Comprehensive Study Notes: An Introduction to Biology and the Chemistry of Life

Properties of Life and Biology as a Science

• Definition of Biology: Biology is defined as the scientific study of life. Biologists recognize life not by a single characteristic, but through a series of properties shared by all living things. An object is considered alive if, and only if, it displays all of the following properties:

  • Order: Every living organism possesses a complex but well-ordered structure.

  • Energy and Matter Processing: Every organism takes in energy and matter, converts them into useful forms (metabolism), and expels energy/waste.

  • Reproduction: All organisms reproduce their own kind. For instance, elephants only give birth to baby elephants; they never produce organisms of a different species.

  • Growth and Development: Information carried by genes controls the specific pattern of growth and development in all organisms.

  • Response to the Environment: All organisms respond to changes in their external surroundings. These responses often function to maintain an organism’s internal environment within narrow, sustainable limits (homeostasis).

  • Evolutionary Adaptations: Traits evolve over countless generations through the reproductive success of individuals with heritable traits best suited to their environments. A specific example is the broad, thin ears of an elephant, which are an evolutionary adaptation designed to dissipate heat.

The Case of Viruses: Living or Nonliving?

• Criteria Evaluation: When applying the standard properties of life to viruses, the classification is not entirely straightforward.

  • Arguments for Life: Viruses are highly ordered and can evolve over time.

  • Arguments against Life: Although viruses can infect a wide range of organisms, they cannot reproduce on their own; they require a host cell.

• Current Scientific Consensus: While the idea is not settled, many biologists agree that viruses are not alive. Instead, they are regarded as existing in a state between living organisms and nonliving chemicals.

Levels of Biological Organization

• Scope of Study: The study of life extends from the microscopic (atoms and molecules) to the global (the biosphere).

• Emergent Properties: At each new level of the biological hierarchy, emergent properties appear. These are properties that were absent from the preceding level. For example, a cell displays emergent properties, such as the ability to reproduce itself, which are not apparent in the individual molecules or organelles that compose the cell.

• Hierarchical Progression: The hierarchy typically progresses as follows:

  • Atoms

  • Molecules

  • Organelles

  • Cells

  • Tissues

  • Organs

  • Organ Systems

  • Organisms

  • Populations

  • Communities

  • Ecosystems

  • Biosphere

Major Themes in Biology

• Energy and Matter Transformation: All activities of a cell require energy and matter. The sun provides the energy that drives nearly every ecosystem on Earth. Organisms regulate the transformation of this energy to sustain life.

• Interconnections: There are deep interconnections within and between the levels of biological systems.

• Structure and Function: Within all biological systems, the structure (the shape) and function (what it does) are correlated. For example, the millions of tiny sacs in human lungs provide a high surface area structure that correlates specifically with the function of gas exchange.

• Information Flow: Information flow is apparent at all levels. All genes are encoded in an identical chemical language (DNA) common to all organisms. Inherited diseases, such as mutations in breast cancer genes (e.g., as cited in the case of actress Angelina Jolie), result from improper information in the gene.

• Evolution: Evolution, defined as the descent with gradual modifications of ancestral species to modern-day ones, is biology's unifying theme. It explains both the common characteristics (unity) and the differences (diversity) of life. One modern application is understanding the development of antibiotic-resistant bacteria through natural selection.

The Process of Science and Inquiry

• Definition of Science: Science is an approach to understanding the natural world through inquiry—a search for information, evidence, explanations, and answers to specific questions.

• Scientific Method Components:

  • Observation: Noticing phenomena (e.g., observing that some cookies are taller than others).

  • Question: Formulating a specific inquiry (e.g., "What ingredient makes the tallest cookies?").

  • Hypothesis: A proposed explanation to a question that can be investigated. A good hypothesis must be testable and falsifiable. Example: "Switching to cake flour over all-purpose flour will lead to taller cookies."

  • Experiment: A test run to provide data that may support or refute the hypothesis (e.g., comparing the height of cookies baked with different flours).

  • Data: The recorded observations that serve as evidence.

• Phases of the Scientific Process:

  1. Exploration: Observing nature, asking questions, reading scientific literature, and seeking information.

  2. Testing: Forming hypotheses, making predictions, running experiments, conducting observational studies, gathering and analyzing data, drawing conclusions, and developing new hypotheses.

