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Biology Week is an annual celebration of the biological sciences that aims to inspire and engage the public in the wonders of biology. The Society of Biology created this awareness day in 2012 to give everyone the chance to learn and appreciate biology, the science of the 21st century, through varied, nationwide events. Our belief that access to education and research changes lives for the better naturally supports the values behind Biology Week, and we are excited to be involved in it year on year.
Biology, as the study of living organisms, has an incredibly vast scope. We’ve identified some key figures from the last couple of centuries who traverse the range of biology: from physiology to biochemistry, sexology to zoology. You can read their stories by checking out our Biology Week 2014 gallery below. These biologists, in various different ways, have had a significant impact on the way we understand and interact with biology today. Whether they discovered dinosaurs or formed the foundations of genetic engineering, their stories have plenty to inspire, encourage, and inform us.
If you’d like to learn more about these key figures in biology, you can explore the resources available on our Biology Week page, or sign up to our e-alerts to stay one step ahead of the next big thing in biology.
Headline image credit: Marie Stopes in her laboratory, 1904, by Schnitzeljack. Public domain via Wikimedia Commons.
They might be short-lived — but between the time a bubble is born (Fig 1 and Fig 2a) and pops (Fig 2d-f), the bubble can interact with surrounding particles and microorganisms. The consequence of this interaction not only influences the performance of bioreactors, but also can disseminate the particles, minerals, and microorganisms throughout the atmosphere. The interaction between microorganism and bubbles has been appreciated in our civilizations for millennia, most notably in fermentation. During some of these metabolic processes, microorganisms create gas bubbles as a byproduct. Indeed the interplay of bubbles and microorganisms is captured in the origin of the word fermentation, which is derived from the Latin word ‘fervere’, or to boil. More recently, the importance of bubbles on the transfer of microorganisms has been appreciated. In the 1940s, scientists linked red tide syndrome to toxins aerosolized by bursting bubbles in the ocean. Other more deadly illnesses, such as Legionnaires’ disease have been linked since.
Figure 1: Bubble formation during wave breaking resulting in the white foam made of a myriad of bubbles of various sizes. (Walls, Bird, and Bourouiba, 2014, used with permission)
Bubbles are formed whenever gas is completely surrounded by an immiscible liquid. This encapsulation can occur when gas boils out of a liquid or when gas is injected or entrained from an external source, such as a breaking wave. The liquid molecules are attracted to each other more than they are to the gas molecules, and this difference in attraction leads to a surface tension at the gas-liquid interface. This surface tension minimizes surface area so that bubbles tend to be spherical when they rise and rapidly retract when they pop.
Figure 2: Schematic example of Bubble formation (a), rise (b), surfacing (c), rupture (d), film droplet formation (e), and finally jet droplet formation (f) illustrating the life of bubbles from birth to death. (Bird, 2014, used with permission)
When microorganisms are near a bubble, they can interact in several ways. First, a rising bubble can create a flow that can move, mix, and stress the surrounding cells. Second, some of the gas inside the bubble can dissolve into the surrounding fluid, which can be important for respiration and gas exchange. Microorganisms can likewise influence a bubble by modifying its surface properties. Certain microorganisms secrete surfactant molecules, which like soap move to the liquid-gas interface and can locally lower the surface tension. Microorganisms can also adhere and stick on this interface. Thus, a submerged bubble travelling through the bulk can scavenge surrounding particulates during its journey, and lift them to the surface.
When a bubble reaches a surface (Figure 2c), such as the air-sea interface, it creates a thin, curved film that drains and eventually pops. In Figure 3, a sequence of images shows a bubble before (Fig 3a), during, and after rupture (Fig 3b). The schematic diagrams displayed in Fig 2c-f complement this sequence. Once a hole nucleates in the bubble film (Fig 2d), surface tension causes the film to rapidly retract and centripetal acceleration acts to destabilize the rim so that it forms ligaments and droplets. For the bubble shown, this retraction process occurs over a time of 150 microseconds, where each microsecond is a millionth of a second. The last image of the time series shows film drops launching into the surrounding air. Any particulates that became encapsulated into these film droplets, including all those encountered by the bubble on its journey through the water column, can be transported throughout the atmosphere by air currents.
