Scientific Method and Experimental Design

Components of an Experiment

Understanding the structure of scientific experiments is fundamental in biology. Each experiment is designed to test hypotheses and answer specific questions about the natural world.

• Control: The part of the experiment that is left unaltered; serves as a baseline for comparison.

• Experimental (Independent) Variable: The variable that is intentionally changed to observe its effect.

• Hypothesis: A testable and falsifiable statement that predicts the outcome of an experiment.

• Experiment: The procedure carried out to test the hypothesis.

• Data: Information collected during the experiment, used to support or refute the hypothesis.

Theory and Reasoning

• Theory: A well-tested and widely accepted explanation for a set of observations or experimental results.

• Deductive Reasoning: Moves from general principles to specific cases (e.g., all mammals have hair; this animal has hair, so it is a mammal).

• Inductive Reasoning: Moves from specific observations to broader generalizations (e.g., observing several swans are white and concluding all swans are white).

Evolution and Classification

Natural Selection vs. Artificial Selection

Both are mechanisms that drive changes in populations, but they differ in their agents and outcomes.

• Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring.

• Artificial Selection: The intentional breeding of organisms by humans for specific traits (e.g., dog breeds).

Homologous vs. Analogous Structures

• Homologous Structures: Structures in different species that are similar due to shared ancestry (e.g., human arm and bat wing).

• Analogous Structures: Structures that serve similar functions but evolved independently (e.g., wings of birds and insects).

Characteristics of Life and Classification

Characteristics of Life (MR. ROUGH)

Living organisms share several key characteristics, often summarized by the acronym MR. ROUGH:

• Metabolism

• Response to stimuli

• Organization (cellular structure)

• Utilization of energy

• Growth and development

• Homeostasis

• Reproduction

Kingdoms and Classification

• Kingdoms: Major groups in biological classification, such as Plantae (plants, mostly multicellular), Animalia, Fungi, Protista, Archaea, and Bacteria.

Are Viruses Alive?

• Viruses do not meet all seven characteristics of life (e.g., they do not metabolize or reproduce independently), so they are generally not considered alive.

Basic Chemistry for Biology

Atoms, Molecules, and Mass

• Mass: The amount of substance in an object.

• Molecules: Groups of atoms held together by chemical bonds.

• Atoms: The basic units of matter, composed of protons, neutrons, and electrons.

pH and Acids/Bases

• pH Scale: Measures the concentration of hydrogen ions () in a solution; ranges from 0 (most acidic) to 14 (most basic), with 7 being neutral.

• Acidosis: Condition where the blood is too acidic (low pH).

• Alkalosis: Condition where the blood is too basic (high pH).

• Buffers: Substances that resist changes in pH by absorbing or releasing hydrogen ions.

Redox Reactions

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

• Mnemonic: "OIL RIG" (Oxidation Is Loss, Reduction Is Gain).

Chemical Bonds

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

• Ionic Bonds: Atoms transfer electrons, resulting in charged ions that attract each other.

• Hydrogen Bonds: Weak attractions between a hydrogen atom in one molecule and an electronegative atom (like oxygen or nitrogen) in another.

Water and Its Properties

Hydrophobic and Hydrophilic Interactions

• Hydrophobic: "Water-fearing"; substances that do not dissolve in water (e.g., oils).

• Hydrophilic: "Water-loving"; substances that dissolve easily in water (e.g., salts, sugars).

Important Elements in Biology

• Most common elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N).

Properties of Water

• High Specific Heat: Water can absorb a lot of heat before its temperature rises.

• Good Solvent: Many substances dissolve in water due to its polarity.

• Cohesion: Water molecules stick to each other (surface tension).

• Adhesion: Water molecules stick to other substances.

• Capillary Action: Movement of water within narrow spaces against gravity.

Macromolecules and Biochemistry

Dehydration vs. Hydrolysis Reactions

• Dehydration Synthesis: Builds macromolecules by removing water to form bonds.

• Hydrolysis: Breaks down macromolecules by adding water to break bonds.

Macromolecules

• Elements: The basic building blocks (e.g., C, H, O, N).

• Monomer: The repeating unit (e.g., amino acid for proteins, monosaccharide for carbohydrates).

• Function: The biological role (e.g., energy storage, structure, catalysis).

• Kcal/gram: Energy content per gram (e.g., carbohydrates and proteins: 4 kcal/g, fats: 9 kcal/g).

• Examples: Starch, cellulose, glycogen (carbohydrates); triglycerides (lipids); enzymes (proteins); DNA/RNA (nucleic acids).

Enzymes

• Function: Biological catalysts that speed up chemical reactions without being consumed.

• Denaturation: Loss of enzyme structure (and function) due to extreme conditions (e.g., heat, pH).

• Hydrogenation: Addition of hydrogen to unsaturated fats, making them more saturated.

• Naming of Sugars and Enzymes: Enzymes often end in "-ase" (e.g., lactase, amylase).

Membrane Components

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Draw and label: Phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails inward.

Isomers and Stereochemistry

• Isomers: Molecules with the same chemical formula but different structures.

• Stereoisomers: Same formula and sequence of bonded atoms, but different 3D orientations.

• Enantiomers: Mirror-image isomers.

DNA and RNA Base Pairing

• DNA: Adenine (A) pairs with Thymine (T); Cytosine (C) pairs with Guanine (G).

• RNA: Adenine (A) pairs with Uracil (U); Cytosine (C) pairs with Guanine (G).

Protein Structure

• Primary Structure (1°): Sequence of amino acids.

• Secondary Structure (2°): Local folding (e.g., alpha helices, beta sheets).

• Tertiary Structure (3°): Overall 3D shape of a single polypeptide.

• Quaternary Structure (4°): Association of multiple polypeptide chains.

Summary Table: Types of Chemical Bonds

Summary Table: Macromolecules

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard introductory biology curricula.