  3. Communication: Sharing data, obtaining feedback, publishing papers, attending scientific meetings, replicating findings, and building consensus.

  4. Outcomes: Building knowledge, solving problems, developing new technologies, informing policies, and benefiting society.

Distinguishing Scientific Concepts

• Hypothesis: Narrow in scope, subject to immediate testing, possesses no prior expectation of truth, and must be falsifiable. Example: The large ears of African elephants are an adaptation for heat regulation.

• Scientific Theory: A well-substantiated explanation that is comprehensive and broad in scope. It has already been supported by a large body of evidence and has never been shown to be false, yet it still must be falsifiable. Example: External adaptations evolve over generations due to reproductive success.

• Fact: Verifiable and considered objectively true based on current evidence. Repeatable experimental results are the prerequisites of science. Example: Elephants are the largest land animals.

Experimental Design and Variables

• Controlled Experiment: A test run multiple times with only one variable changing.

• Variables:

  • Independent Variable: The factor being manipulated as a potential cause.

  • Dependent Variable: The response, output, or effect under investigation.

• Groups:

  • Control Group: Establishes a baseline.

  • Negative Control: A group where no change is expected (e.g., using the same oven).

  • Positive Control: A group where a change is expected (e.g., doubling butter to ensure height can change).

• Blinding:

  • Single-blind: Information is withheld from participants.

  • Double-blind: Information is withheld from both participants and experimenters to reduce bias.

• Placebo Effect: A phenomenon where a patient feels better after believing a treatment was given, even if the treatment was inactive.

Data Visualization and Communication

• Tables: Used to collect, organize, and share raw data.

• Graphs: Visual representations used to summarize and compare data.

  • Bar Graph: Used to compare categories. Often includes error bars to communicate the likelihood of a meaningful difference.

  • Line Graph: Used for data that changes continuously. Uses a vertical y-axis and horizontal x-axis.

  • Pie Chart: Used to convey numerical proportions or percentages where the total equals $100\%$.

Types of Scientific Studies

• Hypothesis-driven Controlled Experiments: Scientists manipulate variables to test a hypothesis (e.g., The Diabetes Control and Complications Trial Research Group study on intensive therapy for type-1 diabetes).

• Observational Studies: Scientists examine subjects without manipulation. These are common in ecology and human health for ethical/practical reasons.

• Epidemiological Studies: A type of observational study that measures links between lifestyle and health over long periods (e.g., a 7-year study of $18,000$ people comparing insulin pumps vs. injections).

• Clinical Trials: Controlled experiments using humans, where subjects are randomly assigned to experimental or control groups, often utilizing a placebo.

Critical Thinking and Pseudoscience

• Critical Thinking: The unbiased analysis and evaluation of information to form a judgment.

• Pseudoscience: Any field falsely presented as having a scientific basis.

  • Features of Science: Adheres to scientific method, repeatable results, testable/disprovable claims, open to outside review, multiple lines of evidence.

  • Features of Pseudoscience: Does not adhere to accepted processes, results depend on opinion or a single person, untestable claims (reliance on beliefs), rejection of external review, overreliance on small data amounts.

  • Examples: Fortune telling, phrenology (personality based on skull measurements), and ESP (Extra-Sensory Perception).

Evaluating Scientific Sources

• Reliability Levels:

  • Primary Source: Original material presented for the first time by the researchers. The "gold standard" is a peer-reviewed journal, where work is evaluated by impartial, anonymous experts.

  • Secondary Source: A description or review of primary sources (e.g., news articles).

  • Wikipedia: A common starting point, but unreliable because anyone can edit it.

• Evaluation Criteria: Consider if the info is current, if the source is primary, author qualifications, lack of conflict of interest, detailed references, and whether experiments are reproducible.

Basic Chemistry of Life

• Matter: Anything that occupies space and has mass. It exists in three states: solid, liquid, or gas.

• Chemistry: The scientific study of matter.

• Atoms and Molecules: Atoms are the smallest units that retain the properties of an element. Atoms bond to form molecules.

• Elements: Basic substances that cannot be broken down (e.g., Sodium). The smallest amount of an element is one atom.

