Malevus

Tag: forest

  • Can Frogs Really Predict the Weather?

    Frogs are weather experts. Some frogs and toads, based on their croaking, egg-laying, and even skin color, are said to allow us to predict whether it will rain soon or not. But what is the truth behind the frogs’ purportedly preternatural weather forecasting abilities?

    Long ago in Switzerland, if you would put a tree frog in a jar half full of water and give it a little ladder to climb, it could forecast good weather by climbing the ladder and bad weather by descending back into the water. Even today, in Germany, a weatherman is referred to as a Wetterfrosch, which translates as “weather frog.”

    Tree frogs are known to climb trees in favorable weather and make an awful noise, croaking sweetly for hours on end, thus the frog weather prediction theory actually has some validity.

    Monitoring the Humidity

    Numerous accounts point out the daily behavioral changes in amphibians and some reptiles related to predicted weather. Some species, for instance, become more active just before it starts to rain, while others are more likely to make their distinctive croaking sounds. The weather probably has a lot to do with this shift in behavior.

    Frogs and toads are highly reliant on accurately monitoring the humidity or temperature of their surroundings. That’s because amphibians are ectothermic, meaning they don’t produce their own heat. So, their blood, muscles, and skin, along with the rest of their organs, are always at the same temperature as their surroundings.

    Exceptionally Sensitive to Moisture Levels

    Frogs’ skin is very porous because of the abundance of glands on its surface. Because of this, they suffer significant water loss due to evaporation. But frogs and toads have a more refined sense of moisture via their skin than people do. In the tropics, for example, certain frog species usually come out of the underbrush when the humidity rises in anticipation of rain.

    Finally, amphibians like frogs and toads produce their offspring in aquatic environments. Thus, in order to effectively reproduce, they have to predict when there will be adequate puddles and pools from rain in which their tadpoles may grow. This means that when the weather or temperature changes, frogs have to adjust their behavior accordingly.

    Climbing Tree Frog

    So why then do frogs choose to remain low when bad weather is approaching, yet climb up when conditions are favorable? There are no precise investigations of the topic available. However, there are two theories among frog scientists as to why this occurs: The tree frog, in contrast to most other frog species, enjoys vertical environments and bright sunlight. Male frogs, especially those still in their juvenile stages, spend most of the late summer sitting on bushy branches and leaves to soak up some rays.

    However, the accessibility of food is equally important. The same goes for tree frogs, who also utilize their perches to swoop down on prey. Insects like mosquitoes are sensitive to weather changes, something our ancestors accounted for in their agricultural guidelines. With less wind and more sunshine, insects may ride the warm updrafts to greater heights in their flights. They tend to linger on the ground if a severe wind and a drop in temperature are expected.

    It is unknown, however, whether tree frogs actively pursue prey higher or lower, or if they instead respond immediately to changes in the weather. One thing scientists can agree on is that frogs and toads frequently respond to a shift in the weather before humans do. And this, of course, has nothing to do with clairvoyance.

  • Why Do Some Female Spiders Eat Their Mates?

    Why do some female spiders eat their mates? You frequently hear the words “I love you so much” said between people newly in love. However, there are certain creatures who take this remark to a new level. They eat members of their own species, sometimes even when they’re mating. Particularly, spiders have a bad name for engaging in “sexual cannibalism.” The black widow spider has gained as much notoriety as the red-backed spider and the native cross spider for its reputation as a predator of male humans. Nevertheless, why do female spiders kill and eat males?

    Sexual Cannibalism

    Sexual cannibalism may be split into two distinct subtypes. The first involves females eating a male before mating, either out of hunger or to prevent mating. This is a common occurrence in a wide variety of animal species. However, this only applies to a tiny fraction of males and is by no means the norm.

    Sexual cannibalism also occurs during and immediately after the mating act. Scientists have discovered that females of certain species will systematically murder males if they so desire. For instance, Latrodectus hasselti, known as the Redback spider or the Australian black widow spider, and Argiope spiders fall within this category. Wasp spiders, recognizable by their striped abdomen of yellow, white, and black, are also members of this family.

    The Reason

    But why would the supposedly cruel and merciless female spiders engage in such strange behavior? They do this so that they may continue mating with different males while keeping the duration of copulation, or sexual intercourse, to a minimum. Finding a mate with the finest genes to inseminate the eggs is the main objective of mating for female spiders.

    In addition, the male spider makes a pleasant source of food and energy for females when consumed after being slain. There is a clear advantage to the children from this as well. Studies have shown that female spiders that consume males have bigger clutches (total number of eggs) than female spiders who are not allowed to consume males.

