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Chapter 1: The Study of Life

The Science of Biology

  • Biology: the study of living organisms and their interactions with one another and their environments
  • Science: knowledge of general truths or general laws, tested by the scientific method
  • The scientific method: a method of research with defined steps including experiments and careful observation

Learning Objectives

  • Identify the shared characteristics of the natural sciences
  • Summarize the steps of the scientific method
  • Compare inductive reasoning with deductive reasoning
  • Describe the goals of basic science and applied science
  • Identify and describe the properties of life
  • Describe the levels of organization among living things
  • Recognize and interpret a phylogenetic tree
  • List examples of different subdisciplines in biology

The Nature of the Earth and Life Through Time (context from Figure 1.1)

  • Earth image from space reminds us that appearance alone does not reveal biodiversity
  • First life forms: microorganisms in oceans, existing for billions of years
  • Familiar life (mammals, birds, flowers) emerged 130–250 million years ago
  • Genus Homo is about 2.5 million years old
  • Modern human appearance: about 300,000 years ago

The Science of Biology: Definitions and the Scientific Method

  • Biology: study of living organisms and their interactions with one another and their environments
  • Science: knowledge of general truths or general laws, tested by observation and the scientific method
  • The scientific method: a sequence of well-defined steps, including experiments and careful observation
  • Example image discussion: cyanobacteria as some of Earth’s oldest life forms; stromatolites formed by cyanobacteria in shallow waters
  • Key point: lifecycle of scientific ideas relies on natural explanations (no supernatural explanations)

The Process of Science

  • Natural sciences cover phenomena in the physical world and related processes
  • Science and biology are restricted to natural explanations, not supernatural explanations
  • The diversity of scientific fields includes astronomy, biology, computer science, geology, logic, physics, chemistry, mathematics, etc.

Scientific Reasoning: Inductive vs Deductive

  • Inductive reasoning: uses related observations to reach a general conclusion
  • Deductive reasoning: uses a general principle or law to forecast specific results
  • Historical note: Sir Francis Bacon (1561–1626) credited as an early figure defining the scientific method

The Scientific Method

  • The method consists of a series of well-defined steps
  • If a hypothesis is not supported by experimental data, a new hypothesis can be proposed

Two Types of Reasoning in Science

  • Scientists use inductive reasoning to arrive at generalizations from observations
  • Scientists use deductive reasoning to forecast specific results from general principles
  • Inductive conclusions can become premises for deductive reasoning in a цикlical process

Basic vs Applied Science

  • Basic science (pure science): seeks to expand knowledge regardless of short-term applications
  • Applied science: aims to use science to solve immediate problems defined by researchers
  • Example: after the discovery of DNA, principles of basic science contributed to applied contexts
  • The Human Genome Project: an example of a collaboration across disciplines; foundational for both basic and applied science

Peer Review: Process and Purpose

  • Scientific progress is typically made through publication of peer-reviewed literature
  • Peer review involves a blind process where scientists submit methods, data, and interpretations; reviewers evaluate validity and merit for publication
  • Typical structure of peer-reviewed papers: Abstract, Introduction, Methods, Results, Discussion, Literature Cited

Reading Peer-Reviewed Articles

  • A peer-reviewed article typically includes an abstract to summarize the work
  • Professional scientific language is used in these articles
  • Practice reading peer-reviewed biology articles; PubMed is a database for accessing such research

The Recall Method: A Study Technique

  • Why use recall: actively retrieving information strengthens memory and long-term retention
  • How to do it: write answers on blank paper without notes, then check and correct
  • Section wrap-up prompts: list the main steps of the scientific method in order; distinguish between a hypothesis and a prediction; next steps if data do not support a hypothesis

Properties of Life

  • Order
  • Sensitivity or response to stimuli
  • Reproduction
  • Growth and development
  • Regulation
  • Homeostasis
  • Energy processing

Order in Biological Systems

  • Organisms are highly organized structures consisting of one or more cells
  • Within each cell, atoms form molecules; molecules form cell components (organelles)
  • Multicellular organisms have tissues; tissues form organs; organs form organ systems (example: the heart, lungs, skin in a toad)

