Chapter 1: Foundations of Biology

Scientific Approaches in Biology

Biology uses different approaches to advance knowledge and solve practical problems. The classification of research approaches is illustrated by "Pasteur's Quadrant" (Stokes, 1997), which compares the relevance of research for fundamental understanding and practical application.

• Theory leads to practice in various scientific professions (e.g., physicist to engineer, biologist to medical doctor).

• Biology is the scientific study of life.

• Themes in biology define all living things.

Characteristics of Life

All living organisms share several key characteristics:

• Energy and Matter: Organisms require energy and matter to maintain order and organization. Entropy (disorder) increases unless energy is used, as described by the second law of thermodynamics.

• Information: Organisms communicate and pass information (often encoded in DNA) to the next generation. DNA is known as genetic material, and its structure allows for storage and transmission of genetic information.

• Organization: Life requires organization of energy, matter, and information.

• Interactions: Organisms interact with their environment, other organisms, and previous generations.

Cell: The Basic Unit of Life

The cell is the smallest unit capable of performing all activities required for life. Organisms can be unicellular or multicellular.

• Prokaryotic Cells: Simpler, smaller, lack internal membrane-bound organelles. Two domains: Archaea and Bacteria. Tubular structure, typically have cell walls.

• Eukaryotic Cells: More advanced, can be unicellular or multicellular, have membrane-bound organelles, one domain: Eukarya. Most have cell walls.

Scales in Biology

Biology spans from molecules to cells, tissues, organs, organisms, populations, communities, ecosystems, and the biosphere. All levels must be living.

Chapter 1: Evolution and Diversity of Life

Classifying the Diversity of Life

Humans group organisms, but classification is always artificial. Scientific classification is based on observations and evolutionary relationships.

• All prokaryotic cells are unicellular.

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

Evolution: Unity and Diversity

Evolution explains both the unity and diversity of life. Changes in organisms arise by evolutionary processes and are passed to future generations.

• Information is passed in DNA from one generation to the next.

• Similar traits in organisms can be explained by descent from a common ancestor.

• Differences between species indicate heritable changes after divergence from a common ancestor.

Natural Selection

Natural selection is the process by which heritable changes that improve survival or reproduction become more common over time.

• Artificial selection is not natural; it is human-directed.

• Natural selection can lead to resistance (e.g., to antibiotics).

Chapter 2: Chemistry of Life

Elements and Atoms

Elements are pure substances made up of one type of atom. Atoms are the smallest units of matter that retain the properties of an element.

• The smallest unit is called an atom.

• Matter occupies physical space and has mass.

• 92 naturally occurring elements; 25 are crucial to life.

Structure of an Atom

• Nucleus: Contains protons (positive charge) and neutrons (no charge).

• Electrons: Negatively charged, orbit the nucleus.

Hydrogen Example

• Atomic number: 1 (number of protons)

• Atomic mass: 1.0079 u

• Mass number = number of protons + number of neutrons

Isotopes

• Atoms with the same number of protons but different numbers of neutrons are called isotopes.

• Example: Germanium (Ge) has atomic mass 72.64, but the number of neutrons varies.

Electron Shells

• The outermost shell is called the valence shell.

• Atoms are most stable when their valence shell is full.

Chemical Bonds

• Covalent Bonds: Electrons in valence shells are shared. Single, double, or triple bonds possible. Strongest type of chemical bond.

• Ionic Bonds: Electrons are transferred from one atom to another, creating ions with positive or negative charges. Weaker in water.

• Weak Chemical Interactions: Hydrogen bonds and van der Waals interactions. Important for protein folding, enzyme substrate binding, and membrane structure.

Chapter 2: Water and Its Properties

Water: Structure and Properties

• Water is a polar solvent, able to dissolve many molecules.

• Hydrogen bonds form between water molecules, giving water unique properties.

• High specific heat: Water resists temperature change.

• High heat of vaporization: Large amounts of energy required to change water from liquid to gas.

Cohesion and Adhesion

• Cohesion: Attraction between water molecules due to hydrogen bonding.

• Adhesion: Attraction between water and other substances.

Hydrophilic and Hydrophobic Substances

• Hydrophilic: Polar molecules that interact with water.

• Hydrophobic: Nonpolar molecules that do not interact with water (e.g., oils, waxes).

pH and Acidity

• pH: Measures the concentration of hydrogen ions () in a solution.

• pH scale:

• pH 7 is neutral; lower is acidic, higher is basic.

• Most biological fluids have pH values between 6 and 8.

• Biological buffers minimize changes in pH.

Chapter 3: Molecules and Bonds

Bonds Within and Between Molecules

• Covalent Bonds: Atoms share electrons; can be polar or nonpolar.

• Ionic Bonds: Atoms transfer electrons; form ions.

• Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom.

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

Hydronium Ions and pH

• Hydronium ion:

• pH is determined by the concentration of hydronium ions.

• pH formula:

Summary Table: Types of Chemical Bonds

Additional info:

• Some context and explanations have been expanded for clarity and completeness.

• Tables have been recreated and summarized for comparison and classification purposes.