Chapter 1 Vocabulary: The Process of Science and Life

1.1 What is life?

• Biology is the scientific study of life.
• Properties of life: order, reproduction, growth and development, energy processing, regulation, response to the environment, and evolutionary adaptation.
• The cell is the structural and functional unit of life.

Checkpoint question: How would you define life?

1.2 The three domains of life

• Scientists arrange diversity into three domains: Bacteria, Archaea, and Eukarya.
• Domains Bacteria and Archaea contain organisms with simple cells.
• Domain Eukarya includes various protists and the kingdoms Fungi, Plantae, and Animalia.

Checkpoint question: To which of the three domains of life do we belong?

• Answer: Eukarya

1.3 Visualizing the concept: life’s hierarchy of organization and emergent properties

• Biologists study life across scales from molecules to the biosphere.
• Life is organized into a hierarchical series of levels; new properties emerge at each level due to the arrangement and interactions of components (emergent properties).
• Key levels (from small to large): Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism → Population → Community → Ecosystem → Biosphere.
• In the figures: Nucleus, DNA, and levels like Proteins and other molecules sit at lower levels; higher levels show organs, systems, and the biosphere.

Checkpoint question: Which of these levels of biological organization includes all of the others in the list: cell, molecule, organ, tissue?

• Answer: Biosphere (the largest level in the hierarchy).

1.4 What is science?

• Science is a way of knowing and an evidence-based process to understand the natural world.
• The scientific approach involves observations, hypotheses, predictions, tests of hypotheses via experiments or additional observations, and analysis of data.
• A scientific theory is broad in scope and supported by a large body of evidence.

Figure sequence (flashlight example):

• Observation: Flashlight doesn’t work.
• Question: Why doesn’t the flashlight work?
• Hypotheses: Batteries are dead; Bulb is burned out.
• Predictions: Replacing batteries will fix the problem; Replacing the bulb will fix the problem.
• Test: Replace batteries; Test: Replace bulb.
• Results determine whether the hypothesis is supported or contradicted.

Checkpoint question: What is the main requirement for a scientific hypothesis?

• Answer: It must be testable (falsifiable).

1.5 Hypotheses can be tested using controlled experiments

• In an experimental test, researchers manipulate one component (independent variable) and observe effects (dependent variable).
• A controlled experiment compares an experimental group with a control group.
• This design helps demonstrate the effect of a single variable.
• Examples: Mouse camouflage experiments show predation differences; clinical trials and observational studies can test hypotheses in humans.

Data example: Camouflage experiment (Table 1.5) shows predator attacks depending on habitat camouflage:

• Beach habitat (light): Attacks on Camouflaged = 2; Attacks on Noncamouflaged = 5; % Attacks on Noncamouflaged = 71%
• Inland habitat (dark): Attacks on Camouflaged = 5; Attacks on Noncamouflaged = 16; % Attacks on Noncamouflaged = 76%

Table 1.5: Results from Camouflage Experiment

• Data source: S. N. Vignieri et al., Evolution 64: 2153-8 (2010).

Checkpoint question: In some studies, researchers try to match factors (sex, age, health) for control and experimental groups. What is this experimental design trying to do?

• Answer: Reduce confounding variables to isolate the effect of the manipulated variable.

1.6 Scientific thinking: Hypotheses can be tested using observational data

• Hypotheses about evolutionary relationships can be tested by comparing observations (e.g., morphology, diet, habitat, DNA sequences).
• Early hypotheses grouped red pandas with raccoons; later grouping with giant pandas; DNA sequence comparisons (observational data) led to red pandas being placed in their own family.

Checkpoint question: Explain why comparisons of DNA sequences are considered observational and not experimental data.

• Answer: Because DNA sequence comparisons rely on observed data without experimental manipulation or controlled trials; sequences are not being deliberately altered or assigned to experimental conditions by the researcher.

1.7 The process of science is repetitive, nonlinear, and collaborative

• Hypothesis formation and testing are core activities.
• Three interacting spheres shape science:
  • Exploration and discovery
  • Analysis and feedback from the scientific community
  • Societal benefits and outcomes

Figure 1.7 illustrates the cycle: Exploration and discovery → Formation and testing of hypotheses → Feedback from the scientific community → Societal benefits and outcomes.

Checkpoint question: Why is hypothesis testing at the center of the process of science?

• Answer: Because hypotheses drive the experimental design, data collection, and interpretation that advance scientific understanding.

1.8 Connection: Biology, technology, and society are connected in important ways

• The goal of science is to understand natural phenomena; technology aims to apply scientific knowledge for specific purposes.
• These fields are interdependent: technological advances enable new science, and scientific discoveries enable new technologies.

Five Unifying Themes in Biology

• Theme 1 (and core): Evolution is the core theme of biology.

• Life’s unity and diversity are explained by evolution, the process of change that has shaped life on Earth.

• Evolutionary diagrams illustrate how natural selection acts on populations with inherited variation, leading to changes in trait frequencies over generations.

• Visuals (summaries):

  • A population with varied inherited traits undergoes differential reproduction, increasing the frequency of traits that enhance survival and reproductive success.
  • Each extant species represents a twig on a branching tree of life, tracing back to common ancestors.

