Sentences with phrase «theories of change vary»

Not exact matches

Here's the rest of it:»... Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case; and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory.

Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certain the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case; and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, should not be considered as subversive of the theory.»

They appear in the fossil record and immediately grow abundant and varied, creating a problem for his theory of slow but continuous change.

A few groups pursued the study of possible mechanisms, for example elaborating theories of how changes in the atmosphere's electric circuit, which varies with the flux of cosmic rays, affected precipitation in the Arctic, Ram et al. (2009), or devising experiments that they hoped would show a direct and strong effect of cosmic rays on clouds, e.g., Svensmark et al. (2007)(which brought a strong press reaction but proved little).