Category Archives: Science ABC

To keep COVID-19 at bay in classrooms, open windows and use glass screens in front of desks

As the pandemic months continue to unfold, the risk of the virus spreading through classrooms remains a hotly contested issue. In a new study, a group of researchers simulated the spread of small aerosols through the classroom, looking at the ways to reduce the spread of aerosols.

According to the study, keeping the desks spread, opening the windows, and using protective screens is the best way to go about things.

Simulation of particle flow in a classroom. Courtesy of Khaled Talaat.

“We considered different window opening conditions and overall we find that opening the windows, even a little, significantly increases the fraction of the particles that exit the system,” Khaled Talaat, one of the authors, tells me in an email.

Physicists have had their own spotlight moments in the pandemic, especially when it comes to flow modeling. We still don’t fully understand through which type of particles the virus spreads with, but understanding the flow of particles is still one of our best bets to understand the risk of transmission. To this end, Talaat and colleagues modeled different classroom environments to see how they would affect aerosol particle spread during talking, coughing, or sneezing.

The computational method the team used is quite similar to ones used in nuclear engineering applications to study radioactive aerosols released from nuclear accidents, Talaat tells me.

The first finding is that opening the window reduces the fraction of potentially infectious particles by nearly 40%, while also reducing aerosol transmission between people within.

Modelling of airflow around a window. Courtesy of Khaled Talaat.

However, even when the student desks are spaced at 2.4 meters (7.8 feet), about 1% of the exhaled particles still spread from desk to desk. A larger desk spread expectedly reduced the spread of aerosols, but also, when the desks are spaced apart is when screens become most useful.

“Protective screens (e.g. glass screens) also significantly reduce aerosol transmission between individuals separated by at least 2.4 meters in the room,” Talaat explains for ZME Science.

“Barriers do not stop small particles directly. However, they influence the local airflow field near the source affecting the trajectory of the aerosol particles. Their effectiveness depends on the air conditioning layout and source location.”

The distribution of aerosols wasn’t homogenous, because of air conditioning and circulation. The geometry of the classroom and the position and size of the windows also affects the flow of particles, but overall, researchers expect that “the findings would qualitatively hold in other classrooms”, although individual differences could depend on many factors.

When it comes to reopening schools, the team ultimately recommends opening windows whenever possible, installing protective barriers, and removing the middle seat — as middle seat students transmit far more particles to others.

Additionally, hand hygiene is crucial, Talaat concludes.

“We encourage students and instructors to sanitize their hands even without coming into contact with other people’s belongings because aerosols from other students can deposit on them and on their own belongings in significant amounts.”

Pollination 101: the basics on what it is and why it matters

Pollination has been in the news a lot recently: pollinators are dying out due to pesticides, diseases, and not being able to find enough food. This is a big problem for many crops and wild plants because many depend on pollinators in order to reproduce. Read on for the steamy details on pollination and how it supports the existence of our crops and wild plants.

What is pollination

Flowers have both male and female parts. The male part is made up of the anthers, which are supported by filaments. The anthers are important because they produce pollen. The female part is made up of a sticky stigma that is connected to an ovary with eggs inside. In order to make seeds, the pollen from the anthers needs to reach the stigma. However, there is a little problem. Plants need their pollen to reach another flower of the same species, but they cannot move. There are two solutions to this problem. The first is that wind can carry the pollen to another flower. The second is that pollinators carry pollen from one flower to another. This method is more efficient for flowers and therefore is used by most wild plants. Flowers want to attract pollinators so they produce sweet nectar at the base of their petals.

The parts a flower. Image credits: ProFlowers.

Pollinators do not know that plants want them to carry their pollen around. They are more concerned with getting food for themselves and their offspring. Nectar contains sugar and nutrients, which can give pollinators lots of energy, and pollen contains protein. Many pollinators have hairs, fur, or feathers. As they drink nectar or collect pollen, they rub against pollen from the anthers, which sticks on their fuzzy bodies. As they move on to the next flower, some of the pollen already on their bodies get stuck on the sticky stigma. The pollinators don’t even know that they are helping the plants out. Once pollen attaches to the stigma, it germinates. Pollen tubes form and stretch down until they reach the ovary. When they touch the egg, they fertilize it and form a seed. The seeds mature and when they are ready, they are released. These seeds grow up to be new plants.

A fly pollinator being an unwitting pollen carrier. Image credits: Forest Wander.

Our tasty food depends on pollination!

5-8 % of global crop production is completely dependent on pollinators. However, this is not the whole picture, as many more crops are tastier, produce higher yields, or improved in some other way by pollination. Of the most used crops, 75% depend on pollination to some degree. For example, tomatoes that are pollinated by insects are bigger and taste better. If pollinators were to disappear, food production would be very strongly affected. Do you like chocolate? It depends on a single type of fly to pollinate it, if it were to go extinct, we’d be in trouble! Many other commodities that we enjoy also depend on pollination, such as coffee, almond milk, and exotic fruits.

Did you know that different fruits and vegetables depend on pollinators in different ways?

Veggies

Curcurbits such as squash, zucchini, pumpkins, melons and watermelons need pollinators. They have separate male and female flowers and need pollinators to transfer pollen from the male flowers to the female flowers. If this does not occur, there aren’t any vegetables.

Squash have male (above) and female (below) flowers. In the female flower, you can see well that the ovary is what will turn into the squash. Image credits: Abrahami.

Soloanaceae such as tomatoes, bell peppers, eggplants, and chili peppers can have male and female parts in the same flower so they are able to self-pollinate but have a higher yield, taste better and are bigger when insect pollinated. They have a special type of anther that needs to be vibrated at a particular frequency to release pollen. Insects such as bumblebees and other types of solitary bees buzz at this frequency and can effectively pollinate these plants.

There are vegetables that are not the fruits of pollination and do not explicitly require pollinators for their production, but need them to produce seeds. For example, roots like potatoes, carrots and onions; flowers like broccoli, leaves like salad, and herbs like thyme, basil, oregano, rosemary are not formed from a plant ovary. However, they do produce flowers that need to be pollinated to produce seeds and therefore for new plants to grow.

Rice flowers.. not so impressive. Image credits: Pixabay.

Some crops like corn, wheat, rice, barley, rye, and oats rely on wind pollination and do not need any insect pollination at all. These are dietary staples so at least their production would be stable in the absence of pollinators. These plants produce billions of pollen grains and only a few of them will reach the female parts of other plants and produce seeds. Some nuts such as walnuts, pistachios, and hazelnuts are wind pollinated. As they don’t need to attract pollinators, they have very small, plain flowers.

Fruits

Some plants are self-incompatible. This means that they need pollen from a different variety. For example, a Gala apple cannot be pollinated by the pollen from another Gala apple. It needs pollen from another cultivar to produce a fruit, though some apple varieties are able to still produce some fruit without pollinators. For this reason, orchards also have crabapples or different types of cultivars that produce a lot of pollen so the apple flowers receive the pollen they need to develop into a fruit. Other examples of crops dependent on pollination are pears and almonds.

Most apples need pollen from another cultivar to produce a fruit. Image credits: PxHere.

There are also fruits and berries that are self-compatible and can produce fruit without pollinators. They do require pollinators to increase the yield and quality of the fruit. For example, a raspberry flower is made up of 100-125 female parts. Each little segment of a raspberry is actually a tiny fruit, so at least 80 of these little fruits need to form to have a normal raspberry. If there are fewer segments, the raspberry falls apart or isn’t so juicy. Pollinators help spread pollen to more stigmas to make sure you have a nice, juicy raspberry. Cherries, peaches, strawberries, and plums are all self-fertile.

Most wild plants need pollinators

Pollinators aren’t just important for making sure that we have enough food to eat, they are important for all of the flowers in our gardens, in meadows, and everywhere else in nature! 90% of wild plants are insect pollinated. Many plant species are completely dependent on pollinators, while others produce more, better quality seeds when they are pollinated. Therefore, wild plants depend on insects so that they can produce new seeds and that new flowers can grow. Not to mention that many insects and other animals depend on plants for food. Some insect larvae, like caterpillars, depend on a single type of plant while they are growing up. For example, monarch caterpillars need milkweed. If they can’t find milkweed, then they don’t survive to make their impressive migration.

We do not know how a loss of pollinators would actually affect the world’s plants. Researchers can only guess what the world would be like without pollinators by looking at places in the world where lots of pollinators have already gone extinct and by performing experiments.

Hawaiian honeycreepers, endangered but important pollinators. Image credits: Gregory “Slobirdr” Smith.

Hawaii is a place where many pollinators have gone extinct so we can look at the effects. Many flowers were pollinated by birds found only on the archipelago. One-third of 52 bird species in Hawaii have gone extinct and many others are so rare that they are not able to pollinate so many flowers. Plants native to Hawaii have thin, curved flowers specially adapted for bird pollination. Due to the loss of their pollinators, 31 of these plant species have gone extinct in the last century. Many other large groups of pollinators have gone extinct, including 52 endemic bee species in the same genus and 26 moth species. The common house plant, Hawaii palm (Brighamia insignis), otherwise known as cabbage on a stick, is possibly extinct in the wild due to the extinction of its only pollinator, a hawkmoth. Although there are many other problems, such as habitat loss and introduction of invasive species and diseases, the loss of pollinators is a major contributing factor to about half of the 1200 native plant species in Hawaii being at risk of extinction. Some plants on Hawaii are now pollinated by invasive birds or mammals, but many are left without pollinators. Hawaii is an extreme case because it has many species found only there that have specialized relationships. In this case, the loss of pollinators can have a big effect.

Wildflowers need pollinators! Image credits: Needpix.

Researchers in Europe have also conducted some experiments to see what a meadow would look like with fewer pollinators. They engineered covers that they placed over parts of meadows so that fewer pollinators would visit those plants. After a four year period, they found out that pollinators are responsible for keeping meadows full of different flower species and producing more new plants. The sections with fewer pollinators had fewer new flowers growing and the ones that did grow weren’t represented by very many different species.

All in all, we have pollinators to thank for a smorgasbord of colorful, tasty food, not to mention the flowers that ornament our balconies, parks, and wild habitats, giving us something nice to look at and giving many animals the food and space that they need.

The science behind why leaves change color in autumn

Ah, autumn—the air is crisper and the trees are turning brilliant shades of gold, red, and brown. In the temperate areas of the world, it gets very cold in the winter and there is not much sunlight, which the trees need to feed themselves. Leaves are delicate and can’t survive the winter, so the tree prepares itself for the cold by taking all useful things from the leaves before they fall. This preparation process is what causes the leaves to display their striking autumn colors. There’s a good reason why different trees have leaves that turn different colors.

Preparing for winter

In the summer, most trees have green leaves because they contain the pigment chlorophyll. This pigment is also used to convert sunlight into energy for the tree. In summer, chlorophyll is constantly replaced in the leaves. When it gets cold, the plants stop making chlorophyll and it breaks down into smaller pieces. The trees can reuse the nitrogen that is in the chlorophyll molecule. This is why leaves change colors before they fall off of the tree; the important nutrients that can be reused are taken out of the leaf. The time when leaves start changing color is more dependent on light than on temperature so leaves start changing color at about the same time each year. When deciduous trees reach this light threshold, carbohydrates are transferred from the leaf to the branch and no new minerals are brought in. The trees prepare to separate with their leaves. 

A leaf turning red in the fall. The green is residual chlorophyll. Image credits: kvd.

A rainbow of autumn colors

The green color of chlorophyll is so strong that it masks any other pigment. The absence of green in the fall lets the other colors come through. Leaves also contain the pigments called carotenoids; xanthophylls are yellow (such as in corn) and carotenes are orange (like in carrots). Anthocyanins (also found in blueberries, cherries) are pigments that are only produced in the fall when it is bright and cold. Because the trees cut off most contact with their leaves at this point, the trapped sugar in the leaves’ veins promotes the formation of anthocyanins, which are used for plant defense and create reddish colors.

However, trees in the fall aren’t just yellow and red: they are brown, golden bronze, golden yellow, purple-red, light tan, crimson, and orange-red. Different trees have different proportions of these pigments; the amount of chlorophyll left and the proportions of other pigments determine a leaf’s color. A combination of anthocyanin and chlorophyll makes a brown color, while anthocyanins plus carotenoids create orange leaves.

The rainbow of autumn colors. Image credits: Pixabay.

