Arxiu d'etiquetes: species

Where do names of species come from?

All known living beings have names that allow us to recognize and classify them. However, only scientific names are valid for scientific purposes. Who does assign these names? Has it been always done the same way? And the most important: is there any rule when assigning a name to an organism?

Previously in All you need is Biology, we talked you about classification and phylogeny of organisms. Now, we bring you the answers to all these questions about nomenclature and taxonomy. Keep reading and you will discover some curiosities!  

The value of scientific names

If someone asks us what a dog or a cat is, of course all of us will know the answer. However, these names are not useful from a scientific point of view (despite biologist use them assiduously), especially when making studies and publishing papers. Common names (such as ‘dog’ or ‘cat’) are not constant: every language, every country, even every region, has their own terms to refer to their organisms. Even sometimes they change through time or are used to appoint different organisms (e.g. the red panda, which is near to mustelids, and the giant panda, a bear, don’t belong to the same family despite being called pandas).

As you see, using only common names in science could put you in trouble. If someone publish that has performed a study about reproduction of macaw populations, we could not know of which species they are talking about; the common name of this bird varies among some countries; moreover, there exist different species of macaws. Thus, the study does not make sense without context.

So, the use of scientific names in science is very important: they are constant worldwide (we avoid translation problems) and refer only to one organism with no ambiguity.

Currently, designation of scientific names follows the binomial nomenclature, that is, a scientific name of a species is composed by two terms: the genus (an upper level of classification than the species) and the specific epithet or name (and not the species, as some people tend to confuse). While the first term has validity by its own, the second one only has it if is preceded by the genus.

Thus, and keeping with the example above, the macaws from this study actually belong to the genus Ara, but there are different related species of macaws belonging this genus (Ara ararauna, Ara glaucogularis, Ara militaris…).

Macaw of the species Ara ararauna. Picture by Ralph Daily, CC.

However, how has the way biologists assign names changed through the time?

Linné, the father of binomial nomenclature

For a long time, biologists have tried to classify and give names to every living being they discover. The science of defining and naming groups of organisms according to their shared features is known as taxonomy.

In the beginning, there was not a clear consensus for naming the species. For the first ‘taxonomists’ it was of a big importance to classify and identify poisonous and medical plants, of which there are ancient documents wrote by Egyptians more than 3000 years ago.

The first person who started to formally classify organisms was Aristotle (384-322 AC). He was the first to differentiate between animals and plants, besides starting the classification of organisms according to their ‘parts’: four legs, warm body, etc.

During the Middle Age and the beginning of the Modern Age, most of scientists followed the Aristotle’s system of classification. Thanks to the improving of observing tools, such as the development of the first optical lenses during XVI and XVII centuries, some biologists started to improve their descriptions, and eventually abandoned this system.

However, among taxonomist still didn’t exist a formal consensus for assigning names. Before the instauration of the binomial system, species were named with a term (the genus) followed by a specific epithet or name composed by one or more words which described the species. This system, known as polynomial system, gave room to really long names such as ‘Plantago foliis ovato-lanceolatus pubescentibus, spica cylindrica, scapo tereti‘. Of course, this was not an optimum system.

During XVI and XVII centuries, Caspar Bauhin made the firt steps to simplify this system, sometimes shortening species names to just two terms. However, it was the Swedish botanical Carl von Linné (or Carolus Linnaeus) who formalized the use of the binomial nomenclature in his publication Species Plantarum (1753). Since then, species were given a name composed only by two terms: the genus and a trivial name designated by its descriptor; e.g., Panthera tigris (tiger).

Carl von Linné. Public domain.

The establishment of this system was favored by three reasons:

  • Its economy: there are needed only two words to identify a species with no error.
  • Its diffusion and general use by scientists, who standardize them and promote their use.
  • Its stability: scientists try to preserve the original name of an organism even if its classification changes through time.

