General Biology: Practice Exam 1 Study Guide (Modules 2–7)

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Scientific Method and Inquiry in Biology

Understanding the Scientific Method

The scientific method is a systematic approach to investigating natural phenomena. Inquiry is essential because it allows scientists to ask questions, form hypotheses, and test predictions through experimentation and observation.

Observation: Gathering information about phenomena or problems.
Hypothesis: A testable explanation for an observation.
Experimentation: Testing hypotheses under controlled conditions.
Analysis: Interpreting data to support or refute the hypothesis.
Conclusion: Drawing inferences and refining hypotheses as needed.

Example: A scientist observes that a flashlight does not work and forms hypotheses about possible causes (e.g., dead batteries, burnt bulb), then tests each hypothesis.

Hypotheses vs. Theories

Distinguishing Hypotheses from Theories

A hypothesis is a specific, testable statement about a single phenomenon, while a theory is a broad, well-supported explanation for a wide range of phenomena.

Hypothesis: Narrow in scope, can be tested directly.
Theory: Broad in scope, supported by extensive evidence, can generate new hypotheses.

Example: "Evolution by natural selection" is a theory, while "If plants receive more sunlight, they will grow faster" is a hypothesis.

Major Limitations of Science

Understanding the Boundaries of Scientific Inquiry

Science cannot test hypotheses that are untestable, supernatural, or not falsifiable. It is limited to natural phenomena and cannot address moral, aesthetic, or supernatural questions.

Testability: Hypotheses must be testable and falsifiable.
Natural Explanations: Science deals only with natural causes and effects.

Classification of Life

Three Domains of Life

All living organisms are classified into three domains based on cellular organization and genetics:

Bacteria: Single-celled prokaryotes with unique cell wall structures.
Archaea: Single-celled prokaryotes, often found in extreme environments.
Eukarya: Organisms with eukaryotic cells, including plants, animals, fungi, and protists.

Prokaryotes vs. Eukaryotes

Prokaryotes: Lack a nucleus and membrane-bound organelles (Bacteria and Archaea).
Eukaryotes: Have a nucleus and membrane-bound organelles (Eukarya).

Unity and Diversity of Life

Comparing and Contrasting Life Forms

All life shares a common ancestry, reflected in universal genetic code and cellular structure, but diversity arises through evolution and adaptation.

Unity: DNA as genetic material, similar cellular processes.
Diversity: Adaptations to different environments, speciation.

Evolution and Natural Selection

Theory of Evolution

Evolution explains the unity and diversity of life. Natural selection is the process by which organisms better adapted to their environment tend to survive and reproduce.

Variation: Individuals in a population vary in traits.
Inheritance: Traits are heritable.
Selection: Some traits confer a survival or reproductive advantage.
Adaptation: Advantageous traits become more common over generations.

Example: Darwin's finches evolved different beak shapes to exploit different food sources.

Chemical Context of Life

Atoms, Elements, Compounds, and Molecules

Atom: Smallest unit of matter retaining properties of an element.
Element: Substance consisting of one type of atom.
Compound: Substance formed from two or more elements in a fixed ratio.
Molecule: Two or more atoms held together by covalent bonds.

Common Elements in Living Matter

CHON: Carbon, Hydrogen, Oxygen, and Nitrogen are the most abundant elements in living organisms.

Structure of Atoms

Protons: Positively charged, in nucleus.
Neutrons: No charge, in nucleus.
Electrons: Negatively charged, orbit nucleus.

Isotopes

Isotopes: Atoms of the same element with different numbers of neutrons.

Chemical Bonds

Covalent and Ionic Bonds

Covalent Bonds: Atoms share electrons.
Ionic Bonds: Atoms transfer electrons, resulting in charged ions.

Electronegativity and Polarity

Electronegativity: Atom's ability to attract electrons.
Polar Covalent Bonds: Unequal sharing of electrons.
Nonpolar Covalent Bonds: Equal sharing of electrons.

Water and Life

Structure and Properties of Water

Polarity: Water is a polar molecule with partial positive (H) and negative (O) charges.
Hydrogen Bonds: Weak attractions between water molecules.
Cohesion and Adhesion: Water molecules stick to each other and to other surfaces.
High Specific Heat: Water resists temperature changes.

pH and Acids/Bases

pH Scale: Measures hydrogen ion concentration; lower pH = more acidic.
Acids: Donate H+ ions.
Bases: Accept H+ ions or donate OH- ions.

Equation:

Carbon and Molecular Diversity

Organic Molecules and Functional Groups

Carbon: Forms four covalent bonds, allowing for diverse organic molecules.
Functional Groups: Specific groups of atoms that confer chemical properties (e.g., hydroxyl, carboxyl, amino, phosphate).

Biological Macromolecules

Classes of Biological Molecules

Carbohydrates: Sugars and polymers; energy storage and structure.
Lipids: Fats, oils, phospholipids; energy storage, membranes.
Proteins: Polymers of amino acids; structure, enzymes, signaling.
Nucleic Acids: DNA and RNA; genetic information.

Monomers and Polymers

Monomers: Building blocks (e.g., monosaccharides, amino acids, nucleotides).
Polymers: Chains of monomers (e.g., polysaccharides, polypeptides, nucleic acids).

Dehydration and Hydrolysis Reactions

Dehydration Synthesis: Joins monomers by removing water.
Hydrolysis: Breaks polymers by adding water.

Proteins and Amino Acids

Structure of Amino Acids

Amino Group, Carboxyl Group, Side Chain (R group): Determines properties of each amino acid.

Levels of Protein Structure

Primary: Sequence of amino acids.
Secondary: Alpha helices and beta sheets (hydrogen bonding).
Tertiary: 3D folding (interactions among R groups).
Quaternary: Multiple polypeptide chains.

Protein Denaturation

Denaturation: Loss of structure and function due to environmental changes (e.g., pH, temperature).

Carbohydrates

Structure and Function

Monosaccharides: Simple sugars (e.g., glucose).
Disaccharides: Two monosaccharides joined by glycosidic bond.
Polysaccharides: Long chains (e.g., starch, glycogen, cellulose).

General Formula:

Energy Storage and Structural Polysaccharides

Starch: Energy storage in plants.
Glycogen: Energy storage in animals.
Cellulose: Structural component in plant cell walls.

Summary Table: Major Classes of Biological Molecules

Class	Monomer	Polymer	Main Functions
Carbohydrates	Monosaccharide	Polysaccharide	Energy storage, structure
Lipids	Fatty acids, glycerol	Triglycerides, phospholipids	Energy storage, membranes
Proteins	Amino acid	Polypeptide	Enzymes, structure, signaling
Nucleic Acids	Nucleotide	DNA, RNA	Genetic information