Factual Sciences

The factual or factual sciences are those that deal with the factual (de factum, the Latin word for “facts”) or tangible verification of their hypotheses and premises, based on observation and experimentation, that is, the reproduction of a series of conditions to obtain a predictable result.

For this reason, they depend on empirical content that must be confirmed through experience: such verifiability is key to distinguishing them from other sciences.

They are distinguished from the formal or pure sciences (such as logic and mathematics) in that they pay more attention to procedures (forms) than to contents (facts). Furthermore, the factual sciences use the scientific method for their investigations, while the formal sciences use the logical inductive method.

In turn, the factual sciences are divided into natural sciences (those that deal with the relationships existing in the universe and that do not include the intervention of man) and social sciences (devoted to the study of the relationships that govern the world of beings humans).


See also: Examples of Natural Sciences in everyday life

Examples of factual sciences

  1. Biology, in charge of the study of life in its various variants and possibilities, which encompasses all kinds of living beings, from bacteria and forms of protozoa to higher animals, including humans.
  2. Physics, in charge of studying the laws of operation of nature, in its various variables and possibilities, from applied physics to astrophysics.
  3. Chemistry, whose object of study is the constitution and transformation of matter in its various levels and reactions.
  4. Psychology, in charge of studying the internal working mechanisms of the human mind: its constitutive and evolutionary processes, its possible structures, etc.
  5. Social Psychology, which studies the way in which the human psyche structures its forms of collectivity and relations of influence and emotional, symbolic, and affective reciprocity.
  6. Sociology, interested in the study of human groups and collectives, or of human society as a whole: its processes of formation and its internal struggles, always within the historical-social context in which they are inserted.
  7. Economics, science devoted to the understanding of the processes of wealth generation, production, distribution, and consumption of goods in human society, whether in the framework of the forms of trade of a country or a certain region or as a whole, in which case it is called an economic theory.
  8. The Political Sciences, also called Politology or Political Theory, make political work and its various aspects and formations the subject of its main interest. That includes the systems of government, the forms and social behaviors around power, and the various possible regimes of human organization.
  9. Sexology, whose specific focus is the anatomical (biological) and cultural study of the sexual behaviors and practices of human beings.
  10. Geology, devoted to the study of the composition and internal structure of the Earth, as well as the evolutionary processes that have constituted it throughout geological time. It comprises a compendium of geosciences that undertake the revision of plate tectonics, as well as planetary geology of astrogeology.
  11. Law, also called Laws or Legal Sciences, includes the study of the constitution of the normative and institutional order of the apparatus of human jurisprudence, that is, of the legislative constructions that allow solving human conflicts in a fair, consensual and equitable manner. I also study the historical composition of the different legal regimes, as well as the underlying philosophy and the relationships between them.
  12. History, a discipline whose object of study is the past of the human species and whose method is characteristic of the so-called social sciences. There is a discussion regarding whether History is a Social Science or a Humanistic Science, but the most current trends prefer to include it in the first set of disciplines.
  13. Anthropology, understood as the science that studies the human being from an integral perspective, using for it a combination of tools and knowledge of the various natural and social sciences, trying to cover both the biological evolution of our species, as well as its ways of life and the various cultural and linguistic expressions that characterize it in its complexity.
  14. Human Geography in charge of the study of human societies from a spatial perspective, that is, emphasizing the relationship between societies and their physical means of development. Thus, various cultural landscapes and human regions are established, which contribute to the spatial diagnosis of our presence on the planet.
  15. Paleontology a natural science whose study regime includes the interpretation of the different fossil records, based on methods and foundations closely shared with biology and geology, sister disciplines.


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Biotic and Abiotic Factors

The  Biotic factorsDifference between biotic and abiotic factors are the living components of ecosystems: living things. The term can be used to speak of individuals as each organism that inhabits the system, globally as the total population that inhabits the same area or place, or as a community with a group that has a characteristic or that establishes a relationship.

The biotic factors, by their own definition, are those that have life and then movement, therefore they must acquire energy (carry out a feeding process).

In this way, it can be said that biotic factors are responsible for having an active behavior in the ecosystem, generating relationships through the need for survival (this could be discussed in the case of the human being, who expanded his needs beyond survival itself).

It is common for biotic components of an ecosystem to be divided between organisms that produce their own food (usually vegetables), consumers of already produced food (animals), and decomposers of dead animals (some fungi and bacteria ).


