General Biology Study Guide: Scientific Inquiry and Chemistry of Life

Chapter 1: Scientific Inquiry and Properties of Life

Properties of Life

Living organisms share several fundamental characteristics that distinguish them from non-living matter.

• Order: Organisms exhibit complex organization, from cells to tissues to organs.

• Regulation: Ability to maintain stable internal conditions (homeostasis).

• Growth and Development: Organisms grow and develop according to genetic instructions.

• Energy Processing: Use of energy to power activities and chemical reactions.

• Response to Environment: Ability to sense and respond to stimuli.

• Reproduction: Production of offspring, passing genetic material to the next generation.

• Evolutionary Adaptation: Populations change over time through adaptation and natural selection.

The Scientific Method

The scientific method is a systematic approach to investigating natural phenomena.

• Observation: Gathering information about the natural world.

• Question: Formulating a question based on observations.

• Hypothesis: Proposing a testable explanation.

• Prediction: Making predictions based on the hypothesis.

• Experiment: Testing the hypothesis under controlled conditions.

• Analysis: Interpreting data and drawing conclusions.

• Communication: Sharing results with the scientific community.

Variables in Experiments:

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

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

• Control Variables (Constants): Factors kept the same to ensure a fair test.

Graphing Variables: The independent variable is typically plotted on the x-axis, and the dependent variable on the y-axis.

Charles Darwin and Natural Selection

Charles Darwin was a naturalist who developed the theory of evolution by natural selection.

• Descent with Modification: Species change over generations, giving rise to new species.

• Adaptation: Traits that improve survival and reproduction become more common in populations.

Darwin's Observations: He observed variation among organisms and noted that more offspring are produced than can survive.

Four Steps of Natural Selection:

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

2. Inheritance: Some traits are heritable.

3. Overproduction: More offspring are produced than can survive.

4. Differential Survival and Reproduction: Individuals with advantageous traits survive and reproduce more successfully.

Unity and Diversity: Organisms share common features (unity) but also exhibit differences (diversity) due to evolution.

Chapter 2: Chemistry of Life

Basic Chemical Concepts

Understanding chemistry is essential for studying biological processes, as all living things are composed of matter.

• Matter: Anything that has mass and takes up space.

• Element: A substance that cannot be broken down into simpler substances by chemical means.

• Compound: A substance formed by the chemical combination of two or more elements.

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

Subatomic Particles and Atomic Structure

• Proton: Positively charged particle in the nucleus; has mass.

• Neutron: Neutral particle in the nucleus; has mass.

• Electron: Negatively charged particle orbiting the nucleus; negligible mass.

Atomic Number: Number of protons in an atom; determines the element.

Mass Number: Sum of protons and neutrons in the nucleus.

Valence Electrons: Electrons in the outermost shell; determine chemical behavior.

Electron Shells: Energy levels where electrons reside; each shell can hold a specific number of electrons (e.g., 2 in the first shell, 8 in the second).

Isotopes and Radioactivity

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

• Radioactive Isotopes: Unstable isotopes that decay over time, emitting radiation.

• Half-life: Time required for half of a radioactive sample to decay.

• Radiometric Dating: Technique for determining the age of materials using radioactive isotopes.

• Radioactive Tracers: Used in medicine to track biological processes.

Example: Carbon-14 dating is used for relatively recent fossils, but not for dinosaurs due to its short half-life.

Chemical Bonds

Chemical bonds hold atoms together in molecules and compounds.

• Covalent Bond: Atoms share electrons; can be single, double, or triple bonds.

• Nonpolar Covalent Bond: Electrons are shared equally.

• Polar Covalent Bond: Electrons are shared unequally, creating partial charges.

• Ionic Bond: Electrons are transferred from one atom to another, forming ions (cations and anions).

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

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

• Hydrophobic Interaction: Nonpolar molecules aggregate to avoid water.

Energy in Chemical Systems

• Potential Energy: Stored energy due to position or structure.

• Kinetic Energy: Energy of motion.

Chemical Reactions

• Reactants: Substances that start a chemical reaction.

• Products: Substances formed by a chemical reaction.

• Chemical Equilibrium: State where reactants and products are present in stable concentrations.

General Chemical Reaction Equation:

$\text{Reactants} \rightarrow \text{Products}$

Essential and Trace Elements

Elements required for life are classified as essential or trace elements.

• Essential Elements: Elements required in large amounts (e.g., C, H, O, N, P, S).

• Trace Elements: Required in small amounts (e.g., Fe, I, Zn).

Example: The human body contains essential elements such as carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).

Periodic Table and Atomic Calculations

• Finding Atomic Number and Mass: Atomic number is usually above the element symbol; atomic mass/weight is below.

• Calculating Subatomic Particles:

  • Number of protons = atomic number

  • Number of neutrons = mass number - atomic number

  • Number of electrons = atomic number (in a neutral atom)

• Periodic Table Organization: Elements are arranged by increasing atomic number; chemical behavior is determined by valence electrons.

Application: Chemistry in Biology

• Food Labels: Chemical salts (e.g., NaCl) can be identified on food labels.

• Relationship: Biological processes depend on chemical interactions and elements.

Summary Table: Subatomic Particles

Particle	Charge	Location	Mass
Proton	+1	Nucleus	1 amu
Neutron	0	Nucleus	1 amu
Electron	-1	Electron shell	~0 amu

Summary Table: Types of Chemical Bonds

Bond Type	Description	Example
Covalent	Atoms share electrons	H2O
Ionic	Electrons transferred; ions formed	NaCl
Hydrogen	Weak attraction between molecules	Between water molecules
Van der Waals	Transient weak interactions	Gecko feet adhesion

Additional info: Some content was inferred and expanded for clarity and completeness, including definitions, examples, and tables.