Concept 1.1: The Study of Life Reveals Common Themes

Five Unifying Themes in Biology

Biology is the scientific study of life, and its complexity is organized around several unifying themes that help us make sense of biological information.

• Organization: Life is structured in a hierarchical manner, from molecules to the biosphere.

• Information: Living organisms store, transmit, and use information, primarily in the form of DNA.

• Energy and Matter: Life requires the transfer and transformation of energy and matter.

• Interactions: Organisms interact with each other and their environment.

• Evolution: Evolution is the fundamental organizing principle of biology, explaining both the unity and diversity of life.

Theme 1: New Properties Emerge at Successive Levels of Biological Organization

Biological organization is based on a hierarchy of structural levels, each building on the levels below. Each level of biological organization has emergent properties—new characteristics that arise from the arrangement and interactions of parts as complexity increases.

• Biological Molecules: At the lowest level, atoms are ordered into complex molecules.

• Cells: Molecules are organized into organelles, which make up cells—the fundamental unit of structure and function in living things.

• Tissues, Organs, and Organ Systems: In multicellular organisms, cells form tissues, which form organs, which form organ systems.

• Organisms: Individual living things.

• Populations: Groups of individuals of the same species living in a particular area.

• Communities: All the organisms in a particular ecosystem.

• Ecosystems: Communities plus the nonliving environment.

• Biosphere: All life on Earth and all the places where life exists.

Emergent properties are not present at the preceding level. For example, photosynthesis occurs in intact chloroplasts, but not in a mixture of chloroplast components.

Theme 2: Life's Processes Involve the Expression and Transmission of Genetic Information

• Cells contain genetic material in the form of DNA (deoxyribonucleic acid).

• DNA encodes the instructions for building and maintaining an organism.

• Gene expression is the process by which information from a gene is used to synthesize a functional product, usually a protein.

Theme 3: Life Requires the Transfer and Transformation of Energy and Matter

• All living things require energy to carry out life’s activities.

• Energy flows through an ecosystem, usually entering as light and exiting as heat.

• Chemical elements are recycled within an ecosystem.

Theme 4: Organisms Interact with Other Organisms and the Physical Environment

• Interactions can be beneficial, harmful, or neutral.

• Interactions between organisms and their environment affect both parties.

• Humans have a significant impact on the environment, including contributing to global climate change through the burning of fossil fuels.

Theme 5: Evolution, the Core Theme of Biology

• Evolution explains both the unity and diversity of life.

• Natural selection is the process by which populations adapt to their environment over generations.

• All living organisms are related by descent from common ancestors.

Biological Classification and Diversity

Taxonomy and Domains of Life

• Taxonomy is the branch of biology that names and classifies species into a hierarchical order.

• Three domains of life: Bacteria, Archaea, and Eukarya.

• Domain Eukarya includes four kingdoms: Plantae, Fungi, Animalia, and Protists (the latter is a diverse group, not a true kingdom).

Scientific Inquiry and the Process of Science

Making Observations and Forming Hypotheses

• The scientific method involves making observations, forming logical hypotheses, and testing them.

• A hypothesis is a tentative answer to a well-framed question, testable and falsifiable.

• Science uses both inductive reasoning (drawing generalizations from specific observations) and deductive reasoning (predicting specific results from general premises).

Types of Data and Experiments

• Qualitative data: Descriptions (e.g., Jane Goodall’s observations of chimpanzee behavior).

• Quantitative data: Numerical measurements.

• Experiments can be controlled or comparative, and data are analyzed to support or refute hypotheses.

Hypothesis-Based Science

• Uses deductive reasoning: If a hypothesis is correct, then we should observe a particular outcome.

• Scientific hypotheses must be testable and falsifiable.

• Not all hypotheses are scientific (e.g., supernatural explanations are outside the bounds of science).

Feedback Regulation in Biological Systems

• Negative feedback: The accumulation of an end product slows the process (e.g., high ATP inhibits an enzyme in ATP production).

• Positive feedback: The end product speeds up its own production (e.g., blood clotting).

Evolution: The Core Theme of Biology

Unity and Diversity of Life

• Evolution accounts for the similarities and differences among living things.

• Natural selection leads to adaptation and speciation.

• Fossil evidence and molecular data support the theory of evolution.

Examples and Applications

• Darwin’s finches on the Galápagos Islands are an example of adaptive radiation and natural selection.

• Comparative anatomy and DNA sequence comparisons are used to determine evolutionary relationships.

Key Terms and Definitions

• Emergent Properties: New characteristics that arise at each level of organization.

• Cell: The fundamental unit of life.

• DNA: The molecule that stores genetic information.

• Gene Expression: The process by which information from a gene is used to synthesize a functional product.

• Taxonomy: The science of classifying organisms.

• Hypothesis: A testable explanation for an observation.

• Inductive Reasoning: Deriving general principles from specific observations.

• Deductive Reasoning: Predicting specific results from general principles.

• Negative Feedback: A regulatory mechanism in which a process is slowed by its own products.

• Positive Feedback: A regulatory mechanism in which a process is sped up by its own products.

Sample Equations and Formulas

• Photosynthesis (simplified):

• Cellular Respiration (simplified):

Summary Table: Levels of Biological Organization

Additional info:

• Some context and examples have been expanded for clarity and completeness.

• Tables have been reconstructed to summarize key classification and organizational concepts.