Category Archives: Biology

How Did Humans Become Earth’s Dominant Species?

The story of human evolution is the story of our species acquiring dominance. This episode goes back over three million years to examine clues in the human genome that explain how humans evolved from being tree-dwelling apes to becoming the world’s most dominant primate.

Humans earth's dominant species
How did humans become the dominant species on Earth?

Recommended post – Why does CO2 have such a large impact on global warming?

We explore how genetics has underpinned human evolution, from our rise from primates on the African plains to our spread across the globe. This article asks how genetics can be even more influential in shaping future evolution. The amazing story of the human race is told through location film and state-of-the-art computer visualization.

Video: By what means did the human species become Earth’s dominant species?

Recommended post – Can fashion influence human evolution?

The video is absolutely amazing. It offers a lot more information that is really interesting to me. I wonder why my grade school teachers weren’t able to teach this way.

The key to humanity’s global dominance is energy

We humans use energy for much more than just powering our metabolism, unlike nearly every other creature on Earth.

Thousands of years ago, humanity discovered fire, which led to our exceptional relationship with energy.

We used fire for much more than just keeping warm, warding off predators, and enhancing our hunting ability.

Recommended post – Are humans getting more intelligent?

When did humans become the dominant species?

The Pleistocene epoch is thought to be the time when humans began changing the global environment. This contributed to the mass extinction of megafauna, including giant kangaroos and mammoths on almost every continent. However, some date it to the advent of agriculture some 7,000 years ago.

Recommended posts:

Volcanic Lightning and the Origin of Life

The recent volcanic eruption on the island of La Palma has put the phenomenon of volcanism in all its facets in the spotlight. Apart from getting acquainted with lava flows, and ash ejections, it was possible to observe impressive electrical discharges in the ash cloud above the volcano.

These volcanic Lightning is a very strange and relatively common phenomenon in eruptions. Moreover, the presence of volcanic Lightning can have a significant impact on the environment near the volcano where they occur.


Video: Epic volcanic lightning recorded in Chile during eruption


Volcanic lightning and the origin of life

A very important aspect of this phenomenon is its possible involvement in the origin of life. Billions of years ago, volcanic activity on Earth was much greater than it is today. It is therefore certain that volcanic lightning was a very frequent and almost continuous phenomenon. Laboratory experiments and computer models have attempted to simulate these conditions.

And indeed, volcanic electrical discharges have been found to be the source of some of the molecules necessary to explain how life began. This makes the study of the production and consequences of volcanic lightning an area of ​​great scientific interest.

How is volcanic lightning produced?

Lightning on volcanoes is produced by a variety of mechanisms, some of which are similar to those that occur in thunderclouds.

In the cloud, ice crystals and water droplets move at high speed and are at the mercy of strong winds. Friction and collisions between crystals and droplets result in electrical charges. When the accumulated charge reaches a certain value, lightning is generated.

Two basic mechanisms of electrical charge production have been proposed in volcanic eruptions. It is important to note that these mechanisms are not mutually exclusive and are probably acting simultaneously in eruptions.

Triboelectric effect

Triboelectricity is the electricity generated by rubbing and scraping materials. It is the origin of the electricity that draws scraps of paper onto a comb after we rub them against our clothes. Or the clicking sounds we hear when we take off a garment in a dry environment. And it is also the mechanism that charges thunderclouds with electricity, as described above.

During the expulsion of gases and ash through the volcanic cone, strong currents are produced that cause a turbulence and a very intense friction of the expelled ash grains and lava.

This friction gives rise to the electric charge that, once it reaches a certain value, causes the electric discharge that we observe as lightning.

Scientists have been able to reproduce this phenomenon on a small scale. They expelled gases and ash at high pressure through a tube. As the gases exited the mouth of the tube, electric sparks – lightning – a few centimeters long were produced.

Fractoelectric charging

The second mechanism, Fractoelectric charging, results from the violent fracturing of the volcanic material as it emerges from the crater. These fractures and the pulverization also generate significant electrical charges. Again, when the amount of charge reaches a critical value, lightning strikes.

