Changes

Changes of a species from its normal state are called [[mutation]]s. Sometimes they happen on their own, but they can also happen when a parent is exposed to something that will affect the way they reproduce. High doses of [[X-rays]] can produce mutations, and so can some chemicals. According to the [[theory of natural selection]], most mutations are neutral, some are deleterious (harmful), and a very small proportion are beneficial such that they improve the individual's chance of survival and reproduction, thus passing on to the next generation. Some mutations can be both helpful and harmful. For example, people from some [[Africa]]n countries carry a gene for an illness called [[sickle-cell anemia]]. This illness causes health problems, but people who have the gene for sickle-cell anemia are also less likely to catch [[malaria]], a serious illness common in Africa.

Changes of a species from its normal state are called [[mutation]]s. Sometimes they happen on their own, but they can also happen when a parent is exposed to something that will affect the way they reproduce. High doses of [[X-rays]] can produce mutations, and so can some chemicals. According to the [[theory of natural selection]], most mutations are neutral, some are deleterious (harmful), and a very small proportion are beneficial such that they improve the individual's chance of survival and reproduction, thus passing on to the next generation. Some mutations can be both helpful and harmful. For example, people from some [[Africa]]n countries carry a gene for an illness called [[sickle-cell anemia]]. This illness causes health problems, but people who have the gene for sickle-cell anemia are also less likely to catch [[malaria]], a serious illness common in Africa.

==References==

==References==