Tag: biology

Posted in Science & Nature

Shrew

Posted on by Jinavie

A shrew is a small rodent, similar in size to a rat, that has many fascinating characteristics.

Funnily enough, this animal has a notorious name in history. Ancient Egyptians considered shrews the spirits of darkness and the English believed that if a shrew ran over a lying animal, the animal would suffer great pain. The name shrew comes from the Middle Age English word shrewe, which meant “evil” or “scolding person”.
This is probably attributable to the putrid smell a shrew makes when threatened, and its poisonous bite.

Despite its tiny figure, the shrew has the greatest surface-area-to-weight ratio out of any mammal on the face of the Earth. Because of this, they also have a high heat expenditure, meaning they have to eat constantly to replenish the energy. This means that they sometimes die from starvation during prolonged naps.
Also, they have an extremely high heart rate, averaging about 700 beats per minute. When they are frightened, the heart rate can spike leading to cardiac arrest. For example, shrews are known to die from being frightened by the sound of thunder.

An animal that dies if it naps too much or when thunder strikes – the shrew is a very sad animal.

Posted in Science & Nature

From Cell To Birth: Growth

Posted on by Jinavie

After implantation, the embryo quickly grows from a ball of cells into what will be a fully-formed baby. However, it first needs a way to feed: the placenta.
It is an organ that actively takes nutrients and oxygen from the mother’s blood, exchanging it for the embryo’s waste products. It is extremely effective in keeping the fetus alive and protects it from infections or the mother’s immune system.
The blood is carried by the umbilical cord, which plugs into the belly button. This cord is the lifeline throughout term, and disrupting the blood supply will lead to permanent brain damage or even death.

In the first 10 weeks, the blastocyst develops into a very primitive disk-like object that shares no resemblance to a person. It keeps growing and differentiating at a rapid rate (almost doubling in size per week) until it forms an embryo that is more familiar, roughly about week 6. Interestingly, a human embryo looks almost identical to embryos of rabbits, chickens, turtles and fish, showing how all animals shared a common ancestor in the course of evolution. At this stage, the embryo has features such as gills, a tail and a fish-like appearance.

After 10 weeks, the embryo has grown to about 5~8cm (almost 10~20 times the size at week 6), and is now called a fetus. It begins to properly grow organs, and resembles a miniature baby with primitive features.
It continues to grow for the next 30 weeks, continuously relying on the mother for nutrition and life support.

Many different factors contribute to premature birth and IUGR (intrauterine growth restriction), which leads to the birth of a small baby. This may result in less developed organs (especially the lungs) and may affect the health of the newborn throughout its life. There are also many poisons known to harm the development of the embryo/fetus, such as alcohol, nicotine, cocaine, heroin and much more. These should be avoided from a few weeks before conception onwards (even after birth while breastfeeding).

By about 38 weeks, the lungs (the last organs to fully mature) are ready and the fetus is upside down. It is ready to leave the womb, and thus sends a signal to the mother, known as labour. This is when the arduous process of childbirth begins.

(Full series here: https://jineralknowledge.com/tag/arkrepro/?order=asc)

Posted in Psychology & Medicine

Fear

Posted on by Jinavie

The ten things people are most afraid of are as following (according to a study of 1000 people in France in 1990):

  1. Snakes
  2. Nauseatingly high places
  3. Spiders
  4. Rats
  5. Bees
  6. Enclosed spaces
  7. Fire
  8. Blood
  9. Darkness
  10. Crowds/audience

Ants do not feel fear. The reason is simple. An ant does not know the meaning of death or its own frailty. It may worry about the survival of its city and the entire society, but even then they do not fear their own death.

To understand why they are never afraid, one must first consider that an anthill acts as a single organism. Each ant acts like a cell in the human body.
When we clip our nails, are our fingertips afraid? When we shave, is the hair scared as the razor approaches it? When you dip your feet in the bath to check the temperature, does the toe shudder in fear? Because they do not act as an autonomous unit, they do not feel fear.

Similarly, when we pinch our right hand with the left hand, the right hand does not feel contempt towards the left hand. If the left hand has more rings, the right hand does not envy it. If you forget self and think of the community like an organism, all your worries disappear. Perhaps this is how ants run such a successful, efficient society.

(from The Encyclopaedia of Relative and Absolute Knowledge by Bernard Werber)

Posted in Psychology & Medicine

Madness

Posted on by Jinavie

“As mad as a hatter” – this is a well-known English idiom, particularly famous after Lewis Carroll created the Mad Hatter character in his work Alice in Wonderland. However, what is less known is the fact that this idiom is based on actual events.

In the 18th and 19th centuries, hatters used mercury to treat felt (traditionally made from rabbit fur or the more luxurious beaver fur). Unfortunately, mercury is a highly toxic heavy metal, which causes severe damage in the human body. In the case of mercury poisoning (also known as Minamata disease or the Mad Hatter disease), it infiltrates neurons to cause severe neurological symptoms. For example, it can impair vision and hearing, cause paresthesia (pins and needles), anxiety, depression, tremors and hallucinations. The famous physicist, Isaac Newton, also suffered from Mad Hatter disease.