Figure 3: Photographs, before, during, and after bubble ruptures. The top panel illustrated the formation of small film droplets; the bottom panel illustrates the formation of larger jet drops. (Bird, 2014, used with permission)
Another source of droplets occurs after the bubble has ruptured (Fig 3b). The events occurring after the bubble ruptures is presented in the second time series of photographs. Here the time between photographs is one milliseconds, or 1/1000th of a second. After the film covering the bubble has popped, the resulting cavity rapidly closes to minimize surface area. The liquid filling the cavity overshoots, creating an upward jet that can break up into vertically propelled droplets. These jet drops can also transport any nearby particulates, also including those scavenged by the bubble on its journey to the surface. Although both film and jet drops can vary in size, jet drops tend to be bigger.
Whether it is for the best or the worst, bubbles are ubiquitous in our everyday life. They can expose us to diseases and harmful chemicals, or tickle our palate with fresh scents and yeast aromas, such as those distinctly characterizing a glass of champagne. Bubbles are the messenger that can connect the depth of the waters to the air we breathe and illustrate the inherent interdependence and connectivity that we have with our surrounding environment.
Biomechanics is the study of how animals move. It’s a very broad field, including concepts such as how muscles are used, and even how the timing of respiration is associated with moving. Biomechanics can date its beginnings back to the 1600s, when Giovanni Alfonso Borelli first began investigating animal movements. More detailed analyses by pioneers such as Etienne Jules Marey and Eadweard Muybridge, in around the late 1800s started examining the individual frames of videos of moving animals. These initial attempts led to a field known as kinematics – the study of animal movement, but this is only one side of the coin. Kinetics, the study of motion and its causes, and kinematics together provide a very strong tool for fully understanding the strategies animals use to move as well as why they move the way they do.
One factor that really changes the way an animal moves is its body size. Small animals tend to have a much more z-shaped leg posture (when looking at them from a lateral view), and so are considered to be more crouched as their joints are more flexed. Larger animals on the other hand have straighter legs, and if you look at the extreme (e.g. elephant), they have very columnar legs. Just this one change in morphology has a significant effect on the way an animal can move.
We know that the environment animals live in is not uniform, but is cluttered with many different obstacles that must be overcome to successfully move and survive. One type of terrain that animals will frequently encounter is slopes: inclines and declines. Each of the two different types of slopes impose different mechanical challenges on the locomotor system. Inclines require much greater work from the muscles to move uphill against gravity! On declines, an animal is moving with gravity and so the limbs need to brake to prevent a headlong rush down the slope. Theoretically, there are many ways an animal can achieve successful locomotion on slopes, but, to date, there has been no consensus across species or animals of differing body sizes as to whether they do use similar strategies on slopes.
From published literature we generated an overview of how animals, ranging in size from ants to horses, move across slopes. We also investigated and analysed how strategies of moving uphill and downhill change with body size, using a traditional method for scaling analyses. What really took us by surprise was the lack of information on how animals move down slopes. There was nearly double the number of studies on inclines as opposed to declines. This is remarkable given that, if an animal climbs up something inevitably it has to find a way to come back down, either on its own or by having their owner call the fire department out to help!
Most animals tend to move slower up inclines and keep limbs in contact with the ground longer; this allows more time for the muscles to generate work to fight against gravity. Although larger animals have to do more absolute work than smaller animals to move up inclines, the relative stride length did not change across body size or on inclines. Even though there is much less data in the literature on how animals move downhill, we did notice that smaller animals (<~10kg) seem to use different strategies compared to large animals. Small animals use much shorter strides going downhill than on level terrain whereas large animals use longer strides. This difference may be due to stability issues that become more problematic (more likely to result in injury) as an animal’s size increases.
Our study highlights the lack of information we have about how size affects non-level locomotion and emphasises what future work should focus on. We really do not have any idea of how animals deal with stability issues going downhill, nor whether both small and large animals are capable of moving downhill without injuring themselves. It is clear that body size is important in determining the strategies an animal will use as it moves on inclines and declines. Gaining a better understanding of this relationship will be crucial for demonstrating how these mechanical challenges have affected the evolution of the locomotor system and the diversification of animals into various ecological niches.
Image credit: Mountain goat, near Masada, by mogos gazhai. CC-BY-2.5 via Wikimedia Commons.
