Biology & Life

What is Biology?

Biology is the scientific study of life, encompassing the structure, function, growth, origin, evolution, and distribution of living organisms.

• Scientific study of life: Uses observation, experimentation, and evidence-based reasoning.

7 Characteristics of Life

All living organisms share fundamental characteristics that distinguish them from non-living matter.

1. Reproduction: Ability to produce offspring, either asexually or sexually.

2. Growth/Development: Progression from a single cell to multicellular complexity.

3. Energy/Matter Use: Intake and transformation of energy (food, water, sunlight); loss of energy as heat.

4. Cells: Basic unit of life; organisms may be unicellular or multicellular.

5. Order: Organized structure from atoms to organisms.

6. Response to Environment: Homeostasis, balance, and equilibrium in response to stimuli.

7. Evolution: Adaptation and change over generations via natural selection.

• Are Viruses Alive? No; viruses do not meet all 7 characteristics.

The Scientific Method

Steps of the Scientific Method

The scientific method is a systematic approach to inquiry, involving observation, hypothesis formation, experimentation, and analysis.

1. Observation: Gathering data about phenomena.

2. Hypothesis: Formulating a testable explanation.

3. Prediction: Making logical predictions based on the hypothesis.

4. Experiment: Testing predictions through controlled experiments.

5. Conclusion: Analyzing results and revising hypotheses as needed.

• Attributes of Science: Testable, repeatable, falsifiable, evidence-based.

• Theory: Well-tested, evidence-supported explanation (e.g., Evolution).

Modules in Chapter 2: The Chemistry of Life

2.1 All life is made of molecules, which are made of atoms

Atoms are the basic units of matter, and molecules are combinations of atoms bonded together. Understanding atomic and molecular structure is foundational to biology.

• Atoms: Smallest unit of matter; consists of protons, neutrons, electrons.

• Molecules: Two or more atoms bonded together.

• Concept of levels: Subatomic particles → atom → molecule.

• Important Terms: atom, molecule, subatomic particle (proton, neutron, electron).

• Application: Explain how atoms combine to form molecules; relate atomic structure to molecular structure.

2.2 All matter consists of chemical elements

Elements are pure substances consisting of only one kind of atom. They are defined by atomic number and mass.

• Element: Pure substance with only one kind of atom.

• Periodic table: Atomic number, atomic mass.

• Key elements in biology: C, H, O, N, P, S.

• Trace elements: Elements required in small amounts.

• Important Terms: element, atomic number, atomic mass, trace element, essential element.

• Application: Identify biologically important elements; read periodic table; compare major vs. trace elements.

2.5 Chemical bonds and properties of water

Chemical bonds hold atoms together in molecules. Water's unique properties are essential for life.

• Covalent bond: Atoms share electrons.

• Ionic bond: Atoms transfer electrons.

• Hydrogen bond: Weak attraction between polar molecules.

• Properties of water: Cohesion, adhesion, solvent abilities, high specific heat.

• Functional groups: Groups of atoms (e.g., hydroxyl, carboxyl, amino) that affect molecular behavior.

• Important Terms: covalent bond, ionic bond, polar/nonpolar, hydrogen bond, buffer, adhesion/cohesion, hydrophobic/hydrophilic, functional group.

• Application: Given examples, classify bonds; explain water's special properties; relate molecular structure to biological phenomena.

Modules in Chapter 4: Energy and Life

4.1 The concept of energy in biology

Energy is essential for biological systems, driving processes such as metabolism and growth.

• Energy forms: Kinetic, potential.

• Thermodynamics: Laws governing energy flow and transformation.

• Energy transformations: Energy is transferred and transformed in living organisms.

• Important Terms: energy, kinetic potential, entropy, system vs. surroundings, closed/open system.

• Application: Apply thermodynamics to biological processes; explain how organisms transform energy.

4.2 ATP and energy currency of the cell

ATP (adenosine triphosphate) is the primary energy carrier in cells, enabling cellular work.

• Role of ATP: Powers cellular processes.

• ATP structure: Three phosphate groups, ribose, adenine.

• ATP hydrolysis: Releases energy.

• Important Terms: ATP, ADP, phosphate bond, energy coupling.

• Application: Draw/label ATP; explain ATP → ADP + P releases energy; trace ATP usage in cellular processes.

4.3 Enzymes & reaction rates

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.

• Enzyme structure: Active site, substrate specificity.

• Enzyme activity: Affected by temperature, pH, inhibitors, cofactors.

• Important Terms: enzyme, substrate, active site, activation energy, inhibitor, denaturation.

• Application: Explain enzyme mechanism; effects of pH, temperature, inhibitors; distinguish competitive vs. noncompetitive inhibitors.

Photosynthesis & Cellular Respiration

Photosynthesis (in chloroplasts)

Photosynthesis is the process by which plants convert light energy into chemical energy stored in sugars.

• Equation:

• Light Reactions: Capture sunlight; split water.

• Calvin Cycle: Use energy to build sugar from CO2.

Cellular Respiration

Cellular respiration is the process by which cells break down glucose to release energy in the form of ATP.

• Stages: Glycolysis, Krebs cycle, electron transport chain.

• Equation:

• Role of oxygen: Final electron acceptor in electron transport chain.

Ecology & Ecosystems

Definitions

Ecology studies interactions between organisms and their environment. Ecosystems include all biotic and abiotic factors in a given area.

• Ecology: Interaction between organisms & environment.

• Ecosystem: All biotic + abiotic factors in an environment.

Ecosystem Processes

• Energy Flow: Sun → producers (photosynthesis) → consumers → heat.

• Biogeochemical Cycles: Carbon cycle, nitrogen cycle, etc.

