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 evolution]], most mutations will be harmfulare neutral, but some will help are deleterious (harmful), and a member very small proportion are beneficial such that they improve the individual's chance of a species to survive survival and will pass reproduction, thus passing on to its offspringthe 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.