How to name an organism: the nomenclature codes

Taxonomy and nomenclature are two different but inseparable concepts. While taxonomy is the science of describing and classifying organisms, nomenclature is the tool that allows taxonomists to assign names to those organisms.

In 1758, Linné stated the basis for an objective classification of species in the 10th edition of one of his most famous publications, Sistema Naturae:

  • Each species must have an own scientific name, unique and universal.
  • When a species is given more than one name by different scientists, the oldest one must prevail.
  • Scientific names are composed by two Latin or Greek terms: the first one corresponds to the genus and the second one, to the species belonging this genus.
  • The first letter of the genus must be written in upper case, while the specific epithet or names must be written in lower case. Moreover, both terms must be written in italic or underlined.

Cover of the 10th edition of Sistema Naturae. Public Domain.

Nomenclature has been getting more and more complex over the years. Nowadays, there are international codes of nomenclature for every group of organisms, like the ICZN (International Code of Zoological Nomenclature) or the ICN (International Code of Nomenclature for algae, fungi, and plants), amongst others. Taxonomist from each branch must obey their own codes when naming an organism.

Two of the most important rules when giving a name are the validity and the availability of the name. Let’s imagine we discover a new species of wasp of the genus Polistes: in one hand, the name (Polistes x) must be available, that is, it must accomplish the needed requirements to be assigned to our species. These requirements are gathered in the international codes, which are based on the Linné’s criteria. Moreover, a name is available when it is accompanied by a formal (published) description. Availability of a name can change under certain circumstances; e.g., a name considered unavailable can be available again if is republished following the code’s criteria.

In the other hand, a name must be valid, that is, it must have not been used to designate another organism, or considered invalid. For example, two taxonomists one before the other describe the same species and give it different names; in this case, the valid name would be the oldest one, so the second one would become a junior synonym according to the priority principle, thus getting invalid for its use.

When giving names gets out of hand…or not

Usually, when giving name to a species taxonomists get inspired by specific features of the organism (Dosidicus gigas (giant squid)), its native location (Synergus mexicanus (gall wasp from Mexico)) or in honor to relatives or other scientists.

However, nomenclatural world is full of curiosities, from scientists that give extravagant names to their species to the ones that get inspired by their favorite characters or TV shows:

  • There exists a genus of moths called La (by Bleszynski, 1966). Its ambiguity with the feminine article ‘La’ in Spanish (‘the’ in English) makes search engines go crazy. Moreover, some of the species belonging this genus were given names like La cerveza, La cucaracha or La paloma (literally, ‘The beer’, ‘The cockroach’ and ‘The dove’ in Spanish, respectively).
  • While some taxonomists give species short names, others prefer them longer: Gammaracanthuskytodermogammarus, Rhodophthalmokytodermogammarus and Siemienkiewicziechinogammarus are genera of amphipods from the Baikal lake given by the naturalist Dybowski. For sure he had much fun with this!
  • During a long time, it was a common practice to use specific epithets and names to insult other scientists (e.g. stupidus). Fortunately, this is currently prohibited.
  • Abra cadabra, Aha ha, Attenborosaurus (dinosaur genus given after the naturalist David Attenborough), Acledra nazgul, Desmia mordor (in honor to the Lord of the Rings), amongst others.

It is important to note that the international codes try to avoid this kind of names; but it is still funny! If you haven’t had enough, take a look to this list. It will not disappoint you!

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Do you still think naming an organism is an easy task?

References

Main picture property of Irene Lobato Vila (author of this post) took at the Smithsonian’s National Museum of Natural History (Washington D.C., EUA).

The living space of organisms

We all have our own living space, the place where we feel comfortable, like we were at home. We also have our routines, habits and that list of preferences that make us unique. Each of us, ultimately, have our own ecological niche, an extensive concept for each species that share the Earth with us. From it comes an important ecological processes such as competition or speciation, a key concepts for understanding the assembly and dynamics of natural ecosystems.

