Extinciones masivas a lo largo de la historia de la tierra.
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2016-07-12
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Jaén: Universidad de Jaén
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[ES]Cuando pensamos o escuchamos la palabra extinción, quizás pensemos que solo tiene aspectos negativos, pero este concepto va mucho más allá. Si profundizamos podremos encontrar en él tanto facetas positivas como negativas. La parte positiva es la aparición de nuevas especies que sigue a todo proceso de extinción, especialmente si se trata de extinciones masivas, mientras que en las negativas tendremos, por el contrario, la desaparición de un organismo o de un cierto porcentaje de la biodiversidad existente.
Tras la aparición de las primeras formas de vida hace aproximadamente unos 3.500 millones de años, han ocurrido cinco grandes extinciones masivas, también llamadas “Extinciones en masa “. Pero en ningún caso ello ha supuesto el fin de la vida, por supuesto que no, ya que a toda gran extinción le sigue una gran revolución evolutiva.
De hecho, tras la extinción del límite K-T (que será en la que más se profundice en este trabajo), que ocurrió hace unos 66 millones de años y en la que desapareció aproximadamente el 11% de las especies existentes en el planeta, nació la biodiversidad que conocemos en la actualidad. Algunos de los actuales linajes de mamíferos han evolucionado gracias a esa extinción, dotándolos de un hábitat más tranquilo, con menos depredadores, en el que interaccionar y evolucionar les fuese más fácil.
[EN]When we think or hear the word extinction, we may think that only negative aspects are involved, but this concept goes far beyond. When we delving into it, we will find both positive and negative aspects. The good piece of news is the emergence of new species following any process of extinction, especially if it comes to mass extinctions, while the negative piece of news, on the contrary, is the disappearance of an organism or a certain percentage of the existing biodiversity. 5 After the appearance of the first forms of life approximately 3,500 million years ago, there have been five major massive extinctions, also called "Mass Extinctions". But any of these events have represented the end of the life, of course no, because every great extinction is followed by a great evolutionary revolution. For example, the KT boundary extinction (in which we will deepen later), occurred some 66 million years ago and caused the dissapearance of about the 11% of the species accommodated on the planet. But, after this extinction, the currently existing biodiversity was born. Some of the current lineages of mammals have evolved from this extinction, which provided them with a quieter habitat, with fewer predators, and in which to interact and to evolve among them was easier.
[EN]When we think or hear the word extinction, we may think that only negative aspects are involved, but this concept goes far beyond. When we delving into it, we will find both positive and negative aspects. The good piece of news is the emergence of new species following any process of extinction, especially if it comes to mass extinctions, while the negative piece of news, on the contrary, is the disappearance of an organism or a certain percentage of the existing biodiversity. 5 After the appearance of the first forms of life approximately 3,500 million years ago, there have been five major massive extinctions, also called "Mass Extinctions". But any of these events have represented the end of the life, of course no, because every great extinction is followed by a great evolutionary revolution. For example, the KT boundary extinction (in which we will deepen later), occurred some 66 million years ago and caused the dissapearance of about the 11% of the species accommodated on the planet. But, after this extinction, the currently existing biodiversity was born. Some of the current lineages of mammals have evolved from this extinction, which provided them with a quieter habitat, with fewer predators, and in which to interact and to evolve among them was easier.