Comprehensive Environmental Science Study Notes

Definition & Scope of Environmental Science (ENVI SCI)

• Dynamic, interdisciplinary field examining interactions between living (biotic) and non-living (abiotic) components.

• Classical view = natural-science focus; modern view = integrates Humanities, Social & Natural Sciences.

• Key foci:

  • Human impacts on conditions, objects, circumstances surrounding organisms/communities.

  • Exploration of complex, nested environmental systems (local → global; short → long term).

Interdisciplinary Structure & Levels of Inquiry

• Hierarchy: Organism → Population → Community → Ecosystem → Biosphere.
  • Sample questions: population growth drivers? trophic cascades? global $CO_2$ response?

• Conceptual lenses: Descriptive, Functional, Evolutionary.

• Taxonomic breadth: Plant, Microbial, Fungal, Animal, Avian, Protozoan.

• Spatial/temporal arenas: Marine, Terrestrial, Freshwater, Paleo-, Tropical Ecology.

• Processes studied: Behavioral, Physiological, Biogeochemical, Socio-economic.

Why Study the Environment?

• Human behaviour directly alters biosphere; future depends on evidence-based action.

• Global challenges: Climate change, Habitat loss, Population growth, Rapid development.

• Need systems thinking to link individual behaviour ↔ collective outcomes.

Tragedy of the Commons (Hardin 1968)

• Definition: Individually rational use of shared, limited resources ⇒ collective ruin.

• Key logic: Benefit to individual > cost borne individually, but total cost > total benefit.

• Quote: “Freedom in a commons brings ruin to all.”

• Real examples: Overgrazing, deforestation, overfishing, sewage dumping, air pollution.

• Climate crisis analogy: Atmosphere as commons; short-term national gains from fossil fuels vs global long-term cost.

Global Environmental Stress Indicators

1. Forests: $\sim1\text{ M ha yr}^{-1}$ lost (1980–1990); degradation via fuelwood & lack of regulation.

2. Soil: $10\%$ vegetated land moderately degraded; $20\%$ irrigated soils losing productivity ⇒ food security threat.

3. Fresh Water: $20\%$ humans lack safe drink; $50\%$ lack sanitation; $\tfrac{2}{3}$ population water-stressed by $2025$.

4. Marine Fisheries: $25\%$ at capacity; $35\%$ over-fished; aquaculture↑ but causes pollution & mangrove loss.

5. Biodiversity: $\approx14$ million spp.; $1{-}11\%$ risk extinction/decade, esp. coastal.

6. Atmosphere: Rising $CO_2$; industrial nations missed $1990$ targets by $2000$.

7. Toxic Chemicals: >100{,}000 commercial chemicals; POPs dispersed globally.

8. Hazardous Wastes: Heavy metals, radioactive legacies.

9. Waste Management: Domestic/industrial waste ↑; per-capita tripled in developed world in <20 yrs.

The Process of Science

• Scientific Method cycle: Observation → Question → Hypothesis → Prediction → Experiment → Analysis → Conclusion → Communication.

• Hypothesis = testable explanation; Theory = well-supported framework.

• Study types:
  • Observational: compare natural groups; relies on replication & repeatability.
  • Manipulative: control vs treatment; identifies cause-effect.
  • Social research parallels: Independent/Dependent/Control variables; ethics & reflexivity.

• Core design terms:

  • Response variable, Explanatory/Treatment variable, Controlled (confounding) variables.

Basic Science Process Skills

• Observing, Classifying, Measuring, Inferring, Predicting, Communicating (e.g., PAGASA storm-surge warning system).

Systems Thinking

• Seeks whole-picture interconnections; vital in tech-driven, globalised world.

• Cultural, Civic, Scientific, Aesthetic dimensions → informed decisions & nature stewardship.

Environmental Chemistry: Soil, Water & Atmosphere

• Studies natural & anthropogenic chemical processes in lithosphere, hydrosphere, atmosphere.

• Key elemental cycles: C, N, P, S, O, H.

Atomic & Molecular Foundations

• Atom: protons (+), neutrons (0), electrons (–). Atomic # = protons; Mass # = p + n.

• Molecules vs Compounds; examples: $H<em>2O, CO</em>2, NO<em>2, CaCO</em>3$.

• Important environmental molecules: water (solvent/climate), $CO<em>2$ (GHG/photosynthesis), $NO</em>3^-$ (nutrient/eutrophication), $O_3$ (UV shield & pollutant).