Low temperatures still above the freezing point help to produce anthocyanin, which produces a bright red color. An early frost weakens the color by destroying the creation of anthocyanins, however. Drought can also cause leaves to fall off without changing color. Where just a few tree species dominate, like in New England and Northeast Asia, color displays are intense but short. Diverse forests mean a longer display. Cloudy and warm falls like those in Europe cause dull colors.

Where the stem of the leaf attaches to the tree, a layer of cells forms that eventually cuts the tissue that attaches the leaf to the tree. There is a closed scar on the branch where the leaf was attached; the leaf is then free to fall when prompted by wind, gravity, rain, and so on. When the leaves die and the chloroplasts are completely broken down, leaves turn a boring brown.

And that is the science behind why the leaves that fall in the autumn are everything from red and yellow to orange and bronze to, finally, brown.

fabulous hair

How fast hair grows, and other hairy science

On average, your scalp hair grows 0.35 to 0.45 millimeters a day — that’s half an inch per month. Depending on your ancestry (genetics), diet and hormonal state (pregnant women grow hair a bit faster; it’s also thicker and shinier), your hair will grow at a higher or lower rate.

fabulous hair

Why hair grows

The human body contains roughly 5,000,000 hair follicles, and the function of each hair follicle is to produce a hair shaft. Our early ancestors used to have most of their bodies covered in hair, like our other primate cousins. This served to conserve heat, protect from the sun, provide camouflage and more. Today, however, humans stand out from the 5,000 mammal species because they’re virtually naked, but why is that?

Scientists believe that our lineage has become less and less hairy in the past six million years since we shared a common ancestor with our closest relative, the chimpanzee. Our ape ancestors spent most of their time in cool forests, but a furry, upright hominid walking around in the sun would have overheated. One of the main theories concerning our lack of fur suggests that temperature control played a key role. Bare skin allows body heat to be lost through sweating, which would have been important when early humans started to walk on two legs and began to develop larger brains than their ape-like ancestors. Nina Jablonski, a professor of anthropology at Pennsylvania State University, says there must have been a strong evolutionary pressure to control temperature to preserve the functions of a big brain. “We can now make a very good case that this was the primary reason for our loss of hair well over 1 million years ago,” she said.

“Probably the most tenable hypothesis is that we lost most of our body hair as an adaptation to being better at losing heat from our body, in other words for thermal regulation,” Professor Jablonski said.

“We became very good sweaters as a result. We lost most of our hair and increased the number of eccrine sweat glands on our body and became prodigiously good sweaters,” she told the American Association for the Advancement of Science meeting in Boston.

Besides sweating, losing our furry coat may have also been driven by having fewer parasites infesting our bodies like ticks, lice, biting flies and other “ectoparasites.” These creatures can carry viral, bacterial and protozoan-based diseases such as malaria, sleeping sickness and the like, resulting in serious chronic medical conditions and even death. By virtue of being able to build fires and clothing, humans were able to reduce the number of parasites they were carrying without suffering from the cold at night or in colder climates.

Despite exposing us to head lice, humans probably retained head hair for protection from the sun and to provide warmth when the air is cold, while pubes may have been retained for they role in enhancing pheromones or the airborne odors of sexual attraction. The hair on the armpits and groin act like dry lubricants, allowing our arms and legs to move without chafing. Eyelashes, on the other hand, act as the first line of defense against bugs, dust, and other irritating objects. Everything else seems to be superfluous and was discarded.  It’s important to note, however, that we haven’t exactly shed our fur. Humans have the same density of hair follicles on our skin as a similarly sized ape. Just look at your hands or feet: they’re covered in hair, but the hair is so thin you can barely make them out.

How hair grows

HairFollicle_Large

Image: Apollo Now

Hair, on the scalp and elsewhere, grows from tiny pockets in the skin called follicles. Hair starts growing from the bottom of the follicles called the root, which is made up of cell proteins. These proteins are fed by blood vessels that dot the scalp. As more cells are generated, hair starts to grow in length through the skin, passing an oil gland along the way. Emerging from the pit of each of these follicles is the hair shaft itself. By the time it’s long enough to poke out through the skin, the hair is already dead, which is why you can’t feel anything when you get your hair cut.

The hair shaft is made out of a hard protein called keratin. There are three main layers to the hair shaft. The inner layer is called the medulla, the second is the cortex and the outer layer is the cuticle. It is both the cortex and the medulla that holds the hair’s pigment, giving it its color.

Some quick facts about hair:

  • You’re born with all the hair follicles you’ll ever have – about 5 million of them. Around 100,000 of these are on your scalp.
  • The hair on your head grows about 6 inches a year. The only thing in the human body that grows faster is bone marrow.
  • Males grow hair faster than females due to testosterone.
  • You lose between 50 to 100 strands of hair each day. That’s because follicles grow hair for years at a time but then take a break. Because follicle growth isn’t synced evenly, some take a break (causing the hair to fall out), while the vast majority continue business as usual.
  • Some follicles stop growing as you age, which is why old people have thinning hair or grow bald.
  • Everybody’s hair is different. Depending on its texture, your hair may be straight, wavy, curly, or kinky; thick or thin; fine or coarse. These are determined by genetics, which influences follicle shape. For instance, oval-shaped follicles make hair grow curly while round follicles groom straight hair.
  • Like skin, hair comes in various colors as determined by the same pigment called melanin. The more melanin in your hair, the darker it will be. As you grow older, your hair has less and less melanin, which is why it fades color and may appear gray.

Hair growth cycle

Hair-Growth-Cycle-White

Image: Belgravia Center

Follicles have three phases: anagen growth, catagen no growth, preparing for rest, and telogen rest, hair falls out. At its own pace, each strand of hair on your scalp transitions through these three phases:

  • Anagen. During this phase, cells inside the root start dividing like crazy. A new hair is formed that pushes out old hair that stopped growing or that is no longer in the anagen phase. During this phase, the hair grows about 1 cm every 28 days. Scalp hair stays in this active form of growth for two to six years, but the hair on the arms, legs, eyelashes, and eyebrows have a very short active growth phase of about 30 to 45 days. This is why they are so much shorter than scalp hair. Furthermore, different people, thanks mostly to their genetics, have differing lengths of the anagen period for a given body part compared to other people.  For the hair on your head, the average length of the anagen phase is about 2-7 years.
  • Catagen. About 3% of all the hair on your body this very instant is in this phase. It lasts two to three weeks and during this time, growth stops.  During this phase, the hair follicle will actually shrink to 1/6 of its original length.
  • Telogen. About 6 to 8 percent of all your hair is in this phase — the resting phase. Pulling out a hair in this phase will reveal a solid, hard, dry, white material at the root. On a day-to-day basis, one can expect to shed between 100 to 150 pieces of hair. This is a normal result of the hair growth cycle. When you shed hair, it’s actually a sign of a healthy scalp. It’s when the hair loss is excessive that you should feel worried and contact a doctor.

Why hair only grows to a certain length

 

Each hair grows out of a follicle and as the hair gets longer and heavier, the follicle eventually can’t hold on much longer and it sheds the hair. But that’s okay: it then starts growing another one. How long you can grow your hair depends on your genetics, and in general, Asians can grow their hair longer than Europeans. This may be surprising for many, but as in all mammals, each of us has a certain hair length beyond which the hair simply won’t grow. Hair length is longest in people with round follicles because round follicles seem to grip the hair better. So, people with straight hair have the potential to grow it longer. Shorter hair is associated with flat follicles. A study published in 2007 also explains why Japanese and Chinese people have thick hair: their follicles are 30% larger than that of Africans and 50% larger than that of Europeans.

In most cultures, women keep their hair longer than men. Cultural rules aside, hair length is actually sexual dimorphic. Generally, women are able to grow their hair longer than males. European males can reach a maximum length of wavy hair to about shoulder length, while the maximum for straight hair is about mid-back length. For European females, wavy hair can usually reach the waist, and straight hair can reach the buttocks or longer.

The world's longest documented hair belongs to Xie Qiuping (China) at 5.627 m (18 ft 5.54 in) when measured on 8 May 2004.

The world’s longest documented hair belongs to Xie Qiuping (China) at 5.627 m (18 ft 5.54 in) measured on 8 May 2004.

How to grow your hair faster and longer

While genetics caps your hair length, it is possible to accelerate its growth rate.

1. First of all, your hair growth reflects your general body health. Eat a diet rich in marine proteins, vitamin C (red peppers), zinc (oysters), biotin (eggs), niacin (tuna) and iron (oysters) to nourish strands.
2. If changing your diet isn’t possible, you can try supplements with marine extracts, vitamins, and minerals that nourish your follicles.
3. Besides general health, the next thing you should mind is your scalp health. Use a shampoo that gently exfoliates oil and debris from the scalp as well as a conditioner to moisturize scalp and hair.
4. Trimming is a proven method to grow your hair longer. Although in itself trimming doesn’t promote growth, it does help prevent breakage and, therefore, increases hair length.

Things that actually hurt your hair:

1. Silicone shampoos dry out the hair and degrade it. Blow dryers and flat iron produce similar effects, breaking the hair shafts. Use these products as rarely as possible.
2. UV light bleaches and breaks down hair. When you’re out at the beach, wear a hat to protect your scalp.
3. Salt and chlorine water both soften and dry the hair.
4. Bleaching, dyeing, hair extensions and perms also damage hair.

 

Pi.

What is Pi (π) and what is it good for?

If you have a straight line but want a circle, you’re going to need some Pi.

Pi.

Image via Max Pixel.

I’m talking about the number, not the delicious baked good. It’s usually represented using the lowercase Greek letter for ‘p’, ‘π’, and probably is the best known mathematical constant today. Here’s why:

The root of the circle

Pi is the ratio of a circle’s diameter to its circumference. No matter the size of a circle, its diameter will always be roughly 3.14 times shorter than its circumference — without fail. This ratio, π, is one of the cornerstones upon which modern geometry was built.

Bear in mind that (uppercase) ∏ is not the same as (lowercase) π in mathematics.

For simplicity’s sake, it’s often boiled down to just two digits, 3.14, or the ratio 22/7. In all its glory, however, pi is impossible to wrap your head around. It’s is an irrational number, meaning a fraction simply can’t convey its exact value. Irrational numbers include a value or a component that cannot be measured against ‘normal’ numbers. For context, there’s an infinite number of irrational numbers between 1.1 and 1.100(…)001. They’re the numbers between the numbers.

There is no unit of measurement small enough in rational numbers that can be used to fully express the value of irrational ones. They’re like apples and oranges — both fruits, but very different.

Real numbers.

Apart from the fact that it implies there are numbers which are neither rational or irrational (there aren’t), this Euler diagram does a good job of showcasing the apples/oranges relationship between the two groups.
Image credits Damien Karras.

Because it can’t properly be conveyed through a fraction, it follows that pi also has an infinite string of decimals. Currently, we’ve calculated pi down to roughly 22.4 trillion digits. Well, I say ‘we’, but it was actually our computers that did it.

Truth be told, we don’t actually need that many digits. They’re very nice to have if you’re NASA and people live or die by how accurate your calculations are — but for us laymen, 3.14 generally does the trick. It’s good enough because it’s just about at the limit of how accurately we can measure things around us. We simply don’t need that much precision in day-to-day activity.

Go around the house, pick up anything round, and run a length of string along its circumference. Unwind it and measure it with a ruler. Measure the circle’s diameter with the same ruler, use this value to divide the circumference, and you’ll get roughly 3.14 each and every time. In other words, if you cut some string in several pieces, each equal to the diameter in length, you’d need 3.14 of those strips to cover the circumference.

Because this simplification is so widely-used, we celebrate Pi day on March 14 (3/14) every year.

If you do happen to need a more-detailed value for Pi, here it is up to 100 million decimal places.

What’s it for?

Pi is used in all manner of formulas. For example, it can be used to calculate a circle’s circumference (π times diameter), or its area: A=πr2 — how I keep this formula lodged in my neurons is using the “all pies are square” trick. It’s also used in calculating various elements of the sphere, such as its volume (3/4πr3) or surface area (4πr²).

But it also shows up in a lot of engineering and computational problems. Weirdly enough, pi can be used to obtain the finite sum of an infinite series. For example, if you add up the inverse of all natural squares — 1/12+1/22+1/32+….+1/n2 — you get π2/6.

