We explain what living beings are and what are the shared characteristics that differentiate them from inert matter.
what is a living being?
From the point of view of biology , living beings or living beings, also known as organisms , are very complex forms of organization of matter , capable of functioning as a system that is perpetuated over time, exchanging energy and matter with their environment .
These forms of life differ from inert matter in that they comply with the elementary processes of existence, which are:
- Nutrition, that is, taking from the environment (or from other beings) the necessary materials to perpetuate one’s own existence .
- The interaction, that is, the establishment of links of all kinds with other living beings and with the environment, whether by way of competition , cooperation , symbiosis or antagonism .
- Reproduction, that is, the formation of new individuals of the same species , which remain once the organism completes its life cycle .
- Death, finally, is the return to the environment of the matter and energy that were used to exist, and the inevitable end of all life.
Living beings are the fundamental object of study in biology, and are (according to the most accepted hypothesis) the result of complex chemical processes that occurred on our planet in its primitive stages of geological formation.
Finally, all living beings have common basic and elemental characteristics, which we will describe in detail below.
It can help you: Adaptation of living beings
Characteristics of living beings
1. They have a certain degree of cellular organization
All living things are made up of cells.
All living beings are the result of a very rigorous organization of the matter that makes them up, and the basic unit of the organization of life is the cell . This means that from the most complex beings (such as mammals ) to the simplest (such as bacteria ), we are all made up of cells.
In fact, depending on how many there are, we can talk about two types of living beings:
- Unicellular living beings, whose bodies are made up of a single cell. These organisms can exist individually and freely, or form colonies of organisms that live together, without ever ceasing to be unique and unicellular organisms. For example: amoebas and paramecia, free-living microscopic organisms .
- Multicellular living beings, whose bodies are made up of lots of cells of various types, organized at such a complex level that they constitute tissues, organs, etc. In the case of these organisms, the cells sacrifice their autonomy to form a much more complex whole, so that none can survive without the rest. For example: chickens, trees, mushrooms and human beings .
All living beings are made up of cells, although their respective cells have different levels of complexity : some are simple and have few organelles, others are more complex and perform various specialized biochemical processes: epidermal cells, bone cells, and muscle cells, for example, they perform different tasks and therefore have different compositions, shapes, and organelles.
2. They maintain an internal order or homeostasis
Mechanisms such as sweat allow living beings to maintain their internal balance.
In order for living things to continue to live, their bodies must regulate their vital functions and maintain a delicate internal balance . Eating too much (or too little) of a certain nutrient, losing too much temperature or having too little water are some examples of situations that can break this balance and endanger the continuity of existence.
To do this, organisms have developed different mechanisms that allow them to counteract the effect of the environment on their bodies and adapt to situations to preserve their inner balance.
For example, when it’s very hot, our skin sweats to hydrate itself and for the evaporation of sweat to cool us down; On the other hand, when it is very cold, our bodies shiver so that the movement of the muscles generates heat. These measures try to counteract the effect of environmental temperature on our bodies.
The same is true at the cellular level: the cells of our body are kept at a level of acidity slightly higher than that of plasma, since this is conducive to their fundamental chemical reactions . To ensure that said pH is maintained, they release or hoard ions and salts from the environment depending on what is convenient at the time.
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3. They react to environmental stimuli
Living things adapt to their environment to preserve themselves.
Living beings do not exist in a vacuum, but proliferate in an environment that they share with other forms of life and with different natural processes, dynamics and mechanisms, many of which have a certain incidence on homeostasis.
For this reason, living beings relate to the environment, that is, they perceive the stimuli around them and orient themselves in the environment according to what is best for them , just as we do when it is sunny and we look for a shadow.
For this, living beings have different sensory devices that communicate the outside of the body with the inside of the body , and are capable of recognizing environmental stimuli such as sound , light, smell, pH, etc., and subsequently reacting to them. in an appropriate way. In this way, living things adapt to their environment in order to preserve themselves.
For example, certain plants have a mechanism of positive phototropism, that is, they change the position of their leaves and stems depending on the presence of the sun, in order to expose them to the greatest possible amount of sunlight ( essential for photosynthesis ).
Other plants, less in need of sunlight, on the other hand, have negative phototropism and tend to flee from the sun, limiting or moderating the amount of light their leaves receive. In this way, the plants adapt to the amount and orientation of the surrounding sunlight, depending on what is best for them.
4. They go through a life cycle
The life cycles of different species can be very different from each other.
Every living being is at some point in its respective life cycle or circuit, that is, in the set of stages or vital moments that it must go through from birth to death . Life cycles can be very different from one another, which is why some living things are long-lived and lead slow lives, while others live frantically and die out quickly.
Every life cycle consists of the following stages:
- Birth ,the appearance of a new individual of a species in the world, either by being expelled from the mother’s womb, hatching an egg, or emerging from an ancestor cell.
- Growth ,a stage of accumulating resources from the environment in order to invest them in the expansion of the body itself, that is, in increasing in size and complexity, developing new organs or preparing for metamorphosis .
