Talk:Introduction to evolution/LEAD

Biological evolution is the change of all groups of living things over time. The theory of evolution is an explanation for these observed changes. The theory of evolution includes the idea that all life on earth now and in the past is related, forming a large family.

Evolution results because not all organisms are the same as their parents or each other. Sometimes, a difference gives one organism an advantage, and this organism is more able to survive and reproduce because of its special difference. If this difference is also inherited by the offspring of the different organism, the offspring will be more able to survive and reproduce, passing along the special difference, and maybe some new differences as well. As these changes in add up, generation after generation, the group of organisms change over time. This change is called evolution.

The changes that are inherited are called "traits", and are passed along to offspring because the instructions for making the traits are passed along to the offspring. These instructions are written out in long molecules called DNA. The instructions are written in letters, which are grouped into word-like units, called "genes".

Changes in these genes, called (mutations), can become a new feature in the offspring of a living organism. These new features are almost always just minor changes. Because no two organisms have exactly the same traits, they will live and reproduce differently, some more effectively than others. Scientists call this process natural selection. Over time, favorable traits become more common in the descendents of the organisms. Over many generations, new traits accumulate in a population to such a degree that the organism has changed and scientists recognize it as a new species. The result of four billion years of evolution is the diversity of life around us, and it is estimated that 1.75 million different species are alive today.

Evolutionary biology is the study of evolution, especially the natural processes that led to the variety of organisms alive today and produced innumerable varieties that are long extinct. The understanding of evolutionary biology has advanced far beyond the pioneering work of Charles Darwin in the mid-19th century. The next important step brought in Gregor Mendel's research work with plants, which helped to explain the hereditary patterns of genetics. This led to an understanding of the mechanisms of inheritance in the modern evolutionary synthesis of the 1930s. The discovery of the structure of DNA and advances in the field of population genetics provided insight into the source of variations in organisms. With the benefit of modern research, scientists are getting a better understanding of speciation, the development of new species from ancestral species. Research by scientists in many different fields confirms evolution as the principal theory that governs our understanding of animals, plants, farming, medicine, dinosaurs and any other scientific or technical field that is involved with living things.