Most branches of science stumble into pi in their calculations at one point or another. Computer scientists use it to gauge how fast or powerful a computer is, and how reliable its software, by having the device crunch numbers and calculate pi. It’s very useful for determining both circular velocities (how fast something is spinning) as well as voltage across coils and capacitors. Pi can be used to describe the motion of waves on a beach, the way light moves through space, the motion of planets, or to track population dynamics if you’re into statistics.

Another place pi pops up (that you wouldn’t suspect) is in the value of the gravitational constant. This shows how fast an object will accelerate towards the ground as it’s falling. Its most widely-accepted value is 9.8 m/s2. The square root of that value is 3.1305-ish, which is close to the value of pi. That’s actually because the original definition of a meter involved a pendulum that took 1 second to swing either way. Wired has a more comprehensive explanation here.

Pi also underpins modern global positioning systems (GPS) since the Earth is a sphere. So give a little mental thanks to mathematics the next time you’re drunkenly thumbing your phone to hail an Uber.

Who discovered pi?

Domenico Fetti Archimedes.

“Archimedes Thoughtful” by Domenico Fetti, currently at the Gemäldegalerie Alte Meister in Dresden, Germany. Archimedes calculated one of the most accurate values for Pi during the Antiquity.

Pi is not a newcomer to the mathematical stage by any means. We refer to it using the letter ‘π’ from the ancient Greek word ‘περίμετρος’ — perimetros — which means ‘periphery’ or ‘circumference’. It was introduced by William Jones in 1706 and further popularized by Leonhard Euler. The notation was likely adopted in recognition of the efforts of one great ancient mathematician: Archimedes.

Archimedes put a lot of effort into refining the value of pi. He was also the first to use it to calculate the sum of an infinite number of elements over 2,200 years ago, and it’s still in use today.

But he wasn’t the first to realize the importance of pi(e). In his book A History of Pi, professor Petr Beckmann writes that “the Babylonians and the Egyptians (at least) were aware of the existence and significance of the constant π” as far back as 4,000 years ago. They likely only had rough estimations of its exact value (maths was still a new ‘tech’ back then) but they were in the right ballpark.

“The ancient Babylonians calculated the area of a circle by taking 3 times the square of its radius, which gave a value of pi = 3. One Babylonian tablet (ca. 1900–1680 BC) indicates a value of 3.125 for pi, which is a closer approximation,” writes Exploratorium in a look at the history of pi.

They add that ancient Egyptian mathematicians also settled on a quite-ok-for-the-time value of 3.1605, as revealed by the Rhind Papyrus. Chinese and Indian mathematicians also approximated the value of pi down to seven or five digits, respectively, by the 5th century AD.

Further work, most notably that of Archimedes, helped refine this value. He used the Pythagorean Theorem to measure the area of a circle via the areas of inscribed and circumscribed regular polygons. If you slept during math class, that’s the polygon inside the circle and the one that contains the circle, respectively. It was an elegant method, but it did have its limits — since the areas of those two polygons aren’t exactly the same as the surface area of the circle, what Archimedes got was an interval that contained pi. He was aware of this limitation. His calculations revealed that pi must fall between 3 1/7 and 3 10/71 — which is between 3.14285 and 3.14085. Today we know that the five-digit value of pi is 3.14159, so that result isn’t at all bad for a guy without a proper pen to write it down with.

The first method to calculate the exact value of pi came up during the 14th century, with the development of the Madhava-Leibniz series. By the time the 20th-century swang by, pi was known down to about 500 digits.

Atomium ball.

What are isotopes

Atoms are the building blocks of matter. The screen you’re reading this on, the brain you’re reading with, they’re all very organized groups of atoms. They interact in specific ways, obeying specific rules, to maintain the shape and function of objects.

None of it works, however, unless the right atoms are involved. If you try to put the wrong ones into a protein or water molecule, it breaks apart. It’s like trying to cobble together a picture using pixels of the wrong colors.

Atomium ball.

Image in Public Domain.

Given how rigorous chemistry is on this, it’s surprising to see how much variety these ‘right’ atoms can get away with. Each element on the periodic table encompasses whole families of atoms who behave the same despite some important differences — isotopes.

What are isotopes?

Isotopes are atom families that have the same number of protons, but different numbers of neutrons. The term is drawn from ancient Greek words isos and topos, meaning ‘equal place’, to signify that they belong to the same elements on the periodic table.

Atoms are made of a dense core (nucleus) orbited by a swarm of electrons. The protons and neutrons that form the core represent virtually all of an atom’s mass and are largely identical except for their electrical charges — protons carry a positive charge, while neutrons don’t have any charge. The (negatively charged) electron envelope around the core dictates how atoms behave chemically.

The kicker here is that since neutrons carry no charge, they don’t need an electron nearby to balance them out. This renders their presence meaningless in most chemical processes.

To get a bit more technical, the number of protons within an atom’s nucleus is its ‘atomic number’ (aka the ‘proton number‘, usually notated ‘Z‘). Since protons are positively charged, each atom worth its salt will try to keep the same number of electrons in orbit to balance out its overall electric charge. If not, they’ll try to find other charge-impaired atoms and form ionic compounds, like literal salt, or covalent bonds — but that’s another story for another time.

thorium-atom.

Electron shells are made of several layers/orbitals. Although depicted round here, that’s only for simplicity’s sake. These orbitals can form very complicated shapes.
Image via Pixabay.

What’s important right now is to keep in mind that these atomic numbers identify individual elements. The atomic number is roughly equivalent to an element’s numeric place in the periodic table, and in broad lines dictates how an element tends to behave. All isotopes of an element have the same atomic number. What they differ in is their ‘mass number‘ (usually abbreviated ‘A‘), which denotes the total number of protons and neutrons in an atom’s core.

In other words, isotopes are atoms of the same element — but some just weigh more.

For example, two isotopes of Uranium, U-235 and U-238, have the same atomic number (92), but mass numbers of 235 and 238, respectively. You can have two isotopes of the same mass, like C-14 and N-14, that aren’t the same element at all, with atomic numbers 6 and 7, respectively. To find out how many neutrons an isotope harbors, subtract its atomic number from its mass number.

Do isotopes actually do anything?

For the most part, no. Generally speaking, there’s little to no difference in how various isotopes of the same element behave. This is partly a function of how we decide what each element ‘is’: roughly three-quarters of naturally-occurring elements are a mixture of isotopes. The average mass of a bunch of these isotopes put together is how we determine those elements’ standard atomic weights.

But, chiefly, it comes down to the point we’ve made previously: without differences in their electron shell, isotopes simply lack the means to change their chemical behavior. Which is just peachy for us. Taken together, the 81 stable elements known to us can boast some 275 stable isotopes. There are over 800 more radioactive (unstable) isotopes out there — some natural, and some we’ve created in the lab. Imagine the headache it would cause if they all behaved in a different way. Carbon itself has 3 stable isotopes — would we even exist today if each had its own quirks?

One element whose isotopes do differ meaningfully, however, is the runt of the periodic table: hydrogen. This exception is based on the atom’s particular nature. Hydrogen is the simplest chemical element, one proton orbited by one electron. Therefore, one extra neutron in the core can significantly alter the atom’s properties.

Hydrogen Isotopes.

Hydrogen’s isotopes are important enough for industrial and scientific applications that they received their own names.
Image credits BruceBlaus / Wikimedia.

For example, two of hydrogen’s natural isotopes, H-2 and H-3, have 1 and 2 neutrons respectively. Carbon (Z=6) has 2 stable isotopes: C-12 and C-13, with 6 and 7 neutrons respectively. In relative terms, there isn’t a huge difference in the neutrons’ share in their cores: they represent 50%, and 66.6% of the atoms’ weight in H-2, H-3, and 50% and 54-ish% of the total mass in C-12 and C-13. In absolute terms, though, the difference is immense: one neutron will double the mass of a hydrogen atom — two neutrons will triple it. For comparison, a single neutron is just 16.6% of a carbon atom’s mass.

While isotopes are highly similar chemically, they do differ physically. All that weight can alter how isotopes of light elements, hydrogen especially, behave. One example of such differences is the kinetic isotope effect — basically, heavier isotopes of the same element tend to be more sluggish during chemical reactions than lighter isotopes. For heavier elements, this effect is negligible.

Another quirky property of isotopes is that they tend to behave differently when exposed to infrared range than the ‘default’ elemental atoms. So, molecules that contain isotopes will look different to the same molecule sans isotopes when seen through an infrared camera. This, agian, is caused by their extra mass — the shape and masses of atoms in a molecule change how it vibrates, which in turn, changes how they interact with photons in the infrared range.

Where do isotopes come from?

Long story short, isotopes are simply atoms with more neutrons — they were either formed that way, enriched with neutrons sometime during their life, or are originated from nuclear processes that alter atomic nuclei. So, they form like all other atoms.

Lighter isotopes likely came together a bit after the Big Bang, while heavier ones were synthesized in the cores of stars. Isotopes can also form following the interaction between cosmic rays and energetic nuclei in the top layers of the atmosphere.

CNO cycle.

The carbon-nitrogen-oxygen (CNO) cycle, one of the two known sets of fusion reactions by which stars convert hydrogen to helium. P or ‘proton’ here is a positive hydrogen ion (aka hydrogen stripped of its electron).
Image credits Antonio Ciccolella / Wikimedia.

Isotopes can also be formed from other atoms or isotopes that have undergone changes over time. One example of such a process is radioactive decay: basically, unstable isotopes tend to shift towards a stable configuration over time. This can cause one unstable isotope to change into a stable one of the same element, or into isotopes of other elements with similar nucleic structures. U-238, for example, decays into Th-234.

This process, known as beta decay, occurs when there are too many protons compared to neutrons in a nucleus (or vice-versa), so one of them transforms into the other. In the example above, the uranium atom is the parent isotope, while the thorium atom is the daughter isotope. During this process, the nucleus emits radiation in the form of an electron and an antineutrino.

What are isotopes good for?

One of the prime uses for isotopes is dating (like carbon dating). One particular trait of unstable isotopes is that they decay into stable ones — but they always do so with the exact same speed. For example, C-14’s half-life (the amount of time needed for half of all isotopes in a sample to decay) is 5,730 years.

C-14 is formed in the atmosphere, and while an organism is alive, it ingests about one C-14 atom for every trillion stable C-12 isotopes through the food it eats. This keeps the C-12 to C-14 ratio roughly stable while it is alive. Once it dies, intake of C-14 stops — so by looking at how many C-14 atoms a sample has, we can calculate how far down C-14’s half-life it’s gone, meaning we can calculate its age.

At least, in theory. All our use of fossil fuels is pumping more C-14 isotopes into the atmosphere than normal, and it’s starting to mess up the accuracy of carbon dating.

To see how many C-14 atoms something has, we use accelerator mass spectrometry — a method that separates isotopes via mass.

PET (Positron-emission tomography) scans use the decay of so-called ‘medical isotopes‘ to peer inside the body. These isotopes are produced in nuclear reactors or accelerators called cyclotrons.

Finally, we sometimes create ‘enriched’ materials, such as enriched Uranium, to be used in nuclear reactors. This process basically involves us weeding through naturally-occurring uranium atoms via various methods for heavier isotopes, then separating those. The metal that we’ve already removed the heavier isotopes from (which are more unstable and thus more radioactive than ‘regular’ uranium) is known as ‘depleted uranium’.

How your body heals itself after a wound

The body is pretty amazing. Cuts and other wounds can happen for lots of different reasons; you could trip and fall or have a more serious accident. Luckily, the body is well equipped to seal up a wound and heal it quite quickly. When our layer of skin is broken, a few very important steps occur that help to keep out harmful bacteria and build a new layer of skin.

The first steps of healing

The first thing that happens when the skin is penetrated is that you bleed. Normally, the blood cells stick together and form clots quite quickly, within the range of seconds to minutes. A type of blood cell called a platelet and a protein called fibrin help to form the clots and keep them in place. The clots form an initial layer that keeps more blood from being lost. Once they dry, these clots turn into scabs. The body needs to seal up the wound as soon as possible, because the skin exists to keep germs out and without a protective layer, bacteria can come in and cause infections.

The stages of wound healing. Image credits: OpenStax College.

Next, any bacteria at the site are taken care of and the healing process begins. At this point, the wound is initially inflamed and the surrounding skin can be warm to the touch and red. The blood vessels open up a bit again and deliver much-needed oxygen and nutrients to the wound. The white blood cell called a macrophage steps in to tackle any unwanted bacteria and produce growth factors that help to repair the wound. At this point, a clear fluid can often be seen on or around the wound that help to clean the area. After dead cells and bacteria are taken care of, the macrophages leave. This step is important because inflammation that lasts too long is a sign that the healing process isn’t going so smoothly. This stage takes two to five days on average.

Producing scar tissue

After the initial swelling, the tissue starts to get rebuilt underneath the scab. More blood cells come to the scene to build new tissue. Collagen — tough white fiber– is built first, as a result of chemical signals, and it serves as a framework on which other tissues can be built. Broken blood vessels also need to be repaired. Granulation tissue fills the wound and skin tissue forms on top of it. It starts forming at the edges and works its way to the center. When the skin below it is ready, the scab sloughs off on its own. A deep cut can take three to six weeks to heal.

When the scab comes off, new scar tissue underneath is revealed. Scar tissue is different from skin tissue in that it doesn’t contain sweat glands or hair follicles. It can still be a bit tender and reddish at first, but it strengthens over time. It takes about three months for the scar tissue to become as strong as normal skin and a few years to heal completely. Superficial wounds usually heal without a scar, while permanent scars are more likely with deeper wounds, though they do fade over time.

Helping and disrupting the healing

It is important to keep wounds clean and covered to help with the healing process. Minor wounds should be washed with water and covered with sterile gauze or a bandage. Major wounds should be treated with a doctor’s advice.

It’s is important to make sure that a wound is well covered. Image credits: Public Domain Pictures.

Usually the healing process goes smoothly, especially if you take care of it well. However, there are cases where it doesn’t go as well as wished. If a wound doesn’t have adequate blood supply then it doesn’t receive the ingredients that it needs to heal, namely oxygen and nutrients. It can take twice as long or even longer to heal. It can take longer for the wounds of elderly people, and people with diabetes, high blood pressure, obesity, and other vascular diseases to heal. Stress, smoking, certain medicines, and heavy alcohol drinking can also interfere with wound healing. There are some warning signs that a wound isn’t healing properly that include pus and a fever, which could mean that it is infected. In this case, it is important to see a doctor.

The wound healing process allows us to be active and survive life’s little accidents by regenerating our largest organ.

mitosis artsy.

What Are Five Stages of Mitosis?

mitosis artsy.

“Mitosis or Fusion?” artwork.
Image credits Mike Lewinski / Flickr.

Our bodies are collections of cells, all bunched up and working together to help you successfully navigate adult life. Being the ideal heap of cells, however, involves some growing and quite a lot of maintenance. If it sounds like hard work, it’s because it probably is. Luckily for us, cells have a secret ace up their sleeves: they can simply copy-paste themselves to create new, identical members. This process — called mitosis or, more colloquially, cell division — is what allows organisms to grow, develop, and heal with virtually no conscious effort.

I’m a huge fan of not making any conscious effort — so let’s all appreciate all the work our cells aren’t putting us through while we take a look at mitosis.

Readers be warned: we will be using the animal cell as a template to discuss the processes involved. There will be some differences here and there between how these and other types of cells handle mitosis.

What is mitosis?

Mitosis is one of two types of cellular division — the other being meiosis. They’re largely identical, with the key difference being that mitosis results in two daughter cells, each with the same number and type of chromosomes as their parent, while meiosis results in cells that only have half of the parent’s chromosomes. Mitosis is how regular cells — the ones that make up your tissues, your pet’s tissues, or the yeast that fermented your beer — multiply. Meiosis is how our bodies produce sex cells, like sperm and eggs.

While it goes on without us actually doing anything (beyond staying fed and not-dead, obviously), there’s a lot of work involved in mitosis. We’ve classified the steps of this process in ‘phases’ that each cell must go through before it can divide. These are, in order:

Interphase

Interphase.

This isn’t strictly speaking part of the meiosis process; rather, it’s more of a default-state for cells. They spend most of their lifespan in interphase, performing their usual functions and getting all stocked up on nutrients. As baby-cell-making time swings around, i.e. the later stages of interphase, cells start duplicating their internal structures — they create two copies of their DNA and of each organelle.

Interphase is generally broken down in two to three separate sub-phases:

  • Growth (G1) phase, during which the cell doubles-down on synthesizing virtually its full array of proteins, especially the structural proteins it will need to grow.
  • Synthesis (S) phase: this is when the cell’s chromosomes are duplicated.
  • [In some cases] Growth (G2) phase, which is very similar in form and function to the G1.

Prophase

Prophase.

This is when the cell starts going into reproduction mode proper. One of the first things that happen during prophase is that the cell’s (now double-helping of) DNA condenses into pairs of chromosomes. Think of it like archiving a folder on your computer — all the information is still there, only much more compact and easier to share with your kids.

Another important event is the formation of the mitotic spindle. This starts with the cell’s centrioles — the organelles that secrete these microtubules, made from the protein that forms the spindle and cellular support skeleton — moving to the poles. From there, they release microtubules, gradually pushing them towards the middle, where they’ll eventually fuse. The mitotic spindle will elongate the cell during prophase, which will come in handy during division.

Finally, the cell’s nucleolus — the largest structure inside the nucleus, which assembles ribosomes — disappears, setting the stage for the nucleus to break down.

Metaphase

Metaphase.

During a brief time window called prometaphase (the “before metaphase”), the membrane around the chromosomes breaks down. This will release the chromosomes inside the cell, and they will affix to the mitotic spindle on the equatorial plane.

The spindle is there to ensure that each daughter cell will receive a full copy of the original’s DNA. It does this by pulling the chromosome pairs onto its filaments, right across the equatorial plane — an imaginary line that falls roughly along the cell’s midline. This sorts the genetic data, so to speak, ensuring that each of the new cells-to-be will get one chromosome from each pair before the cell divides. Not all microtubules stick to a chromosome — those that do are known as kinetochore microtubules. The other microtubules will span the cell and grab on to microtubules coming from the other side, to stabilize the spindle.

Kinetochore.

The mitotic spindle in a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in red.

During metaphase proper, all chromosomes are drawn into place on the spindle across the equatorial plane. By this time, each chromosome’s kinetochore — a complex protein structure associated with the chromosomes that, among other things, contains a molecular motor — should be attached to microtubules from opposite spindle poles.

Eukaryotic cells go through a lot of effort to ensure genetic integrity during mitosis — else they risk their health and that of the organism. Before proceeding to the next phase, the cell has to pass the ‘spindle checkpoint’: if all chromosome pairs are on the equatorial plane, and properly aligned (one half toward each end of the spindle), the cell gives the green light. If not, it pauses the mitosis process until everything is set.

Anaphase

Anaphase.

During anaphase, the ‘glue’ holding each chromosome pair together breaks down and their members get pulled to the opposite sides of the cell — by this point, each half of the mother cell harbors a complete copy of its DNA, and the actual division can begin.

The chromosomes are pulled by kinetochore microtubules, which start to shorten towards the opposing centromeres. At the same time, the structural microtubules grow, pushing at each other, elongating the cell; imagine stretching a piece of chewing gum between your fingers — that’s roughly the shape cells take during this phase. All this activity is powered by motor proteins, such as the one in the chromosomes’ kinetochores that pull them along microtubules.

Telophase

Telophase.

By this point, the cell is nearly done dividing, hurray!

Since cells are really a tidy lot, the new daughter cells start re-forming their internal structures even while they’re still connected along the membrane. The mitotic spindle is the first structure to be broken down, its building blocks recycled into the new cells’ support skeletons. Each set of chromosomes comes together, and the nuclei form, fully-equipped with their own membranes and nucleoli.

Finally, the chromosomes begin to unpack, reforming into long strands of DNA in the nucleus.

Cytokinesis

Cytokinesis.

Sometimes considered as the later part of telophase, this stage sees the division of cytoplasm (the gooey stuff inside cells) between the two daughters. Cytokinesis can actually start as early as during anaphase (most notably for certain plant cells) but always ends shortly after telophase.

In animal cells, the process of cytokinesis constricts their membranes where they meet — like a piece of string tied around a balloon. That string is a band of actin filaments. The goal of this contraction is to progressively pull the membranes into an ‘8’ shape, after which the cells pop free of each other.

Plant cells, which tend to reinforce their membranes with compounds such as cellulose and hemicellulose, don’t employ the same mechanism. Instead, they form a structure called a cell plate down their middle, splitting the two daughter cells with a new wall.

And voilà! Two new cells, identical to their parent, are now ready to mingle and toil for the collective good.

Wrongtosis

Despite all the checks and balances biology set in place to make sure mitosis goes through smoothly, sometimes it doesn’t. For cells, any errors that take place during mitosis can have significant effects. For us, multicellular organisms that we are, not so much — but it can still affect us.

One of the most abhorred outcomes of bad mitosis is cancer(link). Faulty copies or improper distribution of chromosomes during mitosis can induce genetic errors, which can cause mutations in daughter cells. Some mutations are silent (they don’t have an impact on the sequence’s role) but those that alter amino acid synthesis (called missense mutations) often have an impact on the cell’s workings. Over time, enough such mutations can add up, disrupting the cell’s normal activity, leading to the formation of tumors. Cancer occurs when mutated tumor cells override their natural limits and checks on mitosis, starting to reproduce uncontrollably.

Another way mitosis can go awry are chromosome abnormalities(link). In short, sometimes the chromosome pairs fail to attach to the spindle, and a daughter cell will end up with an extra or a missing chromosome after division (a condition known as aneuploidy). This error can have far-reaching effects on the body. For context, Down’s syndrome is caused by the presence of an extra chromosome in every cell — it arises from aneuploid sperm or eggs, so it’s a meiotic, not a mitotic error. Still, it illustrates what a body-wide difference of a single chromosome can do. Meiotic chromosomal abnormalities generally only affect one or a small number of cells, based on random mutation.

Cell mutations can also lead to mosaicism(link). This describes a condition in which some cells in the body have a mutant version of a gene, while others carry the normal version. In somatic cells (your body’s cells, bar your eggs or sperm) these mutations generally don’t even produce a noticeable effect. But, if the mutant gene is widespread enough, and is missense, it can have a major impact. Two examples of conditions linked to mosaicism are hemophilia, a blood-clotting disorder, and Marfan syndrome, which produces unusually long limbs.

The unique types of ecosystems in the world

Ecosystems are little bubbles of life in which all components interact with each other to form a connected web. Both living and nonliving factors interact in this interconnected system. There are both terrestrial and aquatic ecosystems, and there are many, many different types of both. Basically, the environment and climate determine what sorts of animals and plants can inhabit a certain region. Interactions between plants and animals are also important factors.

Saltwater ecosystems

Broadly speaking, aquatic ecosystems can be broken up into freshwater and saltwater systems. Marine ecosystems cover about 71% of the Earth’s surface and there are a number of different types. The oceanic zone is the open part of the ocean where pelagic animals, such as whales and tuna, live. The benthic zone is the bottom of the ocean where invertebrates live. Near-shore ecosystems include the intertidal zone, estuaries, salt marshes, sandy shores, coral reefs, lagoons, and mangrove swamps.

The Amazon estuary. Image credits: NASA.

Some areas can be really huge, like the open ocean where the flat landscape goes on and on. Some areas are far more constrained, such as a whale fall, which is the ecosystem that forms when a dead whale falls to the sea floor—it provides so much food that a whole ecosystem forms, dependent on the whale carcass. Marine ecosystems are determined by multiple factors, including temperature, geology, light, location, and tides.

Hydrothermal vents are extremely specialized habitats. Image credits: NOAA.

The differences in regions of the ocean are so extreme that animals and plants have adapted especially for their area. For example, some sharks can swim long distances in open water, organisms that live near hydrothermal vents needs to be able to withstand extreme temperatures, and deep sea organisms need to live without light and hence without photosynthesis.

Freshwater ecosystems

Freshwater ecosystems only make up about 0.8% of the Earth’s surface. There are three main types of freshwater ecosystems. Lentic ecosystems are made of slow moving water, like lakes, ponds, and pools. Lotic ecosystems involve moving water, like streams and rivers. Wetlands are areas that have soil which is moist or soaked with water for most of the year. There are many different zones even within lakes. The littoral zone is close to the shore and can have rooted plants growing in it. Deeper in the lake, there is a photic zone that sunlight can reach and thus supports photosynthetic algae. In deeper lakes, there is also an aphotic zone that sunlight does not reach and thus is supported by nutrients and matter that falls down from above.