- Reproduction ,the stage in which individuals reach their peak of growth, change and mature, and prepare to bring new members of the species into the world.
- Old age and death, stage of gradual loss of internal balance and weakening of vital functions, which ends in one way or another in death.
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5. They have a metabolism
Metabolism allows living beings to harness matter and energy.
All living beings need matter and energy to keep their biochemical cycles going, as well as to repair themselves, move, grow or undergo metamorphosis.
Said energy and matter need to come from somewhere, and for this there is metabolism , that is, the ability to process nutrients from the environment and store them to undertake later tasks . Otherwise, we would have to be eating all day to sustain ourselves.
There are many forms of metabolism, depending on each life form, but in general they consist of chains of chemical reactions that occur inside the organism in a controlled and specific way, from certain substances that are taken from the environment and that when transformed they serve as fuel for the body.
For example, the human body requires organic matter to break down and thus obtain glucose, a type of sugar that is very useful chemically. Said sugar is then oxidized (that is, put to react with the oxygen taken from the environment when breathing) and subjected to different biochemical processes.
As a result, Adenosine Triphosphate ( ATP ) molecules are obtained , a molecule of pure chemical energy that can be used for many different purposes.
There are two fundamental metabolic processes:
- Anabolism, which consists of composing complex substances from simpler ones, as plants do by combining water, sunlight, and atmospheric carbon dioxide to compose a wide range of sugars and starches, essential to keep the body running.
- Catabolism, which consists of the reverse process: breaking down complex substances into simpler ones, generally with the help of specialized proteins called enzymes , just as we do with the organic matter that we ingest when eating, and that we break down into the different nutrients that we need absorb during digestion.
Similarly, metabolisms comprise two types of cycle, which are:
- The material cycle, that is, the one destined to obtain material nutrients that serve to build new tissue, especially in phases of growth or repair, or to manufacture substances with a specific purpose, such as reproductive cells.
- The energy cycle, that is, the one destined to obtain energy to keep the body going or to undertake other tasks later. For the latter, energy must be conserved in some way, generally by manufacturing substances (such as fat) that can then be broken down to recover the energy contained in their molecules .
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6. They are nourished and excreted
Every living being takes nutrients from the environment and discards substances that it does not need.
To keep metabolism going, living things must get matter and energy from the environment, and this can be done in many different ways. But once the matter is obtained and processed, however, their bodies must also discard the compounds that are not useful to them or that are dangerous to them, that is, excrete.
- nutrition. _ It consists of taking from the environment the necessary materials to start the metabolism. This includes the intake of organic and inorganic matter, to feed different metabolic processes such as respiration or photosynthesis. Beings capable of making their own food, such as plants, are known as autotrophs ; those that instead take food from other living beings or from substances released by them, as is the case with animals, are known as heterotrophs . The latter, moreover, can be primary consumers (they feed on autotrophs), secondary consumers (they feed on primary consumers or other secondary ones) or detritophagous (they feed on waste and debris).
- Theexcretion The excretion process consists in the release into the environment of those substances produced during the metabolism chain, but which are useless or dangerous for the body. For example, in the case of humans, the excretory system is responsible for collecting the ammonia (NH 4 ) generated during respiration and, along with other substances, expelling it from the body through urine. Naturally, the excretion of certain organisms can serve as a nutrient for others.
7. They reproduce
Life begets new life, but through different processes.
Life exists based on its reproduction: all living beings come from other living beings that existed before them , whether we are talking about human beings, fungi , plants, etc. Life engenders new life, and for this it can resort to processes of a different nature, such as:
- Asexual reproduction ,in which an organism gives life to another genetically identical (or very similar, if random mutations occur) to the parent , through cell division and replication of genetic material. This is the oldest method of reproduction that exists, and it is characteristic of the most primitive unicellular beings, such as bacteria. A bacterium feeds on the environment, reaches the right size, and then divides into two bacteria, which will start the cycle again.
- Sexual reproduction ,more complex than asexual reproduction and typical of multicellular living beings, requires the cooperation of two living beings of the same species (one female and the other male) to join their sexual cells or gametes and combine the other’s with the other. half of your genetic information . Thus, a totally new individual is produced, provided with its own DNA , the result of the random fusion of the DNA of its parents. This is how human beings reproduce: after the fusion of an egg and a sperm, a new member of the species comes into the world.
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8. They evolve
Evolution does not affect a single individual but the species as a whole.
To evolve is to adapt to the environment in the long term . It is a process that is not actually carried out by living beings individually, but rather affects the species as a whole, as the offspring present certain traits that are beneficial for them to deal with the environment and compete more advantageously with other rival living beings. .
Evolution is responsible for the fact that the same community of living beings, distributed in two different environments , ends up producing two different species after many generations have elapsed. That is the reason, for example, that the fauna and flora are different on each of the continents, despite the fact that many species have very similar traits, given that they are evolutionarily related.
