Millions of super-rats are overrunning the United Kingdom. Big, beefy and fearless, they lurk around every corner. These are the Jean-Claude Van Dammes and Jet Lis of rodents, and they eat rat poison for breakfast.
Sounds like the premise of a bad B-movie, doesn't it? Unfortunately, these tough pests are the real deal. The so-called "super-rats" really do plague Great Britain, and their resistance to pesticides is one way we can see evolution in everyday life.
England's super-rats have developed a resistance to common rat poison, thanks to the evolutionary process called natural selection. Years ago, in order to deal with overwhelming rat infestations, many people in England started trapping problem areas with rodenticide. At first, the traditional rat poisons proved effective at killing their targets. But a few especially strong rats ate these poisons and survived. When these poison-resistant rats bred, they passed along their poison-resistant genes to their offspring. Then the offspring survived and bred, producing yet another resistant generation. In time, most of the weaker rats died off, leaving a new breed of rodents that could chow down on what used to be lethal doses of poison without even becoming sick [source: Barkham]. This is how natural selection works: Successful genes begin to dominate the gene pool, and eventually the entire population evolves in a way that's beneficial for long-term survival.
It's not just rats who've evolved to develop a resistance to pesticides. Some species of insects and even weeds have done the same. It may not seem like such a big deal that nature is evolving for its own survival, but pesticide-resistant animals and plants are a big problem for farmers. These genetic super-pests pose a real threat to farmers' bottom lines -- and, more importantly, the world's food supply.
It may seem like there's no way to combat the process of natural selection, but scientists say that simply decreasing our dependence on chemical pesticides may help solve the problem of super-pests. There are natural ways of deterring pests. For example, farmers can bring in certain species of birds to pick off rats on the farm. Of course, evolution by means of natural selection will still win the day. If enough farmers follow this method, they may inadvertently end up breeding new generations of rats who are especially good at avoiding avian predators.
Many people don't believe the theory of evolution - - which explains how life and people arose through a natural process - - even though we can see signs of it around us every day. The theory of evolution is made up of three parts:
• A change in a species' DNA is only considered a mutation if it affects the species' offspring or the species' descendents.
• Only the best species can reproduce, and thus, survive. This isn't a result of some mandated policy to do away with one species. Instead, the better species withstands the forces of nature. This is called "natural selection."
• As a species' mutations spread and become more pronounced, new species evolve.
In the world of medicine, doctors often find that medications they've prescribed for years suddenly become ineffective. This is because new strains of bacteria develop and evolve. Farmers find that their insecticides no longer keep pesky insects in check. New "versions" of the old insects are not affected by the old insecticides because they have undergone an evolutionary process. The new insects and bacteria are living proof of evolution's theory of natural selection. If the change is beneficial, the new version survives. In the examples, the bacteria survive because mutations have eventually made the bacteria immune to the medications. Similarly, insects have evolved new traits that make old insecticides harmless.
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