Evolution
Urban environments can exert novel selective pressures on organisms sometimes leading to new adaptations. For example, the weed Crepis Sancta, found in France, has two types of seed, heavy and fluffy. The heavy ones land near the parent plant, whereas the fluffy seeds float further away on the wind. In urban environments, seeds that float far often land on infertile concrete. Within about 5-12 generations the weed has been found to evolve to produce significantly more heavy seeds than its rural relatives. Among vertebrates, a case is urban great tits, which have been found to sing at a higher pitch than their rural relatives so that their songs stand out above the city noise, although this is probably a learned rather than evolved response. Urban silvereyes, an Australian bird, make contact calls that are higher frequency and slower than those of rural silvereyes. As it appears that contact calls are instinctual and not learnt, this has been suggested as evidence that urban silvereyes have undergone recent evolution so as to better communicate in noisy urban environments.
Read more about this topic: Urban Wildlife
Famous quotes containing the word evolution:
“What we think of as our sensitivity is only the higher evolution of terror in a poor dumb beast. We suffer for nothing. Our own death wish is our only real tragedy.”
—Mario Puzo (b. 1920)
“The evolution of sense is, in a sense, the evolution of nonsense.”
—Vladimir Nabokov (1899–1977)
“By contrast with history, evolution is an unconscious process. Another, and perhaps a better way of putting it would be to say that evolution is a natural process, history a human one.... Insofar as we treat man as a part of nature—for instance in a biological survey of evolution—we are precisely not treating him as a historical being. As a historically developing being, he is set over against nature, both as a knower and as a doer.”
—Owen Barfield (b. 1898)