Early scientists of evolution did not explain how the major changes that created new species of organisms began. The work of botanists in the 1890s first helped explain the question of evolutionary development. Hugo de Vries studied genetic families in a flower called the evening primrose. He noticed that sometimes traits would appear in new plants that were not there before. The trait could not be found anywhere in the parents of the plant. De Vries believed that it began because of a sudden change of a specific gene. Genes are biological codes for inherited traits. They are passed from parent to offspring. They determine things such as hair color, paw size, or wingspan. De Vries believed that a change of this code introduces new characteristics. In addition, these characteristics can then be passed to future offspring. He called such hereditary changes mutations
People who study genes today understand mutations as a change in the order of deoxyribonucleic acid or DNA. DNA is made up of individual units called nucleotides. These nucleotides form long spiraling chains. The location of nucleotides along the DNA chain determines the characteristics of an organism. DNA provides the genetic information for living organisms in the same way that the hard drive of a computer carries information. Just as a picture on a computer screen becomes distorted when one changes its digital coding, a mutation happens when a specific sequence of DNA is altered. Mutations may involve the removing or changing of only one or a few nucleotides. The result, however, may be very dramatic.
Many mutations are harmful and can even kill an organism. For example, if one were to randomly change a setting in the hard drive of a computer, the result to would be harmful rather than helpful. Every once in a while, however, a mutation gives an organism a certain advantage over other individuals. For example, webbed toes allow for faster swimming. Similarly, thicker coats allow for being able to live in cold temperatures. These changes help on organism live. The trait is then passed on its offspring. These offspring are more likely to survive and produce other offspring that will also live. Thus, through mutation, a species can develop characteristics that allow it to live in different environments.
Scientists believe that most mutations are caused by mistakes in the DNA replication during reproduction or development. Mutations can also be a result of exposure to things in the environment. These are called mutagens. Some mutagens occur naturally. Ultraviolet radiation from the sun, for example, can damage DNA. It does so by changing the chemical structure of nucleotides. Many organisms have evolved ways to repair the damage by removing and replacing altered nucleotides. Too much exposure to ultraviolet radiation, however, is one of the leading causes of cancer. This is particularly true of skin cancer in humans. Other forms of radiations include cosmic rays, x-rays, and the emissions of radioactive materials. They also produce mutagenic effects.
People have created other mutagens that are now in the earth's environment. Many industrial chemicals change genetic sequencing by changing the nucleotides of DNA. The first chemical mutagen discovered was mustard gas. Mustard gas was developed during World War I as a way to kill the enemy. Since then, many chemicals have been created that cause mutations. Examples include insecticides and food preservatives. Many mutations caused by chemicals lead to different kinds of cancer. These chemicals are often referred to as carcinogens. The number of these chemicals in the environment can affect the number of mutations in an organism. Many people are concerned that more chemical mutations may be a danger to humans. Despite all of the negative things that can happen with genetic mutations, they are still an important part of survival. Without mutations, species would not have the ability to adapt to new environments. Such mutations in a species are necessary for survival in earth's constantly changing environment.