• Example: Common ancestors and branching relationships among raccoons, red pandas, weasels, giant pandas, skunks, seals, dogs, wolves, and foxes.

• Checkpoint question: Explain the cause and effect of unequal reproductive success.

• Answer: Individuals with advantageous traits reproduce more successfully, passing those traits to offspring, increasing their representation in subsequent generations (natural selection).

1.10 Evolution connection: Evolution in everyday life

• Evolutionary theory informs medicine, conservation, and agriculture.
• Humans act as agents of evolution through artificial selection (breeding) that changes crops, livestock, and pets relative to wild ancestors.

Checkpoint question: Explain how humans are agents of both artificial selection and natural selection.

• Answer: Artificial selection: humans intentionally select for preferred traits (e.g., crop and livestock breeding). Natural selection: human-modified environments can alter selective pressures, affecting trait frequencies in wild populations.

1.11 Life depends on the flow of information

• Biological processes depend on the transmission and use of information.

• DNA provides heredity and programs cell activities by coding for proteins.

• External and internal environment signals regulate gene expression and cellular processes.

• DNA–RNA–Protein flow (illustrative):

  • DNA contains the genetic information
  • RNA transcribed from genes carries information for protein synthesis
  • Proteins carry out cellular functions
  • Information flow diagram: $ext{DNA} <br /> ightarrow ext{RNA} <br /> ightarrow ext{Protein}$

• Figure 1.11a shows a DNA sequence; Figure 1.11b shows gene X being transcribed to RNA and translated into Protein X or Y; Figure 1.11c shows signaling from the environment regulating insulin production and glucose uptake.

Checkpoint question: How is signaling information involved in the expression of genetic information?

• Answer: Signaling pathways regulate when and how genes are transcribed and translated, integrating external/internal cues with genetic programs.

1.12 Theme: Structure and function are related

• Structure determines function across scales.
• At the molecular level, the structure of a protein determines its function (e.g., hemoglobin transports oxygen).
• At the cellular level, the long extensions of nerve cells enable transmission of impulses.
• Visual examples include the Radial sesamoid bone (the “false thumb”) illustrating specialized structure.

Checkpoint question: Look at the structure of your hand and explain how its structure supports its function.

• Answer: The arrangement and attachment of bones, joints, muscles, and nerves provide grasping ability, dexterity, and fine motor control.

1.13 Theme: Life depends on the transfer and transformation of energy and matter

• Energy flows through an ecosystem in one direction: sunlight enters, chemical energy is produced by producers, energy passes to consumers, and energy exits as heat.
• Matter cycles within ecosystems: atoms and molecules move from atmosphere/soil into producers, then consumers, decomposers, and back to the environment.
• Figure 1.13 illustrates the flow of energy and the cycling of matter.
• Example captioned: Sun → Inflow of light energy → Outflow of heat; Producers convert light to chemical energy; Decomposers recycle chemicals back to soil.

Checkpoint question: Describe how photosynthesis transforms energy and matter.

• Answer: Photosynthesis captures solar energy to synthesize chemical energy-rich compounds (glucose) from CO2 and water, incorporating carbon and releasing O2; this chemical energy enters the food chain and matter cycles through producers, consumers, and decomposers.

1.14 Theme: Life depends on interactions within and between systems

• Life spans multiple scales from molecules to the global biosphere.
• Emergent properties arise from interactions among components of a system.
• Systems biology models the behavior of biological systems by analyzing interactions among parts.

Checkpoint question: A box of bicycle parts won’t do anything, but if the parts are properly assembled, you can take a ride. What does this illustrate?

• Answer: Emergent properties of a system depend on the proper integration and interaction of its parts.

Closing study objectives (You should now be able to…)

• Describe seven properties common to all life.
• Compare the three domains of life.
• Describe the levels of biological organization from molecules to the biosphere, noting interrelationships.
• Describe emergent properties.
• Define science and distinguish between a hypothesis and a scientific theory.
• Describe the structure of a controlled experiment.
• Explain how hypotheses can be used to test observational data.
• Explain how science is repetitive, nonlinear, and collaborative.
• Describe the relationship between science and technology.
• Describe the process and products of natural selection.
• Explain how evolution impacts the lives of all humans.
• Explain how DNA determines an organism’s structures and functions.
• Describe the relationship between structure and function in biology.
• Compare the dynamics of nutrients and energy in an ecosystem.
• Explain how systems biology is used to understand biological systems.

Glossary-like references (constructs to remember):

• Emergent properties: new properties arising from interactions among parts at lower levels.
• Central dogma-inspired flow (informational): $ext{DNA} <br /> ightarrow ext{RNA} <br /> ightarrow ext{Protein}$
• Energy flow in ecosystems: $ext{Sun} <br /> ightarrow ext{Producers} <br /> ightarrow ext{Consumers} <br /> ightarrow ext{Heat}$
• Three domains: Bacteria, Archaea, Eukarya
• Key vocabulary: hypothesis, controlled experiment, independent variable, dependent variable, theory, observation, prediction, data, analysis, replication, controls.