INTRODUCTION

When you are asked how you would describe close people, the first thing that comes to your mind is their way of being when you’re with them and what they loves to do. We know what is the first thing they always ask in a restaurant, what annoys them, what sites they like to frequent, what they like to do when they have free time and even how they behave when they like someone. If we have also lived with them, we could guess almost their daily routine since they wake up until they go to bed. Although we do not always have the same behaviour, there are many traits, hobbies and routines that characterize and differentiate us. Each of us have our comfort zone, our hobbies, food preferences and people with whom we love spending our free time.

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The dietary preferences of each of us and our routines and hobbies serve as a comparison to illustrate the diversity of ecological niches in the natural world. Source: Flickr, George Redgrave.

THE ECOLOGICAL NICHE OF A SPECIES

This “living space” that all of us have and in which we feel identified, is also comparable to the ecological niche of the organisms. The ecological niche of a species is a concept that always has been presented us as the “occupation”, “profession” or “work” that an organism carries up in the place where it lives (Wikipedia or CONICET), but the definition includes more than that. Hutchinson (1957) defined it as: ” n-dimensional hypervolume, where the dimensions are environmental conditions and resources, that define the requirements of a species to persist over time.” Despite the confusing definition, it is interested to point out the term “n-dimensional” as the ecological niche is based on this idea. An ecological niche is nothing more than all those multidimensional species requirements. In other words, the ecological niche of a species would be everything that involve the species and make it to prosper and survive where it is. Refers, ultimately, to all those variables that affect them in their daily lives, both biological variables -the contact with other species- and the physical and chemical ones-the climate and the habitat where they live-. An ecological niche of a species would be the spectrum of food it eats or can consume, the time of the day in which it is active to perform its functions, the time of the year and the way it carries out the reproduction, the predators and preys, the habitat it tolerates and all those physical and chemical factors that allow this species to remain viable.

warblers
These 5 species of warblers of North America seem to occupy the same habitat (the fir), but actually not. The truth is that each warbler occupies a different position in the tree. Source: Biology forums.

To give an illustrative example, let us place ourselves in the African savannah. The main grazing ungulates and those which perform mass migrations are compound by zebras, wildebeest and Thomson’s gazelles. At first glance, you might think that their ecological niche is very similar: same habitat, same routine, same predators and same food. The same food? Absolutely not. During migration, zebras go ahead, devouring tall grass, which is the worst quality. They are followed by wildebeest, which eat what remains standing, and these are followed by Thomson gazelle, which eat the high-quality grass, which is starting to grow again.

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Although at first glance it may seem that feed on the same food, each species focuses on a different part of the plant. Source: Abierto por vacaciones.

CAN TWO SPECIES LIVE TOGETHER WITH THE SAME NICHE IN THE SAME PLACE?

The competitive exclusion principle, proposed by Gause (1934), states that two species occupying the same niche can not coexist in the long term as they come into competition for resources. Thus, in a competitive process for the same ecological niche, there is always a winner and a loser. In the end, one of the competitors is imposed by another, and then two things can happen: the extinction of the loser one (image A) or a traits displacement in order to occupy another niche (image B). In fact, the competitive exclusion principle is behind the current problems with invasive species. Invasive species niche is very similar to native species niche and, when they converge in the same habitat, the invasive species end up displacing native species, as they are better ecological competitors. It also often happens, of course, the opposite: the exotic species is worse than its counterpart and the competitor fails to thrive in the new environment.

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Image A | This study was conducted in order to observe the effect of competitive exclusion in two species of protists. Both species occupy almost identical ecological niches, but they are not living together in nature. The density of one falls sharply when they are forced to share the same space, until it eventually disappears. This same process occurs with invasive species. Source: Jocie Broth.

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Image B | When the 3 species of Darwin’s finches (in different colors) coexist on the same island, a trait displacement occurs by competitive exclusion. Individuals from the ends tend to have very similar bill depths to those of the other species, resulting in a niche overlap and subsequent competition. The final boundaries are established thanks to this process. Source: Nature.

