Descent with Modification: A Darwinian View of Life

 Keen observers of living things have long noted that organisms are well suited to their environments, that there is a rich diversity of life on Earth, and that life shows a striking unity.  Charles Darwin’s fascination with ―endless forms most beautiful‖ led him to propose a scientific explanation for these broad observations.  On November 24, 1859, Darwin published his hypothesis in On the Origin of Species by Means of Natural Selection, ushering in the era of evolutionary biology.  Darwin defined evolution as descent with modification, proposing that Earth’s many species are descendants of ancestral species that were very different from those alive today. ○ Evolution can also be defined more narrowly as a change in the genetic composition of a population over time.  Evolution is both a pattern and a process. ○ The pattern of evolutionary change is revealed in observations about the natural world. ○ The process of evolution consists of the mechanisms that have produced the diversity and unity of living things.