Ch. 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 term comes from the Greek words bios (life) and logos (study).

• Life is incredibly diverse, from microscopic bacteria to giant sequoias, but all life shares certain fundamental properties.

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

Characteristics of Life

Defining Features

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

• Order: Organized structure and complexity.

• Regulation: Ability to maintain internal stability (homeostasis).

• Energy Processing: Use of energy to power activities and chemical reactions.

• Response to Environment: Reacting to environmental stimuli.

• Reproduction: Ability to produce offspring.

• Growth and Development: Consistent growth and development controlled by inherited DNA.

• Evolutionary Adaptation: Populations evolve over generations through adaptations.

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
Organelle	Functional components within cells
Cell	Basic unit of life
Tissue	Group of similar cells performing a specific function
Organ	Body part composed of tissues with specific functions
Organ System	Group of organs working together
Organism	Individual living thing
Population	Group of organisms of the same species in an area
Community	All living organisms in an area
Ecosystem	Community plus the nonliving environment
Biosphere	All ecosystems on Earth

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

Natural Selection & Evolution

Adaptation and Fitness

• Adaptation: Inherited traits that enhance an organism's ability to survive and reproduce in a particular environment.

• Fitness: The ability of an organism to survive and reproduce.

Natural Selection

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

• Natural selection leads to adaptation in populations over generations.

Example: Giraffes with longer necks can reach more food and are more likely to survive and reproduce, passing on the trait.

Taxonomy and Classification

Introduction to Taxonomy

Taxonomy is the branch of science that classifies, identifies, and names organisms. Organisms are classified into hierarchical categories:

Domain	Kingdom	Phylum	Class	Order	Family	Genus	Species
Bacteria	---	---	---	---	---	---	---
Archaea	---	---	---	---	---	---	---
Eukarya	Animalia, Plantae, Fungi, Protista	---	---	---	---	---	---

Domains of Life: The three domains are Bacteria, Archaea, and Eukarya.

Energy Acquisition

• Autotrophs: Organisms that produce their own food (e.g., plants via photosynthesis).

• Heterotrophs: Organisms that obtain energy by consuming other organisms (e.g., animals).

Energy flows from the sun to producers (autotrophs) and then to consumers (heterotrophs).

Scientific Method

Steps of the Scientific Method

• Make an observation

• Ask a question

• Form a hypothesis

• Make a prediction

• Test the prediction (experiment)

• Analyze data and draw conclusions

• Report and publish results

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 given to plants
Dependent Variable	Measured outcome	Growth of plants
Control Variable	Kept constant	Type of plant, soil, light

Controls in Experiments

• Negative Control: Group where no effect is expected (e.g., placebo).

• Positive Control: Group where a known effect is expected.

Controls help validate the results of an experiment by providing a baseline for comparison.

Main Theories of Biology

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

• Gene Theory: Hereditary information is encoded in genes.

• Evolutionary Theory: All organisms share a common ancestor and have evolved over time.

Additional info: These notes are based on the content and structure of a study prep guide for Chapter 1 of a General Biology textbook, focusing on foundational concepts such as the nature of life, scientific inquiry, and biological organization.