THE FUNCTIONAL EQUIVALENCE

We have seen that to share ecological niche is synonymous of having conflict between species. However, there is a situation in which problem do not take place. The hypothesis of functional equivalence proposed by Hubbell proclaims that if the niches are identical and the species life parameters (fertility, mortality, dispersion) are also the same, none of them has a competitive advantage over the other, and the battle ends in tables. This fact seems to occur only in a very stable ecosystem in a Panama rainforest island (Barro Colorado). Different species of trees, as having almost identical parameters of life, do not compete between them and are distributed randomly, as if the individuals of different species belong to the same species. Furthermore, it seems that speciation in this kind of rainforest could also occur by chance, which would have caused the high density of species that harbor these forests.

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Tropical forests have a tree species density unique in the world. One hectare of tropical forest may contain up to 650 tree species, more than the number of tree species present in both Canada and continental US. Will Hubbell’s functional equivalence theory be behind the explanation for this curious fact? Source: Flickr, Jo.

NEW NICHES, NEW SPECIES

Speciation, or the creation of new species, usually occurs when new ecological niches are created or the existing become unoccupied. In both cases, to occupy a new ecological niche imply a gradual differentiation from the initial population to become a genetically distinct species. As an example of formation of new ecological niches we have the case of the emergence of angiosperms. Their booming opened many new possibilities, thanks both to increasing diversity of seeds and fruits (which, in turn, increased the number of specialized species) and the emergence of complex flowers, which allowed the explosion of many pollinators (facilitating the emergence of new insectivores). As an example of unoccupied niche, there is the famous case of the extinction of non-avian dinosaurs. Dinosaurs dominated a lot of niches, from land to air ecosystems, and even the aquatic environment. Those empty niches was occupied by many mammals, thanks to their high fertility and plasticity (flexibility to adapt into different habitats). That eventually led large ratios of speciation in a short time, what is known as adaptive radiation.

Eomaia_NT
This is Eomaia scansoria, an extinct species of mammals that lived at the same time as the dinosaurs. The extinction of the dinosaurs opened up a wide range of possibilities to mammals, which, although they were expanding, remained in the background. Their great plasticity led them to colonize many habitats, by occupying the free ecological niches left by the dinosaurs. Source: Wikipedia.

ASSEMBLY OF COMMUNITIES

As we have seen, the ecological niche is behind fundamental ecological and evolutionary processes. All living communities today have been formed thanks to the niches of different species. Through competition, species niches were overlaping, and the communities were assembled like a puzzle. When a piece disappears, another takes its place, playing the role that the other had in the community. However, knowing the whole ecological niche of a species is arduous and, in most cases, impossible. As in human relationships, an exhaustive knowledge of everything that influences the life of a species (or the living space of a person) is of great importance in order to ensure their long-term preservation.

REFERENCES

Ricard-anglès

Classification and phylogeny for beginners

In this blog, we usually use therms related with the classification of living beings and their phylogeny. Due to the difficulty of these therms, in this post we will explain them for those who are introducing to the topic. 

INTRODUCTION

Before introducing in the topic, it is necessary to explain two concepts, which are usually confused: systematics and taxonomy.

Systematics is the science of the classification and reconstruction of phylogeny, it means that is responsible for reconstructing the origin and diversification of a taxon (unit that we want to classify, such as a species, a family or an order).

On the other hand, taxonomy is the study of the principles of scientific classification, the order and the name of organisms.

In other words, while systematics is responsible for creating systems of classification, which are represented by trees, taxonomy establishes the rules and methods to identify, name and classify each species in the different taxonomic categories based on systematics.

ABOUT SPECIES AND BEYOND

We cannot begin to talk about how to classify species without knowing what is a species and other classification levels of organisms.

WHAT IS A SPECIES?

Along history, it has been given several definitions to the concept species with different approaches.

