General Biology: Foundational Concepts and Key Topics

Three Scientific Domains

Overview of Biological Classification

The three domains of life represent the broadest classification of living organisms, based on genetic and cellular differences.

• Bacteria: Single-celled prokaryotes with unique cell wall structures.

• Archaea: Single-celled prokaryotes distinct from bacteria, often found in extreme environments.

• Eukarya: Organisms with eukaryotic cells, including animals, plants, fungi, and protists.

Life’s Hierarchical Sequence: Molecule to Biosphere

Levels of Biological Organization

Biological systems are organized in a hierarchy from the smallest chemical units to the entire biosphere.

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

Darwin’s Theory of Natural Selection

Mechanism of Evolution

Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring.

• Variation: Individuals in a population vary in their traits.

• Inheritance: Some traits are heritable.

• Overproduction: More offspring are produced than can survive.

• Differential Survival and Reproduction: Individuals with advantageous traits are more likely to survive and reproduce.

Scientific Method

Steps and Terminology

The scientific method is a systematic approach to inquiry in science.

• Problem/Question

• Hypothesis

• Experimental Design

• Data Collection and Analysis

• Drawing Conclusions

• Sharing Results

Variables:

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

• Dependent Variable: The factor that is measured or observed.

Basic Chemistry Terminology

Atoms, Molecules, and Ions

Understanding the basic units of matter is essential for studying biology.

• Atom: The smallest unit of an element, consisting of protons, neutrons, and electrons.

• Compound: A substance formed from two or more elements chemically bonded together.

• Molecule: Two or more atoms held together by covalent bonds.

• Ion: An atom or molecule with a net electric charge due to the loss or gain of electrons.

3D Structure of an Atom

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• Electron Cloud/Energy Levels: Regions where electrons are likely to be found.

• Atomic Number: Number of protons in an atom.

• Mass Number: Total number of protons and neutrons.

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

Types of Bonding (Covalent vs. Ionic)

Chemical Bonds in Biology

Atoms combine through chemical bonds to form molecules essential for life.

• Covalent Bond: Sharing of electron pairs between atoms.

• Ionic Bond: Transfer of electrons from one atom to another, resulting in oppositely charged ions.

• Additional types: Hydrogen bonds, van der Waals interactions.

Example: Water (H2O) has polar covalent bonds between hydrogen and oxygen.

Elements in Living Organisms

Major and Trace Elements

Living organisms are primarily composed of a few key elements.

• Four Most Common Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

• Trace Elements: Elements required in small amounts, such as iron (Fe), iodine (I), and zinc (Zn).

Chemical Equations and pH

Balancing and Understanding Reactions

• General Structure of an Equation: Reactants → Products

• Balancing Equations: Ensuring the same number of each atom on both sides of the equation.

• pH Scale: Measures the concentration of hydrogen ions ($[H^+]$) in a solution.

Equation:

$\text{pH} = -\log_{10}[H^+]$

Organic Compounds

Major Classes and Functions

• Carbohydrates: Sugars and polymers of sugars (monosaccharides, disaccharides, polysaccharides).

• Lipids: Hydrophobic molecules including fats, oils, and phospholipids.

• Proteins: Polymers of amino acids; perform a wide range of functions.

• Nucleic Acids: DNA and RNA; polymers of nucleotides.

Example: Starch (a polysaccharide) is a storage form of glucose in plants.

Hydrolysis and Dehydration Synthesis

Building and Breaking Down Molecules

• Dehydration Synthesis: Joins monomers by removing a water molecule.

• Hydrolysis: Breaks polymers into monomers by adding water.

Microscopy

Magnification and Resolution

• Magnification: The ratio of an object's image size to its real size.

• Resolution: The ability to distinguish two close objects as separate.

Cell Types: Prokaryotic vs. Eukaryotic

Key Differences

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles (e.g., bacteria, archaea).

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

Plant Cells vs. Animal Cells

Similarities and Differences

• Similarities: Both have a plasma membrane, cytoplasm, and organelles.

• Differences: Plant cells have a cell wall, chloroplasts, and a large central vacuole; animal cells do not.

Organelles of Eukaryotic Cells

Structure and Function

• Endomembrane System: Includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vesicles.

• Energy Processing: Mitochondria (cellular respiration) and chloroplasts (photosynthesis in plants).

• Structure, Support, and Communication: Cytoskeleton, cell wall (plants), and cell junctions.

DNA vs. RNA

Comparison of Nucleic Acids

Feature	DNA	RNA
Type of Sugar	Deoxyribose	Ribose
Nitrogenous Bases	A, T, C, G	A, U, C, G
Strands	Double-stranded	Single-stranded

Types of Junctions

Cell Communication and Adhesion

• Tight Junctions: Prevent leakage of extracellular fluid between cells.

• Desmosomes: Anchor cells together.

• Gap Junctions: Allow communication between animal cells.

• Plasmodesmata: Channels between plant cells for transport and communication.