BackGeneral Biology I: Study Guide for Exam 1 (Chapters 1 & 2)
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Chapter 1: Introduction to Biology and the Scientific Method
Properties of Life
Living organisms share several key characteristics that distinguish them from non-living matter.
Order: Living things exhibit complex but ordered organization.
Regulation: Organisms can regulate their internal environment (homeostasis).
Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.
Energy Processing: Living things obtain and use energy for maintenance and growth.
Response to Environment: Organisms respond to environmental stimuli.
Reproduction: Organisms reproduce their own kind.
Evolutionary Adaptation: Populations evolve over generations through adaptations.
The Scientific Method
The scientific method is a systematic approach to understanding the natural world through observation and experimentation.
Steps of the Scientific Method:
Observation: Gathering information about phenomena.
Question: Formulating a question based on observations.
Hypothesis: Proposing a testable explanation.
Prediction: Making a logical prediction based on the hypothesis.
Experiment: Testing the hypothesis through controlled experiments.
Analysis: Interpreting the data collected.
Conclusion: Drawing conclusions and communicating results.
Experiment: A scientific test carried out under controlled conditions.
Variables:
Independent Variable: The factor that is changed or manipulated by the researcher (plotted on the x-axis of a graph).
Dependent Variable: The factor that is measured or observed (plotted on the y-axis of a graph).
Control Variables (Constants): Factors kept the same throughout the experiment to ensure a fair test.
Charles Darwin and the Theory of Evolution
Charles Darwin was a naturalist who developed the theory of evolution by natural selection, explaining how species change over time.
Descent with Modification: The idea that species change over generations, giving rise to new species while sharing a common ancestor.
Darwin's Observations:
Variation exists within populations.
More offspring are produced than can survive.
Organisms compete for limited resources.
Traits that enhance survival and reproduction become more common in a population.
Four Steps of Natural Selection:
Variation in traits exists among individuals.
Some variations are heritable.
More individuals are produced than can survive (struggle for existence).
Individuals with advantageous traits survive and reproduce more successfully.
Unity and Diversity: All living things share fundamental characteristics (unity), yet display a wide variety of forms and functions (diversity). For example, all organisms use DNA as genetic material, but the structure and function of organisms vary greatly.
Chapter 2: The Chemical Context of Life
Basic Chemistry Concepts
Understanding the chemical basis of life is essential for studying biology. Atoms, elements, and molecules form the foundation of biological structures and processes.
Matter: Anything that has mass and takes up space.
Element: A substance that cannot be broken down into other substances by chemical means. Examples: carbon, hydrogen, oxygen.
Essential Elements: Elements required for an organism to survive, grow, and reproduce (e.g., C, H, O, N).
Trace Elements: Elements required in very small amounts (e.g., iron, iodine).
Atom: The smallest unit of an element that retains its properties.
Subatomic Particles:
Proton: Positively charged particle in the nucleus.
Neutron: Neutral particle in the nucleus.
Electron: Negatively charged particle orbiting the nucleus.
Atomic Number: Number of protons in an atom.
Mass Number: Sum of protons and neutrons in an atom.
Atomic Mass (Atomic Weight): The average mass of an atom, accounting for all isotopes.
Isotopes: Atoms of the same element with different numbers of neutrons.
Radioactive Isotopes: Unstable isotopes that decay, emitting radiation; used in dating fossils (e.g., carbon dating).
Chemical Bonds and Interactions
Atoms combine to form molecules through chemical bonds, which are essential for the structure and function of biological molecules.
Chemical Bond: The force that holds atoms together in a molecule.
Covalent Bond: A bond formed when two atoms share one or more pairs of electrons.
Single Bond: Sharing of one pair of electrons.
Double Bond: Sharing of two pairs of electrons. (Additional info: Not explicitly listed but commonly covered.)
Nonpolar Covalent Bond: Electrons are shared equally between atoms.
Polar Covalent Bond: Electrons are shared unequally, resulting in partial positive and negative charges.
Partial Positive/Negative: In polar covalent bonds, the atom with higher electronegativity attracts electrons more strongly, becoming partially negative (δ−), while the other becomes partially positive (δ+).
Ionic Bond: A bond formed when one atom transfers electrons to another, resulting in oppositely charged ions that attract each other.
Hydrogen Bond: A weak bond between a hydrogen atom (partially positive) and an electronegative atom (often oxygen or nitrogen).
Van der Waals Forces: Weak attractions between molecules due to temporary partial charges.
Hydrophobic Interaction: The tendency of nonpolar molecules to cluster together in water.
Electron Configuration and Chemical Reactivity
The arrangement of electrons in an atom determines its chemical behavior.
Valence Electrons: Electrons in the outermost shell; determine chemical reactivity.
Valence Shell: The outermost electron shell of an atom.
Orbital: A region of space where an electron is likely to be found.
Electronegativity: The ability of an atom to attract electrons in a covalent bond.
Chemical Reactions
Chemical reactions involve the making and breaking of chemical bonds, transforming reactants into products.
Chemical Reaction: A process that changes one set of chemicals into another.
Reactants: Substances that start a chemical reaction.
Products: Substances produced by a chemical reaction.
Chemical Equilibrium: The state in which the rate of the forward reaction equals the rate of the reverse reaction.
Example: Water Formation
When hydrogen and oxygen react to form water:
Reactants:
Product:
Summary Table: Types of Chemical Bonds
Bond Type | Description | Strength (Relative) | Example |
|---|---|---|---|
Covalent | Atoms share electrons | Strong | H2O (water) |
Ionic | Transfer of electrons; attraction between ions | Strong (in dry conditions) | NaCl (table salt) |
Hydrogen | Attraction between H (δ+) and electronegative atom (δ−) | Weak | Between water molecules |
Van der Waals | Temporary attractions due to fluctuating charges | Very weak | Between nonpolar molecules |
Additional info: Some terms and examples were expanded for clarity and completeness based on standard General Biology curriculum.