  • Morphological concept of species: a species is a group of organisms with fix and essential features that represent a pattern or archetype. This concept is totally discarded nowadays, despite morphological features are used in guides to identify species.

INFO-BALLENA
Despite all guides use morphological features to identify species, morphological concept of species is not used (Picture: Revista Viva).

  • Biological concept of species: a species is a group of natural populations which reproduce among them and reproductively isolated and have their own niche in nature. So, a species has common ancestry and share traits of gradual variation.  This definition has some problems: it is only applicable in species with sexual reproduction and it is not applicable in extinct species.
  • Evolutionary concept of species: a species is a single lineage of ancestor-descendent populations that maintains its identity in front of other lineages and has its evolutionary tendencies and historical destination. This approach and the biological one are, in fact, complementary because they are talking about different phenomenons.
  • Phylogenetic concept of species: according to this point of view, a species is an irreducible group of organisms, diagnostically distinguishable from other similar groups and inside which there is a parental pattern of ancestry and descendants.  This point of view covers sexual and asexual reproduction.

ensatina_phylogeny
According to the phylogenetic definition of species, A, B and C are different species. In the C group, all of them are the same species with different types (Picture: Sesbe).

BEYOND SPECIES

Species are classified into a hierarchical system based on more taxonomical categories. From the highest to the lowest category, organisms can be classified in: Domain> Kingdom> Phylum> Class> Order> Family> Genus> Species> Subspecies> Variety> Form. 

We are giving an example: imagine dogs.  Dogs, like wolf, are included in the same species: Canis lupus, but dog is the subspecies Canis lupus familiaris. The naming of a species is its genus (Canis) followed by the specific epithet (lupus). The other taxonomical categories of dogs are: Eukarya Domain, Animal Kingdom, Chordata Phylum, Vertebrata Subphylum, Mammalia Class, Carnivora Order and Canidae Family.

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Dogs and wolfs are included in the same species, but they are different subspecies (Picture: Marc Arenas Camps).

HOW IS TREE OF LIFE RECONSTRUCTED?

To reconstruct tree of life, it is the relationships between living and extinct species (phylogeny), we use traits. Traits are features of organisms that are used to study the variation inside a species and among them.

To reconstruct the phylogeny, it is used the shared traits among different taxa. We have to distinguish two types of similarity: when similarity of traits is a result of a common lineage is called homology, while when it is not the result of common ancestry is known as homoplasy.

Probably, it will be easier to understand it with an example. The wings of owls and quails are similar because they have the same origin (homology), but the wings of insects, birds and bats, despite they have the same function, they do not have the same origin (homoplasy).

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The wings of insects, birds and bats are an homoplasy (Picture: Natureduca).

There are three types of homoplasy:

  • Parallelism: the ancestral condition of a variable trait (plesiomorphic) is present in the common ancestor, but the derived state (apomorphic) has evolved independently. An example is the development of a four-cavity heart in birds and mammals.
  • Convergence: in this case, the homoplastic trait is not present in the common ancestor. The structures originated by convergence are called analogy. An example is the wings of insects and birds.
  • Secondary loss or reversion: consist on the reversion of a trait to a state that looks ancestral. So, it looks and old state but, in fact, is derived.

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Biological parallelism, convergence and reversion (Picture: Marc Arenas Camps).

There are different types of traits that are used to order living beings: morphological, structural, embryological, palaeontological, ethological, ecological, biochemical and molecular.

Species that share derived states of a trait constitute clades and the trait is known as synapomorphy. Synapomorphies are traits that were originated in a common ancestor and are present in that ancestor and all its descendants. So, mammary glands are a synapomorphy of mammals.

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Mammary glands are a synapomorphy of mammals (Picture: Tiempo de éxito).

After the selection of traits, the several classification schools use them in different ways to get the best relationship between living beings.