  • See also: Examples of Living and Non-Living Beings

Examples of biotic factors

HenMycobacterium Tuberculosis
Pine treesNoctiluca
Bacillus mycoidesFirs
Daisy flowerProstate
Human beingBacillus licheniformis
OstrichApple trees
DuckBacillus megaterium
RattlesnakeTreponema Pallidum
Escherichia ColliPenguin
CypressesReishi mushroom

They can serve you:

  • Examples of Flora and Fauna
  • Examples of Domestic and Wild Animals

Abiotic factors

The abiotic factors have to do precisely with everything that is outside the biotics, that is, everything that gives the ecosystem the characteristics that allow it to generate the life of the species that are related to it. Indispensably these will be elements that lack life, and therefore will not be responsible for changes within the ecosystem.

The action of living beings can have different effects on the abiotic factors of the ecosystem, even transforming it: however, since it is these factors that allow life, it is possible that a transformation produced by one species restricts the survival of another.

Around the preservation of certain abiotic factors, it is frequent that new relationships are established within the ecosystem. When the modification occurs, or when new organisms enter an already configured system, they may have to go through a process of adaptation to the new conditions.

Examples of abiotic factors

Visible lightMeasurement of acidity or alkalinity of soils
AirGeographical accidents
TinMaterial of which the soil is made
Geographical spaceMatch
CalciumInfrared light
SalinityContents and characteristics of the Earth’s atmosphere
Ultraviolet lightWater availability
SulfurAvailability of essential nutrients
FluorineDay length
PotassiumAtmospheric pressure


Abiotic Factors

An ecosystem is a system made up of various groups of organisms and the physical environment in which they relate to each other and to the environment. In an ecosystem we find.

  • Biotic factors: They are organisms, that is, living beings. They range from bacteria to the largest animals and plants. They can be heterotrophs (they take their food from other living things) or autotrophs (they generate their food from inorganic substances). They are related to each other by relationships of predation, competition, parasitism, commensalism, cooperation, or mutualism.
  • Abiotic factors: They are all those that constitute the physical-chemical characteristics of an ecosystem. These factors are in constant relation to biotic factors since they allow their survival and growth. For example water, air, light.

Abiotic factors may be beneficial for some species and not for others. For example, an acidic pH (abiotic factor) is not favorable for the survival and reproduction of bacteria (biotic factor) but it is favorable for fungi (biotic factor).

Biotic factors establish the conditions in which organisms can live in a certain ecosystem. For this reason, some organisms develop adaptations to these conditions, that is, evolutionarily, living beings can be modified by biotic factors.

On the other hand, biotic factors also modify abiotic factors. For example, the presence of certain organisms (biotic factors) in the soil can change the acidity (abiotic factor) of the soil.

See also:  Difference between biotic and abiotic factors

Examples of abiotic factors

  • Water: The availability of water is one of the main factors that affect the presence of organisms in an ecosystem since it is essential for the survival of all life forms. In places where there is no constant availability of water, organisms have developed adaptations that allow them to spend more time without contact with water. In addition, the presence of water affects the temperature and humidity of the air.
  • Infrared light: It is a type of light invisible to the human eye.
  • Ultraviolet radiation: It is electromagnetic radiation. It is not visible. The earth’s surface is protected from most of these rays by the atmosphere. However, UV-A rays (wavelength between 380 to 315 nm) reach the surface. These rays do little damage to the tissues of various organisms. By contrast, UV-B rays cause sunburn and skin cancer.
  • Atmosphere: From what has been said about ultraviolet radiation, it can be understood that the atmosphere and its characteristics affect the development of organisms.
  • Temperature: Heat is used by plants during photosynthesis. In addition, for all organisms there is a maximum and minimum environmental temperature at which they can survive. This is why global temperature changes result in the extinction of various species. The microorganisms called extremophiles can tolerate extreme temperatures.
  • AirAir content affects the development and health of organisms. For example, if there is carbon monoxide in the air, it is harmful to all organisms, including humans. Wind also affects plant growth, for example trees that live in areas that have frequent winds in the same direction grow crooked.
  • Visible light: It is essential for the life of plants since it intervenes in the photosynthesis process. Animals are allowed to look around for various activities such as foraging or protecting themselves.
  • Calcium: It is an element that is found in the earth’s crust but also in seawater. It is an important element for biotic factors: it allows the normal development of leaves, roots, and fruits in plants, and in animals it is essential for bone strength, among other functions.
  • Copper: It is one of the few metals that can be found in nature in its pure state. It is absorbed in the form of a cation. In plants, it participates in the photosynthesis process. In animals, it is found in red blood cells, participates in the maintenance of blood vessels, nerves, the immune system, and bones.
  • Nitrogen: Forms 78% of the air. Legumes absorb it directly from the air. Bacteria convert it to nitrate. Nitrate is used by various organisms to make proteins.
  • Oxygen: It is the most abundant chemical element in mass in the biosphere, that is, the sea, air, and soil. It is an abiotic factor but it is released by abiotic factors: plants and algae, thanks to the photosynthesis process. Aerobic organisms are those that need oxygen to convert nutrients into energy. Human beings, for example, are aerobic organisms.
  • Altitude: Geographically, the altitude of a place is measured taking into account its vertical distance from sea level. Therefore, when indicating the altitude, it is indicated, for example, 200 masl (meters above sea level). Altitude affects both temperature (decreases 0.65 degrees every 100 meters of altitude) and atmospheric pressure.