• Disruption: Fossil fuel burning & deforestation increase CO2 → climate change.

Greenhouse Gases & Climate Impacts

• Greenhouse Gases: CO2, CH4, N2O, H2O vapor, O3.

• Greenhouse Effect: GHGs trap heat in atmosphere.

• Methane (CH4): Shorter life in atmosphere than CO2, but much more potent.

• Climate Impacts: Ocean warming, acidification, melting ice caps, sea level rise.

Levels of Ecology

• Organismal Ecology: Individual organisms.

• Population Ecology: Study of population changes.

• Community Ecology: Species interactions.

• Ecosystem Ecology: Energy and nutrient flow.

Population Growth

• Exponential: J-curve; unlimited resources.

• Logistic: S-curve; limited by carrying capacity.

Community Ecology

Species Interactions Table

Species interact in various ways, affecting population dynamics and ecosystem stability.

• Climate Change Effects: Uncoupling of mutualisms, range shifts, disrupted herbivory and competition.

Trophic Structure

Food Chain vs. Food Web

• Food Chain: Linear sequence of energy transfer.

• Food Web: Interconnected chains; reflects complexity.

Trophic Levels

1. Primary Consumers (herbivores)

2. Secondary Consumers

3. Tertiary Consumers

4. Quaternary Consumers

• Impact of Loss at Lower Levels: Fewer producers → fewer consumers.

Keystone Species & Ecosystem Stability

Case Studies

• Paine's Sea Star Removal: Removal leads to ecosystem collapse.

• Otters & Kelp Forests: No otters → many urchins → no kelp.

• Orca Overpredation: Fewer otters → more urchins → no kelp.

Ecological Footprints

• Amount of land/water/fuel needed per person (in hectares).

• High footprints → lower global carrying capacity.

• Global inequality: If all lived like Americans, we'd exceed Earth's capacity.

Fossil Fuels & Biofuels

• Fossil Fuels: Ancient organic material (coal, oil, gas); high CO2 output.

• Biofuels: Made from living matter; still require land, water, fertilizer.

• Generations of Biofuels:

  • 1st Gen – Food crops (e.g. corn)

  • 2nd Gen – Non-food (wood, inedible plant parts)

  • 3rd Gen – Algae (lipid-based)

Modules in Chapter 12: Molecular Genetics

12.1 The Genetic Material

DNA is the genetic material, capable of storing and transmitting genetic information.

• Key experiments: Griffith, Avery, Hershey & Chase.

• Properties: Information storage, replication, mutation.

12.2 Structure of DNA

DNA structure is a double helix composed of nucleotides. Replication ensures genetic continuity.

• Replication origin, replication fork, enzymes (helicase, primase, DNA polymerase, ligase).

• Semiconservative replication: Each new DNA has one old and one new strand.

• Differences in prokaryotes vs. eukaryotes.

12.3 The Genetic Code of Life

The genetic code translates DNA sequences into proteins via codons.

• Central dogma: DNA → RNA → protein.

• Codons: Triplets of nucleotides; redundancy/universality.

12.4 First Step: Transcription

Transcription is the process of synthesizing RNA from DNA.

• Initiation, elongation, termination.

• RNA processing in eukaryotes: splicing, 5' cap, poly-A tail.

12.5 Second Step: Translation

Translation converts mRNA into a polypeptide chain (protein).

• tRNA, ribosome, codon-anticodon pairing.

• Stages: Initiation, elongation, termination, post-translational modifications.

12.6 Structure of the Eukaryotic Chromosome

Eukaryotic chromosomes are organized into chromatin, with regulatory mechanisms affecting gene expression.

• Chromatin: Euchromatin vs. heterochromatin.

• Telomeres, centromeres.

• Gene expression regulation.

12.7, 12.8, 12.9 Mutations, Gene Regulation, Biotech Tools

Mutations alter genetic information; gene regulation controls expression; biotechnology tools manipulate DNA.

• Mutation types: Point, frameshift, silent, missense, nonsense.

• Gene regulation: Epigenetics, transcription factors.

• Biotechnology tools: PCR, cloning, restriction enzymes, electrophoresis.

12.11 Non-coding RNAs

Non-coding RNAs regulate gene expression and have diverse functions.

• Types: miRNA, siRNA, splicing variants.

Key Themes Across These Sections

• Information flow in biology: DNA → RNA → Protein.

• Structure-function relationships: Molecular structure determines function.

• Regulation and control: Not all DNA is expressed; regulation via chromatin, transcription factors, RNAs.

• Energy & thermodynamics: Physical/chemical laws govern biological processes.

• Mutations and variation: Sources of genetic change; effects on evolution and disease.

• Tools and techniques: PCR, cloning, electrophoresis; applications in research and medicine.

Possible Study / Practice Questions

1. Draw and label the steps of DNA replication. What enzymes are involved, and what are their roles?

2. Explain semiconservative replication and summarize the experiments that proved it.

3. Given a DNA sequence, provide its mRNA transcript (including processing if eukaryotic) and translate to amino acids using a codon table.

4. Describe how chromosome structure (euchromatin vs heterochromatin) affects gene expression.

5. Explain enzyme kinetics: how changes in pH, temperature, inhibitors affect enzyme activity.

6. Describe several types of mutations and predict their effects on protein product.

7. How do functional groups in molecules determine their chemical behavior? Give examples.

8. Discuss how ATP functions as energy currency in cells. What makes the bond breakage release energy, and how is ATP regenerated?

9. Describe tools used in molecular biology (PCR, gel electrophoresis, restriction enzymes, cloning) and their purposes.

Additional info: Some content was expanded for clarity and completeness, including definitions, examples, and academic context.