REFERENCES

  • Notes of the subject Advanced Biology Basics, Degree in Biology (University of Barcelona).
  • Hickman, Roberts, Larson, l’Anson & Eisenhour (2006). Principios integrales de zoología. Ed. McGraw Hill (13 ed).
  • Izco (2004). Botánica. Ed. McGraw Hill (2 ed).
  • Shnek & Massarini (2008). Biología. Ed. Médica Panamericana (7 ed).
  • Vargas (2009). Glosario de Cladística: Introducción a la sistemática filogenética.
  • Cover picture: Tree of life mural, Kerry Darlington

Difusió-anglès

Evolution for beginners

Biological evolution is still not well understood by general public, and when we speak of it in our language abound expressions that confuse even more how mechanisms that lead to species diversity work. Through questions you may have ever asked yourself, in this article we will have a first look at the basic principles of evolution and debunk misconceptions about it.

IS EVOLUTION REAL? IT IS NOT JUST A THEORY OR AN IDEA WITHOUT EVIDENCES?

Outside the scientific field, the word “theory” is used to refer to events that have not been tested or assumptions. But a scientific theory is the explanation of a phenomenon supported by evidence resulting from the application of the scientific method.

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The scientific method. Image by Margreet de Heer.

Theories can be modified, improved or revised if new data don’t continue to support the theory, but they are always based on some data, repeatable and verifiable experiments by any researcher to be considered valid.

So few people (sic) doubts about the heliocentric theory (the Earth rotates around the Sun), or the gravitational theory of Newton, but in the popular imagination some people believe that the theory of evolution made by Charles Darwin (and Alfred Russell Wallace) is simply a hypothesis and has no evidence to support it. With new scientific advances, his theory has been improved and detailed, but more than 150 years later, nobody has been able to prove it wrong, just the contrary.

WHAT EVIDENCE WE HAVE THAT EVOLUTION IS TRUE?

We have many evidences and in this post we will not delve into them. Some of the evidence available to us are:

  • Paleontological record: the study of fossils tell us about the similarities and differences of existing species with others thousands or millions old, and to establish relationships respect each other.
  • Comparative anatomy: comparison of certain structures that are very similar between different organisms, can establish whether they have a common ancestor (homologous structures, for example, five fingers in some vertebrates) if they have developed similar adaptations (analogous structures, for example, the wings of birds and insects), or if they have lost their function (vestigial organs, such as the appendix).

Homologous organs in humans, cats, whales and bats
Homologous organs in humans, cats, whales and bats

  • Embryology: the study of embryos of related groups shows a strong resemblance in the earliest stages of development.
  • Biogeography: The study of the geographical distribution of living beings reveals that species generally inhabit the same regions as their ancestors, although there are other regions with similar climates.
  • Biochemistry and genetics: chemical similarities and differences allow to establish relationships among different species. For example, species closely related to each other have a structure of their DNA more similar than others more distant. All living beings share a portion of DNA that is part of your “instructions”, so there are also found in a fly, a plant or a bacterium, proof that all living things have a common ancestor.

IS IT TRUE THAT ORGANISMS ADAPT TO THE ENVIRONMENT AND ARE DESIGNED FOR LIVING IN THEIR HABITAT?

Both expressions, frequently used, mean that living beings have an active role to adapt to the environment or “someone” has designed them to live exactly where they are. It is a typical example of Lamarck and giraffes: as a result of stretching the neck to reach the higher leaves of the treescurrently giraffes have this neck for giving it this use. They have a necessity, they change their bodies to success. It is precisely upside down: it is the habitat that selects the fittest, nature “selects” those that are most effective to survive, and therefore reproduce. It is what is known as natural selection, one of the main mechanisms of evolution. It needs three requirements to act:

  • Phenotypic variability: there must be differences between individuals. Some giraffes necks were slightly longer than others, just as there are taller people than others, with blue or brown eyes.
  • Biological fitness: this difference has to suppose an advantage. For example, giraffes with a slightly longer neck could survive and reproduce, while the others don’t.
  • Heredity: these characters must be transmitted to the next generation, the offspring will be slightly different to that feature, while “short neck” feature transmits less and less.