The different zones in a lake. Image credits: Geoff Ruth.

Wetlands can be part of lakes since they form naturally as part of the shore. Over long periods of time, lakes fill up with sediment and turn into wetlands. Different types of wetland are swamps, marshes, fens, and bogs. Swamps are forested wetlands while marshes don’t typically have woody vegetation; they both tend to be near a river and contain pools of water. Mires, such as fens and bogs, are wet peatlands that have wet soil but usually not pools of water. Wetlands are very productive ecosystems and hold a high number of plant and animal species.

A swamp. Image credits: Pixabay.

Parts of rivers host different ecosystems depending on the speed of the water. Fast moving water contains higher concentrations of dissolved oxygen than areas where water pools up. Rivers can get nutrients from nearby trees or from algae in the river. Fish may prefer faster moving parts of the river, while small animals and invertebrates might prefer slower parts so that they don’t get swept away.

A slower moving river. Image credits: Tomio344456.

Terrestrial ecosystems

Terrestrial ecosystems make up the remaining 28.2% of the Earth’s surface. They have less water and more light and gases than aquatic ecosystems. It is impossible to talk about every ecosystem on land, because there are so many, but, in general, they are determined by climate and geology.

Climate: There are six main climatic areas on land in which specific ecosystems can form. They are tundra, taiga, temperate forest, tropical rain forest, grassland, and desert. The climate determines what kind of species can live there. For example, in a tropical rainforest, many plants can grow because of the warm temperature and abundance of water. They then create many niches that animals can inhabit and comprise an ecosystem. Rainforests can host many ecosystems, on the ground, in the canopy, and in the different layers of the forest. In the tundra, plants are limited due to the temperature and light conditions. They are usually quite hardy and grow low to the ground. They don’t provide much habitat complexity and only a small number of animals can live off of these plants. Therefore, climate is very important in determining the type of ecosystem.

Tropical rainforests host many different ecosystems. Image credits: John Atherton.

Geology: There are many ecosystems that occur for reasons other than climate—they can also depend on geology. For example, caves can occur all over the world in sedimentary rock that has been worn away by water to form holes and caverns in which unique species live. Mountains are formed by the collision of tectonic plates or erosion. Since it is colder, with less light and oxygen as you go up in altitude, there are also different ecosystems at different altitudes.

Caves provide a unique environment for some animals. Image credits: Pixabay.

This is only an overview of the types of ecosystems in the world—there are so many interesting and specialized types.

What are ecosystems and why they’re important

Earth has a wide variety of ecosystems that maintain its function and make it wondrous. While most of us are familiar with the term “ecosystem”, a lot of people may be unsure about what that term actually means. And that’s understandable — several different definitions are often used for the same term. However, the best all-encompassing definition for an ecosystem is all of the living organisms (plants, animals, and bacteria) and the nonliving components (air, water, soil, weather) that interact with each other as a system. The size of an ecosystem can range from a small tide pool to a giant desert. All the members of the system are interconnected, so the loss or change of one factor can have large effects rippling through the entire ecosystem.

An ecosystem is a little bubble of life made up of living and nonliving components. Image credits: Tsilia yotova.

 

External and internal factors

Energy enters an ecosystem from the sun, which plants utilize, as well as carbon dioxide, which is used for photosynthesis. Animals eat the plants, moving the energy and matter through the ecosystem. When organic matter dies, decomposers break it down, releasing carbon dioxide back into the atmosphere.

Other larger external factors determine an ecosystem’s climate, time, topography, and material at the earth’s surface — these factors are not influenced by the ecosystem itself; they simply exist. Rainfall and temperature determine the amount of water and energy available to a system. Climate determines what sort of biome an ecosystem is in — these factors make one region a desert, another one fertile land, and another one a lake.

Different climate zones on Earth. Image credits: Waitak.

Internal factors change how different species interact with each other. For example, if one species contracts a disease and dies off, it affects the whole system. These factors both control and are controlled by ecosystem interactions. In this way, there are different from external factors.

Different types

Ecosystems are often a part of a larger biome, which should not be confused with an ecosystem: biomes are large areas of land based broadly on climate type and the species present. They are not based on the interactions between living and nonliving parts of a system.

An ecosystem is defined as such because the species that interact form a network that depends on the environment. So a forest, such as the Amazon rainforest, can host many different ecosystems: a soil ecosystem, an understory ecosystem, a canopy, and a forest floor ecosystem. All the members of each system interact with one another and form a closed system.

A tide pool is a very small ecosystem. Image credits: Little Mountain 5.

Ecosystems are dynamic: they can change based on external or internal factors. The variation in climate can cause situations such as droughts, where all but the most resistant plants die. The animals and microorganisms that depend on these plants would also be affected. New species sometimes also arrive. For example, a new bird that eats a certain insect can come to an area. That insect will now be less abundant and affect the plants that it used to feed upon as well as the other animals that eat this plant. The animals and plants that live in an ecosystem are perfectly suited to these particular living conditions. Changes in external factors, like temperature, can change the plants grow and, therefore, the animals that eat the plants might adapt, move, or die in response.

Ecosystem services

The normal functioning of an ecosystem provides humans with an abundance of services that we depend upon or that can significantly improve our quality of life. For example, pollination is necessary for about 75% of our crops, trees provide us with timber, and the oceans provide us with fish. The list of ecosystem-provided services is very, very long and includes several more nuanced entries that we tend to take for granted, like clean air, a stable climate, and safe drinking water.

Pollination is an important ecosystem service. Image credits: Pixabay.

Human influence

Human action is currently disrupting a large number of ecosystems. For example, by removing most of the fish from the ocean, the whole food chain and system are disrupted and can no longer function properly. The result is running out of certain types of seafood that we enjoy. Introducing invasive species also influences ecosystems because these invasive species outcompete several of the native species that are necessary for the system to work properly.

On a larger scale, humans are even capable of influencing external factors. By causing the earth to warm via increased carbon dioxide emissions, it influences which plants and animals can live where. It is true that new species often enter ecosystems and that climate can naturally fluctuate but the current changes are so frequent and sudden that the ecosystems cannot adapt to new equilibrium. We are also shooting ourselves in the foot because disrupting ecosystems could have disastrous effects on ourselves: no pollination and hence few crops, bad air quality, fewer fish, and contaminated water are just a few examples. Maintaining the balance of the ecosystem benefits us personally.

 

 

 

 

 

 

The different types of plants in the world

There is an incredible number of different plants in the world. Humans separate plants according to particular traits. Some of the most important differences between plants are whether they have seeds or vascular tissue. Plants have been grouped into twelve different phyla depending on these characteristics. Incidentally, learning about the types of plants also takes us on an evolutionary journey as plants emerged from aquatic systems and increased in complexity.

The different types of plants represented in an evolutionary tree. Image credits: Maulucioni.

Plants without seeds

Algae: There are three different types of algae: red, green, and brown. They live in water and, for this reason, are considered primitive plants. All plants started off growing in water, and as single celled organisms. More evolutionarily advanced plants left the water. Algae are photosynthetic organisms that range from unicellular organisms to large multicellular forms.

Liverworts and hornworts:

Liverworts are small plants that grow in damp environments. They do not contain the vascular tissue that transports water from the roots to leaves, which is why liverworts are usually very small and need to live in moist places. Liverworts grow simply by expanding themselves. They do not have a true root, stem or leaves. Hornworts are similar, but have a sporophyte, which is a horn-like structure.

A liverwort. Image credits: Lairich Rig.

Mosses:

Mosses are close relatives of liverworts and thrive in similar environments, damp areas near water sources. However, they do not require soil to grow, which is why you can see rocks and trees covered in moss. Mosses grow apically — in other words, stems grow from their tips or other special points on the stem. Flowering plants also grow this way.

Mosses growing on rock. Image credits: brewbooks.

Vascular plants without seeds

Ferns:

Ferns need wet environments to reproduce so the sperm cell can swim to join with the egg cell. A new fern develops from the resulting zygote. However, ferns can survive periods with less water better than mosses and worts. Millions of years ago, ferns dominated the land and were the most common plants. There were massive fern forests.

The underside of a fern, showing the spores. Image credits: Pixabay.

Other types:

There are several other plants that have vascular tissue but lack seeds. Whisk ferns are primitive ferns that lack typical plant organs, such as leaves. Clubmosses have branching stems with simple leaves. Horsetails, also called snake grass or puzzlegrass, are found in the only extant (still living) genus in its family. More species within the same family existed millions of years ago, including very tall trees. Club mosses and horsetails are considered fern allies since all of these plants reproduce by spores and not by seeds.

Horsetails are a very ancient type of plant. Image credits: Rror.

Plants with seeds

Gymnosperms

Cycads:

Cycads are trees that like moisture and heat, therefore, they mostly grow in Central America, Africa, Southeast Asia, and Australia. They generally have long, thin leaves, and produce a cone-like structure which makes them look like palms with cones. Cycads possess a crown of large compound leaves and a thick trunk. There are only a few species left, but they were very common during the Jurassic period, which is often called the “Age of Cycads.”

A cycad. Image credits: Pixabay.

Ginkgo:

There is currently only one ginkgo species in existence, Ginkgo biloba. It has not changed very much since the Permian period — when it covered large parts of the world — and is therefore called a living fossil. They have fan-shaped leaves, and trees are either male or female. They produce fleshy seeds that have a strong odour. Ginkgo is only found naturally in central China, but has been purposefully planted in gardens and parks around the world. Flowering plants, however, are outcompeting it.

A gingko tree. Image credits: Pixabay.

Gnetophyta:

The phylum gnetophyta is also a gymnosperm and consists of three genera that are not closely related. There are about 70 species in total. Ephedra is the largest genus, and its plants grow in deserts. Welwitschia plants grow in the desert in southwestern Africa; they have long, thin leaves. The last genus in the phylum is the namesake called Gnetum.

A plant from the Welwitschia genus. Image credits: Bries.

Conifers:

Conifers have woody trunks and produce cones with seeds. They grow mostly in cold northern climates and keep their leaves throughout the year. Conifers have naked seeds that are protected by cones, and the male and female cones are produced on the same tree. The pollen cones are male and produce the pollen that is spread to the female gametophyte found inside the seed cone. Seed cones are female and contain eggs on scales that form seeds when fertilized.

Conifers have seeds in protective cones. Image credits: John Haslam.

Angiosperms

Flowering plants:

Flowering plants, also called angiosperms, have male and female parts. The male parts produce pollen that is dispersed, and upon reaching the female parts produces an embryo that develops into a seed. Wind and pollinators, like bees, can pollinate these plants. Angiosperms produce flowers and fruit, and the seeds are produced and protected within this fruit. Angiosperms are divided into two groups. Monocotyledons (monocots) have one seed leaf, while dicotyledons (dicots) have two seed leaves. Monocots have parallel veins, scattered vascular tissue, and flower parts that grow in multiples of three. Dicots have net-like veins, vascular tissue in rings in the stems, flower parts that grow in multiples of 4 or 5, and are often woody. Angiosperms form the plant group most equipped to handle dry conditions, which is why they are now the most widespread plant type.

Flowering plants. Image credits: Mostafameraji.

We are now living in the era of flowering plants. Evolutionarily, they are the most advanced and they make up the largest proportion of plants in the world. There are still many other diverse plant species that grow alongside them.

Are viruses alive?

Chances are that you have been infected by a virus, whether it be the common cold or chicken pox or one of the many others. Viruses are common, but there are more to them than they appear. They are more difficult to treat because antibiotics cannot be used against them. The reason for this is that they aren’t alive in the way we’re used to things being alive. In fact, it’s very difficult to classify them as “alive” or not.

Here’s why.

Not fitting the definition of life

Viruses are not even cells. They have genetic material, such as RNA or DNA, surrounded by a protein coat but that is about it. They don’t have any organelles or even a membrane.

Most of the time viruses are inactive. They do not use any energy and cannot replicate themselves on their own. The only time when viruses are “alive” is when they come into contact with a host cell. They bind to receptors on the cell, inject their genetic material in, and hijack the cell’s energy and replication tools to make copies of themselves.

