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General Biology: Foundations, Scientific Method, and Chemistry of Life

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Chapter 1: Foundations of Biology and the Scientific Method

Learning Goals Overview

This section introduces the foundational concepts of biology, focusing on the characteristics of life, adaptation, and the scientific method. Understanding these principles is essential for further study in biology.

  • Condition of Life: Living organisms share certain characteristics, such as organization, metabolism, growth, adaptation, response to stimuli, and reproduction.

  • Adaptation and Natural Selection: Populations evolve over time through natural selection, where individuals with traits better suited to their environment are more likely to survive and reproduce.

  • Unique Adaptations: Different populations develop unique features that help them thrive in specific environments. For example, polar bears have thick fur and fat layers for cold climates.

The Scientific Method

The scientific method is a systematic approach to investigating natural phenomena. It involves several key steps:

  1. Observation: Gathering information about a phenomenon.

  2. Question: Formulating a question based on observations.

  3. Hypothesis: Proposing a testable explanation or prediction.

  4. Experiment: Designing and conducting experiments to test the hypothesis.

  5. Data Collection: Gathering and recording results.

  6. Analysis: Interpreting data to determine if it supports the hypothesis.

  7. Conclusion: Drawing conclusions and communicating results.

Variables in Scientific Experiments

  • Independent Variable: The factor that is changed or manipulated in an experiment.

  • Dependent Variable: The factor that is measured or observed in response to changes in the independent variable.

  • Controlled Variables (Constants): Factors that are kept the same throughout the experiment to ensure a fair test.

Graphical Data Interpretation

  • Abstracting and Interpreting Graphs: Understanding how to read and interpret data presented in graphical form is crucial for drawing valid conclusions from experiments.

  • Drawing Conclusions: Use trends and patterns in graphs to support or refute hypotheses.

Chapter 2: Chemistry of Life

Elements and Compounds

All matter is composed of elements and compounds, which are fundamental to biological processes.

  • Element: A pure substance consisting of only one type of atom (e.g., Oxygen, Carbon).

  • Compound: A substance formed when two or more elements are chemically bonded (e.g., H2O).

  • Examples: Water (H2O), Carbon Dioxide (CO2), Sodium Chloride (NaCl).

Atomic Structure

  • Protons: Positively charged particles in the nucleus.

  • Neutrons: Neutral particles in the nucleus.

  • Electrons: Negatively charged particles orbiting the nucleus.

  • Atomic Number: Number of protons in an atom.

  • Mass Number: Sum of protons and neutrons.

  • Charge: Determined by the difference between protons and electrons.

Example: Carbon-12 has 6 protons, 6 neutrons, and 6 electrons.

Electron Configuration and Covalent Bonds

  • Valence Electrons: Electrons in the outermost shell determine bonding behavior.

  • Covalent Bonds: Atoms share pairs of electrons to achieve stable electron configurations.

  • Bonding Capacity: Determined by the number of unpaired electrons in the valence shell.

Electronegativity and Bond Polarity

  • Electronegativity: The tendency of an atom to attract electrons in a bond.

  • Nonpolar Covalent Bond: Electrons are shared equally (e.g., O2).

  • Polar Covalent Bond: Electrons are shared unequally, creating partial charges (e.g., H2O).

  • Partial Charges: In polar molecules, the more electronegative atom has a partial negative charge (δ−), and the less electronegative atom has a partial positive charge (δ+).

Ionic vs. Covalent Bonds

  • Ionic Bond: Formed when electrons are transferred from one atom to another, resulting in oppositely charged ions (e.g., Na+ and Cl− in NaCl).

  • Covalent Bond: Involves sharing of electron pairs between atoms.

Comparison Table:

Bond Type

Electron Movement

Example

Covalent

Shared

H2O

Ionic

Transferred

NaCl

Hydrogen Bonds

  • Definition: Weak attractions between a hydrogen atom (partially positive) and an electronegative atom (such as oxygen or nitrogen) in another molecule.

  • Example: Hydrogen bonds between water molecules contribute to water's unique properties.

Properties of Water

  • Cohesion: Water molecules stick together due to hydrogen bonding.

  • Adhesion: Water molecules stick to other substances.

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

  • Solvent Abilities: Water dissolves many substances, supporting chemical reactions in living organisms.

Solubility in Water

  • Hydrophilic Substances: Polar and ionic compounds dissolve readily in water.

  • Hydrophobic Substances: Nonpolar compounds do not dissolve well in water.

pH, Acids, and Bases

  • pH: A measure of hydrogen ion concentration in a solution.

  • Formula:

  • Acids: Substances that increase hydrogen ion concentration ([H+]) in solution; pH < 7.

  • Bases: Substances that decrease hydrogen ion concentration ([H+]) in solution; pH > 7.

  • Neutral: pH = 7 (pure water).

Example: Lemon juice (acidic, pH ≈ 2), household ammonia (basic, pH ≈ 11).

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