Chapter 1: Evolution, the Themes of Biology, and Scientific Inquiry – Study Notes

Introduction to Biology

Definition and Scope

• Biology is the scientific study of life. The suffix -ology means "the study of."

• Life is incredibly diverse, from microscopic bacteria to giant sequoias, but all living things share certain fundamental properties.

• Biology examines life at all levels, from molecules to the entire biosphere.

Characteristics of Life

Shared Properties of Living Organisms

• All living organisms share characteristics that distinguish them from nonliving things:

• Order: Living things are highly organized, with cells as their basic units.

• Evolutionary adaptation: Populations evolve over generations through adaptations that enhance survival and reproduction.

• Response to the environment: Organisms respond to environmental stimuli.

• Regulation (Homeostasis): Organisms maintain stable internal conditions.

• Energy processing: Organisms obtain and use energy to power activities.

• Growth and development: Organisms grow and develop according to inherited instructions.

• Reproduction: Living things reproduce their own kind.

Note: Viruses are not considered alive because they lack many of these characteristics.

Life's Organizational Hierarchy

Levels of Biological Organization

• Life consists of multiple parts organized in a hierarchical pattern, from smallest to largest:

Level	Description
Atom	Smallest particle of an element
Molecule	Group of atoms bonded together
Organelle	Functional components within cells
Cell	Basic unit of life
Tissue	Group of similar cells performing a specific function
Organ	Body part composed of multiple tissues
Organ System	Group of organs working together
Organism	Individual living thing
Population	All individuals of a species in an area
Community	All populations in a given area
Ecosystem	Community plus the physical environment
Biosphere	All environments on Earth that support life

Emergent Properties: New properties arise at each level that are not present at the preceding level. For example, life emerges at the cellular level, not at the level of molecules or atoms.

Natural Selection & Evolution

Adaptation and Fitness

• Living organisms are well-suited to their environments due to adaptation.

• Fitness refers to an organism's ability to survive and reproduce in its environment.

Natural Selection

• Described by Charles Darwin as the process by which individuals with advantageous traits survive and reproduce more successfully.

• Natural selection requires:

  • Variation in traits within a population

  • Heritable traits

  • Different reproductive success

• Over generations, natural selection can lead to evolution, or changes in the genetic makeup of populations.

Taxonomy and Classification

Taxonomic Hierarchy

• Taxonomy is the branch of science that classifies, identifies, and names organisms.

• Major taxonomic ranks (from broadest to most specific):

Domain	Kingdom	Phylum	Class	Order	Family	Genus	Species
Bacteria	Animalia	Chordata	Mammalia	Primates	Hominidae	Homo	sapiens

Three Domains of Life

• All life is classified into three domains:

  • Bacteria: Prokaryotic, unicellular organisms

  • Archaea: Prokaryotic, often found in extreme environments

  • Eukarya: Eukaryotic organisms, includes kingdoms Animalia, Plantae, Fungi, and Protista

Energy Acquisition and Flow

Autotrophs vs. Heterotrophs

• Organisms are classified by how they acquire energy:

  • Autotrophs (producers): Make their own food, usually via photosynthesis

  • Heterotrophs (consumers): Obtain energy by eating other organisms

• Energy flows from the sun to producers to consumers, with energy lost as heat at each transfer.

Scientific Method and Inquiry

Steps of the Scientific Method

• Science is a way of knowing, based on inquiry and evidence.

• Steps include:

  1. Make observations

  2. Ask a question

  3. Formulate a hypothesis

  4. Make predictions

  5. Design and perform experiments

  6. Analyze data

  7. Draw conclusions

  8. Peer review and publish

• Hypothesis: A testable explanation for an observation.

• Theory: A broad explanation supported by a large body of evidence.

Experimental Design

Variables

Variable Type	Definition	Example
Independent Variable	Manipulated by the researcher	Amount of water
Dependent Variable	Measured outcome	Growth of plant
Controlled Variable	Kept constant	Type of plant, sunlight

Controls in Experiments

• Negative control: Group where no effect is expected

• Positive control: Group where a known effect is expected

Basic Theories of Biology

• Cell Theory: All organisms are made of cells; all cells come from preexisting cells.

• Homeostasis: All organisms maintain a relatively constant internal environment.

• Evolution: All organisms evolved from a single common ancestor.

Additional info: These notes are based on the first chapter of a standard college-level General Biology textbook and cover foundational concepts necessary for further study in biology.