Posted on 20 July 2011.
Posted in What Is/Are...?Comments Off
Posted on 17 July 2011.
The xylem and phloem are the two kinds of tissues that transport water and other nutrients within plants. The xylem carries water up through the plant. The phloem transports nutrients, most notably glucose, down throughout the plant.
In Classical Greek, “xylem” translates to “wood.” This makes sense, as the most common xylem tissue is wood. The xylem supply all of the parts of a plant with water by transporting water up through the plant. Xylem are long tubes called vessels. They pump water from the roots up, replacing the water that plants lose to transpiration and photosynthesis.
Plants depend on xylem to replace the water that evaporates off of their leaves. The xylem can transport their sap through transpirational pull. In transpirational pull, water transpires, or evaporates, off of plant surfaces into the atmosphere. As transpiration pulls water out of the plant, the water tension within the plant pulls water from the plant’s roots and soil back into the leaves. This water tension is strong enough to lift water hundreds of meters above the ground into the highest branches of trees. However, for transpirational pull to work, the xylem vessels must be very compact in diameter, as this compactness maximizes pressure.
The xylem can also pull water and nutrients up through the plant via root pressure. Through osmosis, plants absorb water into their roots. This osmosis then forces sap up the xylem and into the leaves. The xylem are also aided by capillary action, the force by which water adheres to the surface of xylem pipes. This capillary action balances gravity.
Phloem is the second transporting tissue in vascular plants. The phloem carry nutrients, most notably glucose, down throughout the plant. Like “xylem,” “phloem” derives from Ancient Greek. “Phloem” translates to “bar,” which makes sense, as phloem is the innermost layer of bark in trees. Phloem transport the nutrients that plants produce in photosynthesis. The phloem’s transportation is called translocation. Translocation moves the phloem’s sugar-rich sap from sugar sources to sugar sinks. Plants generally store their sugars in their roots, and the phloem transports sugar from the roots to the growing areas in the plant, the sugar sink.
The xylem and phloem both transport vital commodities through plants. However, the xylem and phloem differ in several ways. While the xylem transport mostly water, the phloem transport nutrients, especially glucose. The xylem are made up of dead cells, while the phloem are made up of living cells. Xylem only transport sap upward, while the phloem are multidirectional—they move sugars wherever they’re needed. To work, the xylem rely on water tension, while the phloem rely on translocation.
Posted in Water and the EnvironmentComments Off
Posted on 16 July 2011.
A bubble is a globule of one thermodynamic phase inside of another, like a gas in a liquid. We commonly find bubbles in boiling water, carbonated sodas, sea foam, and gas pockets in glass. Learning about bubbles can teach us about many concepts, like shape, transparency, mirrored surfaces, colors, and flexibility.
Bubbles are produced by the scientific process of nucleation. Nucleation occurs when a small pocket of one thermodynamic phase forms inside of another. In bubbles, the thermodynamic phase of a gas forms inside of the thermodynamic phase of a liquid. However, pure water is not stable enough to produce a lingering bubble. We use soap to stabilize bubbles, allowing them to linger for longer. Many incorrectly believe that soap increases water’s surface tension. This is not true. In fact, soap decreases water’s surface tension. Soap does not strengthen bubbles, it merely stabilizes them.
We use bubbles in many ways, both practical and fun. We use bubbles in ultrasounds to help us better see babies. We use bubbles to better understand mathematical concepts, like minimal surface area. Performance artists use bubbles for their aesthetic properties. We also use bubbles as toys. Children have been playing with bubbles since the 1600s. Toy stores sell about two hundred million bottles of bubble mixture every year.
When disturbed, bubbles pulsate, or rapidly oscillate in size. These oscillations destabilize bubbles, leading them to eventually tear apart. The popping of bubbles below produces most of the liquid sounds that we hear.
If you would like to learn more about bubbles, you can do so by observing them yourself. Enjoy educational, fun homemade bubbles by mixing your own bubble solution. Simply combine ½ a cup of dishwashing liquid, two teaspoons of sugar, and two cups of water to make bubbles whenever you want.
Posted in Water UseComments Off
Posted on 15 July 2011.
Introduced species are species that now live outside of their native range. These species are introduced to new areas–usually over previously inaccessible bodies of water–by human activity, either deliberately or accidentally. The Environmental Protection Agency defines introduced species as “species that have become able to survive and reproduce outside the habitats where they evolved or spread naturally.”
