a goal that many animals share—more offspring. 

To do that, they examined genetic and behavioral data of a group of chimpanzees in Tanzania. They found that males who had a larger number of social ties with other males did tend to have more offspring. Males with at least two social ties to other males were over 50% more likely than other males in the dataset to have had any given offspring.

Previous research has shown that animals that form more coalitions—two or more individuals join to act aggressively towards a third—rise in rank and have more offspring. The team thinks that males who form more social bonds may be more likely to form coalitions, which could be why they’re also observed to have more reproductive success. The team also looked at what effect social ties to an alpha male had, and found that friendship with an alpha male also increased a male chimp’s chance of having an offspring.

What’s interesting is that social bonds with either multiple males or with an alpha male can lead to reproductive success. Male chimps don’t necessarily have to have friends in high places, they just need to have friends.

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• ScienceDaily - Building bonds between males leads to more offspring for chimpanzees

Are you a twin? No, well are you sure?

You could be a twin, but the twin is within, or a chimera.

A chimera is a mythological beast with the head of a lion, the body of a goat, and the tail of a dragon. However, in biology a chimera is an organism made up of two distinct genetic lines.

It's what happens when twin embryos fuse in the womb. The fusion results in what looks like a single embryo, but the genetic material from each twin remains separate.

What does that mean? Does a chimera have one arm from one twin and the other arm from the other twin?

Well, it's something like that. It's not like the arms would look different, exactly, or that the body's organs wouldn't be compatible or not work properly.

However, they do contain different and distinct sets of chromosomes. If you're a chimera, your liver could be composed of cells with one set of chromosomes while your heart, say, consists of cells with an entirely different set.

" Chimera (Genetics)." Wikipedia. Re-accessed for re-run on July 30, 2018.