Both mechanisms, occur simultaneously. The contribution of each to the initiation of lightning depends on many factors, e.g., the:

  • Composition of the lava
  • The gases
  • The ejection velocity

Clouds above the volcano

Sometimes the water vapor present, emitted from the volcano itself or present in the nearby atmosphere, creates large clouds above the volcanic cone. Processes can occur in these clouds that are almost identical to a thunder cloud. Therefore, lightning may also occur.

Volcanic lightning, like thunderstorm lightning, poses a potential hazard to people and animals in the vicinity of the eruption. Regardless of the mechanism that produces them, volcanic lightning is known to occur 20 and 30 km from the volcano. Therefore, precautions must be taken in the vicinity of an eruption.

Since the eruption itself is a major hazard, people usually leave the vicinity of the crater quickly, so lightning strikes are very rare.

Lightning disturbs the volcanic environment

In recent years, scientists have been able to identify some of the consequences of volcanic lightning. For example, ash floating on the volcano can be struck by lightning. Because of the very high temperatures that can be reached during these discharges (more than 20,000 ℃), the ashes melt. When it solidify again, it take the form of microscopic spheres.

These volcanic glass spheres can affect health if inhaled. They can also change the chemical properties of the particles themselves and the soil when they fall out of the air.

In addition, lightning is a major source of gases that are harmful to health. They produce nitrogen oxides (NOx) and ozone. NOx are the main pollutants in large cities. Ozone is a desirable gas for protection from ultraviolet light as long as it is at high altitudes, in the stratosphere. Its presence near the surface is not desirable and can also cause respiratory problems.

Related post: The Most Active Volcanoes on Earth

How Does the Eyes See Things – Short Answer

The human eye processes a great deal of information about everything around you, sending all these signals to the brain, which in turn allows you to see:

  • Shapes
  • Colors
  • Textures
  • Movements


VISION: light bouncing off objects and entering the eye.
How exactly does the human eye work and how do our eyes see?

Learn more about the human eye, how light passes through the lens and sends signals, via the optic nerve, to the brain.

  1. Light is reflected off objects and travels in a straight line to the eye.
  2. The light passes through the cornea, into the pupil, and through the lens.
  3. The cornea and lens adjust to the light (refract) so that the retina refocuses.
  4. Photoreceptors in the retina convert light into electrical impulses.
  5. The electrical impulses travel through the optic nerve to the brain.
  6. The brain processes the signals to create an image.


Function of the human eye.
Function of the human eye

Your eyes have a crucial function in almost everything you do. Here are some of the main functions of the human eye:


The eyes are housed in orbits in the skull to be protected from injury. The eyelashes and eyelids keep dust and dirt from entering. For the same reason, the eyebrows have an arched shape to deflect sweat away from the eyes.


Tears – a salty fluid that contains protein, water, mucus, and oil – are released from the lacrimal gland that is located in the upper, outer region of the human eye. Reflex tears protect the eye from irritating elements such as smoke, dust, and wind. Emotional tears, on the other hand, are a response to sadness or joy – there is a theory that “a good cry” can help the body rid itself of toxins and other waste substances.

Each time you blink, a salty secretion (the basal tears) from the lacrimal gland passes over the entire surface of the eye, keeping the eyeballs hydrated and clean. The muscles of the upper eyelid are responsible for controlling the opening and closing movement that occurs in the human eye.


There are six extraocular muscles that control the movement of the human eye. Of these, four stand out, which move the eyeball up, down, left, and right; while the other two adjust the eyes to compensate for head movement.


The eyes receive light and convert it into electrical impulses that are in turn sent to the brain, which processes these signals to form the images we see.


Illustration of a A detailed depiction of eye. How does the eye work.
How does the eye work – eye structure.

To understand how your eyes work, it is worth knowing the parts and components of their structure.


Below we show the different parts that make up the human eye and a brief explanation of how they allow you to see the world around you.

1. Optic nerve

This is the nerve located at the back of the eye that sends signals from the retina to the brain.

2. Conjunctiva

This is a thin membrane that protects the eye by helping to keep it moist. It lines the inside of the eyelid and the surface of the eyeball.

3. Aqueous humor

This is a transparent liquid found in the space between the iris and the cornea. This ocular component maintains ocular pressure and gives the front of the eye its rounded shape.

4. Vitreous humor

A gelatinous substance that fills the inside of the eye, giving shape and volume.

