General Biology: Fundamental Characteristics, Cell Theory, Genetics, Evolution, and Taxonomy

Five Fundamental Characteristics:
- Cells: All organisms consist of membrane-bound cellular compartments.
- Replication: All organisms reproduce.
- Information: Organisms process genetic information and environmental signals.
- Energy: Organisms acquire and process chemical energy.
- Evolution: Populations undergo genetic change across generations.
Three Unifying Theories:
- Cell Theory: All organisms are composed of cells, which arise from preexisting cells.
- Chromosomal Theory of Inheritance: Genetic information is stored in genes located on chromosomes.
- Theory of Evolution by Natural Selection: Species change over time due to differential reproductive success.

Robert Hooke ( $1665$ ): Observed dead cork tissue cell walls and coined the term "cells."
Anton van Leeuwenhoek ( $\approx 1665$ ): Observed living single-celled organisms ("animalcules") using single-lens microscopes.
Cell Definition: Highly organized compartment enclosed by a protective membrane barrier; the simplest unit of life.

Components of Scientific Inquiry:
- Theory: Broad explanation supported by extensive evidence.
- Hypothesis: Testable and falsifiable statement.
- Experiment: Controlled test evaluating a single factor.
- Prediction: Measurable or observable result.
Experimental Variables:
- Independent Variable: Factor manipulated by the experimenter (plotted on $x\text{-axis}$ ).
- Dependent Variable: Factor measured to determine effect (plotted on $y\text{-axis}$ ).
- Control Group: Baseline group used for comparison.

Competing Hypotheses:
- Spontaneous Generation: Organisms arise spontaneously from non-living matter.
- All-Cells-from-Cells: Cells arise strictly from preexisting cells via cell division.
Louis Pasteur's Experiment ( $1862$ ):
- Compared boiled nutrient broth in straight-necked flasks (open to airborne micro-organisms) and swan-necked flasks (trapped micro-organisms in U-bend).
- Microscopic growth occurred only in open straight-necked flasks, disproving spontaneous generation.

Chromosome Basis: Genes are located on chromosomes made of $\text{DNA}$ (Sutton & Boveri, $1902$ ).
$\text{DNA}$ Structure: Double helix composed of nucleotides with complementary base pairing (Adenine-Thymine, Guanine-Cytosine) discovered by Watson & Crick ( $1953$ ) using Rosalind Franklin's X-ray crystallography data.
Central Dogma: Describes genetic flow: $\text{DNA} \rightarrow \text{mRNA} \rightarrow \text{Protein}$ .

Nutritional Needs: Acquiring chemical energy ( $\text{ATP}$ ) and building block precursors.
Metabolic Pathways:
- Photosynthesis: Synthesizes sugars from sunlight and $\text{CO}_2$ to produce $\text{ATP}$ .
- Cellular Respiration: Catabolic processes break down carbohydrates, fats, and proteins for $\text{ATP}$ generation; anabolic pathways build biological molecules from intermediates.

Core Claims (Darwin & Wallace, $1858$ ): Species share common ancestry and undergo descent with modification.
Requirements: Heritable trait variation and differential reproductive success.
Mechanism: Natural selection acts on individuals, but evolution occurs in populations over time.
- Fitness: Relative ability to produce surviving offspring.
- Adaptation: Heritable trait increasing fitness in a given environment.

Tree of Life: Genealogical diagram connecting all species to a common ancestor, established using $\text{DNA}$ and $\text{RNA}$ sequence alignments.
Three Major Domains:
- Eukarya (Eukaryotes): Cells contain a membrane-bound nucleus and organelles.
- Bacteria & Archaea (Prokaryotes): Single-celled organisms lacking a membrane-bound nucleus.

Taxonomic Hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Binomial Nomenclature: Scientific names are italicized with capitalized Genus and lowercase species (e.g., Homo sapiens).