General Biology: The Study of Life and Chemistry of Biology – Structured Study Notes

Biology: The Study of Life

Defining Life

Biologists define life by a set of key characteristics that distinguish living organisms from non-living matter.

• Order: Living things exhibit organized structure.

• Evolutionary Adaptation: Populations evolve over generations.

• Regulation: Ability to maintain internal environment (homeostasis).

• Reproduction: Ability to produce offspring.

• Response to the Environment: React to stimuli.

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

• Energy Processing: Acquire and use energy.

Important Terminology

• Theory: Explanation for a broad class of phenomena, supported by substantial evidence.

• Hypothesis: Testable statement explaining a specific observation.

• Prediction: Measurable or observable result expected if hypothesis is valid.

• Experimental Design: Structure of an experiment to test hypotheses.

Theories Discussed in Biology

• Cell Theory: All organisms are made of cells; cells arise from pre-existing cells.

• Theory of Evolution by Natural Selection: Species change over time; traits are inherited and populations evolve.

• Chromosome Theory of Inheritance: Hereditary information is transmitted via chromosomes.

Life is Cellular: Cell Theory

Cell Division and Spontaneous Generation

Cell theory states that all living organisms are composed of cells, and all cells arise from pre-existing cells.

• Spontaneous Generation: Disproven hypothesis that life can arise from non-living matter.

• Cell Division: Cells replicate by dividing; new cells are produced from existing cells.

Life's Processes: Information and Energy

Energy Processing

Organisms require energy to survive and grow. Most organisms use sunlight or chemical energy to produce ATP.

• Photosynthesis: Plants and some bacteria convert sunlight into chemical energy.

• Cellular Respiration: Organisms break down molecules to produce ATP.

Evolution and Natural Selection

Darwin and Wallace's Contributions

Darwin and Wallace proposed that species are related by common ancestry and change over time through natural selection.

• Natural Selection: Process by which individuals with advantageous traits survive and reproduce more successfully.

• Population: Group of individuals of the same species living in the same area.

Fitness and Adaptation

• Fitness: Ability of an individual to produce viable offspring.

• Adaptation: Trait that increases fitness in a particular environment.

Tree of Life: Evolutionary Relationships

Phylogenetic Tree

Phylogenetic trees display evolutionary relationships among species based on genetic data.

• Branches represent common ancestry.

• Tree of life includes three major domains: Bacteria, Archaea, and Eukarya.

Taxonomy and Classification

• Taxonomy: Science of naming and classifying organisms.

• Domain: Highest taxonomic rank; includes Bacteria, Archaea, Eukarya.

• Phylum: Major lineage within a domain.

Doing Biology: Scientific Method

Nature of Science

Science involves asking questions, forming hypotheses, and testing them through experiments and observations.

• Hypothesis Testing: Two-step process: 1) State hypothesis as precisely as possible; 2) Design experiment to test predictions.

• Experimental Design: Must be controlled and reproducible.

Chemistry of Biology

Basic Atomic Structure

Atoms are the fundamental units of matter, composed of protons, neutrons, and electrons.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

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

Atomic Mass and Structure

• Atomic mass is the sum of protons and neutrons.

• Atomic number is the number of protons.

Electron Shells and Valence

• Electrons occupy shells; outermost shell is the valence shell.

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

Covalent and Polar Covalent Bonds

• Covalent Bonds: Atoms share electrons to fill valence shells.

• Polar Covalent Bonds: Electrons are shared unequally due to differences in electronegativity.

• Electronegativity: Measure of an atom's ability to attract electrons.

Ions and Ionic Bonds

• Ions: Atoms that gain or lose electrons, becoming charged.

• Ionic Bonds: Attraction between oppositely charged ions.

Properties of Water

Structure and Polarity

Water is a polar molecule with unique properties essential for life.

• Cohesion: Attraction between water molecules.

• Adhesion: Attraction between water and other substances.

• Surface Tension: Resistance of water's surface to external force.

• High Specific Heat: Water absorbs and retains heat efficiently.

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

• Density: Water is less dense as a solid (ice floats).

Hydrogen Bonds

• Hydrogen bonds form between water molecules and other polar molecules.

• Hydrophilic substances dissolve in water; hydrophobic substances do not.

Chemical Reactions in Biology

Role of Water

• Chemical reactions involve breaking and forming chemical bonds.

• Reactions are often written as equations:

$\text{Reactant(s)} \rightarrow \text{Product(s)}$

Example:

$\mathrm{H_2O \rightarrow H^+ + OH^-}$

Acids, Bases, and pH

• Acids: Donate protons (H+) in solution.

• Bases: Accept protons or donate hydroxide ions (OH-).

• pH Scale: Measures concentration of H+ ions; logarithmic scale.

• Neutral pH is 7; acids have pH less than 7; bases have pH greater than 7.

• Buffers: Maintain stable pH in biological systems.

Carbon and Organic Molecules

Carbon's Versatility

Carbon atoms can form four covalent bonds, allowing for complex molecules.

• Organic compounds contain carbon and hydrogen.

• Functional groups (e.g., hydroxyl, carboxyl, amino, phosphate, sulfhydryl) confer specific chemical properties.

Macromolecules and Polymers

• Macromolecules: Large molecules made of smaller subunits (monomers).

• Polymerization: Monomers join to form polymers via condensation reactions (dehydration synthesis).

• Hydrolysis: Water breaks bonds between monomers, separating them from the polymer chain.

Table: Properties of Water and Functional Groups

Functional Group	Structure	Properties
Hydroxyl	-OH	Polar, forms hydrogen bonds, increases solubility
Carbonyl	C=O	Polar, found in sugars
Carboxyl	-COOH	Acts as acid, donates H+
Amino	-NH2	Acts as base, accepts H+
Phosphate	-PO4	Contributes negative charge, energy transfer
Sulfhydryl	-SH	Forms disulfide bonds in proteins

Table: Properties of Water

Property	Description
Cohesion	Water molecules stick together
Adhesion	Water molecules stick to other surfaces
Surface Tension	Water surface resists external force
High Specific Heat	Water absorbs and retains heat
High Heat of Vaporization	Water requires energy to evaporate
Density	Ice is less dense than liquid water

Summary

• Life is defined by a set of key characteristics and is studied through scientific theories and methods.

• Cells are the basic unit of life; all organisms are made of cells.

• Evolution explains the diversity of life through natural selection and adaptation.

• Water and carbon are essential for biological molecules and processes.

• Scientific inquiry relies on hypothesis testing and controlled experiments.