Tag: natural selection

Posted in Science & Nature

Red Queen’s Hypothesis

Posted on by Jinavie

In Lewis Carroll’s Through the Looking-Glass, there is a scene where the Red Queen says to Alice: “It takes all the running you can do, to keep in the same place”. Essentially, it means to spend all the effort you can just to keep the status quo. In life, there are so many times when it seems like you’re frantically running just to realise that no progress has been made. Interestingly, the same rule is seen in biology and evolution.

The simple rule of natural selection is that the best adapted species wins. Unfortunately, this means that no matter how well you are doing in the environment, as soon as another species becomes better adapted to a new change, you become the lesser species and eventually destroyed. To prevent this, a species must continuously evolve and adapt just to stay in the same position. Nature despises stagnancy and loves progress. For example, a predator always strives to evolve to better catch the prey while the prey evolves to avoid the predator. This cat-and-mouse arms race allows for continuous evolution and ever-improving fitness. This is the Red Queen’s Hypothesis.

A fascinating extension of the hypothesis is that it may be a cause for having sex. Sex is one of the most intuitive inventions of Mother Nature that allows for massive genetic variation. The Red Queen Hypothesis has been used to suggest that this may have evolved to speed up the process of evolution so that hosts could beat parasites in the ongoing arms race. The greatest act of love may simply be a mechanism for us to stay competent in this ever-changing world.

Posted in Science & Nature

Grandmother Hypothesis

Posted on by Jinavie

There are many physiological events that puzzle scientists. Menopause is one of these as it is very uncommon in other mammals. Why do human females stop having periods after aging? From an evolutionary point of view, an organism that has lost reproductive function cannot aid evolution and thus it is a mystery how a trait like menopause survived natural selection. The leading theory in how such a phenomenon happened is the grandmother hypothesis.

According to this hypothesis, as humans are social animals menopause can still be an evolutionary advantage despite not being able to produce offspring. This is because older women can invest the massive amount of energy and time required to upkeep childbearing in other places. For example, they can help their family and society grow by working or taking care of children instead. Furthermore, as the probability of miscarriages and congenital defects rise with aging (generally after a woman hits the age of 30, the chances of a healthy pregnancy decreases), menopause has the function of protecting the gene pool of the species. These facts combined lead to the conclusion that after an individual has reached a certain age, taking care of their children or grandchildren instead of birthing more offspring is more effective in propagating their own genes. Also, there is no one that can propagate massive amounts of wisdom and information to the next generation like the elderly.

In modern society, menopause has more significance than at any point in the history of human beings. As our average life span has surpassed 80 and heading towards 90, almost half of a woman’s life is post-menopause. In some ways, the grandmother hypothesis contains within it a certain philosophy regarding life. As we age, we give birth to children and raise them until they become independent, at which point we escape our basic biological duty of reproducing to lead our “own” lives. Senescence is like a second spring after one’s “biological” life. It is the start to a new life – a more “human” life of your own where you can focus on seeking pure happiness.

Posted in Psychology & Medicine

Superbug

Posted on by Jinavie

Frequently on the media, the word “superbug” is used as if it were the new Black Death or the coming apocalypse. What is a superbug and why is it so feared?
Superbug is the colloquial nickname for drug-resistant bacteria. For example, one of the most famous superbugs is MRSA (methicillin-resistant Staphylococcus aureus). This strain S. aureus, a common bacteria found on skin and inside the nose, is resistant to a powerful antibiotic called methicillin and thus very hard to treat. Unfortunately, MRSA is most commonly contracted in hospital settings as patients are vulnerable to infections (e.g. after surgery) and hospitals are perfect breeding grounds for superbugs.

The cause of a “normal” bacteria turning into a superbug is due to the incorrect use of antibiotics. When antibiotics are used, they wipe out a significant portion of the bacterial population but fail to kill all of them in the first attack. The surviving bacteria are the more adapted ones that are able to withstand the harsh environment for a little longer. If the patient stops taking the antibiotics and the bacteria remains, these “drug-resistant” bacteria multiply to create a second infection that is resistant to the drug that was used previously. In fact, this is a classic example of natural selection in motion, except that the environmental change is man-made.
This is the reason why doctors are reluctant to prescribe antibiotics for diseases such as the common cold or viral diseases, as the risk of developing superbugs is greater than the benefit (which is zero in viral diseases as they do nothing) of the treatment. It is also why a course of antibiotics must be finished even if the patient is feeling well, so that even the surviving bacteria are eventually killed.