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The variability in the population causes individuals with favorable characteristics to reproduce more and pass on their genes to the next generation, increasing the proportion of those genes. Image taken from Understanding evolution

Over the years these changes are accumulated until the genetic differences are so big that some populations may not mate with others: a new species has appeared.

If you thought that this is similar to artificial selection that we do with the different breeds of dogs, cows who give more milk, trees bearing more fruit and larger, congratulations, you think like Darwin as it was inspired by some of these facts. Therefore, living beings are mere spectators of the evolutionary process, depending of changes in their habitat and their genetic material.

WHY ORGANISMS ARE SO DIVERSE?

Genetic variability allows natural selection act. Changes in the genetic material (usually DNA) are caused by:

  • Mutations: changes in the genome that may be adverse or lethal for survival, indifferent or beneficial to survival and reproduction. If they have benefits, they will pass to the next generations.
  • Gene flow: is the motion of genes between populations (migration of individuals allows this exchange when mate with others in a different population).
  • Sexual reproduction: allows recombination of genetic material of different individuals, giving rise to new combinations of DNA.

Populations that have more genetic variability are more likely to survive if happen any changes in their habitat. Populations with less variability (eg, being geographically isolated) are more sensitive to any changes in their habitat, which may cause their extinction.

Evolution can be observed in beings with a very high reproduction rate, for example bacteria, since mutations accumulate more quickly. Have you ever heard that bacteria become resistant to our antibiotics or some insects to pesticides? They evolve so quickly that within a few years were selected the fittest to survive our antibiotics.

ARE WE THE MOST EVOLVED ANIMALS?

Theory of Evolution has various consequences, such as the existence of a common ancestor and that therefore, that we are animals. Even today, and even among the young ones, there is the idea that we are something different between living beings and we are in a special podium in the collective imagination. This anthropocentric thinking caused Darwin mockery and confrontations over 150 years ago.

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Caricature of Darwin as an orangutan. Public domain image first published in 1871

We use our language to be “more evolved” as a synonym for more complex, and we consider ourselves one species that has reached a high level of understanding of their environment, so many people believe that evolution has come to an end with us.

The question has a mistake of formulation: actually evolving pursues no end, it just happens, and the fact that millions of years allows the emergence of complex structures, it does not mean that simpler lifeforms are not perfectly matched in the habitat where they are. Bacteria, algae, sharks, crocodiles, etc., have remained very similar over millions of years. Evolution is a process that started acting when life first appeared and continues to act in all organisms, including us, although we have changed the way in which natural selection works  (medical and technological breakthroughs, etc.).

SO IF WE COME FROM MONKEYS, WHY DO STILL MONKEYS EXIST?

The truth is that we don’t come from monkeys, we are monkeys, or to be more rigorous, apes. We have not evolved from any existing primate. As we saw in a previous post, humans and other primates share a common ancestor and natural selection has been acting differently in each of us. That is, evolution has to be viewed as a tree, and not as a straight line, where each branch would be a species .

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First scheme of the evolutionary tree of Darwin in his notebook (1837). Public domain image.

Some branches stop growing (species become extinct), while others continue to diversify. The same applies to other species, in case you have asked yourself, “if amphibians come from fish, why are there still fish?”. Currently, genetic analyzes have contributed so much data that they make so difficult to redesign the classical Dariwn’s tree.

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Classification of live organisms based on the three domains Archaea, Bacteria and Eukarya, data of Carl R. Woese (1990). Included in Eukarya there are the Protista, Fungi, Plantae and Animalia kingdoms. Image by Rita Daniela Fernández.

Evolution is a very broad topic that still generates doubts and controversies. In this article we have tried to bring to uninitiated people some basics, where we can delve into the future. Do you have any questions about evolution? Are you interested into a subject that we have not talked about? You can leave your comments below.

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY