Natural Selection, Species Isolation and Real World Example

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`Natural selection' is the process in which organisms with adaptive traits survive and breed in greater number than organisms without such traits. Eventually, almost all of the individuals in the population will have the same adaptive trait. This was the concept presented by Charles Darwin in his book On the Origin of Species. It's also important to point out something else that's going on in our beetle experiment. The green beetles only live in the leaves. The brown beetles only live on the branches. If they ever come together in order to mate, they will be eaten. So, these two types of beetles are now reproductively isolated. This means that over time, this one species of beetle may become two different species with different adaptive traits. Natural selection doesn't just happen with beetles or even just with animals. Organisms are evolving all the time. One of the best examples of natural selection happening in everyday life is antibiotic resistance. When you get an infection, it is usually caused by bacteria. Antibiotics are chemicals that kill bacteria. But, when you take an antibiotic, some of the individual bacteria cells may be resistant to the antibiotic and not be killed. This usually isn't a problem because your immune system can deal with a few stragglers. But over time, those resistant bacterial cells tend to survive and reproduce more than their non-resistant cousins. Eventually, most of the bacteria cells in a region will be resistant to the antibiotic. and the medicine no longer has any effect on the infections. Diseases such as tuberculosis, gonorrhea, and childhood ear infections are now more difficult to treat than they were just a few decades ago. Drug resistance is an especially difficult problem for hospitals with critically ill patients who are less able to fight off infections without the help of antibiotics.

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