5. Retina

The inner part of the eyeball contains millions of photoreceptors (sensors that convert light into electrical impulses). These signals are then sent by the optic nerve to the brain, where they are processed to create an image.

6. Pupil

The black hole in the middle of the eye that allows light to pass through.

7. Iris

The colored part of the eye that controls the amount of light passing through the pupil.

8. Crystalline lens

A transparent disk located behind the iris.

9. Sclera

The “white” part of the eye that protects the eyeball and gives it its firm, regular shape.

The 10 Branches of Biology: Their Goals and Characteristics

The science that deals with living things is constantly evolving and specializing.

Like any self-respecting science, biology spreads its efforts across various disciplines to cover as much knowledge as possible. This is necessary because there is more and more information.

The various branches of biology make it possible to narrow down and focus knowledge in order to investigate and push forward the discovery of new information that reveals the secrets hidden in living things.

The branches of biology (and the subject of study in each)

Biology is divided into a variety of disciplines created to better serve different objects and goals of study, and new ones continue to be added as knowledge advances. Moreover, some of them are related to and partially overlap with other major sciences, such as chemistry or geology, with which they complement each other.

Even taking into account that the boundaries between these fields of research are to some extent blurred, several branches of biology can be distinguished, of which we will mention the most important ones here.

1. Cell Biology

The cell is the original unit of living things, since all living things are made of cells. It is therefore not surprising that one of the branches of biology deals with the study of cells. Formerly called cytology, the field specializes, as the name implies, in knowledge of the structures and functions of cells. This includes not only the processes by which they are kept alive, but also how they contribute to the functioning of the organism in which they reside when they are part of multicellular life forms.

2. Developmental Biology

One of the most impressive phenomena of life is how the union of two gametes can give rise to an entire multicellular organism. I am referring to fertilization by a sperm and an egg (in the case of animals) to form a zygote. This branch of biology is concerned with the study of all cellular processes involved in the development of a new organism through sexual reproduction.

3. Marine Biology

Earth is also known as the blue planet, and indeed nearly 71% of its surface is covered by water. Life in the oceans is no small matter, as evidenced by the fact that there is an entire branch of biology devoted to the study of the sea, from the creatures that inhabit it to their interaction with the environment. The aquatic environment is probably the origin of all life forms, and therefore there is a great diversity of living beings, some of which are completely different from those on land.

4. Molecular biology

While I talked earlier about cell biology, which specializes in the study of the structures and functions of cells, molecular biology focuses on the tools that cells use to carry out these functions. This field studies proteins and the processes they carry out, such as the synthesis of these components or processes related to metabolism. It is a hybrid between biology and chemistry.

5. Botany

Living organisms are the most important object of study in biology, but there is a huge variety of living organisms, so it is necessary to diversify.

Botany is mainly concerned with the study of plants, such as:

  • vegetation
  • shrubs
  • and trees

but also with life forms that are not plants but share characteristics with them, such as:

  • algae
  • fungi
  • and cyanobacteria

What they all have in common is limited mobility and the ability to photosynthesize (except for fungi).

6. Ecology

The environment is a very important element of life and an increasingly relevant topic. Ecology is the branch of biology that deals with the close interactions between living things and their environment or habitat, which form so-called ecosystems.

7. Physiology

While cell biology deals with the functions of cells, physiology is the field that deals with the processes that take place in organs, i.e., the functions performed by a collection of cells. For example, the circulation of internal fluids or the mechanisms of respiration. Physiology applies to both animals and plants.

8. Genetics

The cell is the unit of life, but without DNA it would be nothing. The genetic material contains all the information necessary for the development of an organism. DNA allows cells to form proteins.

For this reason, there is a whole discipline devoted to the study of genetic content, namely genetics. The study of the genome has always been of special interest to biology, and today it is also important for the development of new technologies and technological tools such as gene editing, artificial selection, etc.

9. Microbiology

While botany deals mainly with plants, microbiology focuses on the study of microorganisms, very small single-celled living organisms that can only be seen under a microscope.