It can serve you

  • Biotic and abiotic factors
  • Living and non-living beings
  • Autotrophs and Heterotrophs

Biotic Factors: Definition, Types and Examples

The biotic factors are all living organisms, interacting with other living organisms. Examples of Biotic FactorsOn the other hand, the relationship between organisms in an ecosystem is also called an abiotic factor. These relationships condition the existence of all the inhabitants of the ecosystem, since they modify their behaviors, their way of feeding and reproducing, and in general the conditions necessary to survive.

Among these relationships are relationships of dependency and competition. In other words, biotic factors are living things but always considered in a network of relationships between flora and fauna.

In the ecosystem there are also abiotic factors, which are those that also condition the existence of living beings, but that are not living beings, such as water, heat, light, etc.

 See also: Difference between biotic and abiotic factors

Biotic factors are classified into :

  • Individual factor: An organism individually. That is to say, a horse, in particular, a bacterium, in particular, a tree in particular. When studying changes in an ecosystem, it is important to determine whether a single individual of a species can cause significant changes or not.
  • Population biotic factor: They are the set of individuals that inhabit the same area and that are of the same species. Population biotic factors always modify the ecosystem in which they are integrated.
  • Community biotic factor: They are a group of different biotic populations that live in the same area. The concept of community biotic factors allows observing the relationships between populations but also how the community as a whole is related to other populations that do not belong to the community.

Examples of biotic factors

1. Producers

Producers are those organisms that produce their own food. They are also called autotrophs.

Peach treeRice


2. Consumers

Consuming organisms are those that cannot produce their own food. This includes herbivores, carnivores, and omnivores.

horsePanda bear


3. Decomposers

The decomposers feed on organic matter, breaking it down into its basic elements.

Flies (insect)Azotobacter (bacteria)
Diptera (insect)Pseudomonas (bacteria)
Trichoceridae (insect)Achromobacter (bacteria)
Aranea (insect)Actinobacter (bacteria)
Calliphoridae (insect)Mutualistic fungi
Silphidae (insect)Parasitic fungi
Histeridae (insect)Saprobic fungi
Mosquito larvae (insect)Mold
Carabiners (insect)Earthworms
Acari (insect)Slugs
Beetles (insect)Nematodes


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Types of Fraction: Definition, Types and Examples

The fractionsTypes of fraction are elements of mathematics representing the ratio of two numbers. Proper fraction, improper fraction, and mixed fraction are three basic types of fraction. This is precisely why the fraction is completely associated with the operation of division, in fact, a fraction can be said to be a division or a quotient between two numbers

Being a quotient, fractions can be expressed as their result, that is, a unique number (integer or decimal), so that all of them can be re-expressed as numbers. As well as in the opposite sense: all numbers can be re-expressed as fractions (integers are conceived as fractions with denominator 1).

The writing of the fractions follows the following pattern: there are two written numbers, one above the other and separated by a hyphen, or separated by a diagonal line, similar to the one written when representing a percentage (%). The number that is above is known as the numerator,  the one below is the denominator; the latter is the one that acts as a divisor.

For example, the fraction 5/8 represents 5 divided by 8, so it equals 0.625. If the numerator is greater than the denominator it means that the fraction is greater than unity, so it can be re-expressed as an integer value plus a fraction less than 1 (for example, 50/12 is equal to 48/12 plus 2 / 12, i.e. 4 + 2/12).

In this sense it is easy to see that the same number can be re-expressed by an infinite number of fractions; in the same way that 5/8 will be equal to 10/16, 15/24, and 5000/8000, always equivalent to 0.625. These fractions are called equivalents and always maintain a directly proportional relationship.

In everyday life, fractions are usually expressed in the smallest number possible, for this we look for the smallest integer denominator that makes the numerator also an integer. In the example of the previous fractions, there is no way to reduce it further, since there is no integer less than 8 that is at the same time divisor of 5.

