Chapter 1 – Evolution and the Foundations of Biology

Hierarchy of Life

The biological world is organized in a hierarchy from the largest to the smallest scale, each level building on the previous one.

• Biosphere: All life on Earth and all places where life exists.

• Ecosystem: All living things in a particular area, along with nonliving components.

• Community: Array of organisms inhabiting a particular ecosystem.

• Population: All individuals of a species within an area.

• Organism: Individual living thing.

• Organ/Organ System: Body part(s) that carry out a function.

• Tissue: Group of cells performing a function.

• Cell: Smallest unit of life.

• Organelle: Functional components within cells.

• Molecule: Chemical structure of two or more atoms.

Emergent Properties

Emergent properties are new characteristics that arise at each level of organization, due to the arrangement and interactions of parts as complexity increases.

• Example: A functioning bicycle emerges only when all necessary parts are connected in the correct way.

Cells: The Smallest Unit of Life

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles (e.g., bacteria, archaea).

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

DNA and Genetic Information

• DNA (Deoxyribonucleic Acid): The molecule that stores genetic information.

• Structure: Double helix composed of nucleotides (adenine, thymine, cytosine, guanine) with a sugar-phosphate backbone.

• Gene: A segment of DNA that codes for a protein or RNA molecule.

• Nucleotides: Building blocks of DNA, each consisting of a sugar, phosphate group, and nitrogenous base.

• Chromosome: DNA packaged with proteins.

• Gene Expression: The process by which information from a gene is used to synthesize a functional product (protein or RNA).

Energy Flow and Nutrient Cycling

• Energy flows one-way through an ecosystem (usually entering as sunlight, exiting as heat).

• Nutrients cycle within an ecosystem (e.g., carbon, nitrogen cycles).

Interactions in Ecosystems

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

• Consumers (heterotrophs): Organisms that consume other organisms for energy.

Evolution and Diversity

• Evolution: The process of change that has transformed life on Earth; explains both unity and diversity of life.

• Three Domains: Bacteria, Archaea (both prokaryotic), and Eukarya (eukaryotic).

• Natural Selection: Mechanism of evolution proposed by Charles Darwin; individuals with advantageous traits survive and reproduce more.

The Scientific Process

• Steps: Observation, Question, Hypothesis, Prediction, Experiment, Analysis, Conclusion.

• Hypothesis: Testable explanation for an observation.

• Null Hypothesis: Statement that there is no effect or difference.

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

• Variables: Independent (manipulated), Dependent (measured).

• Control Group: Group not exposed to the experimental treatment.

• Blind/Double Blind: Methods to reduce bias in experiments.

• Statistics: Used to analyze data; larger sample sizes increase reliability.

• Pseudoscience: Claims lacking scientific evidence.

• Anecdotal Evidence: Personal stories, not reliable for scientific conclusions.

Chapter 2 – The Chemical Context of Life

Elements and Atoms

• Element: Substance that cannot be broken down by chemical means.

• Atom: Smallest unit of an element, composed of protons, neutrons, and electrons.

• Key Elements in Life: Carbon, Hydrogen, Oxygen, Nitrogen (CHON), plus trace elements.

Atomic Structure and Chemical Properties

• Protons: Positively charged, in nucleus.

• Neutrons: Neutral, in nucleus.

• Electrons: Negatively charged, orbit nucleus in shells.

• Electron Shells: Energy levels where electrons reside; arrangement determines chemical properties.

• Valence Electrons: Electrons in the outermost shell; determine reactivity.

Energy in Atoms

• Energy: Capacity to cause change.

• Potential Energy: Stored energy due to position or structure.

• Kinetic Energy: Energy of motion.

• Thermal Energy: Kinetic energy associated with random movement of atoms/molecules.

Chemical Bonds

• Ionic Bonds: Transfer of electrons between atoms.

• Covalent Bonds: Sharing of electrons; can be polar (unequal sharing) or nonpolar (equal sharing).

• Hydrogen Bonds: Weak bonds between partially positive hydrogen and electronegative atom.

• van der Waals Interactions: Weak attractions due to transient local charges.

• Electronegativity: Atom's attraction for electrons in a bond; determines bond polarity.

Chemical Reactions and Equilibrium

• Reactants: Starting materials.

• Products: Resulting materials.

• Chemical Equilibrium: Rate of forward and reverse reactions are equal.

Properties of Water

• Polarity: Water is polar due to unequal sharing of electrons.

• Hydrogen Bonding: Leads to cohesion, adhesion, high specific heat, and surface tension.

• Specific Heat: Amount of heat to change temperature of 1g by 1°C.

• Evaporative Cooling: As water evaporates, it removes heat, cooling surfaces.

• Ice Floats: Solid water is less dense than liquid, insulating aquatic life.

• Solvent of Life: Water dissolves many substances due to polarity.

• Hydrophilic: Water-loving; substances that dissolve in water.

• Hydrophobic: Water-fearing; substances that do not dissolve in water.

Acids, Bases, and pH

• Acid: Increases H+ concentration.

• Base: Reduces H+ concentration (often increases OH-).

• pH Scale: Measures H+ concentration; $ pH = -\log_{10}[H^+] $

Chapter 3 – Carbon and the Molecular Diversity of Life

Organic Compounds and Carbon

• Organic Compounds: Contain carbon and hydrogen.

• Hydrocarbons: Molecules of only carbon and hydrogen.

