Nature of Science

Overview of Scientific Inquiry

Science is a systematic process for understanding the natural world through observation, experimentation, and reasoning. Scientific knowledge is testable, falsifiable, and reproducible, distinguishing it from non-scientific claims.

• Scientific claim: Based on evidence, can be tested and falsified.

• Non-scientific claim: Not testable or falsifiable through the senses.

• Observations: Collection of information used to explain phenomena and make predictions in new situations.

Characteristics of Science

• Focuses on the natural world

• Uses testable ideas

• Relies on evidence

• Involves scientific community

• Leads to ongoing research

• Benefits society

Key Terminology

• Hypothesis: A proposed explanation or prediction, generally lacking evidence/support but testable and potentially falsifiable.

• Theory: An explanation of why or how things happen in the natural world, supported by a broad range of evidence. Theories are based on evidence collected from many tested hypotheses.

• Law: A description of what happens, usually expressed in concise statements or mathematical equations. Laws relate to observable phenomena, such as gravity or inheritance.

Methods of Science

• Hypothesis testing: Proposing ideas, designing experiments, and testing variables.

• Controlled experiment design: Establishes cause/effect relationships by manipulating one variable while keeping others constant.

• Probability: Calculating the likelihood of an expected result, often expressed as a percentage.

• Statistical significance: Measured by p-value (), which indicates the probability that results are due to chance.

• Variability: Represented by error bars in graphs, showing the range of data.

Other Considerations

• Randomness: Correlation does not imply causation.

• Christian view of science: Science is a human endeavor; exercise stewardship over creation.

Properties of Life

Defining Life

Living organisms share several key properties, including organization, information processing, energy and matter exchange, interactions, and evolution.

• Organization: Hierarchical levels from biosphere to molecules.

• Emergent properties: New functions arise from the arrangement and interaction of parts.

• Correlation: Structure and function are related at each organizational level.

The Cell

• Cell: Smallest unit of organization that performs activities for life.

• Eukaryotic cells: Membrane-enclosed nucleus, organelles.

• Prokaryotic cells: No nucleus, smaller, simpler structure.

Genetic Information

• Chromosomes made up of DNA

• Genes are units of inheritance

• Central dogma: DNA → RNA → PROTEIN

Energy and Matter

• All living things must obtain energy and process matter

• Photosynthesis: Producers capture energy

• Consumers: Feed on other organisms

Interactions and Evolution

• Interactions integrate system components

• Evolution: Living organisms are modified descendants of common ancestors

• Microevolution: Small genetic changes over time

• Macroevolution: Large-scale changes, speciation

Origin of Life

Abiogenesis

Abiogenesis theories attempt to explain how life originated through chemical transformations resulting in living cells.

• Life is made of cells, requires energy, shows heredity, reproduction, adaptation, response to stimuli, and maintains homeostasis.

Alternative Theories

• Interventionist: Supernatural intervention created life.

• Naturalistic: Life evolved through natural processes.

• RNA World Hypothesis: RNA was created first, storing genetic and duplicating information.

• Protein World Hypothesis: Proteins formed first, enabling metabolism and homeostasis.

• Directed Panspermia: Life was seeded by extraterrestrial civilization.

• Undirected Panspermia: Life arrived via meteorites and space debris.

Critiques

• Self-replicating RNA is not a cell

• Prokaryotes lack heritable genetic material

• Origin of life remains unresolved

Models for Eukaryote Origin

• Endosymbiotic theory: Eukaryotic cells originated from symbiotic relationships between prokaryotes.

• Evidence: Mitochondria and chloroplasts have their own genome and circular chromosomes.

Chemical Basis of Life

Structure Determines Function

Chemical bonds and molecular structure are fundamental to biological function.

• Covalent bond: Sharing of a pair of valence electrons by two atoms.

• Electronegativity: Atom's attraction for electrons in a covalent bond.

• Ionic bond: Attraction between oppositely charged ions.

• Polar covalent bond: Unequal sharing of electrons.

• Hydrogen bond: Weak bond between polar molecules.

• Van der Waals interactions: Weak attractions due to transient charge differences.

Carbon and Hydrocarbons

• Carbon forms diverse molecules due to its four valence electrons.

• Hydrocarbons: Molecules of hydrogen and carbon.

Isomers

• Isomers have the same molecular formula but different structures and properties.

• Cis-trans isomers: Geometric isomers with different spatial arrangements.

• Enantiomers: Mirror images of each other; important in drug design.

Functional Groups

• Distinctive properties of organic molecules depend on the carbon skeleton and attached chemical groups.

• Common functional groups: hydroxyl, carboxyl, carbonyl, amino, sulfhydryl, phosphate, methyl

ATP

• ATP (adenosine triphosphate) is the cell's energy currency.

• Composed of adenosine and three phosphate groups.

• ATP stores the potential to react with water, releasing energy.

Biological Macromolecules

Overview

Macromolecules are large molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

• Macromolecules are polymers made up of monomers.

• Enzymes catalyze reactions to build or break down polymers.

• Dehydration synthesis forms bonds by removing water; hydrolysis breaks bonds by adding water.

Carbohydrates

Carbohydrates are sugars and polymers of sugars. Glucose is the most abundant monosaccharide.

Alpha and beta glucose are isomers of each other.

Lipids

Lipids are not true polymers but are important for energy storage and membrane structure.

Proteins

Proteins are polymers of amino acids and perform a wide range of functions in cells.

• Make up 50% of dry mass of cells

• Monomer: amino acid (contains amino group and carboxyl group)

• Linked by peptide bonds

• Four levels of protein structure:

  • Primary: Sequence of amino acids

  • Secondary: Alpha helix or beta sheets, stabilized by hydrogen bonds

  • Tertiary: Interactions among R groups, including hydrophobic interactions, ionic bonds, and disulfide bridges

  • Quaternary: Multiple polypeptide chains functioning as one unit

• Sickle cell disease: Single amino acid substitution in hemoglobin causes aggregation and deformation

• Denaturation: Unfolding of a protein, loss of function

Nucleic Acids

• Store and transmit hereditary information

• Sequence of nucleotides programmed by a gene

• Monomer: nucleotide

• DNA: Stores hereditary info (ATCG)

• RNA: Builds protein (AUGC)

Additional info:

• Some context and examples have been expanded for clarity and completeness.

• Equations and formulas are provided in LaTeX format where relevant.