Fractions and Mathematical Operations

Regarding basic mathematical operations between fractions, it should be noted that for addition and subtraction, the denominators must coincide and, therefore, the least common multiple must be sought by means of equivalence (for example, 4/9 + 11/6 is 123/54, since 4/9 is 24/54 and 11/6 is 99/54).

For multiplications and divisions, the process is somewhat simpler: in the first case, multiplication between numerators is used over multiplication between denominators; in the second, a ‘cross’ multiplication is performed.

Fractions in everyday life

It should be said that fractions are one of the elements of mathematics that appear most frequently in everyday life. A huge number of products are sold expressed as fractions, be it kilo, liter, or even arbitrary and historically established units for certain items, such as eggs or invoices, that go by the dozen.

Thus we have ‘half a dozen’, ‘a quarter of a kilo’, ‘five percent discount’, ‘three percent interest, etc., but all of them involve understanding the idea of ​​a fraction.

Examples of fractions

  1. 4/5
  2. 21/13
  3. 61/2
  4. 1/3
  5. 40/13
  6. 44/9
  7. 31/22
  8. 177/17
  9. 30/88
  10. 51/2
  11. 505/2
  12. 140/11
  13. 1/10 8
  14. 6/7
  15. 1/7
  16. 33/9
  17. 7/29
  18. 101/100
  19. 49/7
  20. 69/21

How Many Types of fraction?

Here are the Three Types of fractions..

  • Improper Fraction
  • Proper Fraction
  • Mixed Fraction

Improper Fraction

Considering fractions as proportional relationships between two numbers, a distinction is made between those that exceed unity, called improper fractions, and those that do not, which are their own.

Characteristics of improper fractions

In improper fractions the numerator (the number that is above in the fraction) is always greater than its denominator (the one that is below), so it can also be expressed as the combination between an integer and another fractional number and less than 1.

There is talk of ‘combination’ because in writing they appear like this: the whole number and to its right the fractional number. Although a ‘+’ sign should be formally written between the two, this is usually not done.

Those numbers made up of an integer and a fraction are called mixed numbers, and they are often seen on posters of businesses that sell products by weight.

For example, in an ice cream parlor, hardly anyone chooses to order 5/2 of a kilo of ice cream (much less in a higher ratio, such as 25/10), but they will surely request 2 ½, that is, “two and a half kilos” of frozen.

The exercise of transforming an improper fraction into a mixed number is simple: you have to decompose the numerator so that it is divisible by the denominator, resulting in an integer (in the example, 4/2 = 2), the remaining fraction ( in this case ½) will be the fraction.

For the purposes of mathematical analysis, it is useless to express an improper fraction as the number of units it has and the smallest quotient of one, because what matters is each number separately: the operations between fractions, as well as those that combine fractions and integers, are much simpler as you work with improper fractions.

Although the operations between proper and improper fractions are carried out in the same way, there are certain differential characteristics in both cases, such as the fact that multiplication between improper fractions results in an improper fraction.

While the division between improper fractions depends precisely on which number is located as a dividend (numerator) and which as a divisor (denominator): if the first is greater than the second, then it will be an improper fraction, while if the second is the largest will be a fraction of its own.

A particular case of improper fractions is those that result in a division in which there is no remainder, that is, one in which the numerator is a multiple of the denominator and then it is an integer: these are known as apparent fractions.

Examples of improper fractions

Here are some examples of improper fractions:

  • 4/3
  • 11/21
  • 50/18
  • 100/17
  • 10/9
  • 23/8
  • 4/3
  • 9/21
  • 72/33
  • 41/8
  • 11/10
  • 3/2
  • 7/17
  • 6/5
  • 41/5
  • 100/99
  • 414/200
  • 121/100
  • 77/10
  • 32/9

Mixed Fraction

mixed fraction is the combination of a whole number and a fraction. Every fraction is made up of two numbers, written one above the other separated by a line:

  • The numerator ( above ): is the number of parts taken from the unit. Eg if a person takes two servings of that cake, he takes 2/5. That is, the numerator is 2.
  • The denominator ( below ): is the number of parts that make up the entire unit. Eg if a cake is divided into five portions, the denominator is 5.

When the numerator is greater than the denominator it means that there is more than one complete unit. In these cases, the quantity can be expressed through an improper fraction (a fraction with a numerator greater than the denominator) or through a mixed fraction. A proper fraction can never be expressed as a mixed fraction.

To convert improper fractions to mixed fractions :

  • Divide the numerator by the denominator.
  • Write the quotient as a whole number
  • The rest is the new numerator of the fraction (with the same denominator).

To convert mixed fractions to improper :

  • Multiply the whole number by the denominator.
  • Add the result to the numerator.
  • The result of the sum is the new numerator of the fraction (with the same denominator).

