Exhaustive Study Notes: Intro to Biology, Experimental Design, Chemistry of Life, and Water

Course Introduction, Opportunities, and Class Logistics

• The course incorporates engaging visual elements, including a T-shirt collection that currently includes approximately $15$ shirts (growing from $1$, then $2$ or $3$). For plant biology topics, shirts feature botanical patterns such as leaves, trees, or flowers, including one with the phrase "May the flowers be with you."

• Opportunities exist to participate in scientific research prior to completing introductory biology courses:

  • The Ecological Society of America (ESA) operates an email listserv for university professors, teachers, students, and researchers across academic, government, and consulting sectors.

  • Spring email updates detail undergraduate field opportunities, such as a wildlife research semester in Alaska.

  • A global research consortium is compiling a worldwide river and stream photograph database. Submissions are made via a QR code (posted on Blackboard) for streams in local backyards, metro park hiking trails, the Cuyahoga River, or international locations (e.g., Spain, Turkey, Australia, Japan).

  • Citizen Science: Research projects where any member of the public can record observations and contribute data to scientific databases.

  • Local volunteer opportunities include seasonal bird counts (e.g., organized participation supported by faculty in the chemistry department).

• iClicker and Course Technology Setup:

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Defining Life and the Scientific Status of Viruses

• Essential Criteria of Life:

  • All living organisms consist of one or more cells.

  • Living systems display complex order, organization, and structure.

  • Organisms carry out metabolic processes, reproduce, grow, develop, and maintain internal order.

  • Genetic material (nucleic acids) undergoes evolutionary change over generations.

• Biological Status of Viruses:

  • Structure: A virus consists of a particle of nucleic acid (RNA or DNA) enclosed within a protein coat (capsid). Some viruses acquire a surrounding layer derived from host cell membranes, but many do not.

  • Cellularity: Viruses are not composed of cells and do not contain cellular organelles.

  • Metabolic Activity and Reproduction: Viruses cannot independently perform chemical reactions, grow, or reproduce. They must infect a host organism, enter a host cell, and hijack the host cell's molecular machinery to replicate.

  • Evolutionary Capacity: Viral genetic material mutates and evolves over time. Examples include annual strain variations in influenza targeted by seasonal vaccines and emerging strains of COVID-19.

  • Classification: Biologists categorize viruses as non-living infectious particles rather than living organisms. They occupy a gray area between biotic and abiotic entities, demonstrating that biological systems do not always fit neatly into rigid conceptual categories.

The Hierarchical Organization and Categorization of Life

• Hierarchical Structure of Biological Organization (Smallest to Largest):

  1. Chemical Molecules: Fundamental chemical structures built from bonded atoms.

  2. Organelles: Subcellular functional components formed by complex molecular assemblies.

  3. Cells: The fundamental structural and functional unit of life.

  4. Tissues: A group of specialized cells of the same type working together to perform a specific function.

  5. Organs: A structure composed of multiple tissue types working together to perform complex tasks.

  6. Organ Systems: A group of organs co-functioning to execute broad physiological tasks (e.g., digestive system, respiratory system).

  7. Multicellular Organism: An individual living entity composed of integrated organ systems.

  8. Population: A group of individuals of the same species residing within a defined geographical area.

  9. Community: All interacting populations of different species inhabiting a shared area.

  10. Ecosystem: The biological community interacting with its surrounding non-living (abiotic) environment.

  11. Biosphere: The sum of all ecosystems across the planet.

• Emergent Properties:

  • As biological organization ascends to larger scales, novel properties emerge that are absent at lower organizational levels.

  • Broad scale questions (e.g., ecosystem-level abiotic interactions) cannot be studied solely at lower levels (e.g., individual tissues or cells).

  • Research often spans across scales (e.g., studying population mating behaviors requires analyzing molecular chemical signals).

• Unity and Diversity of Life:

  • Diversity: Planet Earth harbors an immense variety of distinct species.

  • Commonality: All living entities share fundamental features derived from a common ancestor, including cellular organization, identical biological macromolecule classes, and conserved metabolic activities.