Scientists are ambivalent about introducing species to areas that they don’t naturally inhabit. Introduced species are introduced to these new areas by accidental or deliberate human activity. Introduced species can harm the ecosystems of the places that they’re introduced to. However, sometimes introduced species can have no effect on or even help the ecosystems they’re introduced to. For instance, some of the plants that Europeans brought into North America have aided the continent’s biodiversity and productivity. Because introduced species can spread too quickly for us to control and can sometimes help us, most environmentalists consider it impractical and undesirable to simply prohibit introducing non-native species.
Scientists refer to introduced species by many terms, like “non-indigenous,” “non-native,” “exotic,” and even “invasive.” The broadest term applied to introduced species is “non-native,” which can be applied to both agriculturally maintained and wild species. Some introduced species can survive by themselves in nature when introduced—these are “naturalized” species. “Invasive” species threaten ecosystems by spreading or reproducing too widely or too fast, thereby harming the environment or human health.
Through human activity, we introduce species to places that they don’t naturally inhabit. Sometimes we introduce species accidentally, and sometimes intentionally. People usually introduce species intentionally because they will economically gain by doing so. For instance, New Zealand introduced the Monterey Pine to bolster timber crops. We have also introduced species for recreational activities, like game hunting or ornamental gardening. We have also introduced species by bringing pets overseas. When we try to establish introduce these species in the wild, we often have trouble predicting how well the introduced species will fare. For this reason, we often have to make several attempts to establish an introduced species.
Sometimes people accidentally introduce species to new areas. For example, we have spread many rat species spread across the world by unintentionally transporting them aboard ships. Human travel also introduces several species to places where they don’t naturally inhabit. For example, tourists introduced the African killer bee to Brazil.
Posted in World ConservationComments Off
Posted on 14 July 2011.
DDT, the abbreviation for dichlorodiphenyltrichloroethane, is a well-known chemical pesticide with a controversial history.
DDT does not naturally occur. Instead, it must be chemically synthesized. Because DDT has caused so much controversy, it has been marketed under several trade names, like Anofex, Chlorophenothane, Dicophane, and Neocidol. When ingested by insects, DDT causes spasms and eventually death. However, some mutated insects have developed a gene that has made them resistant to insecticides like DDT. When ingested by humans, DDT can disrupt our endocrine systems.
The chemist Othmar Zeidler first synthesized DDT in 1874. However, he was not aware that the chemical could work as an insecticide. Later, in 1939, the Swiss scientist Paul Hermann Muller discovered DDT’s insecticidal properties. He was awarded a Nobel Prize in 1948 for his discovery. DDT was first used as a pesticide during WWII, where it worked so well as an insect killer that some soldiers labeled it the “atomic bomb” of pesticides. After WWII, DDT was made available to farms, where it could be used on crops. It soon became the most popular insecticide.
In 1962, biologist Rachel Carson published a book called Silent Spring, a book that many credit with beginning the environmental movement. In Silent Spring, Carson questioned whether indiscriminately spraying DDT onto crops was harming the environment. She was the first scientist to truly critique the safety of releasing chemicals into the environment without knowing how they would impact us or our world. Carson worried that pesticides like DDT were harming the environment and causing cancer in humans. Largely because of Silent Spring’s popularity, the United States banned DDT’s agricultural usage in 1972.
After being banned, DDT is much less common today. Between 1950 and 1980, worldwide agriculture used over 40,000 tons of DDT each year. In 2009, however, only 3313 tons of DDT were produced, and they were produced mainly for the treatment of malaria, not for agricultural use. Environmentalists believe that the DDT ban has helped endangered species make comebacks, most notably the bald eagle.
Posted in The Global Water CrisisComments Off
Posted on 13 July 2011.
Many are unsure of what is on the ocean floor. The ocean floor, also called the seabed or sea floor, is the bottom of the ocean. The ocean floor comprises seventy-one percent of the Earth’s surface.
To understand what is on the ocean floor, we must first understand the geography of the rest of the ocean. The geography of the ocean is divided into several levels. Each of these levels has its own typical features based on depth, features like topography, marine life, salinity, and soil composition. The ocean’s levels begin with a continental shelf, a gently sloping area of just around 650 feet deep that surrounds continents. The continental shelf then transitions into a continental slope, a steep descent into the ocean. The continental slope then transitions into the abyssal plain, which begins the seabed.