See also: Examples of Own Fractions

Examples of mixed fractions

  • 3 2/5 (three integers and two fifths)
  • 1 2/3 (One whole and 2 thirds)
  • 45 74/100 (forty-five integers and seventy-four hundredths)
  • 62 3/8 (sixty-two integers and three-eighths)
  • 2 5/6 = (Two integers and five-sixths).
  • 5 4/7 = (Five integers and four sevenths).
  • 8 3/10 = (Eight integers and three tenths).
  • 11 2/6 = (Eleven fifths and two sixths).
  • 7 4/10 = (Seven integers and four-tenths).
  • 261 10/14 = (Two hundred sixty-one integers and ten fourteen).
  • 8 7/16 = (Eight integers and seven sixteenths).
  • 16 3/16 = (Sixteen integers and 3 sixteenths).
  • 6 5/6 = (six integers and five sixths).
  • 5 2/7 = (Five integers and two sevenths).
  • 4 2/10 = (four integers and 2 tenths).

Proper Fraction

The fraction in which numerator is less than the Denominator or The fraction in which the degree of the numerator is less than the degree of the denominator is called Proper fraction.

Examples of Proper Fraction

  • 1/2
  • 3/4
  • 5/9

Newton’s three laws of motion

The laws of Newton, also known as the laws of motion are three principles of physics referring to the movement of bodies. These are:

  • The first law or law of inertia.
  • The second law or fundamental principle of dynamics.
  • The third law or principle of action and reaction.

These principles were formulated by the English physicist and mathematician Isaac Newton in his work: Philosophiæ Naturalis Principia Mathematica (1687). With these laws, Newton laid the foundations for classical mechanics, the branch of physics that studies the behavior of bodies at rest or moving at small speeds (compared to the speed of light).


Newton’s laws marked a revolution within the field of physics. They formed the foundations of dynamics (part of the mechanics that studies movement according to the forces that originate it). Furthermore, by combining these principles with the law of universal gravitation, the laws of the German astronomer and mathematician, Johannes Kepler, on the motion of planets and satellites could be explained.

  • See also: Contributions of Isaac Newton

Newton’s First Law – The Inertia Principle

Newton’s first law states that a body only varies its speed if an external force acts on it. Inertia is the tendency of a body to continue as it is.

According to this first law, a body cannot change its state by itself; for it to come to rest (initial velocity: 0) or uniform rectilinear motion, it is necessary for some force to act on it.

Therefore, if no force is applied and a body is in a state of rest, it will remain so; if a body was in motion, it will continue to be in uniform motion at a constant speed.

For example, A man leaves his car parked outside his house. No force acts on the car. The next day, the car is still there. 

Newton extracts the idea of ​​inertia from the Italian physicist, Galileo Galilei ( Dialogue on the two great systems of the world -1632).

Newton’s Second Law – The Fundamental Principle of Dynamics

Newton’s second law states that there is a relationship between the force exerted and the acceleration of a body. This relationship is direct and proportional, that is, the force exerted on a body is proportional to the acceleration it will have.

For example, Juan is 10 years old. The more force Juan applies when kicking the ball, the better the chance that the ball will cross half the court. 

Acceleration depends on the magnitude, direction, and direction of the resulting force, and the mass of the object.

  • It can help you: How is the acceleration calculated?

Newton’s Third Law – The Principle of Action and Reaction

Newton’s third law states that when one body exerts a force on another, the latter responds with a reaction of equal magnitude and direction but in the opposite direction. The force exerted by the action corresponds to a reaction.

For example: When a man trips on a table, he will receive from the table the same force that he applied with the blow. 

Examples of Newton’s First Law

  1. A driver of automobile brakes abruptly and, by inertia, shoots forward.
  2. A stone in the ground is in a state of rest.
  3. A bicycle stored five years ago in a loft comes out of its inertia when a child decides to use it.
  4. A marathoner continues to run several meters beyond the finish line due to the inertia of his career.
  • See more examples in Newton’s First Law

Examples of Newton’s second law

  1. A lady teaches two children to ride a bicycle: one 4-year-old and the other 10-year-old, so that they reach the same place, they will have to exert more force when pushing the 10-year-old boy because his weight is greater.
  2. A car needs a certain amount of horsepower to be able to drive on the road.
  3. Pushing a broken down car among more people will make the car move faster.
  • See more examples in: Newton’s Second Law

Examples of Newton’s third law

  1. If one billiard ball hits another, the second will move with the same force as the first.
  2. A child wants to jump to climb a tree (reaction), he must push the ground to propel himself (action).
  3. A man deflates a balloon; the force with which the air comes out causes the balloon to move from one side to the other.
  • See more examples in: Newton’s third law


Force of gravity Examples

The force of gravity is one of the fundamental interactions that govern the universe and that makes living objects and beings remain fixed on the Earth’s crust, by virtue of a kind of attraction towards the center of the Earth.