Response to Stimuli

  • Organisms respond to diverse stimuli
  • Plants can bend toward light or respond to touch (positive responses to stimuli)
  • Bacteria can move toward/away from chemicals (chemotaxis) or light (phototaxis)
  • Positive response: movement toward a stimulus; negative response: movement away

Response to Stimuli, Continued

  • Note: A companion video highlights ongoing examples in the topic area

Reproduction

  • Single-celled organisms: duplicate DNA and divide to form two new cells
  • Multicellular organisms: produce specialized reproductive cells that form new individuals
  • DNA contains genes passed to offspring; genes influence inherited traits (e.g., fur color, blood type)

Adaptation

  • All living organisms exhibit adaptation to their environment
  • Evolution by natural selection as a mechanism for adaptation
  • Examples: heat-resistant Archaea, nectar-nectar-feeding moth tongue length
  • Adaptations enhance reproductive potential and survival to reproductive age
  • Adaptations are not constant; they can change as environments change

Growth and Development

  • Growth and development are governed by genetic instructions
  • Genes direct cell growth and development and influence inherited characteristics
  • Offspring often resemble parents due to genetic inheritance

Regulation/Homeostasis

  • Cells require appropriate levels of temperature, pH, and chemical concentrations
  • Homeostasis: maintenance of internal conditions despite environmental changes (steady-state)
  • Thermoregulation in polar bears as an example; organisms use various methods to regulate body temperature (e.g., sweating in humans, panting in dogs)

Energy Processing: How Life Uses Energy

  • All organisms use a source of energy for metabolic activities
  • Some organisms capture energy from the Sun and convert it into chemical energy in food (Photoautotrophs; e.g., plants)
  • Other organisms use chemical energy from molecules they take in (Chemotrophs)
  • Key processes: Photosynthesis and Cellular Respiration
  • Photosynthesis: 6 CO2 + 6 H2O + \text{light energy} \rightarrow C6H{12}O6 + 6 O2
  • Cellular Respiration (typical balanced form): C6H{12}O6 + 6 O2 \rightarrow 6 CO2 + 6 H2O + \text{energy}

Think, Pair, Share: A Quick Philosophical Question

  • Question: If a virus has genetic material but is not made of cells, does it meet the definition of life?
  • Activity: Think alone for 1 minute; pair to discuss reasoning; share with class

Levels of Organization

  • Atoms, Molecules, Macromolecules, Organelles, Cells, Tissues, Organs and organ systems, Organisms, populations, and communities, Ecosystems, Biosphere

Biological Levels of Organization (Expanded View)

  • Visual overview showing progression from organelles to biosphere; emphasis on the hierarchical structure of life

The Diversity of Life and Phylogeny

  • Phylogenetic tree: diagram showing evolutionary relationships among biological species based on genetic/physical traits
  • Composed of nodes (branch points) and branches; branch length can reflect relative time
  • Carl Woese (early 1970s) showed life evolved along three domains: Bacteria, Archaea, and Eukarya

Domains of Life

  • Domain Eukarya: organisms with cells containing nuclei; includes fungi, plants, animals, and several protist kingdoms
  • Domain Archaea: single-celled, lacking nuclei; includes many extremophiles in harsh environments like hot springs
  • Domain Bacteria: single-celled, lacking nuclei; a distinct prokaryotic group
  • Both Archaea and Bacteria are prokaryotes

Branches of Biological Study

  • Microbiology: study of structure and function of single-celled organisms
  • Neurobiology: biology of the nervous system
  • Paleontology: fossils to study life’s history
  • Zoology: study of animals
  • Other related fields include physiology, ecology, genetics, forensics, and more

Career Connection: Forensic Scientist

  • Application of science to address legal questions
  • Tasks: analyze hair, blood, and body fluids; process DNA from various materials and environments; provide evidence in court
  • Education path: study chemistry and biology; take math-intensive courses

Concept Mapping: A Powerful Study Skill

  • What is a concept map? A visual tool to organize and connect ideas using bubbles/boxes and lines/arrows
  • Why it works: shows connections, boosts memory through visuals, helps understand the big picture
  • Tips: start broad, add detail, use keywords, use colors/shapes to group ideas, update as you learn
  • Try creating your own concept map to reinforce learning