Introduction to Biology

Characteristics of Life

Biology is the study of living organisms and their interactions with the environment. All living things share certain characteristics that distinguish them from non-living matter.

• Organization: Organisms are composed of one or more cells, which are the basic units of life.

• Energy: Living things acquire and use energy to maintain order and support growth, development, and reproduction.

• Information: Organisms process hereditary information encoded in DNA and respond to environmental information.

• Replication: All living things are capable of reproduction, producing offspring similar to themselves.

• Evolution: Populations of organisms evolve over time through changes in genetic information.

Theories in Biology

Scientific theories are broad explanations supported by a large body of evidence. Two foundational theories in biology are:

• Cell Theory: All organisms are made of cells, and all cells come from pre-existing cells.

• Theory of Evolution by Natural Selection: Species are related by common ancestry and change over time due to natural selection.

Levels of Biological Organization

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

Scientific Method and Experimental Design

Steps in the Scientific Method

• Observation: Gathering information about phenomena.

• Question: Asking questions about observations.

• Hypothesis: Proposing a testable explanation.

• Prediction: Making predictions based on the hypothesis.

• Experiment: Testing predictions through controlled experiments.

• Analysis: Interpreting data and drawing conclusions.

Hypothesis is a testable statement that explains an observation. Null hypothesis states there is no effect or difference. Prediction is a measurable or observable result expected if the hypothesis is correct.

Experimental Design

• Control group: Group not exposed to the experimental variable; used for comparison.

• Constant/controlled conditions: All variables except the independent variable are kept the same.

• Replication: Repeating experiments to ensure reliability.

• Sample size: Larger sample sizes increase reliability of results.

Atoms, Ions, and Molecules

Atomic Structure

Atoms are the smallest units of matter that retain the properties of an element. They consist of:

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles in orbitals around the nucleus.

The number of protons defines the element. Electrons determine chemical reactivity.

Chemical Bonds

• Covalent Bonds: Atoms share electron pairs. Can be nonpolar (equal sharing) or polar (unequal sharing).

• Ionic Bonds: Electrons are transferred from one atom to another, creating ions (cations and anions) that attract each other.

• Hydrogen Bonds: Weak attractions between a hydrogen atom in one molecule and an electronegative atom (like oxygen or nitrogen) in another.

• Van der Waals Interactions: Weak, transient interactions between molecules due to temporary charge differences.

Water and Its Properties

• Cohesion: Water molecules stick to each other via hydrogen bonds.

• Adhesion: Water molecules stick to other polar substances.

• Surface Tension: Cohesion at the surface of water creates a 'skin' that resists external force.

• High Specific Heat: Water can absorb a lot of heat before changing temperature.

• High Heat of Vaporization: Water requires a lot of energy to change from liquid to gas.

• Density: Ice is less dense than liquid water, so it floats.

• Solvent Properties: Water dissolves many substances due to its polarity.

Acids, Bases, and pH

• Acid: Substance that donates protons (H+).

• Base: Substance that accepts protons (H+).

• pH Scale: Measures concentration of H+ ions; lower pH = more acidic, higher pH = more basic.

Buffers help maintain stable pH by absorbing or releasing H+ ions.

Energy and Chemical Reactions

Types of Energy

• Kinetic Energy: Energy of motion.

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

• Chemical Energy: Potential energy stored in chemical bonds.

Thermodynamics in Biology

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

• Second Law of Thermodynamics: Entropy (disorder) increases in spontaneous reactions.

Spontaneous reactions release free energy and increase entropy.

Chemical Evolution

Early Earth conditions allowed for the formation of simple molecules, which could combine to form more complex organic compounds, possibly leading to the origin of life.

Functional Groups in Biological Molecules

Major Functional Groups

Macromolecules and Polymers

Polymerization

• Monomers: Small building blocks (e.g., amino acids, nucleotides, monosaccharides).

• Polymers: Large molecules made by joining monomers (e.g., proteins, nucleic acids, polysaccharides).

• Dehydration Synthesis: Monomers are joined by covalent bonds with the removal of water.

• Hydrolysis: Polymers are broken down into monomers by the addition of water.

ATP and Energy Transfer

• ATP (Adenosine Triphosphate): Main energy currency of the cell; energy is released when phosphate bonds are broken.

Summary Table: Functional Groups

Key Equations

• pH Calculation:

• First Law of Thermodynamics: where is the change in internal energy, is heat, and is work.

• Gibbs Free Energy: where is change in free energy, is change in enthalpy, is temperature in Kelvin, and is change in entropy.

Additional info:

• Some content and explanations have been expanded for clarity and completeness based on standard General Biology I curriculum.

• Tables have been reconstructed and summarized from the original notes for clarity.