The breadth of what is on the ocean floor includes plains, enormous undersea mountain ranges called ocean ridges, isolated mountains called seamounts, and more. The deepest parts of the ocean floor are seabed trenches, which are called hadalpelagic trenches. The deepest trench is the Mariana Trench, which measures over 36,000 feet deep—that’s deeper than Mount Everest is tall. The average depth of the ocean, however, is 12,000 feet—that’s about two miles deep.
The soil in seabeds is full of sediment. This sediment collects from rivers, sea currents, magma, and microoganisms’ activity. In recent years we have discovered a variety of marine life in the deep sea, especially around hydrothermal vents.
For millennia, man has been unable to explore the ocean floor, as the seabed was too deep and pressurized to reach. Because of this, man has long seen the ocean floor as a symbol for mystery and wonder. Fortunately, in recent years we have been able to reach the ocean floor. Scuba divers can now use air tanks to reach shallower parts of the ocean floor. The deepest parts of the ocean floor can be reached with submersibles. Most famously, in 1986, the DSV Alvin explored the seabed wreckage of the Titanic.
The seabed is always changing. Seafloor spreading continually adds new material to the ocean floor. This is why oceanographers have always wanted to monitor what is on the ocean floor. Sailors used to measure the ocean’s depth by using a lead line, a long piece of rope marked off in fathoms (six-foot intervals) with a weight at one end. The sailors would drop the weighted end into the water, and then the sailors would measure how far the line had entered the ocean when the weight reached the sea floor. In recent years, we have used satellites to map seabed and determine what is on the ocean floor.
Posted in What Is/Are...?Comments Off
Posted on 10 July 2011.
When we think of oceans and lakes, we think of sparkling blue waters. However, upon closer investigation, we see that water is clear. The reason why water is clear is that it is made up entirely of oxygen and hydrogen. Because both of these elements are gases, their electrons are unable to absorb or reflect visible light. In fact, water refracts or changes the direction of light. For example, when a T-shirt is soaked with water, it refracts away light, making the object appear darker. This is why absorbed water darkens material, and why water is clear.
We know how and why water is clear, so it probably doesn’t make immediate sense to us that while a small amount of water is clear, lakes and oceans appear to be blue. The reason for this is that water does not absorb much light, but when it does absorb light, it absorbs red, orange and yellow light. As a result, it reflects back the shorter blue wavelengths to observers.
Large bodies of water do not always appear blue. Many rivers can appear brown, green or even gray. These appearances can be explained by the number of dissolved or suspended particles present in water, and the depth of the water. Both particles and water depth influence how light is reflected or refracted to the observer. Color variants arise depending on the following circumstances:
If water is clear, there is a much better chance that it is clean. This is why we must check whether water is turbid or hazy. We can check water clarify with a Secchi Disk. This instrument is a black-and-white circular plastic plate that can be lowered into water. To use a Secchi Disk, first lower it into the water. Stop lowering it when you can’t see it anymore. Next, note the depth (in meters) off of the calibrated line. Then raise the disk back up to where it reappears, again noting the depth off of the calibrated line. Finally, add these two noted depths and divide them by two. This final value can help you gauge water’s clarity. Be sure to compare this value on a weekly basis with measurements at the same lake.
Posted in Why?Comments Off
Posted on 09 July 2011.
We usually think of water as being tasteless, odorless, and colorless. However, this is a misconception. In fact, we like our water to have a taste—in blind taste tests, we prefer tap water to distilled water. Most taste testers agree that water should have a taste, but that it shouldn’t stand out.
Several factors influence the taste of water. Tap water taste changes depending on where you live and the water treatment process in your area. We commonly associate municipal water with the slightly acidic taste of chlorine. Carbonation levels affect carbonated water’s taste. Greater amounts of carbon dioxide make the water taste more acidic—drinkers call this acidity “spritzy” or “sharp,” and may enjoy or dislike this taste based on their own personal preferences. Bottled water brands mislead consumers into thinking that bottled water tastes better than tap water: blind taste tests show that most consumers prefer tap water. When water is used as an ingredient, the water’s taste in turn affect affects the foods and drinks that it helps make.
We think of water as being tasteless, but subconsciously we are always judging its flavor. We consider water’s saltiness, its softness, its earthiness. When most people talk about tap water’s “taste,” they are really referring to its flavor. While taste is merely what one perceives with the tongue, flavor takes into account smell and touch, or mouthfeel, in addition to taste. Our 100,000 taste buds are assess the four basic stimuli of sweetness, sourness, bitterness and saltiness of all of the water that we drink. Most taste testers agree that water should have flavor, but shouldn’t stand out. Most taste testers also agree that water’s flavor is enhanced when we filter out chemicals like sulfur and chlorine.
