Foundations of Biology: Key Concepts, Theories, and Scientific Methods

Introduction to Biology

What is an Organism?

An organism is any living entity that can carry out life processes independently. Organisms can be unicellular (composed of a single cell, like bacteria) or multicellular (composed of many cells, like plants and animals).

• Key Point: Organisms exhibit characteristics such as growth, reproduction, response to stimuli, metabolism, and homeostasis.

• Example: A tree, a bacterium, and a human are all considered organisms.

Fundamental Characteristics of Life

Five Fundamental Characteristics

All living things share five fundamental characteristics:

• Cells: All organisms are made up of membrane-bound units called cells.

• Replication: All organisms are capable of reproduction, either sexually or asexually.

• Information: Organisms process hereditary or genetic information encoded in genes as well as information from the environment.

• Energy: Organisms acquire and use energy to carry out life processes.

• Evolution: Populations of organisms are continually evolving.

Cells

• Definition: The cell is the basic structural and functional unit of life.

• Cell Theory: States that all living things are composed of cells and all cells come from pre-existing cells.

Replication via Cell Division

• Replication: The process by which cells make copies of themselves, essential for growth and reproduction.

• Example: Mitosis in eukaryotic cells; binary fission in prokaryotes.

Processing Information

• Genetic Information: Organisms store genetic information in DNA, which is used to direct cellular activities.

• Environmental Information: Organisms sense and respond to changes in their environment.

Homeostasis

• Definition: The maintenance of a stable internal environment despite changes in external conditions.

• Example: Human body temperature regulation.

Biotic and Abiotic Factors

• Biotic: Living components of an environment (e.g., plants, animals, bacteria).

• Abiotic: Non-living components (e.g., sunlight, water, temperature).

• Relationships: Organisms interact with both biotic and abiotic factors, forming ecosystems.

Requiring and Acquiring Energy

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

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

Evolution

• Definition: The change in the genetic composition of a population over time.

• Mechanism: Natural selection is a primary mechanism of evolution.

Historical Perspectives in Biology

Louis Pasteur and His Contributions

• Key Contributions: Disproved the theory of spontaneous generation through his swan-neck flask experiment, supporting the cell theory.

• Additional info: Pasteur also contributed to the development of vaccines and pasteurization.

Cell Theory vs. Theory of Spontaneous Generation

• Cell Theory: All living things are made of cells; all cells come from pre-existing cells.

• Spontaneous Generation: The outdated belief that living organisms could arise from non-living matter.

• Comparison: Pasteur's experiments provided evidence against spontaneous generation and in favor of cell theory.

Classification and Taxonomy

Tree of Life and Domains

• Tree of Life: A model that shows the evolutionary relationships among all living organisms.

• Three Domains: Bacteria, Archaea, and Eukarya.

• Main Branches: Each domain contains multiple kingdoms and represents major evolutionary lineages.

Taxonomic Classification System

• Hierarchy: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species

• Purpose: Organizes biological diversity and reflects evolutionary relationships.

Binomial Nomenclature

• Definition: The system of naming species using two names: genus and species (e.g., Homo sapiens).

• Formatting: Genus is capitalized, species is lowercase, both italicized.

• Use of Latin: Latin is used for consistency and universality in scientific communication.

Viruses and Living Organisms

• Viruses: Infectious agents that require a host cell to reproduce.

• Not Considered Living: Viruses lack cellular structure and independent metabolism.

• Confusion: Viruses share some characteristics with living things (e.g., genetic material) but do not meet all criteria for life.

Science and the Scientific Method

What is Science?

• Definition: Science is a systematic approach to understanding the natural world through observation and experimentation.

• Two Main Aspects: Gathering empirical evidence and developing explanations (theories) based on that evidence.

What is Considered Science?

• Empirical Evidence: Based on observation or experiment.

• Testability: Scientific ideas must be testable and falsifiable.

Observational vs. Experimental Studies

• Observational Study: Researchers observe subjects without manipulating variables.

• Experimental Study: Researchers manipulate one or more variables to determine effects.

• Comparison: Experimental studies can establish causation; observational studies often identify correlations.

Pseudoscience

• Definition: Claims or beliefs presented as scientific but lacking empirical support or testability.

• Example: Astrology is considered pseudoscience because its claims are not testable or supported by evidence.

Use of the Word 'Theory' in Science vs. Everyday Use

• Scientific Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence.

• Everyday Use: Often refers to a guess or hypothesis without substantial evidence.

• Example: The theory of evolution is supported by extensive scientific evidence.

Key Terms and Definitions

Term	Definition
Archaea	One of the three domains of life; prokaryotic microorganisms distinct from bacteria.
Genes	Units of heredity made up of DNA that code for proteins.
Phylum	A taxonomic rank below kingdom and above class.
ATP	Adenosine triphosphate, the primary energy carrier in cells.
Prokaryote	Organisms without a nucleus, including bacteria and archaea.
Heritable trait	A characteristic that can be passed from parent to offspring through genes.
Pseudoscience	Claims presented as scientific but lacking empirical evidence or testability.
Cell	The basic structural and functional unit of life.
Hypothesis	A testable statement that explains a phenomenon or set of observations.
Replication	The process of copying genetic material or cells.
Domain	The highest taxonomic rank, grouping organisms into Bacteria, Archaea, or Eukarya.
Hypothesis testing	The process of evaluating predictions derived from a hypothesis.
Scientific name	The two-part Latin name of a species (genus and species).
Energy	The capacity to do work; required for all life processes.
Inheritance	The transmission of genetic information from parent to offspring.
Species	The basic unit of biological classification; a group of organisms capable of interbreeding.
Eukaryote	Organisms whose cells contain a nucleus.
Kingdom	A taxonomic rank below domain and above phylum.
Spontaneous generation	The disproven idea that living organisms arise from non-living matter.
Evolution	The change in genetic composition of populations over time.
Null hypothesis	A hypothesis stating there is no effect or difference; used as a default in statistical testing.
Taxonomy	The science of classifying organisms.
Experiment	A procedure to test a hypothesis under controlled conditions.
Observational study	Research where variables are not manipulated by the investigator.
Theory	A well-supported explanation of natural phenomena, based on evidence.
Experimental study	Research involving manipulation of variables to test effects.
Organism	Any living thing.
Tree of life	A diagram showing evolutionary relationships among species.

Scientific Method: Key Steps

1. Observation: Gathering information about phenomena.

2. Hypothesis: Formulating a testable explanation.

3. Experimentation: Testing the hypothesis through controlled experiments.

4. Data Analysis: Interpreting results to draw conclusions.

5. Conclusion: Accepting, rejecting, or modifying the hypothesis based on evidence.

Formulas and Equations

• ATP Hydrolysis (energy release):

$\text{ATP} + \text{H}_2\text{O} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

• General format for a hypothesis test:

$H_0: \text{There is no difference between groups}$ $H_A: \text{There is a difference between groups}$

Summary Table: Domains of Life

Domain	Cell Type	Example Organisms
Bacteria	Prokaryotic	Escherichia coli
Archaea	Prokaryotic	Halobacterium
Eukarya	Eukaryotic	Plants, animals, fungi, protists