The simple structure of a virus, in this case Dengue. Image credits: Girish Khera, Scientific Animations.

Scientists have insisted for a long time that viruses aren’t living because they don’t fit into the box of what life is. They don’t metabolize, respond to changes in the environment, grow, and excrete. The only process that they do actually carry out is reproduction, but they can’t even do that on their own. As they are inactive most of the time and cannot be active without a host, some argue that they are not alive.

Shedding light on viruses

A few recent discoveries have provided some evidence that viruses are or were alive. In 1992, mimiviruses were discovered. They are huge viruses with genomic libraries that are larger than those of some bacteria. Some of them even have the genes for proteins that can translate DNA to create new viruses. Additionally, they have genes for DNA repair, metabolism, and protein folding. So they actually are able to replicate on their own, disproving that all viruses require a host.

In 2015, University of Illinois crop sciences and Carl R. Woese Institute for Genomic Biology professor Gustavo Caetano-Anolles and his graduate student Arshan Nasir traced the evolutionary history of viruses. There are too many random mutations in virus DNA for that to be informative so they examined protein folds. They are the shapes of proteins that are unique to viruses and cells and that are coded by genes but are more stable over time.

The researchers analysed the folds of 3,460 viruses and 1,620 cells from every branch of the tree of life. Some 442 protein folds were shared between cells and viruses while only 66 were unique to viruses. This finding suggests that the viruses and cells evolved together and then diverged and are actually more similar than we think. The viruses could have regressed and become simpler instead of more complex. Perhaps having less cell machinery was more beneficial to the viruses. I mean, look how successful they are.

Protein folds are remarkably conserved in live cells and viruses. Image credits: Marina Vladivostok.

So what are they?

Humans like to classify things in ways that are easy for us to understand. For example, we classify living things based on similar traits. We like to know, is something alive or isn’t it? However, nature doesn’t always work like that. We can base the definition of life on what we know, but then when something like a virus which doesn’t fit out definitions completely, it baffles us.

The way that nature functions is not so black and white. For example, there are parasites, such as bacteria and fungi, that cannot reproduce on their own and need a host to complete their life cycles and survive. They are still considered to be alive. Also, if you take a seed, would you say that it is alive? It doesn’t show any sign of life, but when it is planted and has the right conditions then it germinates and grows. In this respect, viruses are very similar. They are inactive until they reach a host and then they reproduce. I would also argue that only things that are alive would be under the pressure to evolve and to survive. Viruses make copies of themselves by exploiting the environment. They can evolve and are very diverse.

Viruses do show signs of life. They do not fit well with our definitions of life, and that is the main conflict in our confusion about how to classify viruses. Perhaps we need to rethink our definition of “life”.

Why satellites have those golden foils on them — and how it saves a lot of lives

If you’ve ever seen a satellite, odds are it had a golden or silver foil around it. So what’s that about?

The short story

Well, despite the common knowledge of space being “cold,” it’s actually really difficult to get rid of any heat in a vacuum. This is where the foil comes in — it’s all about the insulation. They reflect radiation while keeping some of the heat trapped in.

The Mars Reconnaissance Orbiter fully assembled prior to launch. The golden foil is the Multi Layer Insulation.

Space blankets

It’s called Multi Layer Insulation (MLI for short), and it does just what it says — it’s a multi-layer system designed to insulate the satellite or spacecraft. These layers are usually made of polyimide or polyester films (types of plastics), coated with very thin layers of aluminum. The exact composition of the MLI depends from case to case, but that’s pretty much the gist of it. It’s not a foil, it’s rather a series of layers. You can think of it as a space blanket.

Now, a sensible question would be… insulate it from what? What do satellites need to be insulated from? Well, while the temperature in space is a measly 2.73 Kelvin (-270.42 Celsius, -454.75 Fahrenheit), just a smidge above the absolute lowest possible temperature, satellites can get pretty hot. The Sun shines directly on them, with no atmosphere to filter out some of the energy, and this can raise temperatures high enough to boil water.

Closeup of Multi-layer insulation from a satellite. The metal coated plastic layers and the scrim separator are visible. Image credits: John Rossie of AerospaceEd.org.

Without a highly reflective surface, probes and satellites would just absorb the sun’s energy and heat up to the point of failure, with no possibility of cooling down (because space is a vacuum, and heat can’t travel through vacuums). This is why the MLI is a key feature of spacecraft design — it enables them to remain at a reasonable (functioning) temperature. Since many satellites have complex electronic circuitry on them, they can be highly vulnerable to heat and temperature variation. But it does even more than this.

Lunar landing modules also used similar golden foil. Credits: NASA / Wiki Commons.

The insulating system ensures that the satellite doesn’t overheat, but it’s also what allows it to maintain a sufficient degree of heat. After all, simply radiating all the heat away would leave the spacecraft freezing cold. The system can absorb some of the radiation hitting the satellite, keeping it at a cozy temperature. It’s also resistant to both cold temperatures and ultraviolet radiation, making it suitable for outer space.

MLI is also used as a first line of defense against impact with space dust. Even tiny particles can do great damage, and having several protective layers works as a good buffer.

Saving satellites in space, saving lives on Earth

MLI is basically a thermal blanket (a space blanket, if you wish), and like many other pieces of technology, it also made its way into our day to day lives. Nowadays, space blankets are included in many emergency, first aid, and survival kits. Since they were designed to last in the ungodly conditions of outer space, they can easily withstand wind and rain down on Earth. Couple that with their low weight, and it’s easy to understand why they’ve become so useful for outdoor enthusiasts and emergency workers. These blankets are often given to marathoners or people suffering from hypothermia, and even the US military routinely uses them in some situations. Instead of calling them space blankets, we just call them survival blankets now.

Emergency thermal blanket. Image credits: Dionisis Christofilogiannis.

Like many other technologies, MLI started as a space technology and ended up having a broader impact here on Earth. It’s hard to say just how many lives insulation systems based on it have saved, but the fact that rescue workers use them all across the world is very telling.

They can be used to protect someone from extreme cold as well as extreme heat sources. Similarly to space blankets, they often have a golden and a silver side, but unlike the space blankets, they are more often used to trap heat inside rather than reflect radiation. As rescue teams put it, if you’re saving someone from extreme cold or hypothermia, ‘gold goes to cold’.

How alleles make us who we are

Alleles are very important in determining every single characteristic that we have, from eye colour to metabolism. They determine which type of a trait you have, such as blue eye or a slow metabolism. One allele was given to you by your mother and the other by your father and there is a special way that determines what you will look like.

What is an allele?

First, to know what an allele is, you need to know what a gene is. A gene is a part of DNA that contains the information for a trait. For example, one gene could determine eye colour. Each gene adds a specific ingredient to the recipe that is your body. Genes are located at specific locations on a certain chromosome. Alleles are the different forms that the gene can take. Eyes can be blue, green, brown, and so on. We can make a comparison with ice-cream. The ice-cream flavour would be the gene, and chocolate, mint, vanilla, strawberry would be the alleles. Basically, the gene is the trait and the allele is the form that it takes.

A gene expresses each of our traits. Image credits: National Human Genome Research Institute.

You can’t talk about alleles without mentioning Gregor Mendel. He was a friar who lived in what is now the Czech Republic from 1822 to 1884. He basically discovered alleles and how they work with his experiments on pea plants. Mendel looked at different characteristics of pea plants, such as their size, flower colour, seed colour, and pea form. The friar took the different forms and bred them together. He found that when he bred two different types together, only one form of the characteristic was expressed. For example, when he bred a plant with green seeds with one with yellow seeds, it produced a plant with yellow seeds.

Each parent plant gives their offspring an allele. It is the same in humans. The parents pass their traits on to the next generation, half comes from the mother and half from the father. So the offspring ends up with two alleles.

Dominance and Recessiveness

There are different types of traits. When Mendel bred yellow seeded plants together, most of the offspring produced yellow seeds as expected. However, a few produced green seeds. He developed the theory that explains this occurrence, today called Mendelian Inheritance.

Each allele can be dominant or recessive. Let’s use the example of eye colour. The brown eye allele is dominant over the blue eye allele. The brown eye allele is represented by B and the blue eye by b. If there is at least one B allele then the eyes will be brown, the eyes will be blue only there are two blue alleles (bb). So if a mother has brown eyes (BB) and the father also has brown eyes (BB), then the child will have brown eyes (BB). If both parents have blue eyes (bb) then the child will also have blue eyes (bb). However, if the mom has blue eyes (bb) and the dad has brown eyes (BB) then the child will have brown eyes because brown is dominant over blue.

If one parent has blue eyes (bb) and the other has brown eyes (BB) then all the children will have brown eyes but will carry a blue allele so their children could have blue eyes. Image credits: Purpy Pupple.

Maybe one parent has a brown allele (BB) and the other a blue allele (bb). If this is the case then, there is a ¾ chance that the child will have brown eyes (BB, Bb, Bb, bb). You can also have brown eyes and have a blue eye allele lurking behind (Bb), your child could then have blue eyes depending on your partner’s alleles. All in all, it doesn’t matter what your eyes look like, it depends on which alleles you have. Two partners with brown eyes (both Bb) could still have a child with blue eyes.

Eye colour depends on which alleles you have. Image credits: Pixabay.

These alleles can also determine whether you get genetic diseases. Huntington disease, which causes the death of brain cells, requires one dominant allele to be expressed so parents give it directly to their children. In contrast, many genetic diseases are recessive so they can be in a family for generations without them knowing it. When two recessive alleles come together the child has the disease. Examples are albinism, cystic fibrosis, and sickle cell anemia.

It’s not always so simple as these examples, other traits might be interconnected. If you have one trait, it could affect whether you have other traits. And actually, eye colour is now known to be controlled by multiple genes. But here, in a nutshell, are the basics about alleles.

The reason why ice floats

Ice floats— that’s why the ocean has polar ice and icebergs, and why the ice in your drink floats. If you think about it, it might seem a bit strange because ice is a solid and intuitively, it should be heavier than a liquid and sink. Though this is true for most substances, water is an exception. Its hydrogen bonds and its solid state actually make it lighter than it is as a liquid.

Ice is less dense

Water is an amazing substance that basically fuels life on earth— every living organism needs it. It also has some interesting properties that enable life to be the way that it is. One of the most important properties is that water is the densest at 4 °C (40°F). Hot water and ice are both less dense than cool water. Less dense substances float on top of more dense substances. For example, when you make salad dressing oil floats on top of vinegar because it is less dense. The same is true for everything. If you have a blow-up beach ball in a pool, it floats, if you have a rock, it sinks.

Although it seems heavy, an iceberg is less dense than water. Image credits: NOAA’s National Ocean Service.

The reason why ice is less dense than water has to do with hydrogen bonds. As you know, water is made up of one oxygen and two hydrogen atoms. They are attached by covalent bonds that are very strong. However, another type of bond also forms between different water molecules called a hydrogen bond, which is weaker. These bonds form because the positively-charged hydrogen atoms are attracted the negatively-charged oxygen atoms of nearby water molecules. When water is warm, the molecules are very active, move around a lot, and form and break bonds with other water molecules quickly. They have the energy to push closer to each other and move quickly.

As water gets below 4 °C, the kinetic energy decreases so the molecules don’t move around so much anymore. They don’t have the energy to move and break and form bonds so easily. Instead, they form more hydrogen bonds with other water molecules to form hexagonal lattice structures. They form these structures to keep the negatively charged oxygen molecules apart. In the middle of the hexagons, there is a lot of empty space.

The structure of water molecules as they form ice, notice all the empty space. Image credits: NIMSoffice.

Ice is actually about 9% less dense than liquid water. Therefore, ice takes up more space than water. Practically, this makes sense, because ice expands. It’s why you shouldn’t freeze a glass bottle of water and why frozen water can create bigger cracks in concrete. If you have a liter bottle of ice and a liter bottle of water, then the ice water bottle would be lighter. The molecules are further away from each other at this point than when the water is warmer. Therefore, ice is less dense that water and floats.

When ice melts, the stable crystal structure collapses and is suddenly denser. As water warms past 4 °C, it gains energy and the molecules move faster and further apart. So hot water also takes up more space than colder water and it floats on top of the cooler water because it is less dense. It’s like when you go to a lake to go swimming and the top layer is nice and warm but when you stick your legs below it is suddenly much colder.

Important for our Earth

So why does this even matter? Ice’s buoyancy has important consequences for life on earth. Lakes freeze over on the top in the winter in cold places, which allows fish and other animals to survive below. If the bottom froze, the whole lake could be frozen and almost nothing could survive the winter in the lake. In the northern or southern oceans, if ice sank, the ice caps would all be at the bottom of the ocean, preventing anything from living there. The ocean floor would be full of ice. Additionally, polar ice is important because it reflects light and keeps our planet from getting too warm.

How amber forms — nature’s time capsule

What is amber?

Amber is one of nature’s gems. When a tree is injured, it can create a resin that seals the wound and hardens. Resistant resin that finds its way between layers of sediment fossilizes and becomes hard amber after millions of years. It’s necessary to have exactly the right conditions! Amber is interesting because it can contain creatures and plants from millions of years ago. It has also been used in jewelry for a few thousand years.

Where does amber come from?

You might have thought that amber comes from tree sap. Actually, it is created from resin. The difference is that sap transports nutrients around the tree while resin is semi-solid and acts as a defense response for the plant’s immune system. When the tree has a wound (like a broken branch) or if it is attacked by insects or fungi, it exudes the thick resin that plugs up the injury and prevents further damage. It seals and sterilizes the injury.

Resin dripping from a cherry tree. Image credits: Kreuzschnabel.

When resin is secreted, it’s not certain that it will be turned into amber. More often than not, it gets weathered away. First of all the resin needs to be chemically stable and not degrade over time. It has to be resistant to sun, rain, extreme temperatures, and microorganisms like bacteria and fungi. There are two types of resin produced by plants that can fossilize. Terpenoids are produced by gymnosperms (conifers) and angiosperms. They are composed of ring structures made from isoprene (C5H8) units. Phenolic resins are only produced by Angiosperms. An extinct type of trees called medullosans produced another unique type of resin.

The next factor is that the resin needs to be in the right conditions to fossilize. Young amber could be transported in seawater (it floats), and then buried under sediment to fossilize. In the Baltics, glaciers knocked down many trees and buried them, allowing them to fossilize. Wet clay and sand sediments preserve resin well because they don’t contain much oxygen and the sediments eventually transform into rocks. Intense pressure and temperatures cause the resin to become a solid orange gem. First molecular polymerization forms copal (young amber) and then the heat and pressure drive out terpenes and complete the amber transformation.

Most amber found is about 30-90 million years old, though it’s not sure how long the process to turn resin into amber actually takes. The oldest amber discovered is from the Upper Carboniferous, 320 millions of years ago. Most amber is from pine trees or other conifers, though there are a variety of trees that they can come from. However, most amber is from extinct species because the resin was exuded so long ago.

Perfectly preserved

Amber can be interesting because it can contain pieces of plants, insects, and other creatures. Resin is sticky and liquid, attracting insects because of its sweetness. They get caught in the resin as it hardens and they get preserved. The oldest amber with an organism inside has mites and is from 230 million years ago in north-eastern Italy. Pieces of plants can help identify the source of the amber and insects and other creatures are often perfected preserved which gives information about them. The amber process preserves parts that wouldn’t be preserved through regular fossilization. Amber with remains is also sought after for jewelry because it looks quite nice.

Amber has been used since the stone age (13,000 years) ago in decorations and jewelry. Sold amber can be imitations, the most common are young resins that are not fully formed into amber or stained glass or plastic. A way to know if yours is real is that it should float in saltwater.

An ant inside of Baltic amber. Image credits: Anders L. Damgaard.

Amber can be differently coloured and look in a number of different ways. A light honey colour is typical but amber can range from a white-ish colour to almost black and even blue or red. It depends on the type of tree. Clearer amber is from resin excreted on the bark, cloudier amber comes from the inside of trees.

Amber can be found all around the world. It can be open or underground mined. Most of the world’s extractable amber is found in the Kaliningrad Oblast. Amber has been taken from here since the 12 century. Sometimes amber is washed up from the sea floor and ends up on the beach or collected by diving or dredging. One type of amber called Dominican is a blue colour, and highly prized because it is so rare. It is mined through bell pitting which is dangerous because the tunnels can collapse.

The prized Dominican blue amber. Image credits: Vassil.

Amber is a beautiful stone that takes millions of years to form. Now you can appreciate this fact if you own any amber.

 

The main types of mountains — Earth’s ups and downs

Mountains have always played a central role in human culture, but we’ve only recently come to understand how they form and develop. To this day, these magnificent landforms still hold many secrets. There are several ways to analyze and classify mountains depending on your scientific discipline. Here, we’ll describe some of the more common classifications of mountains in detail.

Aerial view of Mount Everest from the south. The Himalayas are fold mountains. Image credits: airline company Drukair in Bhutan.

The Types of Mountains

Generally, mountains be classified as: fold mountains, block mountains, dome mountains, and volcanic mountains. Plateau mountains, uplifted passive margins, and hotspot mountains are also sometimes considered.

  • Fold mountains — the most common type, they form when two or more tectonic plates collide.
  • Block mountains (or fault-block) — formed through geological processes pushing some rocks up and others down.
  • Dome mountains — formed as a result of hot magma pushing beneath the crust.
  • Volcanic mountains — also known by a simpler name: volcanoes.
  • Other types of mountains sometimes included in classifications are plateau mountains, uplifted passive margins, and hotspot mountains.

Fold mountains

The Rocky Mountains are a great example of fold mountains. Image credits: National Park Service Digital Image Archives.

Fold mountains are the most common and most massive types of mountains (on Earth, at least). Fold mountain chains can spread over thousands of kilometers — we’re talking about the Himalayas, the Alps, the Rockies, the Andes — all the big boys. They’re also relatively young (another reason they’re so tall, as they haven’t been thoroughly eroded), but that’s “young” in geological terms — still tens of millions of years.

In order to understand how fold mountains form and develop, we have to think about plate tectonics. The Earth’s lithosphere is split into rigid plates which move independently of one another. There are seven major tectonic plates and several smaller ones all across the world.

When two plates collide, several things can happen. For instance, if one plate is denser than the other (oceanic plates are typically denser because of the type of rocks that make up the plate), a process called subduction will start: the heavier one will slowly glide beneath the lighter one. If they have relatively similar densities, then they will start to crumple up, driving movement upwards. Essentially, the tectonic plates are pushed, and since neither can slide beneath the other, they build up geological folds. To get a better idea of what this looks like, try to push two pieces of papers towards each other: some parts will rise up, representing the process of mountain formation.

Sometimes, the folding happens inside the continent and is associated with faulting. This is a representation of that process in northern Montana, USA, and Southern Alberta, Canada. Image credits: Greg Beaumont, National Park Service.

This process is called orogeny (giving birth to mountains) and it generally takes millions of years for it to complete. Many of today’s fold mountains are still developing as the tectonic process unfolds. The process doesn’t occur on tectonic edges — sometimes the mountain-generating fold process can take place well inside a tectonic plate.

Block mountains (or fault-block)

While the previous category was all about folds, this one is all about faults: geological faults, that is.

Depiction of the block-faulting process. Image credits: U.S. Geological Survey.

Let’s revisit the previous idea for a moment. Let’s say that while under pressure, some parts of a tectonic plate start to fold. As the pressure grows and grows, at one point the rock will simply break. Faults are those breaks: they’re the planar fractures or discontinuities in volumes of rock. Their size can vary tremendously, from a few centimeters to mountain-sized.

Basically, when big blocks of rock are broken through faulting, some of them can get pushed up or down, thus resulting in block mountains. Higher blocks are called horsts and troughs are called grabensTheir size can also be impressive, though they’re generally not as big as fold mountains because the process which generates them takes place on a smaller scale and involves less pressure. Still, the Sierra Nevada mountains (an example of block mountains), feature a block 650 km long and 80 km wide. Another good example is the Rhine Valley and the Vosges mountain in Europe. Rift valleys can also generate block mountains, as is the case in the Eastern African Rift.

Mount Alice and Temple Crag in the Sierra Nevada. Image credits: Miguel.v

It can be quite difficult to identify a block mountain without knowing its underlying geology but generally, they tend to have a steep side and a slowly sloping side.

Volcanic mountains

Annotated view includes Ushkovsky, Tolbachik, Bezymianny, Zimina, and Udina stratovolcanoes of Kamchatka, Russia. Image taken aboard the ISS in 2013.

Everyone knows something about volcanoes, though we rarely think about them as mountains (and truth be told, they aren’t always mountains).

Volcanic mountains are created when magma deep beneath the surface starts to rise up. At one point, it erupts in the form of lava and then cools down, solidifying and piling on to create a mountain. Mount Fuji in Japan and Mount Rainier are classic examples of volcanic mountains — with Mount Rainier being one of the most dangerous volcanoes in the world. However, it’s not necessary for the volcano to be active to be a volcanic mountain.

The summit of Mauna Kea. Image credits: Pixabay.

Several types of volcanoes can generate mountains, with Stratovolcanoes typically creating the biggest ones. Despite the fact that Mount Everest is the tallest mountain above sea level, Mauna Kea is actually much taller than Everest at a total height over 10,000 meters. However, much of it is submerged, with only 4,205 meters rising above sea level.

Dome mountains

Dome mountains are also the result of magmatic activity, though they are not volcanic in nature.

Southeast face of Fairview Dome in Yosemite National Park. Image credits: Jennie.

Sometimes, a lot of magma can accumulate beneath the ground and start to swell the surface. Occasionaly, this magma won’t reach the surface but will still form a dome. As that magma cools down and solidifies, it is often tougher than other surrounding rocks and will eventually be exposed after millions of years of erosion. The mountain is this dome — a former accumulation of magma which cooled down and was exposed by erosion.

Round Mountain is a relatively recently formed dome mountain. It represents a volcanic feature of the Canadian Northern Cordilleran Volcanic Province that formed in the past 1.6 million years. Black Dome Mountain is another popular example, which is also located in Canada.

Other types of mountains

As we mentioned above, there’s no strict definition of mountain classifications, so other types are sometimes mentioned.

Plateau mountains

Plateau mountains aren’t formed by something going up — they’re formed by something going down. For instance, imagine a plateau that has a river on it. Year after year, that river carves out a part of the plateau, bit by bit. After some time, there might only be a small part of the original plateau left un-eroded, which basically becomes a mountain. This generally takes a very long time even by geological standards, taking up to billions of years. Some geologists group these mountains with dome mountains into a broader category called erosional mountains.

Uplifted passive margins

There’s no geological model to fully explain how uplifted passive margins formed, but we do see them in the world. The Scandinavian Mountains, Eastern Greenland, the Brazilian Highlands or Australia’s Great Dividing Range are such examples, owing their existence to some uplifting mechanism.

Hotspot mountains

The trail of underwater mountains created as the tectonic plate moved across the Hawaii hotspot over millions of years. Image credits: USGS.

Although once thought to be identical to volcanic mountains, new research has shed some light on this belief. Hotspots are volcanic regions thought to be fed by a part of the underlying mantle which is significantly hotter than its surroundings. However, even though that hot area is fixed, the plates move around it — causing it to leave a hotspot trail of mountains.

Animal mitochondrial diagram. Credit: Wikimedia Commons.

What is Mitochondrial DNA and Mitochondrial Inheritance

Mitochondrial DNA: What are mitochondria?

Animal mitochondrial diagram. Credit: Wikimedia Commons.

Animal mitochondrial diagram. Credit: Wikimedia Commons.

Living things are made up of millions of tiny units of life called cells which are composed of extremely small functional parts called organelles. A mitochondrion is a cell organelle that has an extremely important role in the proper functioning of the cell.  Also known as the ‘powerhouse of the cell’, mitochondria are responsible for producing chemical energy called ATP (adenosine triphosphate), which is necessary for all biological processes within the body to occur. Whilst energy production is the most important function of the mitochondria, scientists have placed too much importance on this function and relegated or neglected other important functions.

To be noted that the mitochondria also help in storing calcium, regulating metabolism, controlling cell death, and cell signalling, and carrying out various other functions.