• Biological Domains (The Broadest Categorical Rank):

  • Living organisms are divided into three overarching Domains:

  1. Bacteria: Single-celled organisms constructed from prokaryotic cells.

  2. Archaea: Single-celled organisms constructed from prokaryotic cells.

  3. Eukarya: Single-celled or multicellular organisms constructed from eukaryotic cells.

  • Evolutionary Relationships: Genetic sequencing reveals that despite being prokaryotic, domain Archaea is genetically closer to domain Eukarya than to domain Bacteria.

Fundamental Principles of Scientific Inquiry and Experimental Design

• Key Experimental Concepts:

  • Hypothesis: A tentative, testable explanation formulated for a specific scientific observation or question.

  • Scientific Theory: A comprehensive, broad explanation for natural phenomena that is extensively tested and supported by a vast body of empirical evidence.

  • Independent Variable: The experimental factor that is directly manipulated or varied by the researcher to test its effects.

  • Dependent Variable: The variable that is measured or observed to assess the effect of manipulating the independent variable.

  • Control Variables: Conditions kept strictly constant across all experimental groups to prevent them from influencing the dependent variable.

  • Control Treatment: The baseline group or zero-treatment condition used as a benchmark for comparison against experimental treatments.

  • Confounding Variables: Extraneous variables that cannot be easily separated from the independent variable, potentially distorting experimental results (e.g., attempting to isolate music style when style is inherently confounded by the historical era or age of the music, such as classical jazz versus traditional Australian Aboriginal didgeridoo music).

• Application and Evaluation of Hypotheses:

  • Scientific hypotheses must provide an explanation, yield testable predictions, and remain empirically falsifiable.

  • Non-Hypotheses Examples:

  • "Dogs are better pets than cats": Subjective opinion; untestable.

  • "Aliens exist in other galaxies": Currently untestable; lacks an explanatory mechanism.

  • "Why do leaves change color in the fall?": A scientific question, not a statement of explanation.

  • Valid Scientific Hypothesis Example: "Increasing the temperature of water will increase the rate at which sugar dissolves."

• Study Strategies:

  • Preparing via short-answer prompts rather than multiple-choice options promotes active recall, forces comprehensive memory retrieval, and prepares students for diverse question formulations.

Atomic Structure, Elements, and Isotopes

• Subatomic Particles:

  • Protons: Positively charged particles located in the atomic nucleus. Mass $\neq 0$ (defines the chemical element and its distinct chemical properties).

  • Neutrons: Uncharged (neutral) particles located in the atomic nucleus. Mass $\neq 0$.

  • Electrons: Negatively charged particles orbiting the nucleus in high-speed motion. Mass is negligible (treated as approximately $0$).

• Fundamental Calculations:

  • Atomic Number = Total number of Protons.

  • Atomic Mass = Total number of Protons + Total number of Neutrons.

  • Neutral Atom: Number of Electrons = Number of Protons.

  • Ion: An atom possessing an net electrical charge due to an imbalance between protons and electrons.

  • Cation: A positively charged ion formed by losing electrons ("Cats are positive").

  • Anion: A negatively charged ion formed by gaining electrons (Starts with 'N' for negative).

• Isotopes and Radiometric Dating:

  • Isotope: Variant forms of a single chemical element containing identical proton counts but differing numbers of neutrons.

  • Carbon Isotope Examples:

  • Carbon-12 ($^{12}\text{C}$): $6\text{ protons}$, $6\text{ neutrons}$ (Standard stable form).

  • Carbon-13 ($^{13}\text{C}$): $6\text{ protons}$, $7\text{ neutrons}$.

  • Carbon-14 ($^{14}\text{C}$): $6\text{ protons}$, $8\text{ neutrons}$ (Unstable, radioactive isotope).

  • Radiometric Carbon Dating: Radiocarbon ($^{14}\text{C}$) decays slowly over time at a predictable rate. Measuring residual $^{14}\text{C}$ in organic remains determines time elapsed since organism death. Useful up to approximately $70,000\text{ to }80,000\text{ years}$; older samples require isotopes with longer half-lives (e.g., Uranium isotopes).

Electron Configuration, Orbitals, and Chemical Reactivity

• Electron Shells and Valence:

  • Electrons move constantly within distinct dynamic regions surrounding the nucleus termed orbitals or electron shells.