Organisms studied include:

  • bacteria
  • archaea (formerly called archaebacteria)
  • protozoa (single-celled eukaryotic organisms)
  • and the enigmatic viruses

10. Zoology

The last branch of biology to be discussed here is also one of the oldest in terms of prehistory: zoology, which deals with the study of animals. From sponges to mammals, a wide range of living things falls within its field of study. In addition, several of its subcategories deal with the study of their behavior and overlap to some extent with psychology and cognitive science.

Examples for Natural Selection

The process of natural selection refers to one of the mechanisms of the evolution of the species of living beings proposed by Charles Darwin and Alfred Russel Wallace, from which they explained the design of nature. For example: the white fur of arctic animals that allows them to hide in the snow.

Natural selection occurs through the progressive adaptation of species to their environment. When individuals with certain traits have a higher survival rate than other members of a population, they pass on these heritable genetic traits to their offspring.

Evolution, Genes and Natural Selection

Natural selection is the central basis of all evolutionary change, being also the process through which better adapted organisms displace less adapted ones by the slow and progressive accumulation of genetic changes.

Any contribution of an individual to the next generation is recognized as biological efficiency. The biological contribution is a quantitative trait that encompasses many others, related to survival of the fittest and differential reproduction of different genotypes.

The fundamental thesis of natural selection is that traits are heritable, but nevertheless there is variability in the trait among different individuals. Thus, there is a biological adaptation to the environment, and only certain characteristics of the new features are extended to the whole population.

Each generation is in permanent evolution, and it is precisely the set of variations that occur throughout the generations that constitutes the evolutionary process.

Examples of How Natural Selection Lead to Evolution

  1. The evolution of medicine is based on the fact that the use of antibiotics for bacteria kills some of them, but those that survive become more resistant.
  2. The white fur of arctic animals, which allows them to hide in the snow.
  3. Camouflage of grasshoppers makes them look like leaves.
  4. Giraffes, of which the ones with the longest necks survived.
  5. The color change of a chameleon to protect itself.
  6. The cloning process, constantly under development but already proven in fact, could potentially interfere with natural selection.
  7. Brown beetles have a better chance of survival, and more offspring become frequent in the population.
  8. This is the case for all the species that have been disappearing, and are still disappearing.
  9. Cheetahs, of which the fastest survived.
  10. The evolution of the human being in different species, called hominids.
  11. The deformation of the snake’s jaw to swallow larger prey.
  12. The change of coloration of some moths, motivated by the industrial revolution in England. (The change in the environment was man-made).
  13. The waggle dance of bees.
  14. The insecticide resistance of some insects, evidencing the question of selection as a source of survival.
  15. The shape of the beak of finches changed over time, as they hardened after droughts, allowing them to eat harder seeds.
  16. The ability of humans to learn to speak.
  17. Orchids that are able to trick wasps into ‘mating’ with them.
  18. Non-venomous king snakes, which mimic venomous coral snakes.
  19. The courtship rituals of birds.

Where Do the Pollen Grains of Flowering Plants Develop?

The place of production of the pollen grain differs according to the plant:

  • In gymnosperms (seed-producing plants), the pollen grain is produced in strobiles.
  • While in angiosperms (flowering plants), the pollen grain is produced in flowers, specifically in the anther (the part of the stamen where pollen is produced).

The anther is a kind of tissue-covered pouch that forms spores. The oosphere (unfertilized egg), in turn, is produced in the ovary of the plant.

As plants reproduce, the pollen grain finds the archegonium, the place where the oosphere is produced and located.

The antherozoids (structure or organ producing and containing male gametes) are then released into the pollen tube. Then the pollen tube which moves toward the oosphere in the archegonium.

VIDEO: The Journey of the Pollen Tube

The pollen grain:

  • A pollen grain is the microspore of the plant, That is, the spore that contains the male gametophyte.
  • The pollen grain is produced in the anther of the flower, which is the the terminal part of a stamen of a flower.
  • When germinating, the pollen grain produces the pollen tube. This tube ensures the transport of male gametes to the oosphere.
  • When the pollination is done by the wind, it is called anemophilous pollination. In this case, the Odoriferous gland is absent.
About the author:

Daniel Vol has been writing about science and the environment since 2006.