    Mating Length is the Key Factor

    Even yet, some male spiders still make it through the initial mating without being attacked by the female spiders. Variation exists even within species when it comes to the mortality rate of males following the first successful mating. Males that don’t mate for long enough are also at a higher risk of being eaten.

    Those males who get out of the encounter unharmed, however, don’t attempt to get away and instead go through with a second mating, which almost always ends in tragedy. Unfortunately, this still raises one’s odds of becoming a father and having offspring. When a male tries to push his luck and, in the end, sacrifices himself, this still lets him fertilize more of the female’s eggs.

    Before making love, the St. Andrews Cross spider (Argiope keyserlingi) uses a webbing to tie its mate to itself. Keeping the male around for longer may be desirable from the female’s perspective if she hopes to increase the number of eggs that are fertilized.

    Mates With Smaller Sizes Are More Likely to Be Eaten

    However, sexual cannibalism in spiders does not always seem to be caused by competition for evolutionary benefit. Researchers claim to have identified an alternative cause for this behavior. They claim that when men are physically inferior to their female companions, they are more likely to be eaten. This is true of many species, including the North American wolf spider, Tigrosa helluo.

    It is interesting to see that a seemingly insignificant factor—the size gap between sexes—plays such a crucial role in determining sexual cannibalism. The trade-offs involved in sexual cannibalism are usually rather simple. When a hungry female spider comes upon a “boyfriend” tiny enough to trap, she can’t stop the urge.

    Praying Mantises Also Show This Behavior

    The practice of eating and being eaten is not limited to the sexual partners of spiders. Scientists have known for a long time that the phenomena occur in various clades of animals. Some insects, including praying mantises, have earned a reputation for this behavior. These insects’ males have a very perilous existence before, during, and after mating. One Asian species, Hierodula membranacea, has females that have been seen biting off the males’ heads during intercourse; however, the sexual act continues undisturbed.

    Sources:

    • Sexual Cannibalism: Why Females Sometimes Eat Their Mates After Sex. (n.d.). Discover Magazine.

  • How do plants know when spring is coming

    It is getting closer and closer to spring as the days are getting longer and the temperatures are getting higher. Now that winter is coming to an end, nature will also soon emerge from its slumber: the first tips of new greenery are making their way out of the ground, the buds on many shrubs and trees are beginning to thicken, and crocuses, snowdrops, and daffodils appear to be just waiting to finally bloom. However, how do they determine when the time is right? What causes some flowers to bloom first while others lag behind?

    There is a vast arsenal of different triggers, each of which is effective on its own or in combination with other triggers. Internal factors such as plant hormones, genes, or the minimum size of the plant can also influence whether or not it flowers and when it does so, in addition to external factors such as the length of the day and the temperature of the surrounding environment.

    The chill of winter helps the formation of flowers

    A drop in temperature is the primary stimulant that causes bulb formation in many bulbous plants. For example, daffodils, crocuses, and tulips require at least a few weeks of cold weather during the winter to initiate the first stages of flowering in the bulbs that make up their stems and leaves. These precursors are not activated, and the flower does not begin to sprout until the weather becomes warmer again in the springtime. Particularly low temperatures, on the other hand, can reverse this pushing of the flower. Because of this, the bud will not emerge from the protective soil even if there is an abrupt drop in temperature after the first few warm days.

    Many types of fruit trees even have their own built-in version of a heat counter, which allows the plants to keep track of the number of warm days and calculate with a high degree of precision whether or not the climate is already suitable. The trees won’t start to sprout new growth until after a predetermined number of warmer days have passed. Because of this, even a small number of unusually warm days during the winter cannot cause flowering to begin. The hazelnut, on the other hand, does not have this temperature regulator, and as a result, it can “pleasure” people who suffer from pollen allergies even in the winter, provided that the weather is warm enough for a few days.

    The flowering program is activated when the day length increases

    The length of the days is another factor that plays a significant role, as many plants flourish when the winter nights become shorter and the summer days become longer. As soon as the ratio of daytime to nighttime hours reaches a predetermined point, they will start to bloom. There are several plant species, including crop plants such as lettuce and spinach, for example, that are solely stimulated by light.

    But how exactly do these plants measure the length of the day? There is a possibility that, just like us humans, they could possess an internal clock as well. This ticks about once every twenty-four hours, and as a result, it serves as an inner reference point. Their genes also regulate the minimum amount of light exposure required during this time before they will start to bloom. This limit is different for each species, and it can even change between individuals of the same species.