  • Shell Energy Levels: Shells closer to the nucleus possess lower energy; outer shells possess higher energy.

  • Maximum Capacity Rules:

  • First (innermost) shell: Maximum $2\text{ electrons}$.

  • Second shell: Maximum $8\text{ electrons}$.

  • Valence Electrons: Electrons occupying the outermost shell of an atom.

  • Chemical Stability: Atoms attain maximum thermodynamic stability when their valence shell is either completely filled or completely empty.

• Chemical Behavior Across Periodic Table Groups:

  • Inert (Noble) Gases: Outermost shell is naturally full; completely unreactive under standard conditions.

  • Halogens (e.g., Chlorine, Iodine): Contain a valence shell missing exactly $1\text{ electron}$; readily accept $1\text{ electron}$ to form stable $1-$ anions ($\text{Cl}^-$, $\text{I}^-$).

  • Group 16 (e.g., Oxygen, Sulfur): Missing $2\text{ electrons}$ in valence shell; readily accept $2\text{ electrons}$ to form $2-$ anions ($\text{O}^{2-}$).

  • Alkali Metals (e.g., Hydrogen, Sodium, Potassium): Outer shell contains exactly $1\text{ valence electron}$; readily lose $1\text{ electron}$ to form $1+$ cations ($\text{H}^+$, $\text{Na}^+$, $\text{K}^+$).

  • Group 2 Metals (e.g., Calcium, Magnesium): Outer shell contains $2\text{ valence electrons}$; readily lose $2\text{ electrons}$ to form $2+$ cations ($\text{Ca}^{2+}$, $\text{Mg}^{2+}$).

• Valence and Bonding Capacity:

  • Hydrogen ($\text{H}$): $1\text{ valence opening} \rightarrow 1\text{ covalent bond}$.

  • Oxygen ($\text{O}$): $2\text{ valence openings} \rightarrow 2\text{ covalent bonds}$.

  • Nitrogen ($\text{N}$): $3\text{ valence openings} \rightarrow 3\text{ covalent bonds}$.

  • Carbon ($\text{C}$): $4\text{ valence openings} \rightarrow 4\text{ covalent bonds}$.

Chemical Bonding: Covalent, Ionic, and Polar Interactions

• Covalent Bonds:

  • Formed when two atoms share one or more pairs of valence electrons.

  • Represents the primary, most prevalent bond type in biological structures.

  • Bond Multiplicities:

  • Single Bond: Sharing $1$ pair of electrons.

  • Double Bond: Sharing $2$ pairs of electrons (e.g., Oxygen gas, $\text{O}_2$).

  • Triple Bond: Sharing $3$ pairs of electrons (e.g., Nitrogen gas, $\text{N}_2$, which constitutes $80\text{\%}$ of Earth's atmosphere and is extremely stable due to the high energy required to break triple bonds).

• Electronegativity and Polarity:

  • Electronegativity: The intrinsic measure of an atom's attraction or pull for shared electrons within a chemical bond.

  • Nonpolar Covalent Bond: Equal sharing of electrons occurring between atoms with identical or nearly identical electronegativities.

  • Examples: Bonds between identical atoms ($\text{H}_2$, $\text{O}_2$, $\text{N}_2$), Carbon-Carbon bonds ($\text{C}-\text{C}$), and Carbon-Hydrogen bonds ($\text{C}-\text{H}$).

  • Any biological molecule or region composed purely of carbon and hydrogen is nonpolar.

  • Polar Covalent Bond: Unequal electron sharing resulting from a significant difference in electronegativity between bonded atoms.

  • The highly electronegative atom pulls shared electrons closer, acquiring a partial negative charge ($\frac{1}{-}$ or \text{\delta}^-).

  • The less electronegative atom loses electron density, acquiring a partial positive charge (\text{\delta}^+).

  • Example: Water ($\text{H}_2\text{O}$). Oxygen possesses high electronegativity, pulling shared electrons away from Hydrogen. Consequently, the Oxygen atom bears a partial negative charge (\text{\delta}^-) and the Hydrogen atoms bear partial positive charges (\text{\delta}^+).