Can We Breathe in an Environment of Pure Oxygen

What happens if you breathe pure oxygen: take a look at Divers Alert Network guidelines. Scuba equipment works by forcing compressed air into the lungs at the same pressure as the pressure of the surrounding water. The deeper you dive, the more air you use. For every 33 feet / 10 meters that you descend, the pressure of the water increases in one atmosphere.

There is something called oxygen toxicity. As its partial pressure increases, oxygen becomes increasingly toxic. For example, under normal atmospheric conditions, you are breathing about 0.2 atm of oxygen (21% oxygen at 1 atm). Once you go to a single atmosphere partial pressure, you will still be able to live, but you will have a limited time. Safe limits for recreational dives are 1.4 bar O2 or normal air at a pressure of 7 atmospheres. Even then, you’re starting to get into the nerve zone. 1.6 is considered just silly.

As compensation, deep divers will breathe gas mixtures with lower O2 levels. A 10% O2 mix will allow you to go much deeper. But you will also pass out if you try to breathe it within 30 feet. Because 30 feet is 1 atm of water pressure plus 1 atm of air pressure = 2 atm. 10% O2 x 2 atm = 0.2 atm of oxygen, or just what you breathe normally in the atmosphere.

You probably can survive about 24 hours in 100% oxygen at atmospheric pressure. To live longer, you have to reduce the pressure.

What the Body Does With the Nitrogen We Inhale?

Yes, most of the air is made up of nitrogen (78%). But we don’t need it, we need oxygen, so what does our body do with it?

Well, just as we inhale it, we exhale it since the body does not require it so it does not process it.

From the capillaries, the pulmonary alveoli also receive the main waste product of cellular respiration, carbon dioxide. Through expiration (expulsion of air from the lungs) this gaseous compound is released outside our body. At this stage, the gaseous composition of the air that entered through the airways changes.

Exhaled air contains the same percentage of nitrogen (78%), but the levels of carbon dioxide (4%) and water vapor (2%) increase. Logically, the amount of oxygen expelled decreases. This helps us to reduce the concentration of oxygen and also prevents us from breathing pure oxygen, since pure oxygen could harm us.

Could We Live in an Atmosphere With Oxygen but Without Nitrogen?

So, if our bodies do not absorb nitrogen, we could do without it, right? Unless the lungs evolve in such a way that they can absorb all the oxygen without collapsing, no.

The nitrogen that we inhale serves to keep the pressure in the lungs stable. That is, it prevents them from shrinking. Without nitrogen the lungs will collapse. Why? 

In an atmosphere of pure oxygen, oxygen is rapidly absorbed and the sacks where the simple diffusion of oxygen and carbon dioxide occurs – shrink. This happens because the external pressure is greater than the internal one. There would be nothing left inside the alveoli except a little carbon dioxide.

Which Is the Longest-Living Organism on the Planet

This question came to mind after I read a 2013 news story about Ming. It is a clam from Iceland that was estimated to be 507 years old, which earned it the title of the longest-living animal on the planet.

The clam was named after the dynasty that ruled China in 1499, the year in which its birth was calculated by carbon-14 dating and counting the layers of the interior of its shell. Because, similar to trees that form rings each year by growing, the Bivalvia deposit a new layer on their shell. Unfortunately, Ming passed away during transport to the laboratory where it was to be studied.

For comparison, the oldest human being was a French woman named Jeanne Calment, who lived just over 122 years. This lady’s age falls short of the life span of Jonathan, a tortoise who lived between 187 and 188 years. In turn, the oldest mammal, a bowhead whale, surpassed that record, by living up to 211 years. Moreover, according to researchers at Australia’s national science agency, genome sequence revealed that bowhead whales’ maximum lifespan can be up to 268 years!

But the Ming clam is a baby compared to the oldest known individual tree. The oldest known living specimen is an unnamed tree, which location is kept secret, but it is somewhere in the White Mountains of California. The tree was sampled in the 1950s but its age, 5,067 years, was not determined until laboratory work was completed in 2012. Before that, the oldest known tree was the “Methuselah” tree, 4,789 years old. Its age was verified by crossdating. Meaning it was seeded when we humans were inventing cuneiform writing. The three oldest trees in the world belong to this same species and, to protect the two that are still alive, both their photos and their exact location remain secret.

