Scientific Methodology, Biological Inquiry, and Fundamental Atomic Chemistry

The Internal Flexibility of the Scientific Process

• Scientific inquiry is not a rigid, linear progression but a flexible process comparable to choosing a travel route. For example, a traveler moving toward Boston may initially propose a route through Tennessee but deviate from that path if a more efficient or superior alternative is discovered.

• In research applications, guidelines are rarely followed strictly. Scientists often skip immediately to a "quick and dirty" experiment rather than beginning with a methodical, systematic approach.

• The primary goal of a quick and dirty experiment is to remove the fear of science and gain initial results; failures at this stage are acceptable. These preliminary tests allow researchers to refine their methods for a subsequent, more disciplined, and reproducible execution.

Components of Realistic Scientific Inquiry

• The process of science contains several overlapping components:

  • Hypothesis Formulation and Testing: The core starting point of an investigation.

  • Exploration and Discovery: This involves asking questions, conducting preliminary experiments, and investigating the natural world.

  • Community Analysis (Peer Review): Scientists do not work in isolation; their conclusions are scrutinized by the scientific community. Findings are submitted to journals where three anonymous reviewers typically evaluate the methods and logic. Reviewers may request repetitions of experiments or alternative approaches to ensure the science is moving in the right direction.

  • Societal Benefits and Outcomes: Practical applications often arise from basic research. For instance, studying inhibitors of the enzyme cyclooxygenase led to the development of aspirin. Aspirin is used for its societal benefits as an antithrombotic drug to treat blood clotting disorders and issues related to platelet reactivity.

  • Integration: Science involves a constant loop of reading scientific literature, generating alternative hypotheses based on that literature, and developing new technologies or medicines.

Case Study: Natural Selection and Coat Coloration in Mice

• Background and Observation: Investigating the purpose of coat color patterns in mice involves studying adaptation to environments. There are two distinct populations of mice:

  • Beach Mice: Live in white, sandy beach environments and possess light-colored fur.

  • Inland Mice: Live in areas with darker, brownish ground and possess darker fur.

• Hypothesis: Francis Sumner hypothesized nearly $100$ years ago that these color patterns evolved as adaptations to camouflage the mice from visual predators, such as birds and hawks.

• Verification by Hopi Hopstadt: To test the prediction that mice with coloration non-matching their habitat will suffer higher predation, an experiment was designed:

  • Methodology: Experimental mice were painted with spray paint to either match or contrast with their environment.

  • Containment: To track the mice and prevent escape by burrowing, fences were dug extremely deep into the ground over an area of half a mile to a mile.

  • Monitoring: Chips were implanted in the shoulders of the mice ($Mice \text{ } 1, 2, 3, 4, \text{ etc.}$) to monitor their precise locations.

• Experimental Data:

  • Beach Habitat: Light-colored models (controls) had a low attack rate, while dark-colored models (experimental) suffered an attack rate of approximately $75\%$.

  • Inland Habitat: Light-colored models (non-camouflaged) were attacked at a rate of about $26\%$ or $27\%$, while dark models were well-protected.

• Conclusion: Camouflage significantly affects predation rates. This study highlights the importance of the control group, which represents the standard traits to cancel out extraneous variables.

Experimental Variables and Mathematical Interpretations

• Independent Variable: This is the factor manipulated by the investigator, such as the color the mouse is painted (green, brown, red, etc.).

• Dependent Variable: This is the factor being measured, such as the amount of predation.

• Variable Control: It is impossible to control every variable in field experiments (e.g., the exact number of hawks visiting a site might range from $50$ to $100$ on different days). Instead of eliminating every unwanted variable, researchers use control groups to cancel out their effects.

• Theories vs. Hypotheses:

  • Hypothesis: A specific, testable prediction (e.g., matching coat color protects against predators).

  • Theory: A much broader scope backed by a larger body of evidence (e.g., Darwin’s evolutionary theory). A theory can embed and generate multiple testable hypotheses. One example is the theory that evolutionary adaptations arise by natural selection.

Scientific Integrity and Professional Ethics

• Social Nature of Science: Science is not a lonely pursuit for "crazy" thinkers. It involves constant socialization between graduate students, undergraduates, and professors. Collaboration between different universities is common to refine experimental designs.

• Checks and Balances: Science has internal mechanisms to catch fraud and errors. Notable historical failures include:

  • Texas A&M Professor: Claimed to convert iron into gold in a published paper, but was fired after other universities (like Stanford) could not reproduce the result.

  • The "Mosaic Mouse" Fraud: A researcher used a black pen to mark spots on white mice to fake a genetic strain; he was caught by subsequent investigators.

  • The Rockefeller Postdoc (Ephraim Racker Lab): In the $1980$s, a postdoc used radioactive ink spots on X-ray film to fake protein phosphorylation results. Although initially praised by figures like Watson, the fraud was uncovered when the experiment failed on the West Coast.

