General Biology Study Guide: Themes of Biology, Scientific Method, and Chemistry of Life

Chapter 1 – Themes of Biology and Scientific Method

Characteristics of Life

Biology is the scientific study of life, and living organisms share several key characteristics that distinguish them from non-living matter.

• Reproduction: Ability to produce offspring.

• Growth and Development: Increase in size and change in form during life.

• Energy Use: Metabolism and energy transformation.

• Order: Highly organized structure.

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

• Response to Environment: Reacting to stimuli.

• Evolution: Populations change over time.

• Cell: The smallest unit that displays all characteristics of life.

Example: Escherichia coli (E. coli) is a single-celled organism that exhibits all characteristics of life.

Unity and Diversity of Life

Life on Earth is unified by common ancestry and diversified by evolutionary processes.

• Unity: Shared traits like DNA, ribosomes, and genetic code.

• Diversity: Differences arise from adaptation to different environments and natural selection.

• Darwin's Theory: Natural selection leads to diversity from a common ancestor.

Example: All mammals share hair and mammary glands, but have adapted to various environments.

Emergent Properties

Emergent properties are new characteristics that arise at each level of biological organization due to the arrangement and interactions of parts.

• Definition: Properties not present at lower levels, but emerge as complexity increases.

• Examples:

  • Photosynthesis in chloroplasts (requires organization of molecules).

  • Brain function (requires presence of neurons and their connections).

Levels of Biological Organization

Life is organized into hierarchical levels, each with specific definitions.

• 1. Biosphere: All environments on Earth supporting life.

• 2. Ecosystems: All organisms and nonliving factors in a given area.

• 3. Communities: All organisms inhabiting a particular area.

• 4. Populations: Groups of individuals of the same species in an area.

• 5. Organisms: Individual living things.

• 6. Organs and Organ Systems: Body parts with specific functions.

• 7. Tissues: Groups of similar cells performing a function.

• 8. Cells: Fundamental unit of life.

• 9. Organelles: Specialized structures within cells.

• 10. Molecules: Chemical structures held by bonds.

Scientific Method and Hypothesis Testing

The scientific method is a systematic way to investigate natural phenomena.

• Steps:

  1. Making observations

  2. Formulating hypotheses

  3. Testing hypotheses via experiments

  4. Analyzing data and drawing conclusions

  5. If hypothesis is not supported, revise and repeat

• Hypothesis: A testable explanation for a set of observations, must be falsifiable and testable.

• Scientific Theory: Broader in scope, supported by a large body of evidence, and can generate new hypotheses.

Experimental Design

Experiments are designed to test relationships between variables.

• Experimental Group: Exposed to the treatment.

• Control Group: Not exposed to the treatment; used for comparison.

• Variables:

  • Independent Variable: Manipulated by the researcher (x-axis).

  • Dependent Variable: Measured outcome (y-axis).

• Controlling Variables: Ensures reliable and reproducible results.

Example: In a mouse experiment, the independent variable could be color of mouse, and the dependent variable is percentage attacked.

Energy and Matter in Ecosystems

Energy flows and matter cycles through ecosystems.

• Energy: Transformed from light to chemical energy (photosynthesis), lost as heat.

• Matter: Cycles in ecosystems; never created or destroyed, only changes form.

Example: Plants convert sunlight to chemical energy, which is transferred through food webs.

Chapter 2 – Chemistry of Life and Properties of Water

Chemical Reactions and Conservation of Matter

Chemical reactions rearrange atoms but do not create or destroy matter. The number of atoms in reactants equals the number in products.

• Example Equation: $4\ NH_3 + 5\ O_2 \rightarrow 4\ NO + 6\ H_2O$

• Reactants: Starting molecules

• Products: Final molecules

Ions and Chemical Bonds

Ions are charged atoms or molecules. Chemical bonds form between ions or atoms.

• Anion: Negatively charged ion (more electrons than protons).

• Cation: Positively charged ion (more protons than electrons).

• Ionic Bond: Attraction between oppositely charged ions (e.g., Na+ and Cl- in NaCl).

Atomic Structure and Periodic Table

Atoms consist of protons, neutrons, and electrons. The chemical behavior of an atom is determined by the number of electrons in its valence shell.

• Isotopes: Atoms of the same element with different numbers of neutrons (e.g., Carbon-13 and Carbon-14).

• Major Elements in Biology: Oxygen, carbon, nitrogen, hydrogen.

• Electron Shells: First shell holds 2, second and third hold 8 electrons each.

Chemical Bonds: Covalent, Ionic, Hydrogen

Atoms bond to achieve stable electron configurations.

• Covalent Bonds: Atoms share pairs of electrons (strongest).

• Ionic Bonds: Attraction between oppositely charged ions.

• Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom (e.g., in water).

Order of Strength (in water): Covalent > Ionic > Hydrogen

Electronegativity and Bond Polarity

Electronegativity is the attraction of an atom for electrons in a covalent bond.

• Most Electronegative Atom: Oxygen (in organic molecules).

• Nonpolar Covalent Bond: Electrons shared equally.

• Polar Covalent Bond: Electrons shared unequally, creating partial charges (e.g., O-H bond in water).

Bonds in Water, CO2, and O2

• Water (H2O): Polar covalent bonds.

• Carbon Dioxide (CO2): Nonpolar covalent bonds.

• Oxygen (O2): Nonpolar covalent bonds.

CO2 Emissions and Marine Life

CO2 emissions affect marine ecosystems by causing ocean acidification, which reduces carbonate concentration needed for marine organisms to build shells and skeletons.

• Ocean Acidification: CO2 dissolves in seawater, forming carbonic acid and lowering pH.

• Impact: Reduced calcification, altered marine food webs.

Sample Table: Levels of Biological Organization

Level	Definition	Example
Biosphere	All environments on Earth supporting life	Earth
Ecosystem	All organisms and nonliving factors in an area	Forest ecosystem
Community	All organisms inhabiting a particular area	All plants, animals, and microbes in a pond
Population	Group of individuals of the same species	Population of deer in a forest
Organism	Individual living thing	A single tree
Organ System	Group of organs working together	Digestive system
Tissue	Group of similar cells performing a function	Muscle tissue
Cell	Fundamental unit of life	Neuron
Organelle	Specialized structure within a cell	Mitochondrion
Molecule	Chemical structure held by bonds	Water (H2O)

Additional info: Some explanations and examples have been expanded for clarity and completeness, including definitions, examples, and context for key terms and processes.