Foundations of General Biology: Organization, Evolution, and Chemistry of Life

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Structural Organization and Levels of Life

Levels of Biological Organization

Biological systems are organized in a hierarchical structure, from the simplest to the most complex forms. Each level exhibits unique properties and functions.

Atom: The smallest unit of matter that retains the properties of an element.
Molecule: A group of atoms bonded together (e.g., H2O, CO2).
Cell: The basic unit of life; can be prokaryotic or eukaryotic.
Tissue: Groups of similar cells performing a specific function.
Organ: Structures composed of different tissues working together (e.g., heart, leaf).
Organ System: Groups of organs that perform related functions (e.g., digestive system).
Organism: An individual living entity.
Population: Group of individuals of the same species living in the same area.
Community: All populations of different species in a given area.
Ecosystem: All living (biotic) and nonliving (abiotic) components in an area.
Biosphere: The global ecosystem; all life on Earth and the places where life exists.

Emergent Properties

At each level of organization, new properties arise that are not present at the preceding level. These are called emergent properties.

Example: Table salt (NaCl) has properties different from its constituent elements sodium (Na) and chlorine (Cl).
Example: Neurons individually transmit signals, but together in the brain, they enable complex thought and behavior.

The Scientific Method

Steps of the Scientific Method

The scientific method is a systematic approach to investigating questions and solving problems using empirical evidence.

Observation: Gather information and ask questions about phenomena.
Hypothesis: Formulate a testable explanation or prediction ("If...then..." statements).
Experiment: Test the hypothesis through controlled experiments; results support or contradict the hypothesis.

Example: If a flashlight doesn't work, hypothesize the battery is dead. Replace the battery (experiment); if it works, the hypothesis is supported.

Theory: A broad, well-supported explanation for a natural phenomenon (e.g., theory of evolution, germ theory of disease).

Note: Theories are broader than hypotheses and can generate new hypotheses and predictions.

Evolution: The Core Theme of Biology

Definition and Importance

Evolution is the process of change in the genetic makeup of populations over generations, leading to the diversity and unity of life.

Accounts for both the diversity and unity of living organisms.
Explains adaptation to environments and the emergence of new species.
Central to understanding all biological processes.

Historical Perspectives on Evolution

Carolus Linnaeus (1707–1778): Developed the binomial nomenclature and classification system for species.
Georges Cuvier (1769–1832): Noted that older strata contain fossils less similar to current life; introduced the concept of catastrophism.
James Hutton (1726–1797) & Charles Lyell (1797–1875): Proposed gradual geological change (uniformitarianism).
Jean-Baptiste de Lamarck (1744–1829): Hypothesized evolution via "use and disuse" and "inheritance of acquired characteristics" (now discredited).
Charles Darwin (1809–1882): Developed the theory of natural selection based on observations during the HMS Beagle voyage.

Darwin's Observations and Natural Selection

Species produce more offspring than the environment can support; many do not survive.
Individuals vary in inherited traits; those with advantageous traits are more likely to survive and reproduce (natural selection).
Over generations, beneficial traits become more common in the population.
Descent with modification: Species descend from common ancestors, accumulating modifications over time.

Artificial Selection

Humans selectively breed organisms for desired traits (e.g., crops, domestic animals).
Demonstrates the power of selection in shaping traits.

Evidence for Evolution

Fossil record: Shows changes in species over time.
Homology: Similar structures due to shared ancestry (anatomical, molecular).
Biogeography: Geographic distribution of species supports evolutionary relationships.

Classification and Diversity of Life

Taxonomy and Systematics

Taxonomy is the science of naming, describing, and classifying organisms. Systematics studies evolutionary relationships.

Binomial nomenclature: Two-part scientific naming system (Genus species).
Hierarchical classification: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Domains of Life

Bacteria: Prokaryotic, unicellular, lack membrane-bound organelles.
Archaea: Prokaryotic, unicellular, distinct biochemistry from bacteria.
Eukarya: Eukaryotic, can be unicellular or multicellular, have membrane-bound organelles and nucleus (includes animals, plants, fungi, protists).

Note: Recent studies suggest there may be only two domains of life (Bacteria and Archaea), with Eukarya arising from within Archaea. Additional info: This is an area of ongoing research.

Central Dogma of Molecular Biology

The Central Dogma describes the flow of genetic information:

DNA is replicated and transcribed into RNA.
RNA is translated into proteins.

Chemical Context of Life

Atoms and Elements

All matter is composed of atoms, which are the smallest units of elements. Elements are pure substances that cannot be broken down into other substances by chemical means.

Essential elements: Required in large amounts (e.g., hydrogen, carbon, oxygen, nitrogen).
Trace elements: Required in minute amounts (e.g., iron, iodine).

Structure of Atoms

Composed of protons (positive charge), neutrons (neutral), and electrons (negative charge).
Protons and neutrons are in the nucleus; electrons orbit the nucleus.
Atoms are electrically neutral unless they gain or lose electrons (becoming ions).

Atomic Number, Mass Number, and Isotopes

Atomic number: Number of protons; defines the element.
Mass number: Number of protons plus neutrons.
Isotopes: Atoms of the same element with different numbers of neutrons.
Atomic weight: Weighted average of all isotopes.

Ions and Radioactive Isotopes

Anion: Atom gains an electron, becomes more negative.
Cation: Atom loses an electron, becomes more positive.
Radioactive isotopes: Unstable isotopes that decay over time, emitting radiation (e.g., carbon-14).
Half-life: Time required for half of the isotope to decay.
Applications: Radiometric dating, medical imaging (PET scans).

Chemical Bonds and Interactions

Types of Chemical Bonds

Covalent bonds: Atoms share electrons to fill valence shells (e.g., H2, O2).
Ionic bonds: Transfer of electrons from one atom to another, resulting in oppositely charged ions (e.g., NaCl).
Hydrogen bonds: Weak attractions between partially charged regions of molecules (e.g., between water molecules).
Van der Waals interactions: Weak, transient attractions between molecules due to temporary charge fluctuations.

Chemical Reactions

Involve making and breaking of chemical bonds.
Law of Conservation of Matter: Matter is neither created nor destroyed in chemical reactions.

Properties of Water

Emergent Properties of Water

Cohesion: Water molecules stick together via hydrogen bonds, leading to surface tension.
Adhesion: Water molecules stick to other substances.
High specific heat: Water resists temperature changes, helping regulate climate and body temperature.
Expansion upon freezing: Ice is less dense than liquid water, so it floats.
Versatile solvent: Water dissolves many substances due to its polarity.

Acids, Bases, and pH

Acid: Substance that increases H+ concentration in solution (pH < 7).
Base: Substance that decreases H+ concentration (pH > 7).
pH scale: Measures acidity/alkalinity; logarithmic scale from 0 (most acidic) to 14 (most basic).
Buffer: Substance that minimizes changes in pH by accepting or donating H+.

Buffers and Homeostasis

Buffers help maintain stable pH in biological systems, crucial for enzyme function and metabolic processes.
Example: Blood contains buffers to maintain pH around 7.4.