Tag Archives: Living beings

Why is sore throat a symptom of many common sicknesses?

Your body is a castle. Germs are invaders. Your castle has thick walls but needs gates so you can see out of it, take in supplies and get rid of rubbish.

Gates are weak spots so get attacked more often. The throat is the most open to attack as it is moist, warm and we are constantly moving air (containing viruses/bacteria), food which we have touched with our dirty hands etc. across it.

The throat releases chemicals to make it swell up to deliver more blood (and therefore more infection fighting cells, nutrients etc.) to the site of attack. Swelling causes pain, presumably to make us go easy on parts of the body which are under attack.

Why do tablets sometimes feel like they are stuck in our throat after swallowing?

They’re kind of stuck. They’ll keep moving down your throat but that feeling means that the pill hit the walls of your esophagus when they were too dry so it’s harder for the esophagus to move the pill down.

Think of it like trying to go down a water slide. If the slide is wet you don’t get stuck and go very fast. If the slide is dry your skin creates friction and you go slow or get stuck. You need that lubrication of the water to go down fast.

If it’s a common issue for you try taking pills with a bigger sip of water. Let the pill float in your mouth for a second in the water then swallow.

How do chicken eggs not crack inside their body?

Eggs can crack inside the hen, but it’s not common because eggs are actually pretty strong when forces are applied evenly over the entire shell.

If you wrap your whole hand around an egg trying to make as much surface contact as possible, it’s actually pretty difficult to break the egg by squeezing it. If you pinch the egg between two fingertips, it’s much easier because the force is concentrated on a smaller area of the shell.

Imagine pushing an egg on to the point of a sharpened pencil. It would pierce through pretty easily, right? Now imagine pushing an egg onto a soft ball of clay. It takes much more pressure to break it. So you can imagine if the insides of a hen are pushing on the egg evenly from all directions, it gets even more difficult.

Why are humans more energy-efficient in running than animals with four legs?

The really simple answer is that humans run more efficiently because we let gravity do a lot more of the work. When we go forward we’re basically putting one foot out and falling forward, then pulling ourselves forward and repeating the process with the other foot.

When quadrapedal animals run, they need to propel themselves forward with their front and back legs; the advantages of this are that they can put more of their total muscle mass into running and you get more sources of speed, and run faster/quicker; pretty much any quadraped can out-sprint a human. But humans are the undisputed champions of distance-running on Earth, partly because their run is more energy efficient.

The other thing that helps us run, just as a sidenote, is the fact that our bodies are really good at not overheating. A cheetah for instance can only keep up their vaunted 60 mph run-speed for a very short distance without overheating and exhausting themselves. But our ability to have the airflow of our forward motion wick heat away by evaporating sweat off of us is one of nature’s best heat regulation mechanisms, and allows for humans to run for hours on end without stopping, when properly trained.

How did sexual reproduction first develop in animals?

It is difficult to definitively say how it first came about, but there are some key factors that can be used to determine.

First, the main difference between sexual and asexual reproduction is that sexual reproduction “reorganizes” the parent DNA into a new pattern, while asexual is essentially the parent self-cloning. By being able to reorganize DNA, sexual reproduction had an advantage over asexual reproduction because it caused more mutations to occur in the DNA. This leads to a higher chance that a mutation will be beneficial to the organism, especially because the baby organism gets two sets of DNA to choose from, doubling its genetic resources. It also means that if one parent has a successful mutation that the other parent does not have, the baby organism will have a better chance at acquiring that mutation.

Second, we know that with two (or more) sexes, one sex must be more involved in the reproduction than the other. In most species, this is the female organism, which is able to do the reproductive work of bearing young. The male organism can merely contribute DNA, but does not actually bear young. With 50% of the population unable to make the babies, conditions must be good enough to allow the other 50% to reproduce often enough and quickly enough to maintain the whole species’ population. This means temperature, food sources, and safety from predators or environmental threats needed to be ideal.

