Introduction: Evolution and the Foundations of Biology

Unifying Themes of Biology

  • Five core themes organize biological information: Organization, Information, Energy and Matter, Interactions, and Evolution.
  • Biological Organization:
    • Biological organization spans multiple levels: Biosphere, Ecosystems, Communities, Populations, Organisms, Organs, Tissues, Cells, Organelles, and Molecules.
    • Reductionism breaks down complex biological systems into simpler components, while systems biology analyzes the interactions among system parts.
    • Emergent properties arise from the arrangement and interaction of parts within a system (e.g., photosynthesis requires an intact chloroplast).
    • The cell is the basic unit of structure and function; eukaryotic cells contain membrane-enclosed organelles and a nucleus, whereas prokaryotic cells lack a nucleus or membrane-bound organelles.
  • Genetic Information:
    • Genetic material is stored in DNA (deoxyribonucleic acid) molecules composed of four nucleotides: A, T, C, and G.
    • Gene expression uses genetic information to direct protein synthesis using mRNA as an intermediary.
    • Genomics studies entire sets of genes (genomes) and Proteomics studies complete sets of proteins (proteomes), utilizing high-throughput technology and bioinformatics.
  • Energy and Matter:
    • Energy flows through ecosystems, entering as light energy from the sun and exiting as heat.
    • Chemical elements and matter cycle within ecosystems through producers, consumers, and decomposers.
  • Interactions:
    • Organisms interact with each other and their environment; these interactions can benefit, harm, or affect both parties.
    • Atmospheric CO2CO_2 added by human activity has increased global average temperatures by 1C1^\text{C} since 1900, driving global climate change.

Evolution and the Diversity of Life

  • Evolution explains both the unity and diversity of life through descent with modification from common ancestors.
  • Three Domains of Life:
    • Domain Bacteria (prokaryotic).
    • Domain Archaea (prokaryotic).
    • Domain Eukarya (eukaryotic; includes Kingdom Plantae, Kingdom Fungi, Kingdom Animalia, and Protists).
  • Natural Selection:
    • Proposed by Charles Darwin in On the Origin of Species by Means of Natural Selection (1859).
    • Individuals in a population vary in heritable traits, and populations produce more offspring than can survive.
    • Natural selection favors individuals with advantageous traits best suited to their environment, leading to evolutionary adaptation over generations (e.g., Galápagos finches).

Scientific Inquiry

  • Data and Reasoning:
    • Biological data includes qualitative descriptions (e.g., Jane Goodall's observations of chimpanzee behavior) and quantitative numerical measurements.
    • Inductive reasoning draws general principles from specific observations.
    • Deductive reasoning predicts specific outcomes from general premises using "if… then" logic.
    • Hypotheses must be testable and falsifiable.
  • Controlled Experiments:
    • Controlled experiments compare an experimental group against a control group.
    • The independent variable is manipulated by researchers, while the dependent variable is the measured outcome.
    • Francis B. Sumner hypothesized that mouse coat coloration evolved as an adaptive camouflage against visual predators; Hopi Hoekstra tested this prediction with models of Peromyscus polionotus, demonstrating that non-camouflaged models faced higher predation rates.
  • Scientific Theories:
    • A scientific theory is broad in scope, generates new hypotheses, and is supported by a large body of evidence.