FYFD

Tag: biology

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    Freshwater Mussels

    Freshwater bivalves like these California floater mussels are critical species for the health of our waters. And although we don’t think of mussels as being very mobile, they’re actually quite active. As larvae, the mussels get released from their parent bivalve and attach to the fins or gills of a fish. While they develop, they cling to the fish, hitching a ride until they’re ready to strike out on their own. Considering the fluid forces typical on those areas of a fish, that means the larvae must have some impressive strength!

    Once grown, the mussels anchor themselves using their tongue-like foot and begin their filter-feeding. They draw water in through a cilia-lined inlet, filter out algae, oxygen, and other nutrients, and expel clean water. This constant cycling, though largely invisible to the naked eye, is how bivalves keep their native waterways clean. (Image and video credit: Deep Look)

  • Recreating Infinity

    Recreating Infinity

    In the ocean, tiny organisms can migrate hundreds of meters through the water column. Recreating and tracking those journeys in a lab is quite a challenge, but it’s one the researchers behind the Gravity Machine have conquered. This apparatus uses a wheel to essentially give micro-organisms an infinite water column to traverse while keeping them fixed in the lab microscope’s field of view.

    With the device, researchers can watch organisms switch naturally between rising, sinking, and feeding behaviors as they would in the wild. The group is working to make it so that anyone with a microscope can recreate their set-up for observations. (Image, video, and research credit: D. Krishnamurthy et al.; see also Gravity Machine; submitted by Kam-Yung Soh)

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    A Primer on Blood Pressure

    Some of the most important fluid dynamics goes on every moment inside our bodies. After only a few weeks of gestation, the human heart begins its lifelong task of pumping blood throughout tens of thousands of kilometers’ worth of blood vessels. One of our simplest methods for tracking the health of this critical system is a person’s blood pressure, which measures the forces exerted on our blood vessels as our hearts pump. This video gives a brief primer on blood pressure as well as some of the problems that arise when extended bouts of high blood pressure damage our blood vessels. (Image and video credit: TED-Ed)

  • Bacterial Turbulence

    Bacterial Turbulence

    Conventional fluid dynamical wisdom posits that any flows at the microscale should be laminar. Tiny swimmers like microorganisms live in a world dominated by viscosity, therefore, there can be no turbulence. But experiments with bacterial colonies have shown that’s not entirely true. With enough micro-swimmers moving around, even these viscous, small-scale flows become turbulent.

    That’s what is shown in Image 2, where tracer particles show the complex motion of fluid around a bacterial swarm. By tracking both the bacteria motion and the fluid motion, researchers were able to describe the flow using statistical methods similar to those used for conventional turbulence. The characteristics of this bacterial turbulence are not identical to larger-scale turbulence, but they are certainly more turbulent than laminar. (Image credits: bacterium – A. Weiner, bacterial turbulence – J. Dunkel et al.; research credit: J. Dunkel et al.; submitted by Jeff M.)

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    Why Aren’t Trees Taller?

    Trees are incredible organisms, with some species capable of growing more than 100 meters in height. But how do trees get so big and why don’t they grow even taller? The limit, it turns out, is how far fluid forces can win over gravity.

    To live and grow, trees must be able to transport nutrients between their roots and their highest branches. As explained in the video, there are three forces that enable this transport inside trees: transpiration, capillary action, and root pressure. Of these, you are probably most familiar with capillary action, where intermolecular forces help liquids climb up the inside of narrow spaces, like the straw in your drink. Capillary action can’t lift liquids more than a few centimeters against gravity, though.

    Similarly, root pressure is limited in how far it can raise liquids. Functionally, it’s pretty similar to the way a column of water or mercury can be held up by atmospheric pressure acting at the base of a barometer. But atmospheric pressure can only hold up 10.3 meters of water, so what’s a tree to do?

    This is where transpiration — the most important force for sap transport in the tree — comes in. As water evaporates out of the tree’s leaves, it creates negative pressure that — along with water’s natural cohesion — literally drags sap up from the roots. It’s this massive pull that drives the flow and enables most of a tree’s height. (Image and video credit: TED-Ed)

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    Sundews Weaponize Viscoelasticity

    In nutrient-poor soils, carnivorous plants like the cape sundew supplement their diets by eating insects. To entice their prey, the cape sundew secretes droplets of sugary water. But unwary insects who land to feed soon find themselves unable to pull away from this viscoelastic liquid. Complex molecules in the fluid grant it elasticity, so when insects pull against it, the liquid stretches and pulls back instead of breaking up. Other carnivorous plants, like the pitcher plant, use similar non-Newtonian tricks to trap insects. (Video and image credit: Deep Look)

  • Fungal Fluid Dynamics

    Fungal Fluid Dynamics

    Many plants gain the soil-bound nutrients they need by trading with symbiotic fungi. Underground, these fungi spread networks that gather and store phosphorus, which they then trade with host plants to get the carbon they need. Research shows that the fungi can be shrewd traders, moving phosphorus from nutrient-rich areas to poorer ones in order to maximize their trade gains.

    What you see above are snapshots of some of this transport within the fungal network. Notice how flow within the branching network changes direction. The fungus can force these flow reversals in a matter of seconds, allowing it to move nutrients to wherever the best returns are found. (Image and research credit: M. Whiteside et al.)

  • The Power of a Penguin’s Rectum

    The Power of a Penguin’s Rectum

    When brooding their eggs, penguins can rarely leave the nest, but answering nature’s call is still necessary. To keep the nest clean, Adélie penguins project their feces up to more than a meter away. A new study refines previous calculations on this subject and finds that the penguin’s rectum develops far higher pressures than that of humans.

    In one hypothetical calculation, the authors estimate that a human of average height, capable of developing penguin-like rectal pressures, would project excrement more than 3 meters. In the authors’ words, “He/she should not use usual rest rooms.”

    Knowing the likely range of contact for penguins is important primarily for zookeepers, who understandably would like to avoid such projectiles. (Image credit: H. Neufeld; research credit: H. Tajima and F. Fujisawa; via phys.org)

  • Undulating Keeps Flying Snakes Steady

    Undulating Keeps Flying Snakes Steady

    Flying snakes undulate through the air as they glide. But, unlike on land, these wiggles aren’t for propulsion. A new study shows instead that they are key to the snake staying stable in flight.

    Upon take-off, a flying snake flattens its body, forming a wing-like shape that helps them generate lift and control drag. But while they glide, they also slither and pitch their tail.

    Researchers recorded more than 150 flights by live snakes, then used that data to construct their own digital snake. The model could fly like a real snake or be tested without undulations to see what would happen. The researchers discovered that, without that mid-air slithering, the snake quickly lost control and rolled to the side. (Image and research credit: I. Yeaton et al.; via NYTimes; submitted by Kam-Yung Soh)

  • Quantifying Bioluminescence

    Quantifying Bioluminescence

    Some single-celled organisms, like dinoflagellates, light up when disturbed. This bioluminescence is considered a defense mechanism, triggered by threats to the organism. Now researchers are quantifying just what it takes to light up a single dinoflagellate.

    Dinoflagellates respond both to stress caused by the fluid flow around them and to mechanical deformation — in other words, getting poked. Both methods involve bending and stretching the dinoflagellate’s cell wall, which stretches calcium-ion channels connected to bioluminescence. The researchers found that the intensity of the light produced depended both on the amount and speed of cell wall deformation.

    The model built from their observations should help scientists better understand what forces cause a specific response. That means dinoflagellates could be used as a non-invasive means of understanding fluid flow around swimmers like dolphins or sea lions! (Image and research credit: M. Jalaal et al.; via APS Physics)