We can break down the evolution of sexes a bit more; there is a term “anisogamy” which means reproduction with sperm and egg. This first evolved in tiny cells that contained only one set of chromosomes. Chromosomes are chains of DNA. When the cells would reproduce, the egg would provide one chromosome, and the sperm would provide a different chromosome. For a brief period, the baby cell would contain both chromosomes, and after a short period of development one of the chromosomes would “win” and that chromosome would become the DNA pattern that the new cell would eventually pass onto its own young.

This “anisogamy” developed when two compatible cells evolved, that were slightly different but able to mate with one another. In the first tiny cells that accomplished this, they were too similar to really be called “male” or “female,” but the difference was enough to spark the eventual evolution of male and female.

So, to recap:

Single cells would split in half to reproduce. Then, cells evolved a few changes, and this resulted in different types of cells that contained different sets of DNA. While some of these evolved cells eventually split off into entirely new species from the original cells, some others retained a special compatibility that allowed them to share their DNA, and they could mate with each other. Exactly how they started the ability to share the DNA (i.e. physically have sex, since they did not have vaginas or penises at that point) to make offspring is difficult to know for certain, but it may be similar to how some species of bacteria can “conjugate” or stick together to create new DNA combinations. A bit like the thing absorbing nearby cells and acquiring their DNA. So, the two new types of parent cells were able to provide not one, but two sets of DNA for their offspring to choose from. The offspring would typically end up with the most successful (dominant) DNA. This gave the offspring a better chance at surviving and reproducing, and this adaptation was so successful that it developed into fully fledged male and female versions of a single species.

Does the human body really have a 24 hour body clock?

Kinda, yes. We have a circadian clock, a biological mechanism that works by releasing certain hormones over a 24 hour period, as well as taking external cues such as the Sun. Without external cues, the circadian clock can actually run a bit longer or shorter than 24 hours, and in babies it’s still all messed up (which is why they have an irregular sleep schedule).

Not just humans have a circadian clock, almost every animal does.

This has nothing to do with leap years though, since leap years just add a whole day, not messing with our circadian clock.

Why do calories matter for losing weight but the weight of the food doesn’t?

Actually the weight of the food does matter, but not in the way that you think.

Food is composed of a bunch of different types of chemicals. Most has a fair bit of water in it which we urinate or sweat out after a while. Then there are proteins (building blocks that the body uses to grow or repair itself), carbohydrates (sugars and starches that the body burns to provide energy), fats (same) and fibre (which is the part that the body can’t digest and passes through).

Really only three of those ingredient types – carbohydrates, fats and proteins – are stored by the body for future emergency use and contribute to weight gain. They all become body fat or muscle, and they all contribute to the calorie count of food.

But food that weighs a lot but has really low amounts of those three types, like say celery, has almost all of its weight locked into water and fibre. It actually takes energy to go through the process of digesting food, so a celery stick or two actually helps with weight loss by both filling you up so you don’t eat as much other stuff, and consuming energy to process through your body.

Why do our bodies ache (joints, muscles, etc.) when we are sick?

One of the main reasons that our body aches when we are sick, like with a cold, is that the body’s immune system is producing plenty of antibodies in addition to the effects of all those viruses replicating in our cells killing them and leaving the area ‘raw’ and exposed.

These antibodies also promote the release of histamine which typically dilates (widens) blood vessels near an infection, this allows for more of the body’s defenses to get at the infection. There are histamine receptors in blood vessels that cause them to dilate.

As these chemicals are released into the blood stream they can end up in the muscles or other body parts. Various body systems can have receptors to histamine that can then trigger a pain receptor.

In addition to histamine there are biochemicals called cytokines that are released when the body has an immune response that are also known to trigger a  biochemical pathway that can affect pain receptors.

Histamine and cytokines releases can change the perception of pain receptors in the body making them more sensitive to pain factors.

There are other factors that come into play also such as biochemicals called interleukins that relate to fever conditions and temperature increases, all of which can affect pain receptors in different ways, for example heat receptors.

The overall perception of pains and aches over the whole body can vary from person to person and there may be other combinations of psychological,  physiological or even nutritional factors that may influence this.