On the one hand, gravity is a gravitational field of influence, of which its total composition is not known but which behaves attracting two bodies to each other. On the other hand, gravity is quantifiable and can occur in different magnitudes, which is easily understandable.

People would not be able to walk freely in the world if there were a stronger gravity (in which case we would be too attracted to the ground) or much weaker (in which falls would be like in slow motion and things would become very lighter).

In effect, the way in which life unfolds happens because we live in a gravitational field.  This can be said that the fall of something (free of all force) increases its speed at a rate of 9.81 meters per second.

It is important to clarify that the absence of any force implies that nobody prints an additional force on the object, but also imposes limitations linked to other forces, such as the friction force associated with the presence of air.

Indeed, the force of gravity could be verified mathematically only in a vacuum. Due to the characteristics of the Earth, at the poles, the force of gravity is somewhat greater (9.83 m / s 2 ) and in the equatorial zone, it is somewhat less (9.79 m / s 2 ). Jupiter’s gravitational field is much more intense than that of our planet, while that of Mercury is much weaker.

Gravity scholars

Due to its complexity and difficulty of analysis, the study of gravity consecrated the most important scientists of humanity. Chronologically, Aristotle, Galileo Galilei, Isaac Newton, and Albert Einstein were responsible for the most important contributions in this regard.

Undoubtedly, the last two stand out, the first for providing the relationship between the intensity of attraction with respect to distance and mass, while the second was the one who discovered that matter and space work together, the first distorting the second by means of an intense force field. Both theories were widely supported by mathematical formulations and are considered today to be one of the most important in the history of science.

Examples of the force of gravity

The action of gravity is verified all the time. Here are some examples that show it:

  • The simple act of standing upright anywhere is due to gravity.
  • The fall of the fruits of the trees.
  • The great waterfalls in the falls.
  • The translational movement made by the moon around the Earth.
  • The force that must be done when riding a bicycle to avoid falling.
  • Falling drops of rain.
  • All the constructions made by human beings.
  • The progressive brake that a body presents when being thrown upwards.
  • The movement that a pendulum performs, and any kind of pendulum movement.
  • The difficulty of jumping the more weight one has.
  • Amusement park attractions.
  • The flight of the birds.
  • The journey of the clouds in the sky.
  • Virtually all sports, particularly throwing into a basketball hoop.
  • The need to wear a helmet in outer space, as astronauts are generally seen.
  • The firing of any projectile.
  • The landing of an airplane (where gravity appears to a much lesser extent than the propelling forces).
  • The force that must be done when carrying something heavy in the human body.
  • The indications on the scale assume the force of gravity of planet Earth.
  • The operation of water cables in cities.

Examples of static Friction

The friction is the force that opposes the sliding movement is produced by contact between two surfaces. There are 4 main types of friction: static friction, sliding friction, rolling friction, and fluid friction. The table lamp lying on a table and A box of much weight against the ground are some examples of static friction.

If the normal force is that exerted when a body is supported on a surface, perpendicularly and outwards, the static friction is a force proportional to the normal, at the rate of a value called the coefficient of friction.

The formula, then, is F = Ц * N, where f is the friction or friction force, Ц is the coefficient of friction and N is the normal force. This, however, is restricted to the case of static friction, where the phenomenon occurs below the movement threshold. When that threshold is exceeded, the object begins to slide on the surface, and then the friction becomes less, changing to be called dynamic friction. In everyday life, the concept of friction is directly related to rubbing, scrubbing or rubbing something: the friction force is what makes the opposition, and is what allows people or automated bodies that the human being created to stop a once launched.

The friction force is present to the extent that when it comes to moving a heavy object horizontally, at first the force that must be exerted to remove it from rest is much greater than that which must be done once it is started, where it is much easier to get it moving. This happens because once the static friction has expired, the microscopic joints that kept the surfaces in contact welded break.

Finally, it is common for industries concentrated in the production of certain goods to manipulate the friction force, which tends to optimize it by increasing or reducing it depending on the case: there are times when it is necessary for the surface in contact with the ground to be rough, so as to increase this force. Others, on the other hand, are supported on another surface that sees the reduction of friction necessary, for which tools such as grease or oil are usually used, such as lubricants to reduce friction between components and the energy losses they carry.

