Nervous function, three seconds and a goal

We are not usually aware of everything that surrounds us in our reality and all the number of decisions that our bodies must make in fractions of a second. Or, how our nervous system works and keeps our body connected to the world, how it analyses all the stimuli which we receive and also how it manages precise and concrete actions.

Let’s imagine this situation. A football match, twenty four seconds into the fifty third minute. (52:24)

The score: nil, nil.

The centre forward crosses the middle of the pitch towards the opponents' penalty box. A lot of information arrives in his brain, from his sensory system: his skin sends information about the atmospheric temperature and even about the slight breeze that blows around him; his ears are perceiving the shouts of the crowd and his team mates; he can even notice the smell of the mown grass and humidity of the air wetting the inner surface of his nose.

But only the autonomous part of his brain is reacting to these stimuli, producing sweat, making his body hair stand up on end. The conscious part of his brain, however, is unaware of all this information due to a general phenomena called lateral inhibition. His brain is totally concentrated on things that are supposed really important: the ball, the goal, the goalkeeper and his position.

The centre forward looks at the ball. The light from the sun impacts against the ball, the grass and the goalkeeper, and all this matter reflects the light, that crosses the air and is arrived at the eyes of our player. It moves through the cornea, then goes the iris and the lens that focuses it on the retina. There, the visual information is transformed into an electric impulse that exits the eye via the optic nerve. (1b)

Consecuencias de la Evolución

Especiación y Deriva Génica: Aparición de Nuevas Especies

La especiación trata de explicar el proceso que tiene lugar en los grupos de individuos y que acaban dando lugar a la aparición de nuevas especies.

Se admite cuando dos comunidades de individuos de la misma especie dejan de tener relaciones entre sí y de cruzar sus genes, la distancia genética se irá ampliando. Esto se debe a que las mutaciones de cada grupo no se compartirán, cada grupo tendrá sus mutaciones azarosas y se irán adaptando al medio que les rodea de forma independiente.

El genotipo de los individuos de las dos poblaciones separadas se irá haciendo cada vez más diferente. La evolución de los distintos genotipos de las comunidades debido a mutaciones azarosas se denomina Deriva Génica. Dos comunidades separadas tendrán procesos de deriva génica distintas y por lo tanto tenderán a mostrar diferencias cada vez más acusadas. Si a esto unimos que sobre ambas comunidades pueden actuar factores ambientales distintos, en un espacio de tiempo acabaremos obteniendo comunidades con organismos incapaces de reproducirse entre sí, es decir, comunidades cuyos miembros ya pertenecen a especies distintas. En resumen, los distintos procesos de deriva génica acabarán dando lugar a que dos poblaciones separadas acaben dando lugar a dos especies distintas.