To show the potential risk of superbugs, the case of VRSA can be taken into consideration. When MRSA was first discovered, doctors found it very difficult to treat but luckily they had a secret weapon – vancomycin, one of the most powerful antibiotics known to mankind. However, they soon found that S. aureus and natural selection easily overcame this through a new strain called VRSA – vancomycin-resistant S. aureus. Here was a bacteria that could overcome the greatest weapon man had against bacteria, all because people were taking more antibiotics than needed and not taking the full course prescribed.

Thus, one of the growing problems of modern medicine is the development of new drugs so that we can make a comeback in the arms race against bacteria.

Posted in Science & Nature

Fainting Goat

Posted on by Jinavie

There is a very interesting breed of goats called the Fainting Goat. These goats suffer a genetic condition called myotonia congenita, which produces fascinating yet hilarious situations. When startled by the sudden presence of another animal or even a loud noise, these goats all suddenly freeze and fall to one side. This phenomenon can occur even while running, which causes the goats to crash into the ground, lying on their backs with their legs straight up. This can even occur from the excitement of seeing food and starting to run towards it.

The reason for this peculiar phenomenon is that myotonia congenita damages systems that allow muscles to relax, causing it to become easily excited. Ergo, when a goat is startled, its muscles tense reflexively, causing it to contract suddenly while taking longer to relax. This results in the goat becoming paralysed and falling. Young goats tend to be helpless when this occurs, but more experienced goats prop their legs apart quickly or lean against something to prevent falling (they can even be seen hopping on their stiff legs). These “fainting spells” are painless.

Although this kind of trait is often removed by natural selection (for example, in nature these goats would freeze when they meet a predator, and then proceed to be eaten), humans have bred these goats specifically to save their trait. In old times, these goats were used as “sacrifices” so that they would get eaten first when wolves struck, but nowadays they are bred in certain farms for no particular use. 
Myotonia congenita also affects other animals such as cats, and there are many people in the world affected by this condition too.

Posted in Science & Nature

Fibonacci Number

Posted on by Jinavie

1 1 2 3 5 8 13 21 34 55…

A keen observer would note that each number in the above sequence is the sum of the two numbers before it. These are known as Fibonacci numbers and are among the most famous number sequences in mathematics.

It is famous because of some unique properties. For example, every third number is even, every xth number is the multiple of Fx (e.g. 4th number = 3, 8th number = 21…) and the list goes on. It is also known to approximate golden spirals, a mathematical function that is closely related with yet another famous number: the golden ratio.

However, a more interesting (and more relatable) fact about these numbers is that they appear repeatedly in nature. It has been noted for many centuries that plants tend to follow the Fibonacci sequence in various ways. This includes the number of branches of trees that grow per year, the number of petals on a flower (almost all flowers have a Fibonacci number of petals) and most interesting of all: the arrangement of florets on the face of a sunflower. If one carefully scrutinises the face of a sunflower (also applies to pine cones), they will note that the florets (tiny pieces on the face) are arranged in what appears to be spirals. They are actually arranged on a stack of spirals, both clockwise and anti-clockwise. The number of spirals for both directions are always two Fibonacci numbers next to each other (e.g. 34 and 55).

This is because natural selection pushes the plants to arrange their florets, petals and tree branches in the most efficient manner possible, which is provided by the Fibonacci sequence.

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Posted in Science & Nature

Peppered Moth

Posted on by Jinavie

The peppered moth are a species of night-flying moth that have been studied extensively for over 200 years by biologists. They are known to be prime examples of the power of natural selection.

In England, there are two variants of this moth: one that has a peppery white appearance and another that is much darker, almost black. Originally, the white variant was much more common, as they could easily camouflage themselves on trees covered in light-coloured lichen. 

However, during the Industrial Revolution, the heavy pollution killed the sensitive lichen causing trees to expose their dark bark. This caused the white moth to be extremely visible, making them easy prey for birds and other predators. The change in environment resulted in black moths, that used to be disadvantaged, to have a better chance of survival, causing the black moth population to become superior. 

As people became more aware of air pollution and England began cleaning up its environment, lichen returned to the tree and the table turned once more – the dark moths were now better targets and were heavily preyed on. Instead, the white moth retook the majority position, thus showing how the environment affects which traits survive in a population.