EVOLUTION IN ACTION
Darwin envisioned natural selection acting so slowly that its effects would be imperceptible in a human lifetime. But in the late 1900s, evolutionary biologists began to detect small but significant changes taking place in a handful of species. In the past decade, many more cases of natural selection have come to light, and scientists now realize that species can adapt quickly to changes in their environment. In fact, they are finding that we humans are unwittingly driving some of the fastest bursts of evolution right now. As greenhouse gases drive up the planet's average temperature, for instance, some species are adapting to the changing climate. In California, University of Toronto biologist Arthur Weis and his colleagues found that a seven-year drought had spurred the evolution of field mustard plants. In 2007, they reported that the plants were now genetically programmed to flower eight days earlier in the spring. http://www.pbs.org/wgbh/nova/evolution/ten-great-advances-evolution.html
natural selection, evolution, mutation, variation, heritability, and fitness.
Field mustard. Between 2000 and 2004, southern California had a severe drought. For many plants, including field mustard (a scrawny annual plant with little yellow flowers), a drought means a shorter growing season. A shorter growing season means that plants that flower earlier are more likely to leave seeds than plants that flower later — which are in danger of dying before they’ve finished reproducing. Since flowering time has a large genetic component, a drought — by favoring plants that flower earlier — could cause an evolutionary shift towards early flowering. Has it?
Yes. The beauty of plants is that they make seeds — small packets of genes that can be stored for a period. This means that the genes of the past can, in principle, be compared directly with the genes of today. And an...