Sinopsis
Biology is a subject of enormous scope, and news reports reveal exciting new biological discoveries being made every day. Simply memorizing the factual details of this huge subject is most likely not the best way to develop a coherent view of life. A better approach is to take a more active role by connecting the many things you learn to a set of themes that pervade all of biology. Focusing on a few big ideas—ways of thinking
about life that will still hold true decades from now—will help you organize and make sense of all the information you’ll encounter as you study biology. To help you, we have selected eight unifying themes to serve as touchstones as you proceed through this book.
The study of life extends from the microscopic scale of the molecules and cells that make up organisms to the global scale of the entire living planet. We can divide this enormous range into different levels of biological organization. Imagine zooming in from space to take a closer and closer look at life on Earth. It is spring in Ontario, Canada, and our destination is a local forest, where we will eventually explore a maple leaf right down to the molecular level. Figure 1.4, on the next two pages, narrates this journey into life, with the numbers leading you through the levels of biological organization illustrated by the photographs.
If we now zoom back out from the molecular level in Figure 1.4, we can see that novel properties emerge at each step, properties that are not present at the preceding level. These emergent properties are due to the arrangement and interactions of parts as complexity increases. For example, although photosynthesis occurs in an intact chloroplast, it will not take place in a disorganized test-tube mixture of chlorophyll and other chloroplast molecules. Photosynthesis requires a specific organization of these molecules in the chloroplast. To take another example, if a blow to the head disrupts the intricate architecture of a human brain, the mind may cease to function properly even though all of the brain tissues are still present. Our thoughts and memories are emergent properties of a complex network of nerve cells. At a much higher level of biological organization—at the ecosystem level—the recycling of chemical elements essential to life, such as carbon, depends on a network of diverse organisms interacting with each other and with the soil, water, and air.
Emergent properties are not unique to life. A box of bicycle parts won’t take you anywhere, but if they are arranged in a certain way, you can pedal to your chosen destination. And while the graphite in a pencil “lead” and the diamond in a wedding ring are both pure carbon, they have very different appearances and properties due to the different arrangements of their carbon atoms. Both of these examples point out the importance of arrangement. Compared to such nonliving examples, however, the unrivaled complexity of biological systems makes the emergent properties of life especially challenging to study.
Because the properties of life emerge from complex organization, scientists seeking to understand biological systems confront a dilemma. On the one hand, we cannot fully explain a higher level of order by breaking it down into its parts. A dissected animal no longer functions; a cell reduced to its chemical ingredients is no longer a cell. Disrupting a living system interferes with its functioning. On the other hand, something as complex as an organism or a cell cannot be analyzed without taking it apart.
Reductionism—the approach of reducing complex systems to simpler components that are more manageable to study— is a powerful strategy in biology. For example, by studying the molecular structure of DNA that had been extracted from cells, James Watson and Francis Crick inferred, in 1953, how this molecule could serve as the chemical basis of inheritance. The central role of DNA in cells and organisms became better understood, however, when scientists were able to study the interactions of DNA with other molecules. Biologists must balance the reductionist strategy with the larger-scale, holistic objective of understanding emergent properties—how the parts of cells, organisms, and higher levels of order, such as ecosystems, work together. This is the goal of an approach developed over the last 50 years called systems biology.
Content
- The Chemistry of Life
- The Chemical Context of Life
- Water and Life
- Carbon and the Molecular Diversity of Life
- The Structure and Function of Large Biological Molecules
- The Cell
- A Tour of the Cell
- Membrane Structure and Function
- An Introduction to Metabolism
- Cellular Respiration and Fermentation
- Photosynthesis
- Cell Communication
- The Cell Cycle
- Genetics
- Meiosis and Sexual Life Cycles
- Mendel and the Gene Idea
- The Chromosomal Basis of Inheritance
- The Molecular Basis of Inheritance
- From Gene to Protein
- Regulation of Gene Expression
- Viruses
- Biotechnology
- Genomes and Their Evolution
- Mechanisms of Evolution
- Descent with Modification: A Darwinian View of Life
- The Evolution of Populations
- The Origin of Species
- The History of Life on Earth
- The Evolutionary History of Biological Diversity
- Phylogeny and the Tree of Life
- Bacteria and Archaea
- Protists
- Plant Diversity I: How Plants Colonized Land
- Plant Diversity II: The Evolution of Seed Plants
- Fungi
- An Overview of Animal Diversity
- An Introduction to Invertebrates
- The Origin and Evolution of Vertebrates
- Plant Structure, Growth, and Development
- Resource Acquisition and Transport in Vascular Plants
- Soil and Plant Nutrition
- Angiosperm Reproduction and Biotechnology
- Plant Responses to Internal and External Signals
- Plant Form and Function
- Animal Form and Function
- Basic Principles of Animal Form and Function
- Animal Nutrition
- Circulation and Gas Exchange
- The Immune System
- Osmoregulation and Excretion
- Hormones and the Endocrine System
- Animal Reproduction
- Animal Development
- Neurons, Synapses, and Signaling
- Nervous Systems
- Sensory and Motor Mechanisms
- Animal Behavior
- Ecology
- An Introduction to Ecology and the Biosphere
- Population Ecology
- Community Ecology
- Ecosystems and Restoration Ecology
- Conservation Biology and Global Change
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