General Biology Exam 1 Study Guide: Scientific Method, Chemistry of Life, and Atomic Structure

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Scientific Method and Experimental Design

Formulating Hypotheses and Variables

The scientific method is a systematic approach used in biology to investigate phenomena, acquire new knowledge, or correct and integrate previous knowledge. It involves making observations, forming hypotheses, conducting experiments, and analyzing results.

Hypothesis: A scientific hypothesis must be testable and falsifiable. This means it can be evaluated through experiments and can be proven wrong.
Variables in Experiments:
- Independent Variable: The variable that is manipulated by the experimenter.
- Dependent Variable: The variable that is measured or observed in response to changes in the independent variable.
Controlled Scientific Experiment: An experiment in which only one variable is changed at a time, while all other variables are kept constant.
Observational Study: A study where the researcher observes and records behavior or phenomena without manipulating variables. Example: Observing bird migration patterns over time.

Example: Testing the effect of sunlight on plant growth by varying light exposure (independent variable) and measuring plant height (dependent variable).

Domains of Life

Classification of Living Organisms

All life is classified into three domains based on genetic and cellular differences:

Bacteria
Archaea
Eukarya

Example: Humans belong to the domain Eukarya.

Chemical Basis of Life

Atoms, Elements, and Isotopes

Atoms are the basic units of matter, composed of protons, neutrons, and electrons. Elements are substances made of only one type of atom. Isotopes are atoms of the same element with different numbers of neutrons.

Atomic Number: Number of protons in an atom.
Mass Number: Sum of protons and neutrons.
Isotope: Atoms of the same element with different numbers of neutrons.
Radioactive Isotope: An isotope that decays over time, emitting radiation. Used in medical imaging and dating fossils.

Example: Carbon-14 is a radioactive isotope used in radiocarbon dating.

Periodic Table and Element Stability

The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties. Elements are stable when their outer electron shell is full.

Stable Elements: Elements with full valence shells (e.g., noble gases like Helium, Neon).

Element	Atomic Number	Valence Electrons	Stability
Helium	2	2	Stable
Neon	10	8	Stable
Argon	18	8	Stable
Additional info: Other noble gases (Krypton, Xenon) are also stable due to full valence shells.

Atomic Structure Calculations

To determine the number of subatomic particles in an atom:

Protons: Equal to atomic number.
Neutrons: Mass number minus atomic number.
Electrons: Equal to protons in a neutral atom; adjusted for charge in ions.
Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

Example Calculation:

Carbon (atomic number 6, mass number 12): Protons: 6 Neutrons: 6 Electrons: 6 Valence Electrons: 4
Calcium ion (atomic number 20, mass number 40, charge +2): Protons: 20 Neutrons: 20 Electrons: 18 Valence Electrons: 2
Phosphorus ion (atomic number 15, mass number 31, charge -3): Protons: 15 Neutrons: 16 Electrons: 18 Valence Electrons: 5

Chemical Bonds and Water Properties

Covalent and Ionic Bonds

Chemical bonds hold atoms together in molecules and compounds.

Covalent Bond: Atoms share electrons. Example: H2O (water).
Ionic Bond: Atoms transfer electrons, resulting in charged ions. Example: NaCl (table salt).

Polarity and Hydrogen Bonds

Water is a polar molecule, meaning it has a partial positive and partial negative charge due to unequal sharing of electrons. Hydrogen bonds form between water molecules, giving water unique properties.

Polarity: Unequal sharing of electrons creates partial charges.
Hydrogen Bond: Weak attraction between the hydrogen atom of one water molecule and the oxygen atom of another.

Properties of Water

Water's properties are essential for life:

Cohesion: Water molecules stick to each other.
Adhesion: Water molecules stick to other surfaces.
Surface Tension: Water forms a "skin" due to hydrogen bonding.
High Specific Heat: Water resists temperature changes.
Ice Floats: Solid water is less dense than liquid water due to hydrogen bonds.

Example: Water droplets on skin after a shower are due to cohesion and adhesion.

Acids, Bases, and pH

Definitions and Importance

Acids and bases are substances that affect the concentration of hydrogen ions (H+) in a solution.

Acid: Donates H+ ions to a solution.
Base: Accepts H+ ions or donates OH- ions.
pH Scale: Measures the concentration of H+ ions; ranges from 0 (acidic) to 14 (basic), with 7 being neutral.

Example: Lemon juice is acidic (low pH), while soap is basic (high pH).

Ocean Acidification

Ocean acidification occurs when excess CO2 dissolves in seawater, forming carbonic acid and lowering the pH.

Equation:

Impact: Affects marine life, especially organisms with calcium carbonate shells.

Trace Elements and Biological Importance

Essential Elements

Trace elements are required in small amounts for proper biological function.

Examples: Iron (Fe), Iodine (I), Zinc (Zn), Copper (Cu)
Function: Iron is needed for oxygen transport in blood; iodine is required for thyroid hormone production.

Summary Table: Atomic Structure

Atom	Protons	Neutrons	Electrons	Valence Electrons
Carbon (neutral)	6	6	6	4
Calcium (Ca2+)	20	20	18	2
Phosphorus (P3-)	15	16	18	5

Additional info:

Periodic table included for reference to atomic numbers and element classification.
Questions cover foundational topics from Ch. 1 (Biology: The Study of Scientific Life) and Ch. 2 (The Chemical Basis of Life).