Static friction

When the two surfaces are at rest, the force that opposes the start of the movement is called static friction. Since it prevents movement, it can be said that it is equal to the net force applied to the body, only in the opposite direction.

The static friction is always less than or equal to the friction coefficient. However, when friction experiments are carried out on carefully cleaned, smooth metal blocks, the difference between static and kinetic coefficients tends to disappear.

Here are some examples of static friction :

  1. A heavy box against the ground, difficult to lift and move.
  2. A nightstand resting on a light table.
  3. A dry and a wet plastic, where the second has less friction than the first.
  4. Friction toys that mimic force behavior in vehicles, but statically.
  5. The rest of the body when a person leans against the wall.

Dynamic Friction

The dynamic friction is the one that exists in a body that is already in motion and has a constant magnitude. The difference with static friction can be seen in the fact that bodies at rest are very difficult to move (static friction), but when that force has already been overcome it is much easier (dynamic friction).

The coefficient of friction, here, is less than static and dimensionless, because it is the result of dividing two forces: kinetic friction and normal. The number that indicates the level of dynamic friction is the coefficient that is referred to when talking about the generality of the coefficient of friction, as it is the most reliable number.

The following are examples of dynamic friction :

  1. Feet against the ground, when walking.
  2. The wheels of a bicycle against the ground.
  3. The friction between an airplane and the air.
  4. Underwater vehicles, with the friction it exerts on water.
  5. Skates on an ice or concrete rink.

Somatic cells: Definition & Examples

The somatic cells are those that form all the tissues and organs of the body of multicellular organisms, in distinction from sexual or germ cells ( gametes ) and ES cells (stem cells). All the cells that make up the tissues, organs, and those that circulate in the blood and other non-reproductive fluids are, in principle, somatic cells.

This distinction consists not only in the specificity of their functions but in that the somatic cells are of the diploid type, that is, they contain two series of chromosomes in which the total genetic information of the individual is found.

Thus, the genetic material of all somatic cells is necessarily identical. In contrast, sex cells or gametes have unique genetic content, due to the random nature of genetic recombination during its creation, which represents only half of the individual’s total information.

In fact, the cloning technique consists of taking advantage of this total genetic load present in any cell in the body of a living being, something impossible to do with sperm or an egg, since they depend on each other to complete the genetic information of a new individual.

