Now and Nine Years Ago Essays
Introduction: Themes in the Study of Life
Overview: Inquiring About the World of Life
• Organisms are adapted to the environments they live in.
• These adaptations are the result of evolution, the fundamental organizing principle of biology.
• Posing questions about the living world and seeking science-based answers are the central activities of biology, the scientific study of life.
• Biologists ask a wide variety of ambitious questions.
o They may ask how a single cell becomes a tree or a dog, how the human mind works, or how the living things in a forest interact.
• Biologists can help answer questions that affect our lives in practical ways.
• Research breakthroughs in genetics and cell biology are transforming medicine and agriculture.
o Molecular biology is providing new tools for anthropology and criminal science.
o Neuroscience and evolutionary biology are reshaping psychology and sociology.
o New models in ecology are helping society evaluate environmental issues, such as the causes and biological consequences of global warming.
• What is life?
o The phenomenon of life defies a simple, one-sentence definition.
Concept 1.1 Themes help connect the concepts of biology.
• Seven unifying themes will help you organize and make sense of biological information.
Theme 1: Evolution is the core theme of biology, the one idea that makes sense of everything we know about living organisms.
• Life has been evolving on Earth for billions of years, resulting in a vast diversity of past and present organisms.
• At the same time, living things share certain features.
• The scientific explanation for this unity and diversity is evolution: the idea that the organisms living on Earth today are the modified descendants of common ancestors.
• In other words, scientists can explain traits shared by two organisms with the idea that they have