The longevity of clonal plants

To be honest, I thought that this question cannot be developed any further. But the information that I have been gathering while trying to answer it has revealed to me a planet earth I didn’t know existed. It is actually full of centuries-old or even millennial organisms, which use different survival techniques to reach extreme ages.

It turns out that, for some organisms, the 5,000 years of the long-lived pine are not a big deal. Although they exceed this number by playing a little dirty: they clone themselves.

These clonal trees live in colonies made up of genetically identical individuals descended from the same ancestor who have never reproduced sexually. An example of this case is Pando, a colony of populus Quaking aspens composed of 47,000 individuals that share the same root system.

Originally this forest began from a single tree. A genetically identical stem emerged from its roots and, in turn, it took roots from which more identical copies emerged. In other words, the organism itself is a gigantic root from which 47,000 copies of the same tree grow, each with a life expectancy of between 40 and 150 years.

The root system does not care if one of its stems dries out, or even that a fire burns half of them, since it always has clones that will continue to absorb the sunlight necessary to allow its survival. No one can deny that this survival method works. This tree (actually, this root system, but for all practical purposes it’s the same) has lived this way for 80,000 years.

But the life-span limit of clonal organisms does not stop there.

It turns out that a group of Australian researchers took DNA samples from 40 meadows of a seagrass species that is endemic to the Mediterranean Sea (Posidonia oceanica) along 3,200 kilometers. During the investigation, they found genetically identical algae separated by distances of up to 15 kilometers, which is why they concluded that there are entire posidonia meadows made up of endless copies of the same organism that, like the Pando tree, clones itself to spread its roots. The researchers speculate that some of these clone colonies could be between 80,000 and 200,000 years old, although this is a theoretical limit because some areas where it is found could be above sea level between 10,000 and 80,000 years ago.

These algae can expand to form large patches up to 16 kilometers long and weigh 6,000 tons together. By occupying such extensive areas, they guarantee their continuity if one of the areas they occupy runs out of resources. There are more species of clonic plants, but so far none have been recorded to be older than Posidonia oceanica. That does not mean that there are no organisms that live longer.

How about ancient bacteria?

Taking samples from the Siberian permafrost, a team of planetary biologists looked for organisms that live in the most hostile conditions on our planet to get an idea of where they could find living beings on other worlds. And they found something unusual: living Siberian actinobacteria that are between 400,000 and 600,000 years old. These actinobacteria would be, this time, the oldest living beings on the planet.

Well that’s it, right? The list ends here.

Not exactly. If we talk about ancient organisms, we could include bacteria that were revived after 25 to 40 million years spent inside the abdomen of bees preserved in amber. After being revived, the bacteria grew and their DNA was analyzed, finding their kinship with a current bacterium.

Although it was announced in 2001 that bacteria trapped in salt crystals had been revived after 250 million years, the results of this research are not considered entirely reliable.

Are there immortal animals?

But human intervention is not necessary to bring organisms that have been trapped in time back to life, as some can naturally remain dormant for long periods and wake up when conditions are better. Small animals called tardigrades, better known as water bears, can remain in a suspended state for hundreds or thousands of years. Dormant or not, the 600,000 years of actinobacteria are still a short period of time compared to immortality.

Yes, yes, in theory there are animals that have the potential to live forever. Here things start to get weird.

The clams of which I spoke at the beginning belong to the select club of organisms that present negligible senescence, which means that they do not develop apparent signs of aging as time passes and both their reproductive capacities and their physical form remain constant throughout their entire life. What is even weirder, their mortality rates do not increase with age. In other words, the youngest individuals of these species die with the same frequency as the oldest.

Theoretically, these animals could live indefinitely until they fell prey to a predator or died of an injury or infected by a virus.

One group of animals that possesses this superpower is lobsters, which are believed to frequently reach over 100 years of age (apparently, it’s hard to measure the age of a lobster). George’s impressive age, a 140-year-old lobster with an impressive weight of almost 10 kilos of weight, served as an excuse for not being cooked.

Other animals with negligible senescence include some species of turtle, a few fish, plants and bacteria, as well as worms. The clonal organisms that we discussed earlier also fall into this group, because they also have the potential to continue living until an external factor kills them.

