Quotes About Adaptation

The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind.

interpositions

the structure of every organic being is related, in the most essential yet often hidden manner, to that of all the other organic beings ...

It has already been stated that various parts in the same individual, which are exactly alike during an early embryonic period, become widely different and serve for widely different purposes in the adult state. So again it has been shown that generally the embryos of the most distinct species belonging to the same class are closely similar, but become, when fully developed, widely dissimilar.

I find I look at this province with very different eyes then when I arrived. I recollect I then thought of it as singularly level, but now after galloping over the montañas my own only surprise is what could have induced me to have ever called it level!

El aislamiento también es un elemento importante en la modificación de las especies por medio de la selección natural. En un área limitada o aislada, si no es muy grande, serán generalmente casi uniformes las condiciones orgánicas e inorgánicas de la vida, de modo que la selección natural tenderá a modificar de la misma manera a todos los individuos que varíen en la misma especie.

Charles Darwin

It is so easy to hide our ignorance under such expressions as the plan of creation, unity of design

Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare? Yet these relations are of the highest importance, for they determine the present welfare, and, as I believe, the future success and modification of every inhabitant of this world.

puede llegar a deducir que las especies no han sido creadas independientemente, sino que han descendido como variedades de otras especies.

As the species of the same genus usually have, though by no means invariably, much similarity in habits and constitution, and always in structure, the struggle will generally be more severe between them, if they come into competition with each other, than between the species of distinct genera.

Some highly competent authorities are convinced that the setter is directly derived from the spaniel, and has probably been slowly altered from it. It is known that the English pointer has been

immutable productions

Judging from the past, we may safely infer that not one living species will transmit its unaltered likeness to a distant futurity.

like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which most justly excites our admiration. Naturalists continually refer to external conditions, such as climate, food, etc., as the only possible cause of variation. In one very

Charles Darwin

I have called this principle, by which each slight variation, if useful, is preserved, by the term natural selection, in order to mark its relation to man's power of selection. But the expression often used by Mr. Herbert Spencer, of the Survival of the Fittest, is more accurate, and is sometimes equally convenient.

unusual degree. This family became divided eight generations

In a series of forms graduating insensibly from some apelike creature to man as he now exists, it would be impossible to fix on any definite point where the term 'man' ought to be used.

We here see in two distant countries a similar relation between plants and insects of the same families, though the species of both are different. When man is the agent in introducing into a country a new species this relation is often broken:

In the latter country alone, very many (probably several hundred) square miles are covered by one mass of these prickly plants, and are impenetrable by man or beast. Over the undulating plains, where these great beds occur, nothing else can now live. Before their introduction, however, the surface must have supported, as in other parts, a rank herbage. I doubt whether any case is on record of an invasion on so grand a scale of one plant over the aborigines.

It was evident that such facts as these, as well as many others, could only be explained on the supposition that species gradually become modified; and the subject haunted me.

Pueden los instintos adquirirse y modificarse por medio de la selección natural? ¿Qué diremos del instinto que lleva a la abeja a hacer celdas, y que prácticamente se ha adelantado a los descubrimientos de notables matemáticos?

Dos animales caninos, en tiempo de hambre, luchan mutuamente por conseguir el alimento que necesitan; pero la planta que nace en los linderos del desierto lucha por la existencia contra la sequía, aunque con más propiedad se diría que depende de la humedad.