Chapters 1, 2 & 3: Foundations of Biology

Overview

This study guide covers the introductory chapters of General Biology, focusing on the themes of biology, scientific inquiry, the chemical context of life, and the properties of water essential for life.

Evolution, Themes of Biology, and Scientific Inquiry

Definition of Biology

• Biology is the scientific study of life.

• Life is recognized by the activities and characteristics of living things.

• Biology encompasses a vast scope, from molecular processes to global ecosystems.

Properties of Life

Living organisms share several key properties that distinguish them from non-living matter.

• Order: Living things exhibit complex organization.

• Regulation (Homeostasis): Maintenance of stable internal conditions.

• Energy Processing: Acquisition and use of energy for metabolic activities.

• Response to the Environment: Ability to sense and react to stimuli.

• Growth and Development: Increase in size and change in form, guided by genetic information.

• Reproduction: Production of new organisms.

• Evolutionary Adaptation: Populations change over generations to adapt to their environment.

Levels of Biological Organization

Biology studies life at multiple levels, from molecules to the biosphere.

• Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

• Each level shows a correlation between structure and function.

Cell Theory: The Basic Unit of Life

• All living organisms are made of cells.

• The cell is the smallest unit capable of performing all activities required for life.

• Cells contain a membrane, DNA, and cytoplasm.

• Organisms can be unicellular (one cell) or multicellular (many cells).

• Prokaryotic cells (bacteria, archaea): No nucleus, generally smaller.

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

Evolution: The Core Theme of Biology

• Evolution explains both the unity and diversity of life.

• All living organisms are modified descendants of common ancestors.

• Charles Darwin's theory of natural selection describes how species adapt and evolve.

• "Nothing in biology makes sense except in the light of evolution."

Classification: The Diversity of Life

• Approximately 1.8 million species have been identified.

• Each species is given a two-part scientific name: Genus species (e.g., Homo sapiens).

• Life is organized into three domains:

Scientific Inquiry and the Scientific Method

• Science is derived from the Latin word meaning "to know."

• Scientific inquiry involves observation, hypothesis formation, experimentation, and analysis.

• The scientific method steps:

  1. Observation

  2. Hypothesis

  3. Prediction and Experiment

  4. Data Collection and Analysis

  5. Conclusion

• Hypotheses must be testable and falsifiable.

• Experiments include controlled variables (independent and dependent variables).

• A theory is broader than a hypothesis and supported by substantial evidence.

The Chemical Context of Life

Matter, Elements, and Compounds

• Matter is anything that takes up space and has mass.

• Element: A substance that cannot be broken down by chemical reactions.

• Compound: A substance consisting of two or more elements in a fixed ratio.

• Compounds have emergent properties different from their constituent elements.

Elements in the Human Body

Atoms and Atomic Structure

• Atom: The smallest unit of matter retaining the properties of an element.

• Composed of protons (+), neutrons (0), and electrons (-).

• Atomic number: Number of protons.

• Mass number: Protons + neutrons.

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

• Radioactive isotopes decay spontaneously and are used in medicine and dating fossils.

Electron Shells and Chemical Behavior

• Electrons occupy shells with specific energy levels.

• First shell: up to 2 electrons; second shell: up to 8 electrons.

• Valence electrons are in the outermost shell and determine chemical reactivity.

• Atoms with full valence shells are chemically inert.

Chemical Bonds and Molecules

• Atoms with incomplete valence shells form chemical bonds by sharing or transferring electrons.

• Covalent bonds: Sharing of electron pairs between atoms.

• Single covalent bond: One pair shared; double bond: two pairs shared.

• Electronegativity: Atom's attraction for shared electrons.

• Nonpolar covalent bond: Equal sharing of electrons.

• Polar covalent bond: Unequal sharing, leading to partial charges.

• Ionic bonds: Transfer of electrons, resulting in charged ions (cation and anion).

• Hydrogen bonds: Weak attraction between a hydrogen atom and an electronegative atom (e.g., O or N).

• Van der Waals interactions: Weak attractions due to transient charges.

Water and Life

Properties of Water

• Water molecules form hydrogen bonds due to their polar covalent bonds.

• Four emergent properties critical for life:

  1. Cohesive behavior: Water molecules stick together, resulting in high surface tension.

  2. Ability to moderate temperature: High specific heat and heat of vaporization stabilize temperatures.

  3. Expansion upon freezing: Ice is less dense than liquid water, allowing it to float.

  4. Versatility as a solvent: Water dissolves many substances, making it the "solvent of life."

Water as a Solvent

• Solution: Homogeneous mixture of substances.

• Solvent: Dissolving agent (water in aqueous solutions).

• Solute: Substance dissolved.

• Hydrophilic substances: Affinity for water (e.g., salts, sugars).

• Hydrophobic substances: Repel water (e.g., oils).

Acids, Bases, and Buffers

• Water dissociates into hydronium () and hydroxide () ions.

• Acids: Increase concentration.

• Bases: Reduce concentration, often by increasing .

• pH scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

• Each pH unit represents a tenfold change in concentration.

• Buffers: Minimize changes in pH by reversible binding of ions.

Key Equations

• Dissociation of water:

• pH calculation:

Example: Buffer System in Blood

• The bicarbonate buffer system maintains blood pH:

Additional info: This guide expands on the brief points in the slides to provide full academic context, definitions, and examples for foundational biology topics.