How does hibernation work for animals? Does a hibernating animal stay in the same position for entirety of the winter?

There are many forms of hibernation, so not every animal that hibernates does so in the exact same way.

Some animals like bats, for example, sleep deeply and don’t wake up during hibernation; others such as marmots get up from time to time. Also they don’t sleep all the time, but wake up and then sleep again – they don’t stay in the same position, they might turn around and move arms and legs to be comfortable.

What they all have in common is that the hibernation initiates a very passive and reduced state. During the months or weeks of hibernation, the animals don’t eat, so their metabolism is reduced, their body temperature lowered, as is their heart and breathing rate. This is what makes hibernation different from normal sleep. It affects the whole body.

To wake up they need a lot of energy as the body fires up the “engines” again. If a hibernating animal is disturbed during hibernation and has to wake up often, it might die (it will starve during a hibernation phase as it does not have enough energy reserves to survive). The waking up process is also driven by hormones and can occur during hibernation if the animal gets disturbed or has to flee/move.

What are the different blood types, and why can’t we mix them?

Blood types are determined by the presence, or absence, of certain markers on the surface of red blood cells, called antigens. An antigen is a molecule that is of sufficient size and complexity that the body can recognize it as “not self” and mount an immune response to destroy it as a potential invader. There are actually many antigens that can define various blood types but the most important come in two groups; 1) A, B, O, and 2) Rh.

Let’s look at ABO first. A and B are antigens that humans may or may not carry on their red blood cells, but the important thing about A and B is that they are also abundant in our environment, in microorganisms, pollen, and in animal dander. We are constantly exposed to the antigens and as a result, we develop antibodies that will attack and destroy red blood cells that are unlike our own.

We get one gene from each of our parents to determine our ABO type. The gene for A codes for the A antigen, the gene for B codes for the B antigen, there really is no gene for O, it’s more of a blood banker’s placeholder, it doesn’t code for anything at all. If you inherit two A genes you’ll be type A, but you’ll still type as A if you only get one gene for A and one for O.

Whichever way you get there, if you are type A you will carry in your bloodstream antibodies that will fiercely attack red blood cells displaying the B antigen. It goes the same way for people of type B. One copy of the B gene will make you type B if your other one is also a B or if your other is for O. Either way you’ll carry antibodies that will attack any cells showing the A antigen. Of course, you could get genes for both A and B and your type comes out AB and you don’t make antibodies against either antigen. People who are type O make both Anti-A and Anti-B antibodies.

Once they got the ABO grouping sorted out transfusions got a lot safer but still, people occasionally died in obvious transfusion reactions. Something else was going on. For the safety of the humans involved the search for the mystery antigen causing these reactions was done in Rhesus monkeys. People to whom the Rhesus monkey’s blood reacted to were dubbed Rhesus Positive, which got shortened to Rh+. People to whom the monkeys did not react are of course Rh-. Modern blood bankers refer to the Rh antigen as D.

The D antigen is uniquely human, it is not abundant in our environment, the only way for a person to become sensitized to, and develop antibodies to attack the D antigen is to actually be exposed to Rh+ red cells when they themselves are Rh-. The most common way for this to occur is not via transfusions it often occurs in childbirth. When a Rh- woman gives birth to a Rh+ child there is a risk the fetal red blood cells that make get into her bloodstream will be recognized as “not self” and an immune response will soon destroy all of the Rh+ cells, and any such cells her body may encounter in the future.

An ABO mismatch transfusion can be quickly fatal. An Rh- Rh+ mismatch is an entirely different matter. Of course, a Rh- woman of childbearing age should never be given Rh+ cells for the sake of the safety of future pregnancies, but in a life threatening emergency situation there is no reason a man of Rh- blood type couldn’t safely be transfused with Rh+ cells in sufficient quantity to reverse a trend towards death. This would be a once in a lifetime deal. Over several weeks all of the recipient’s transfused Rh+ cells would be destroyed for being “not self” and an enduring immune response would remain.