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

Introduction to Biology

Definition and Scope of Biology

• Biology is the scientific study of life. The term comes from the Greek words bios (life) and logos (study).

• Life is incredibly diverse, ranging from microscopic organisms to large multicellular organisms.

• The cell is the smallest, most fundamental unit of life.

Unicellular vs. Multicellular Organisms

• Unicellular organisms consist of a single cell (e.g., bacteria, some protists).

• Multicellular organisms are composed of many cells (e.g., plants, animals).

Characteristics of Life

Shared Features of Living Organisms

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

• Order: Highly organized structure.

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

• Growth and Development: Increase in size and complexity.

• Energy Processing: Use of energy to power activities.

• Response to Environment: Reacting to stimuli.

• Reproduction: Producing offspring.

• Evolutionary Adaptation: Populations change over generations.

Note: Viruses are not considered alive because they do not exhibit all these characteristics independently.

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	Chemical structure of two or more atoms
Organelle	Functional components within cells
Cell	Basic unit of life
Tissue	Group of similar cells performing a 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 an area
Ecosystem	Community plus the physical environment
Biosphere	All environments on Earth supporting life

Emergent Properties

• Emergent properties arise at each new level of the hierarchy, due to the arrangement and interactions of parts as complexity increases.

• "The whole is greater than the sum of its parts."

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:

• 1) Genetic diversity in a population

• 2) Selective pressure from the environment

• 3) Heritable traits affecting fitness

Evolution by Natural Selection

• Evolution changes the genetic makeup of a population over generations.

• Populations, not individuals, evolve.

Introduction to Taxonomy

Classification of Life

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

• Hierarchical categories are used to classify all life:

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

Three Domains of Life

• All life is classified into three domains:

• Bacteria: Prokaryotic, unicellular organisms

• Archaea: Prokaryotic, often found in extreme environments

• Eukarya: Eukaryotic, includes protists, fungi, plants, and animals

Energy Acquisition in Life

• Organisms are categorized by how they acquire energy:

• Producers (Autotrophs): Make their own food (e.g., plants via photosynthesis)

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

• Decomposers: Break down dead organic matter

Scientific Method

Steps of the Scientific Method

• 1. Pose a question or problem

• 2. Make an observation

• 3. Form a hypothesis

• 4. Design and conduct an experiment

• 5. Collect and interpret data

• 6. Draw conclusions

• 7. Peer review and publication

Predictions, Hypotheses, and Theories

• Prediction: Expected outcome if a hypothesis is correct

• Hypothesis: Testable explanation for an observation

• Theory: Broad explanation supported by a large body of evidence

Experimental Design

Variables

Variable Type	Definition	Example
Independent Variable	Variable controlled or manipulated by the researcher	Amount of water given to plants
Dependent Variable	Variable measured in the experiment	Growth of plants (height, mass)

Controls in Experiments

• Positive control: Group where a known response is expected

• Negative control: Group where no response is expected

False Positives/Negatives

• Well-designed experiments contain control groups to prevent false positives/negatives.

Basic Theories of Biology

Theory	Concept
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 cover the foundational concepts of Chapter 1 in a General Biology course, including the nature of life, biological organization, evolution, taxonomy, the scientific method, and experimental design.