Examples of somatic cells

  1. Myocytes. This is the name given to the cells that make up the various muscles of the body, both the extremities, the chest, and even the heart. These cells are characterized by having a great elasticity that allows them to stretch and recover their original shape, thus allowing movement and strength.
  2. Epithelial cells. They cover the inside and outside of the body, forming a mass called the epithelium or epidermis, which includes certain segments of the skin and mucosa. Protects the body and organs from external factors, often secreting mucus or other substances.
  3. Erythrocytes (red blood cells). Devoid of nucleus and mitochondria in humans, these blood cells are provided with hemoglobin (which attributes the red color to the blood) to transport vital oxygen to the different reaches of the body. Many other species have nucleated red blood cells, like birds.
  4. Leukocytes (white blood cells). Protective and defense cells of the organism, in charge of dealing with external agents that could be causing disease or infections. They normally operate by phagocytizing foreign bodies and allowing their expulsion through the different excretion systems, such as urine, feces, mucus, etc.
  5. Neurons. The nerve cells that make up not only the brain but the spinal cord and the various nerve endings, are in charge of transmitting the electrical impulses that coordinate the body’s muscles and other vital systems. They form gigantic neural networks from the connection of their dendrites.
  6. Thrombocytes (platelets). Cytoplasmic fragments, more than cells, irregular and without a nucleus, are common to all mammals and play vital roles in growth and in the formation of thrombi or clots. Its deficiency can result in bleeding.
  7. Walking sticks or rods. Cells present in the retina of the mammalian eye and that fulfill photoreceptor roles, linked to vision in low light conditions.
  8. Chondrocytes. They are a type of cell that integrates cartilage, where they produce collagen and proteoglycans, substances that support the cartilage matrix. Despite being vital for the existence of cartilage, they make up just 5% of its mass.
  9. Osteocytes. The cells that form the bones together with the osteoclasts, come from the osteoblasts, and allow bone growth. Unable to divide, they play a vital role in the segregation and reabsorption of the surrounding bone matrix.
  10. Hepatocytes. These are the cells of the liver, filter of the blood, and of the organism. They form the parenchyma (functional tissue) of this vital organ, secreting the bile necessary for digestive processes and allowing the different metabolic cycles of the organism.
  11. Plasmocytes. They are immune cells, such as white blood cells, which are distinguished by their large size and because they are responsible for the secretion of antibodies (immunoglobulins): substances of protein order necessary to identify bacteria, viruses, and foreign bodies present in the body.
  12. Adipocytes. The cells that make up adipose tissue (fat) are capable of storing large amounts of triglycerides inside them, practically turning into a drop of fat. These lipid reserves are used when blood glucose levels decrease and it is necessary to go to the energy reservoirs to continue with the body’s functions. Of course, accumulated in excess, these fats can represent a problem by themselves.
  13. Fibroblasts. Connective tissue cells, which structure the interior of the body and provide support to the various organs. Its heterogeneous shape and characteristics depend on its location and activity, vital in tissue repair; but in general lines, they are cells of renewal of the connective fibers.
  14. Megakaryocytes. These large cells, with various nuclei and branches, integrate the hematopoietic (blood cell-producing) tissues of the bone marrow and other organs. They are responsible for producing platelets or thrombocytes from fragments of their own cytoplasm.
  15. Macrophages. Defensive cells similar to lymphocytes, but generated from monocytes produced by the bone marrow. They are part of the first defensive barrier of the tissues, engulfing any foreign body (pathogen or waste) to allow its neutralization and processing. They are vital in the processes of inflammation and tissue repair, ingesting dead or damaged cells.
  16. Melanocyte. Present in the skin, these cells are responsible for the production of melanin, a compound that gives color to the skin and defends it against sunlight. The intensity of the skin pigment depends on the activity of these cells, so their functions vary according to race.
  17. PneumocytesSpecialized cells found in the pulmonary alveoli, vital in the production of pulmonary surfactant: a substance that reduces alveolar tension in the lungs during expulsion from the air, and that also fulfills immunological roles.
  18. Sertoli cellsLocated in the seminiferous tubes of the testicles, they provide metabolic support and support to the cells responsible for the production of sperm. They secrete a good amount of hormones and substances linked to the preparation of gametes and control the function of Leydig cells.
  19. Leydig cells. These cells are also located in the testicles, where they produce the most important sex hormone in the male body: testosterone, necessary for the activation of sexual maturity in young individuals.
  20. Glial cells. Cells of the nervous tissue that provide support and help to neurons. Its role is to control the ionic and biochemical state of the microcellular environment, defending the correct process of neural electrical transmission.

Unicellular and multicellular

The organisms are living things that are formed by one or more cells. Cells are the minimum units of life that have different degrees of complexity depending on their structure or organization.

Unicellular organisms are those that are made up of a single cell, for example, bacteria and yeastsMulticellular organisms are those that are made up of two or more cells, for example, shark, vulture, eucalyptus

Unicellular organisms

Single-celled organisms are microscopic organisms that unite all their vital functions in a single cell. Almost all prokaryotic organisms (that have a cell without a cell nucleus) and some eukaryotic organisms (that have cells with a cell nucleus) are unicellular.

Within the Monera are unicellular organisms all bacteria, eg Escherichia coli, salmonella typhi, and all archaea, for example, the methanogenic archaea. Within the fungi kingdom, yeasts, for example, Pichia, saccharomyces cerevisiae (brewer’s yeast ) ; within the protist kingdom, the protozoa, for example, paramecium and dinoflagellates.

Multicellular organisms

Multicellular organisms are made up of two or more cells that specialize in different vital functions (neurons, epithelial cells, red blood cells). These specialized cells form tissues that in turn make up the organs of the living being.

All animals and plants are multicellular organisms, for example, mammals like the lion, amphibians like the frog, trees like the oak, herbaceous plants like the onion. Some fungi and some organisms of the protist kingdom are also multicellular, for example, mushrooms, algae.  

Characteristics of single-celled organisms

  • They are present in all ecosystems.
  • The number of them far exceeds multicellular organisms.
  • They are considered more primitive than multicellular organisms.
  • They reproduce asexually.
  • There are heterotrophic and autotrophic unicellular organisms.
  • They can group together forming colonies.

Characteristics of multicellular organisms

  • They are also called multicellular.
  • They are eukaryotic organisms.
  • They are made up of specialized cells that can be very different from each other.
  • The cells that make them up are related to each other and need each other.
  • They are microscopic organisms more complex and developed than single-celled organisms.
  • They initially arise from a single cell that multiplies through mitosis or meiosis.

Examples of single-celled organisms



  • More examples in Unicellular organisms

Examples of multicellular organisms

Brown algaeLettucePorphyra
HorseDaisy flowerPortobello
SparrowNematodesChinese mushroom
HydrangeaPalmaria palmataBlack truffle


  • More examples in Multicellular organisms