• Compounds: Combinations of individual elements (e.g., Table Salt).

• Chemical Reactions: Transformations where reactants are rearranged into products. Matter is neither created nor destroyed.

  • $Reactants \rightarrow Products$

The Periodic Table and Essential Elements

• Organization: Elements are ordered by their atomic number.

• Major Elements: Four elements make up the bulk ($96.3\%$) of living cells:

  • Oxygen ($65.0\%$, symbol: $O$)

  • Carbon ($18.5\%$, symbol: $C$)

  • Hydrogen ($9.5\%$, symbol: $H$)

  • Nitrogen ($3.3\%$, symbol: $N$)

• Minor Elements: Seven elements make up $3.7\%$ of the body (e.g., Calcium, Phosphorus, Potassium, Sulfur, Sodium, Chlorine, Magnesium).

• Trace Elements: Fourteen elements are required in tiny amounts ($0.1\%$), such as Boron, Chromium, Cobalt, Copper, Fluorine, Iodine, Iron, Manganese, Molybdenum, Selenium, Silicon, Tin, Vanadium, and Zinc.

Subatomic Particles and Atomic Variation

• Subatomic Particles:

  • Protons: Positive charge, located in the nucleus. The number of protons determines the element's identity.

  • Neutrons: Neutral charge, located in the nucleus.

  • Electrons: Negative charge, orbit the nucleus in specific shells. Electrons have very little mass.

• Isotopes: Variants of an element with the same number of protons but different numbers of neutrons. Some are unstable and emit radiation.

• Ions: Atoms that have gained or lost electrons, resulting in an electrical charge.

  • A Nitrogen atom gaining $3$ electrons becomes a negatively charged ion ($N^{3-}$).

Chemical Bonding

• Ionic Bonds: Involve the transfer of one or more electrons.

  • The donating atom becomes positively charged.

  • The receiving atom becomes negatively charged.

  • The bond is created by the attraction between opposite charges.

• Covalent Bonds: Involve the sharing of one or more electrons. These are the strongest chemical bonds.

  • Single Bond: Sharing one pair of electrons.

  • Double Bond: Sharing two pairs of electrons.

  • Triple Bond: Sharing three pairs of electrons.

  • Nonpolar Covalent: Equal sharing of electrons.

  • Polar Covalent: Unequal sharing (e.g., in $H_2O$, oxygen is more negative while hydrogens are more positive).

• Hydrogen Bonds: Weak attractions between polar molecules. In water, networks of hydrogen bonds are strong enough to form liquid water.

Unique Properties of Water

• Polarity: Water ($H_2O$) is a polar molecule, leading to hydrogen bonding.

• Ice Floats: As water freezes, stable hydrogen bonds hold molecules further apart than in liquid water. Ice is less dense than liquid water. If ice sank, whole bodies of water would freeze solid, making aquatic life impossible.

• Solvent: Water is an effective solvent (dissolving agent) for creating solutions.

• Temperature Regulation: Water has a high capacity to absorb and release heat with minimal change in its own temperature, which moderates planetary climates.

• Evaporative Cooling: Used by organisms (e.g., sweating) to regulate body temperature.

• Cohesion: The tendency of molecules to stick together. Water’s high cohesion creates surface tension, allowing organisms like the wolf spider to stand on water.

pH and Ocean Acidification

• Aqueous Solutions: Solutions where a substance is dissolved in water. Water molecules can break into hydrogen ions ($H^+$) and hydroxide ions ($OH^-$).

• pH Scale: A measure of the concentration of $H^+$ ions.

  • Scale runs from $0$ to $14$.

  • Each number represents a tenfold change in $H^+$ concentration.

  • Acids: Release $H^+$; pH $0$ to $7$.

  • Bases: Remove $H^+$; pH $7$ to $14$.

  • Neutral: pH $7$ (e.g., pure water).

• Buffers: Chemicals that minimize pH changes by accepting or donating $H^+$ ions (e.g., blood buffers during exercise).

• Ocean Acidification: As atmospheric $\text{CO}_2$ levels rise, the ocean absorbs more $\text{CO}_2$. This triggers chemical reactions that lower the pH (increasing acidity). Low pH conditions hinder marine organisms' ability to build shells and skeletons (calcification).