Well, hold on to your pants because there is still the most extreme case to talk about: that of the famous immortal jellyfish. The jellyfish Turritopsis dohrnii begins its life as a polyp. It is a phase in the life cycle of some jellyfish which alternates with a medusoid phase.

Once they have reached maturity and have reproduced, these jellyfish are able to reverse their growth and return to the polyp phase through cell transdifferentiation, a process that allows cells to become other cells. 

The head of the jellyfish turns around, its tentacles are sucked in, and it anchors itself to some substrate to grow and become a productive adult again. The jellyfish can repeat this process indefinitely, making it biologically immortal. A pity that, at 4.5 millimeters in diameter, it is an easy prey for predators.

What Determines the Color of a Hens’ Eggs?

You may have noticed that chicken eggs shells come in different colors. Some people believe that brown-colored eggs are more nutritious than white-shelled eggs. Is this true?

Are brown eggs better than white eggs?

The eggshell is rich in calcium carbonate and acts as a chamber for the development of the embryo. Although many people believe that their color is related to the animal’s diet, this is not quite true.

The pigments that color the shells, hemoglobin or bilirubin, are present on the walls of the oviduct. The color of the shell, which can be white, brown, red, green and even blue, is related to the breed of the hen. Mediterranean chickens, like the Leghorn chicken lay white eggs. American and Asian chickens, like the New Hampshire chicken, lay eggs in shades of brown. A study published in 2020 indicates that the color of the egg shell is genetically determined.

Many people say that the color of the feathers determined the color of a hen’s egg shells. However, sometimes there are white animals with dark colored eggs and vice versa. It is worth noting that some breeds of chicken are able to lay eggs with different shell colors. In fact, the hen’s diet has little to do with the color of eggs it lays.

Some people claim that by looking at the chickens’ ear, it is possible to determine ​​its eggshell color. Chickens with a white disc lay white eggs, and those with a reddish ear disc lay red-shelled eggs. However, this rule is not always valid.

Are Dark Shell Eggs Healthier Than White?

It is important to note that, regardless of the color of the shell, eggs have basically the same nutritional value. Therefore, there is no difference in the acquisition of one or other egg color, only with regard to price.

Unlike the color of the shell, the color of the yolk is directly related to the hen’s food. Chickens that eat more corn, for example, have eggs with a reddish yolk. This is due to depositions of carotenoids (reddish-colored pigments) from the food eaten.

It is for this reason that the egg yolks of free-range chickens are more orange than those of chickens raised indoors. Free-range chickens are normally fed with foods that contain more nutrients, and pigments which color their yolks in dark orange.


Is the Skin a Tissue or an Organ?

When we study the levels of organization of the human body, we learn that cells group together to perform the same function. These groups of cells are tissues. These tissues, in turn, group to form a structure responsible for a specific function in a given system. An organ is a structure formed by several tissues. Given these definitions, a question arises: is the skin a tissue or an organ?

The skin, despite its appearance, is an organ, not a tissue. It consists of two main layers, the epidermis and the dermis, which, in turn, are formed by different tissues. Therefore, the skin is an organ because it is formed by more than one tissue.

It is worth mentioning that the skin has a very impressive characteristic: it is the most extensive organ in our body. Studies reveal that 15% of all our body weight comes from the skin. In adults, this organ can weigh up to 10 kilograms.

The skin has multiple functions, being of vital importance for our survival. Among the main functions attributed to it, we can mention the protection of our organism and perception of stimuli. As well as elimination of some products of our metabolism and the control of temperature by releasing the sweat produced by the sweat glands.


The Tissues That Form the Skin

The skin consists of two layers, the outermost layer called the epidermis and the innermost layer called the dermis. In the epidermis, we find epithelial tissue, which is formed mainly by cells called keratinocytes. The types of cells in this layer are responsible for the production of melanin. It is a pigment that is responsible for the color of the skin and protects the organism from harmful sun rays.

Just below the epidermis, we find the dermis, which is formed by a connective tissue. This layer is responsible for ensuring the elasticity of the skin. In addition, this layer contains growths of nerves, blood vessels, hair follicles and glands.

Below the dermis is the hypodermis. This tissue is not part of the skin. It ensures that the dermis is attached to underlying bone and muscle. The hypodermis is formed by a loose type of connective tissue.