• Scientific Interdependence: Science and technology grow together. An example is DNA sequencing technology:

  • Scientists discovered the enzyme DNA polymerase.

  • Chemists designed dideoxynucleotides (compounds missing the essential oxygen for chain extension).

  • Fred Sanger integrated these to invent dideoxynucleotide sequencing technology, which was essential for the Human Genome Project.

The Chemical Basis of Life

• Matter: Solids, liquids, and gases that occupy space and have mass.

• Elements vs. Compounds: An element cannot be broken down into other substances. A compound consists of two or more elements in a fixed ratio, exhibiting emergent properties (e.g., Sodium is a metal and Chlorine is a gas, but together they form Sodium Chloride, which is a salty solid).

• Elemental Composition of the Human Body:

  • Essential Elements ($4$ Major): Oxygen ($O$), Carbon ($C$), Hydrogen ($H$), and Nitrogen ($N$) constitute approximately $96.3\%$ (or roughly $95\%$) of the body's mass.

  • Other Essential Elements ($4\%$): Calcium ($Ca$), Phosphorus ($P$), Potassium ($K$), Sulfur ($S$), Sodium ($Na$), Chlorine ($Cl$), and Magnesium ($Mg$).

  • Trace Elements ($<0.01\%$): Required in minute quantities, such as Iodine ($I$) for the thyroid and Iron ($Fe$) for red blood cells.

• Toxicity and Environmental Remediation:

  • Some elements, like arsenic, lead, and zinc, are highly toxic. The gold standard for toxicity testing is the use of fish (minnows).

  • Sunflowers are unique because they can survive while absorbing toxic lead and zinc from contaminated water, a process used for decontamination after events like Hurricane Katrina.

Atomic Structure and Subatomic Particles

• Subatomic Particles:

  • Protons ($P$): Positive charge; mass of approximately $1$ Dalton.

  • Neutrons ($N$): Neutral charge; mass of approximately $1$ Dalton.

  • Electrons ($e$): Negative charge; mass is negligible.

• Atomic Nucleus: A central "ball" containing protons and neutrons.

• Electronic Cloud: Electrons do not follow fixed paths like planets; they move rapidly like a buzzing bee or the fire from a rotating stick, forming a cloud of negative charge around the nucleus.

• Defining Numbers:

  • Atomic Number: The number of protons in the nucleus (and electrons in a neutral atom).

  • Mass Number: The sum of protons and neutrons.

  • Neutron Calculation: $\text{Mass Number} - \text{Atomic Number} = \text{Neutrons}$ (e.g., Sodium has an atomic number of $11$ and a mass number of $23$, meaning it has $12$ neutrons).

  • Atomic Mass: Approximately equal to the mass number because protons and neutrons are each roughly $1$ Dalton.

Isotopes and Radioactive Applications

• Isotopes: Variant forms of an element with different numbers of neutrons.

  • $C^{12}$ (normal): $6$ protons, $6$ neutrons.

  • $C^{13}$ (isotope): $6$ protons, $7$ neutrons.

  • $C^{14}$ (radioactive isotope): $6$ protons, $8$ neutrons.

• Decay and Transformation: Radioactive isotopes decay over a "half-life." For example, a neutron in $C^{14}$ can convert into a proton, transforming the Carbon ($6$ protons) into Nitrogen ($7$ protons).

• Medical and Scientific Uses:

  • Fossil Dating: Using isotopes to calculate age backwards.

  • Radioactive Tracing: Labeling glucose with $C^{14}$ to trace metabolic pathways like the citric acid (Krebs) cycle.

  • Medical Diagnosis: Cancerous tissues, which have high metabolic activity, accumulate radioactive tracers more heavily.

  • Thyroid Treatment: Iodine-$125$ is used because iodine only accumulates in the thyroid gland. Its gamma radiation can destroy the remaining thyroid cancer cells after surgery without damaging neighboring parathyroid glands (which control calcium metabolism).

Electron Shells and Energy Levels

• Potential Energy: The energy matter possesses due to its location or structure.

• Shell Distance: The energy level of an electron is determined by its distance from the nucleus.

  • First Shell: Lowest energy.

  • Third Shell: Highest energy relative to the first two shells.

• Excitation: Electrons move to higher shells by absorbing energy (e.g., light) and release energy when falling back to a lower shell.

• Periodic Table Organization: The periodic table is organized by these shells into seven rows called periods. Chemical reactivity is determined by the distribution of electrons in the outermost shell.

Questions & Discussion

• Is the Krebs cycle the same as the Citric Acid Cycle? Yes, it is named after Sir Hans Krebs. He used to tell a story to his students about the importance of having a true hypothesis over a "fictional" goal that lacks an experimental starting point.

• Do we need to know orbitals? The discussion focuses on the atomic structure and shells for now, as those determine biological interactions.

• What are the five periods mentioned? The rows of the periodic table are referred to as periods based on the shell counts of the atoms.