_{Professor of the Graduate School and Robert S. Pepper Distinguished Professor Emeritus in the Electrical Engineering and Computer Science (EECS) Department at UC Berkeley. Ph.D. - UC Berkeley.}

Evolutionary biology is the study of how living organisms have changed over time. It is a broad field that encompasses many different aspects of biology, including genetics, ecology, and morphology. The central idea of evolutionary biology is that all living organisms are related and have evolved from a common ancestor over millions of years.

The theory of evolution by natural selection, proposed by Charles Darwin and Alfred Russel Wallace in the 19th century, is the foundation of evolutionary biology. It states that organisms that are better adapted to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring. Over time, these advantageous traits become more common in a population, leading to the evolution of new species.

One of the key concepts in evolutionary biology is the concept of speciation, which is the process by which one species splits into two or more separate species. This can happen through a variety of mechanisms, such as geographic isolation, genetic drift, and polyploidy.

Evolutionary biologists also study the patterns and processes of evolution at different levels, such as the molecular, genetic, population, and species levels. For example, molecular evolution is the study of how genes and proteins change over time, while population genetics is the study of genetic variation within and among populations.

Evolutionary biology also has important implications for understanding the diversity of life on Earth, as well as for understanding the relationships between different organisms. This knowledge can be used to help protect endangered species and to understand the impact of human activities on biodiversity.

The field of evolutionary biology is also closely linked to other fields, such as ecology, genetics, and anthropology. For example, ecologists use evolutionary biology to understand how organisms interact with their environment, while geneticists use evolutionary biology to understand how genes and genomes change over time.

Overall, evolutionary biology is a fascinating and important field that helps us understand the history and diversity of life on Earth. It draws on many different disciplines and provides a framework for understanding the past, present, and future of life on our planet.