[panel style=”panel-success” title=”Mitochondria DNA facts at a glance” footer=””]

  • Mitochondria have their own genome of about 16,500 bp that exists outside of the cell nucleus. Each contains 13 protein-coding genes, 22 tRNAs, and 2 rRNAs.
  • They are present in large numbers in each cell, so fewer samples are required to construct an evolutionary tree.
  • They have a higher rate of substitution (mutations where one nucleotide is replaced with another) than nuclear DNA making it easier to resolve differences between closely related individuals.
  • They are inherited only from the mother, which allows tracing of a direct genetic line.
  • They don’t recombine. The process of recombination in nuclear DNA (except the Y chromosome) mixes sections of DNA from the mother and the father creating a garbled genetic history.

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What is Mitochondrial Inheritance?

mitochondria inheritance

Credit: Khan Academy

Mitochondrial DNA is a special type of DNA and many people are not even aware this type of DNA actually exists. The human cell has two type of DNA: Nuclear DNA and Mitochondrial DNA. We even have 2 separate genomes – the nuclear DNA genome (which is linear in shape) and the Mitochondrial DNA genome (which is circular). Mitochondrial DNA is pretty basic in that it only contains 37 genes. Compared to nuclear DNA, which contains some 20,000 encoding genes, we can see that MtDNA has limited but important protein-coding functions. 13 of the 37 genes carried on MtDNA are involved in enzyme production.

What is also peculiar to MtDNA is the fact that this DNA is maternally inherited – males and females inherit a copy of MtDNA from their mother. Nuclear DNA, on the other hand, is inherited equally from both parents; a child will inherit 50% of their nuclear DNA from the mother and the other 50% from their father.

A MtDNA copy is passed down entirely unchanged, through the maternal line. Males cannot pass their MtDNA to their offspring although they inherit a copy of it from their mother.

This mode of inheritance is called Matrilineal or Mitochondrial Inheritance. There are a mitochondrial DNA testing services available which can help determine maternal lineage or whether the people tested share the same maternal line. Lineage DNA testing using MtDNA is ideal for testing ancient biogenetic origins and tracing one’s unique lineage. For instance, scientists have used MtDNA to compare the DNA of living humans of diverse origins to build evolutionary trees. MtDNA analyses suggest humans originated in Africa, appeared in one founding population some 170,000 years ago, then migrated to other parts of the world.

Mitochondrial Diseases

The severity of a mitochondrial disease in a child depends on the percentage of abnormal (mutant) mitochondria in the egg cell that formed him or her. Credit: MDA.org

The severity of a mitochondrial disease in a child depends on the percentage of abnormal (mutant) mitochondria in the egg cell that formed him or her. Credit: MDA.org

If there are any abnormalities in the mother’s mitochondria, they will be inherited by her offspring but if the father has abnormal mitochondria, he will not pass on the defect to his children since males do not pass on their MtDNA. Mitochondrial DNA plays such a pivotal role in providing the cell with energy that ineffective MtDNA functioning can lead to the cell malfunctioning or cellular death altogether. The areas that are mainly affected by MtDNA diseases include brain, heart, liver, skeletal muscles, kidney and the endocrine and respiratory systems.

Cause:

Around 15% of mitochondrial diseases are due to a defect in the mitochondrial DNA itself. This defect can arise due to any number of external factors like exposure to harmful radiation, toxins, etc. or due to internal mix up by the cell. The majority of mitochondrial diseases are due to a defect in the nuclear DNA that controls the synthesis of mitochondrial proteins. A small but significant percentage of mitochondrial diseases are not inherited but acquired.

Since mitochondria are present in all types of cells, except red blood cells, a defect in one type of mitochondrial gene may produce an abnormality in the brain whereas, in another individual, it may produce a disease in the kidneys.

Types:

Since mitochondria are so widespread in the body and control incredibly diverse functions, the diseases of the mitochondria are just as diverse.

They most commonly cause neuromuscular diseases called mitochondrial myopathies that have typical symptoms of muscular weakness, loss of tone and restricted movement as well as sensory loss and loss of motor control.

Others include:

  • Leigh Syndrome: It presents with seizures, memory loss, and respiratory failure.
  • Leber’s Hereditary Optic Neuropathy: There is a progressive loss of vision due to nerve damage. It leads to blindness in both eyes.
  • Wolff-Parkinson-White Syndrome: It is a disease of the heart in which conduction defects occur.
  • Diabetes and Deafness- This is a combination of both diabetes mellitus and deafness that occurs due to mitochondrial disease.
  • Other diseases include abnormalities of the muscles in the gastrointestinal tract, limbs, heart, lungs, etc.

Overall, there is muscle weakness, poor growth, and visual and memory loss. Other organ systems may also be involved resulting in heart diseases, lung diseases, kidney diseases, disturbed bowel movements and liver problems, brain damage and hearing loss. Studies have also found links between certain cancers and MtDNA – they have linked the two via by-products known as reactive oxygen species (ROS) produced by MtDNA. Mitochondrial diseases are an intensive and diverse group of inherited or acquired defects that cause mild to severe organ damage and dysfunction resulting in a poor quality of life. They do not have a cure and are progressive, often leading to death.

 

Why eating lots of sugar makes you fat

It’s no secret that binging on sweets and sodas often makes you gain weight. The body uses carbohydrates for energy, but too many simple sugars get broken down into glucose and enter the bloodstream very quickly. This speed is what is responsible for a sugar rush and crash. Sugar alone doesn’t make you full, so you may still eat more and more. After taking what it needs for energy, the body stores extra sugar in fat cells. Eating an excess of sugar for a long time, without exercising to burn it off, can result in a weight gain.

Digestion

The grains that we eat and call carbs are almost pure glucose. They go into the bloodstream slowly because it takes a while for the enzymes in the intestine to break them all down. Glucose then travels through the portal veins. The first stop is the liver. If the liver needs energy, then it will take in glucose. If the liver already has enough energy, then most glucose bypasses the liver and goes to the rest of the body. Other parts of the body take the glucose that they need for energy, such as muscles or organs.

Sugar goes first to the stomach, then the small intestine, liver, and whichever cells need energy. Image credits: Ties van Brussel.

Fructose from juices and soda also goes into the intestine and is delivered straight to the liver. However, an enzyme in the liver is permanently turned on so it always takes fructose even if it already has enough energy. Only a tiny fraction of fructose gets delivered to the rest of the body. When too much fructose or glucose builds up in the liver, it gets stored as fat. When there is more liver fat, more fat is released into the bloodstream. This, in turn, results in higher levels of triglycerides and cholesterol, which could cause heart disease. When someone eats a lot of sugar for a long time, without burning it off, the fat accumulates and make them fat.

Insulin: the sugar police

The liver works with the pancreas to regulate blood sugar and fat cells. Pancreas beta cells keep track of the amount of glucose in the bloodstream and release the hormone insulin to control the amount. Insulin is like police that keeps the amount of glucose in the bloodstream at a good level. Let’s say you eat a whole carton of ice-cream. After going through digestion, the sugar enters the bloodstream. When the pancreas senses that there’s a lot of sugar, it secretes insulin, which causes sugar to go to cells, such as liver and muscle, so they can use it as energy. If you consume more sugar than you need, it is stored for when you need a boost. Either way, it’s taken out of the bloodstream if there’s too much. When the body needs energy, like between meals and during the night, low insulin lets sugar be released into the blood.

People with diabetes need to constantly monitor their blood sugar. Image credits: stevepb.

When there is too much liver fat, insulin can’t work very well, which can cause diabetes. The body doesn’t produce enough or any insulin and blood sugar can reach levels that are dangerous for the body. Diabetes sufferers need to constantly measure their blood sugar and take insulin externally if it is too high.

Best carbs

Carbohydrates are the main source of energy for our body. However, not all carbs are equal— a soda is not digested in the same way as pasta or bread. The best sugars come from fresh produce or from complex carbs, like pasta. They provide sustained energy while sugary treats don’t fill you up. When you eat food that contains simple sugars like those found in soda, the digestive system breaks them down and releases them into the bloodstream very quickly. They are empty calories; they only give energy, but nothing else nutritional. Energy from soda or candy spikes very quickly, but the sugar from a piece of fruit lasts longer because it also contains fiber which slows down digestion. Additionally, fructose, found in sweeteners, sauces, salad dressing, among others, doesn’t suppress hunger. Your body doesn’t know when you’ve had enough so it keeps getting turned into fat. Indeed, in a study, people that ate fructose gained lots of stomach fat.

Products that you wouldn’t expect, like salad dressing, contains lots of fructose. Image credits: Mike Mozart.

The recommended amount of sugar for an adult is 25 g a day. However, the average person eats more than twice as much. It’s not completely your fault, it does feel good to eat sugar. When you eat sugar, the brain releases dopamine and serotonin which boost the mood. Unfortunately, eating too much sugar comes with a slew of heart problems, including obesity, heart disease, and diabetes. There is too much of a good thing.

 

 

5 romantic animals that mate for life

Who doesn’t want a lifelong love? Having one partner for a whole lifetime may be a human ideal, but some animals are also faithful to their partners. Okay, it’s probably not because of love, but for survival. Having a lifetime partner helps a female protect herself and her young better. Paternal care is more common in these animals, meaning that their offspring usually have a better chance of survival. Other possible reasons are that it’s hard to find a mate, there are net benefits, or for territory defense. For whatever reason, these animals prefer to spend their lives together with a single partner, similar to humans. Here are some animals that are secret romantics and mate for life:

Common loon

After they mate, loon (Gavia immer) pairs stay very close to each other, usually less than 20 m (65 feet) apart. They each keep an eye on each other and make sure that their partner doesn’t stray before the eggs are laid. If they do become separated, both the male and the female make an effort to be close to each other again. In most other animals, it’s either the male or the female that is clingy, not both. As a team, the loons are better at capturing fish and taking care of their young. They only lay a few eggs, which require extensive parental care. It’s also easier to defend their territory against intruders, who may try to displace the male and take over the female and territory.

Other notable birds: macaws, albatross, barn owls

Shrimp

Venus’ flower-baskets are beautiful hollow glass sponges. However, the focus here isn’t on the sponge, but on what lives inside of it. Shrimp in the genus Spongicola use the inside of the sponge as their home. The sponge cavity is so tiny that there is only enough room for two shrimp inside. Because of this, these shrimp mate for life. They are stuck in these sponges for their whole lives. The pair passes their time cleaning the sponge and eating food that drifts through the sponge pores. After they breed, their tiny offspring disperse out through the sponge pores, but they will eventually find the same fate: a tiny home with a single mate. In Japan, it was a common wedding present to give one of these sponges with two dead shrimp inside, as a symbol of lifelong unity. Romantic or creepy?

One pair lives in each of these single sponge “towers”. Image credits: NOAA

Other notable invertebrates: termites, mosquitos

Skinks

Multiple species of skinks, Australian lizards, take only one mate. Shingleback skinks (Tiliqua rugosus) live alone most of the year but find their same partner every mating season. They have a two-month long “courtship” period before they mate, in which they get to know each other and engage in lots of licking and touching. They form loyal pairs for up to 20 years; their average lifespan is 15 years. Gidgee skinks (Egernia stokesii) live in small family groups (up to 17 lizards) that last for at least 5 years. Breeding partners stay together and mate together year after year.

 

Shingleback skinks are romantics at heart. Image credits: Dcoetzee

Other notable reptiles: Australian sleepy lizards, von Höhnel’s chameleon

Prairie voles

These voles (Microtus ochrogaster) are unusual from most other rodents in that they find a partner, groom each other, build a nest, and raise their young together. The rodents live for just a year or two and can better look for food and have more offspring together. Higher levels of certain neurotransmitters keep them bonded and promotes aggression towards any non-mate. Instead of being attracted to foreign voles, they are programmed to be aggressive. Prairie voles also mourn the death of their partners. These voles are used as models to help understand mating and monogamy in humans.

Prairie vole pairs mate and raise their young together. Image credits: theNerdPatrol

Other notable mammals: gray wolves, beavers, gibbons

Largemouth bass

Unusually for fish that fertilize their eggs externally, largemouth bass (Micropterus salmoides) are loyal to their partner. After a courtship ritual, the successful male can fertilize the eggs that the female lays. Males and female both build a nest, usually on a log or rock. When the eggs are laid, they both care for them. They often remain with their hatchlings up to a month after they hatch, which is an extremely long time for fish. This is the first evidence an animal that fertilizes eggs externally is faithful to their partner.

The largemouth bass is a secret romantic. Image credits: Trisha M Shears

Other notable fish: seahorses, French angel fish, angler fish

Maybe it’s animal nature, but from a human perspective, these animals are quite the romantics!