    An instrument measures how bright its surroundings are

    Plants are able to detect light through phytochromes proteins
    Plants are able to detect light through phytochromes proteins, just like bacteria and fungi. (Credit: NSF)

    Plants have light sensors embedded in their tissues so that they can determine whether or not it is bright or dark in their immediate environment. Plants are able to detect and absorb light through a group of photoreceptor proteins known as phytochromes. They make use of them to keep track of the length of the day, and then use a complicated mechanism to compare this learning with the time kept by their inner clock. If the specified limit value is then surpassed in the spring, this will trigger an all-domino effect of physical changes, and the plant will begin to bloom as a result of these modifications.

    It is the other way around for flowers that do not bloom in spring but rather in fall or winter; for them, the dark phase of the night must first reach a minimum duration before they form a flower. It is already adequate for plants with such short day lengths to turn on the light for only a brief period each night to prevent them from blooming again. These can include things like the poinsettia or the flaming beetle, for instance. Horticulture requires the shading of certain plant species because the light from moving vehicles, for example, is enough to prevent flowers from opening properly.

  • How Much Energy do Trees Need in Kilowatt-Hours

    How much energy do trees need in kilowatt hours in order to continue living? For the first time, researchers have calculated how much work a tree must do to pump water up from its roots to its leaves, a process that requires a lot of energy due to the pull of gravity and the resistance of the tree’s vascular system. As a result, each tree uses 0.0056 watts per square foot or 0.06 watts per square meter of surface area, and together, trees produce 9.4 trillion kilowatt hours per year for their water transport, which is almost equivalent to our worldwide energy output from hydropower.

    There are over three trillion trees on Earth or roughly 422 trees for every human. The oxygen they produce by photosynthesis is vital to all life on Earth and acts as a natural temperature regulator. Trees also have a considerable cooling impact due to the evaporation of water from their leaves. Rainforests with a large enough surface area, like the Amazon, create their own microclimate and, essentially, provide their own rainfall.

    XYlem
    Xylem, which looks like a network of bundles that resemble a ladder, is how plants move water upwards. This part reveals their holes. (Credit: The Sinhyu/Getty Images)

    The Suction is Produced by Evaporation and Photosynthesis

    But before a tree can do any of that, it has to put in a lot of effort: it has to get the water from the ground all the way to the top. A tree has to fight against both gravity and the friction created by its tube system to do this. Water transport in the tree is completely passive: the suction caused by evaporation in the crown draws the water upwards, while human blood circulation is propelled by its own pump, the heart.

    However, the energy required for this mode of transportation is considerable. The light provides this by facilitating both the transpiration of water through the leaves and its transformation during photosynthesis. Plants would not be able to produce enough energy via their own metabolism alone to meet this requirement.

    To get water from one place to another in a tree, how much work does the tree have to put in? Scientists have finally made a more accurate calculation of this. They did this by combining data from biophysical models and satellite images of forest cover with measurements of sap ascent and the plant’s circulatory system.

    Annual Global Use of 9.4 Petawatt Hours

    To get water from their roots to their leaves, plants in worldwide forest ecosystems need 0.0056 watts per square foot or 0.06 watts per square meter of energy. Sounds like not much, but it’s 14.2% of the energy a tree requires to convert sunlight into sugar during photosynthesis. This labor, in contrast to photosynthesis, is passive, and it increases when environmental conditions like temperature and humidity change, making more water available for photosynthesis.

    In order to get water from their roots to their leaves, trees have to expend a lot of energy.
    In order to get water from their roots to their leaves, trees have to expend a lot of energy. (Little Dinosaur/Getty Images)

    Overall, this amounts to a massive sum: worldwide, all forest ecosystems need 9.4 petawatt-hours per year for sap ascent, which is equal to the entire annual output of all man-made hydroelectric power. The same figure in kilowatt-hours is 9.4 quadrillion. In tropical rainforests, trees accomplish most of this labor by transporting water, which uses up around 18% of the energy produced by photosynthesis.

    It is About Stem Resistance

    Also unexpected: the researchers found that the energy needed to overcome gravity accounts for just a tiny portion of the total energy required in the upward transfer of water in the tree. Most of the energy is used to overcome the resistance in the tree’s circulatory system. The internal resistance of a drought-adapted juniper tree, for example, is rather great, whereas the black poplar that grows in a floodplain acts like a giant water pump.

    Therefore, the estimated worldwide energy required for tree sap to ascent is likewise very unknown, falling somewhere between 7.4 and 15.5 petawatt-hours. These unknowns highlight how little we understand about the biogeography of plant resistance and, to a lesser degree, transpiration. It’s astounding that no one has ever attempted to measure a global energy flow on this scale. So far, this appears to have just slipped between the cracks.