Another mad character from Alice in Wonderland is the March Hare. As one may deduce from his name, he is modelled after a normal hare. The reason why the March Hare is mad is that March is around the time when rabbits enter their mating season, and male hares are in heat. They then have only one thing in mind: sex. 

Maybe, as the Cheshire Cat explains, “we’re all mad down here”.

image

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

Cricket

Posted on by Jinavie

The sound of crickets in the autumn night is quite inspiring. Only male crickets can make this clear and beautiful sound, by rubbing their serrated wings against each other.

There are four kinds of cricket chirps: an attracting song (for females), a courting song (when a female is near), an aggressive song (when a male is near) and a copulatory song (after a successful mating). Each song is played at a different volume and pitch.

As all insects are cold-blooded, they are heavily affected by temperature. In the case of crickets, this is reflected in the frequency of chirps, which increases proportionately to the temperature. Using this, one can calculate the air temperature from the number of chirps a Snowy Tree cricket makes (count the number of chirps in 14 seconds plus 40 to get the temperature in Fahrenheit).

Finally, cricket chirps cannot be heard via cellphones. This is because a cricket chirp is usually around 6500Hz frequency, while most cellphones operate at a maximum of 3300Hz.

Posted in Science & Nature

Matador

Posted on by Jinavie

The word “Spain” often brings upon an image of a handsome matador taunting a fierce bull with his red cape. Because of this, it is commonly thought that the colour red aggravates bulls, and this is often used in cartoons.

However, as bulls are colour blind, they cannot tell a red cape apart from a blue cape. They are actually responding to the movement of the cape and being provoked by the matador. Furthermore, the bulls used in bullfights tend to be a more aggressive breed. This type of charging behaviour is common in large herbivores such as hippos, rhinos and elephants, as it is very useful in nature when faced with a predator.

Also, the real reason the cape is red is not only because it symbolises passion and power, but because it also hides the blood from the bull during the fight.

Posted in Science & Nature

Locust

Posted on by Jinavie

Locusts are a well-known symbol of destruction. The path of a locust swarm is bound to be left bare with nothing in sight. The most amazing feature of this insect is its reproductive abilities, which can be considered explosive. Furthermore, increased tactile stimulation of a locust’s hindleg causes it to release a neurotransmitter called serotonin, which causes mutual attraction, change of colour and increased consumption of food, thus priming them for reproduction. This allows them to reproduce even faster as the population grows, letting it easily reach numbers of billions in a short time. A large population then causes the locusts to swarm and migrate, and some species can cover distances of up to 500km. These swarms have been known to cover over 1000 square kilometres of land, and any food source in its path is instantly eaten up and used as fuel for reproduction. Because of this, locusts have become an icon of horror and destruction since ancient times as it can destroy crop fields within a matter of hours. This symbol is employed by the bible also, for example as the eighth plague of Egypt.

In some ways, a locust swarm can be seen as natural selection at its best. Explosive reproduction and voracious appetite is the basics of survival, skills that allow a species to beat the fierce competition of “the survival of the fittest”. Although humans curse locusts for destroying crop, they are not the only species that breed thoughtlessly and consume all resources in their path.

Posted in Science & Nature

Parthenogenesis

Posted on by Jinavie

It is often believed that for complex organisms such as animals, sexual reproduction is a must to produce offspring. Asexual reproduction is common in bacteria and (some) plants, but even tiny beings such as insects use sexual reproduction to produce a mass of variable offspring. 

However, it has been found that despite having two clear sexes – male and female – there are cases where a certain species is able to reproduce without the need of sexual intercourse. In these cases, the female’s eggs spontaneously divides to form a new offspring without being fertilised by a sperm. Furthermore, sometimes the egg either fuses with another egg or undergo several genetic mixing and mutation to produce some variety in genetic pool, thus avoiding the issue of asexual reproduction (where the entire population can be wiped out by a single disease due to identical genetic makeup). This is known as parthenogenesis, and it has been documented in many insects, fish, reptiles and even birds. 

Obviously, as there is no donation of a Y chromosome, every offspring born from parthenogenesis is female. Because of this, some species such as the New Mexico whiptail, a lizard that is capable of both sexual reproduction and parthenogenesis, the population has completely rid itself of males, making it a completely female species. Curiously, they still engage in “mock sex”, giving them the nickname “lesbian lizards”.

Although parthenogenesis has never been documented in mammals in nature, it has been induced artificially in mice, rabbits and monkeys. However, they all developed severe developmental issues due to the numerous mutations in the egg required for parthenogenesis. 
But if in the future, human parthenogenesis is perfected, it is possible that humanity too could end up as an all-female society.

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.