All water molecules are made up of two hydrogen atoms combined with one oxygen atom. However, water’s taste nevertheless varies. The taste of water varies because water is a universal solvent. That is, water dissolves a little bit of everything it touches. As water travels, it picks up dissolved mineral traces from everything it touches, traces that affect the way the water tastes. This is why the taste of water varies depending on where it comes from.
Posted in TasteComments Off
Posted on 08 July 2011.
What is an isolation tank? You may have heard people talking about isolation tanks recently, but you may not know what they are yourself. An isolation tank is a lightless, soundproof tank in which a person floats in skin temperature salt water. Isolation tanks employ sensory deprivation as a tool for meditation and relaxation. Some consider isolation tanks a form of alternative medicine. Isolation tanks go by many names, such as float tanks, sensory deprivation tanks, and floatation baths.
Isolation tanks are designed to cut off all stimuli. The water in isolation tanks is filled with Epsom salt, which increases the water’s salinity and density, allowing users to float more easily with their faces above the water. Because the users’ ears float below the water, hearing is reduced. Other users use ear-plugs to further cut off sound. Users float with their arms by their sides, reducing skin sensation. To reduce smell, the water is treated as little as possible. The water temperature is carefully matched with the air temperature, cutting down one’s feeling of having a body boundary. In short, the isolation tank is designed to eliminate as many stimuli as possible.
People usually use the isolation tank while naked. While users can technically wear swimsuits, this is discouraged because the elastic on swimsuits can uncomfortably compress skin, producing extraneous negative stimuli. Because the water should be altered by external forces as little as possible, users must bathe before entering the tank. After their isolation tank session, users must bathe again to cleanse their skin of the Epsom salt. For this reason, a shower is usually installed in the same room as the tank. This allows the user can switch directly from the shower to the tank and the tank to the shower.
The isolation tank was created in 1954 by medical practitioner John C. Lilly. John C. Lilly, a trained psychoanalyst, wanted to experiment with sensory deprivation. Several theories about sensory deprivation were circulating in Lilly’s. These theories held that the brain could go to sleep if all stimuli were cut off to it. Lilly decided to test these theories with the isolation tank, an experimental environment that would isolate the individual from external stimulations. He used this experimental environment to study awareness and consciousness. Experimenters at other universities continue his studies today. What is an isolation tank? A relaxation technique whose benefits are still being researched today.
Posted in What Is/Are...?Comments Off
Posted on 05 July 2011.
There are many, many different types of bodies of water. Some bodies of water occur naturally. Others, like reservoirs and harbors, are man-made. Although water formations that move around, like rivers and streams, aren’t always considered bodies of water, there is no other English term for moving bodies of water, so they are typically grouped with other bodies of water. Some bodies of water are less well-known and culturally and geographically limited in scope. For instance, the Spanish have named the “arroyo,” a creek that temporarily fills with water after a heavy rain or a rainy season. The Australians have named the “billabong,” a pool of water that forms when a river changes its course. Some major bodies of water include oceans, seas, and rivers.
The largest bodies of water are oceans, enormous pools of saltwater. Oceans are continuous bodies of water that divide into smaller seas. Although interconnected, we typically describe oceans as separate. Earth’s oceans run about two miles deep. They are home to about 230,000 known marine species, and perhaps ten times that number of unknown marine species. Although interconnected into one global saltwater body that oceanographers sometimes call the “World Ocean,” Earth’s oceans are usually described as five separate bodies of water. This allows us to specify which part of the World Ocean we’re talking about. These five oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean, and the Arctic Ocean.
Seas are large bodies of water that are usually connected with oceans. The term “sea” is sometimes incorrectly used as a synonym for the term “ocean.” However, oceanographers see seas and oceans as two different kinds of bodies of water. Seas are smaller saltwater bodies that are usually interconnected with oceans, but can sometimes be disconnected from oceans. For instance, the Caspian Sea is in fact a saltwater lake.
Rivers are moving, usually freshwater bodies of water. They typically flow into other bodies of water, like oceans, seas, lakes, and other rivers. However, they can sometimes flow into the ground or dry up before reaching other bodies of water.
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