  • Biological Generalization: If oxygen is involved in a bond with carbon or hydrogen, the bond exhibits polar properties.

• Ionic Bonds:

  • Formed when an atom with high electronegativity completely strips an electron away from an atom with low electronegativity, generating fully charged ions.

  • The resulting positive cation and negative anion are held together by electrostatic attraction.

  • Common in inorganic crystals and minerals (e.g., Sodium Chloride, $\text{NaCl}$).

Chemical Reactions: Dehydration Synthesis and Hydrolysis

• Chemical Reaction: A process wherein existing chemical bonds within starting compounds (reactants) are broken, atoms are rearranged, and new chemical bonds are formed to yield distinct resulting compounds (products).

• Key Categories of Biological Reactions:

  • Dehydration Synthesis (Condensation Reaction):

  • Etymology: Dehydration (loss of water) + Synthesis (building/producing).

  • Definition: A chemical reaction that links smaller subunit molecules together to construct a larger molecule through the removal of water.

  • Mechanism: A hydroxyl group ($-\text{OH}$) is removed from one monomer and a hydrogen atom ($-\text{H}$) is removed from another. A new covalent bond forms directly between the two monomers, and the removed components combine to form a free water molecule ($\text{H}_2\text{O}$).

  • Hydrolysis:

  • Etymology: Hydro (water) + Lysis (breaking/cleavage).

  • Definition: A chemical reaction that breaks complex polymers down into smaller subunits using water.

  • Mechanism: A covalent bond between molecular subunits is cleaved. A water molecule ($\text{H}_2\text{O}$) is simultaneously broken into an $-\text{OH}$ group (which attaches to one released subunit) and an $-\text{H}$ atom (which attaches to the other released subunit).

Physicochemical Properties of Water and Their Biological Significance

• Essential Role: Water ($\text{H}_2\text{O}$) is the fundamental solvent essential for all known living organisms. Organisms adapted to desiccation enter dormant states and require water restoration for metabolic reactivation.

• Key Physicochemical Properties of Water:

  1. Hydrogen Bonding:

  • Because water is polar, the partial positive hydrogen (\text{\delta}^+) of one water molecule is electrostatically attracted to the partial negative oxygen (\text{\delta}^-) of a neighboring water molecule.

  • Individual hydrogen bonds are weak, but collective hydrogen bonding imparts unique physical properties to liquid water.

  1. Cohesion and Adhesion:

  • Cohesion: The tendency of water molecules to stick to each other via hydrogen bonding (produces high surface tension).

  • Adhesion: The tendency of water molecules to cling to other non-water polar or charged surfaces.

  1. Universal Solvent Properties:

  • Polarity enables water to readily dissolve ionic compounds and polar covalent molecules.

  • Dissolution Mechanism: Water molecules form hydration shells around ions, orienting partial negative oxygens toward cations (e.g., $\text{Na}^+$) and partial positive hydrogens toward anions (e.g., $\text{Cl}^-$).

  • Hydrophilic ("Water-loving"): Substances that are polar or charged and readily dissolve in water.

  • Hydrophobic ("Water-fearing"): Nonpolar, uncharged substances (e.g., oils, lipids) that do not dissolve in or mix with water.

  1. High Specific Heat:

  • Water absorbs or releases large amounts of heat energy before undergoing a significant change in temperature, buffering biological systems against sudden thermal fluctuations.

  1. Density Anomaly of Solid Water (Ice Floats):

  • Solid water (ice) is less dense than liquid water due to the expansion of its stable, hydrogen-bonded crystal lattice.

  • Environmental Impact: Ice floats on liquid water bodies, forming an insulating surface layer that protects aquatic organisms below during freezing winters. Exceptionally severe cold that freezes shallow ponds solid causes catastrophic winter fish kills.

  1. Ionization of Water:

  • Water molecules spontaneously dissociate into Hydrogen ions ($\text{H}^+$) and Hydroxide ions ($\text{OH}^-$):        $\text{H}_2\text{O} \rightleftharpoons \text{H}^+ + \text{OH}^-$

  • The relative concentration of free $\text{H}^+$ ions in solution defines its pH, directly impacting biological structure and reaction rates.