• Macromolecules: Large molecules (carbohydrates, lipids, proteins, nucleic acids).

• Carbon's Versatility: Forms four covalent bonds, allowing diverse structures.

Chemical Groups and ATP

• Chemical Groups: Functional groups attached to carbon skeletons; seven important ones include hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, methyl.

• ATP (Adenosine Triphosphate): Main energy currency of the cell.

Macromolecules: Polymers and Monomers

• Polymers: Long molecules made of repeating units (monomers).

• Dehydration Reaction: Joins monomers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

• Polysaccharides: Many monosaccharides (e.g., starch, cellulose, glycogen).

• Functions: Energy storage, structural support.

Lipids

• Fats: Glycerol + fatty acids; energy storage.

• Phospholipids: Major component of cell membranes.

• Steroids: Four fused rings (e.g., cholesterol).

Proteins

• Amino Acids: Building blocks of proteins; differ by side chains (R groups).

• Polypeptides: Chains of amino acids linked by peptide bonds.

• Protein Structure: Four levels – primary (sequence), secondary (alpha helix, beta sheet), tertiary (3D shape), quaternary (multiple polypeptides).

• Denaturation: Loss of structure and function due to environmental changes.

• Enzymes: Proteins that act as catalysts to speed up reactions.

Nucleic Acids

• DNA and RNA: Store and transmit genetic information.

• Polynucleotides: Chains of nucleotides.

• Pyrimidines: Cytosine, thymine, uracil (single ring).

• Purines: Adenine, guanine (double ring).

• Deoxyribose: Sugar in DNA; Ribose: Sugar in RNA.

• Prime ('): Denotes carbon positions in sugar ring.

• Double Helix: Structure of DNA; two antiparallel strands.

Chapter 4 – A Tour of the Cell

Cell Types and Organelles

• Prokaryotic Cells: No nucleus, simple structure (bacteria, archaea).

• Eukaryotic Cells: Nucleus, complex organelles (plants, animals, fungi, protists).

• Organelles: Specialized structures with specific functions.

Microscopy and Cell Fractionation

• Light Microscopes: Use light to view cells.

• Electron Microscopes: Use electrons for higher resolution (TEM for internal, SEM for surface).

• Cell Fractionation: Technique to separate cell components.

Cellular Structures

• Cytoplasm: Region between plasma membrane and nucleus.

• Animal vs. Plant Cells: Plant cells have cell walls, chloroplasts, central vacuole; animal cells have lysosomes, centrioles.

• Surface Area to Volume Ratio: Limits cell size; higher ratio favors efficient exchange.

Membranes and the Endomembrane System

• Phospholipids: Main component of biological membranes.

• Plasma Membrane: Selective barrier around cell.

• Endomembrane System: Includes nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, plasma membrane.

• Protein Secretion: Synthesized in rough ER, modified in Golgi, transported via vesicles.

Endosymbiosis Hypothesis

• Mitochondria and chloroplasts originated from engulfed prokaryotes.

Cytoskeleton and Cell Movement

• Microtubules, Microfilaments, Intermediate Filaments: Provide support, movement, and shape.

• Motor Proteins: Move along cytoskeletal fibers.

• Centrosomes, Centrioles, Basal Bodies, Dyneins: Involved in cell division and movement.

• Cilia and Flagella: Structures for movement; powered by dynein arms.

• Actin and Myosin: Proteins involved in muscle contraction and cell movement.

Cell Walls and Extracellular Matrix (ECM)

• Cell Wall: Found in plants, fungi, some protists; provides support.

• ECM: Network outside animal cells; composed of glycoproteins (e.g., collagen).

Cell Junctions

• Plant Cells: Plasmodesmata (channels between cells).

• Animal Cells: Tight junctions, desmosomes, gap junctions.

Chapter 5 – Membrane Transport & Cell Signaling

Membrane Structure and Function

• Fluid Mosaic Model: Membrane is a fluid structure with proteins embedded in or attached to a double layer of phospholipids.

• Proteins: Serve as transporters, receptors, enzymes, anchors.

Transport Across Membranes

• Selective Permeability: Only certain molecules can cross.

• Diffusion: Movement from high to low concentration.

• Osmosis: Diffusion of water across a membrane.

• Passive Transport: No energy required (diffusion, facilitated diffusion).

• Active Transport: Requires energy (ATP) to move substances against gradient.

• Aquaporins: Channel proteins for water transport.

• Cotransport: Coupled transport of two substances; often uses a gradient created by active transport.

• Bulk Transport: Exocytosis (out), endocytosis (in), phagocytosis (cell eating), pinocytosis (cell drinking), receptor-mediated endocytosis (specific uptake).

Cell Signaling

• Signal Transduction Pathway: Series of steps by which a signal on a cell's surface is converted to a specific response.

• Second Messengers: Small molecules/ions that relay signals inside the cell (e.g., cAMP, Ca2+).

• G-Protein Coupled Receptors (GPCRs): Membrane receptors that activate G-proteins, triggering signaling cascades.

• Phosphorylation: Addition of phosphate group to a protein, often activating it.

• Phosphorylation Cascade: Series of protein kinases activating each other by phosphorylation.

• Testosterone Signaling: Steroid hormone passes through membrane, binds receptor, alters gene expression.

Additional info: These notes expand on the study guide's outline, providing definitions, examples, and context for foundational biology concepts relevant to the first five chapters of a General Biology course.