Chemical Bonds

• Ionic (electron transfer) e.g., $NaCl, CaCO<em>3, NO</em>3^-$; covalent (electron sharing) e.g., $H<em>2O, CH</em>4, DDT$.

• Properties govern solubility, mobility, toxicity.

Ions & Isotopes

• Cations $K^+, Ca^{2+}$; Anions $NO<em>3^-, PO</em>4^{3-}$ drive soil fertility & water quality.

• Isotopes: $^{14}C, ^{18}O, ^{15}N, ^{13}C$ for dating, tracing sources, paleoclimate.

Acids, Bases & pH

• $pH=-\log[H^+]$; scale $0{-}14$.

• Environmental examples: Acid rain $SO<em>2+H</em>2O\rightarrow H<em>2SO</em>4$ ($pH\approx4.2{-}5$); soil liming with $CaCO_3$; aquatic carbonate buffer.

Lithosphere Processes

• Cation Exchange Capacity (CEC), decomposition, complexation.

• Contaminants: Heavy metals (Pb, Cd, Hg), fertilizers → nitrates.

Hydrosphere & Water Chemistry

• Healthy pH $6.5{-}8.5$; acid mine drainage ↑ $Al^{3+}$ toxicity.

• Processes: solubility/speciation, biodegradation, eutrophication.

Atmospheric Chemistry

• Key gases $N<em>2, O</em>2, CO<em>2, O</em>3$; pollutants $SO<em>2, NO</em>x, VOCs$.

• Photochemical smog: $VOCs + NO<em>x + h\nu \rightarrow O</em>3$.

Systems Linkage Examples

• Acid rain ↓ soil pH & harms lakes.

• Agricultural runoff → water eutrophication → $N_2O$ emissions.

• Wildfires ↔ air particulates, soil nutrients, hydrology.

Energy & Matter: Nucleosynthesis, Fusion & Fission

• Nucleosynthesis forms elements via fusion (stars) or fission/decay.

• Big Bang produced $H, He, Li$; stellar fusion (pp-chain, triple-alpha, CNO) creates up to Fe; s-process & neutron capture beyond Fe.

• Fusion example: $^2H + ^3H \rightarrow ^4He + n + 17.6\,MeV$.

• Fission example: $^{235}U + n \rightarrow ^{141}Ba + ^{92}Kr + 3n + 200\,MeV$.

• Conditions: $T\ge 10^8\,^{\circ}C$, high pressure, plasma confinement.

Bioenergetics & Thermodynamics

• First Law: Energy conserved; conversions (e.g., light → chemical).

• Second Law: Transfers inefficient; entropy ↑; life needs constant energy.

• ATP (adenosine triphosphate) = universal cellular energy currency.

• Cellular respiration yields $\approx38$ ATP/glucose: Glycolysis (2 ATP) + Krebs + ETC (36 ATP).

Photosynthesis

• Overall equation: $6CO<em>2 + 12H</em>2O + h\nu \rightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2 + 6H_2O$.

Light Reactions (Thylakoid)

• Photosystems II ($P<em>{680}$) & I ($P</em>{700}$).

• Non-cyclic (linear) flow: $H<em>2O\rightarrow NADPH$; produces $ATP, NADPH, O</em>2$ via electron transport & proton gradient.

• Cyclic flow (PS I only): $ATP$ generation when $NADP^+$ scarce; no $O_2$.

Calvin Cycle (Stroma)

• Phases: Carbon fixation (RuBP + $CO_2$ via Rubisco) → Reduction → RuBP regeneration.

• For one glucose: $6$ turns, $18$ ATP, $12$ NADPH.

• Limitations: high $N$ demand (Rubisco $\approx25\%$ leaf N), light-dependent ATP/NADPH supply, $CO_2$ diffusion limits.

Photorespiration & Alternative Pathways

• Rubisco also oxygenates RuBP → photorespiration (uses $O<em>2$, releases $CO</em>2$, wastes ATP).

• $C_4$ pathway (Hatch-Slack): Spatial separation (mesophyll vs bundle sheath); enzyme PEP-carboxylase.

• CAM plants: Temporal separation (night $CO_2$ uptake as malate; day Calvin cycle).

Global Significance

• Photosynthesis fixes $\sim160$ Gt C yr$^{-1}$, produces atmospheric $O_2$; basis of GPP & NPP ($NPP=GPP-R$).

Terrestrial Biomes & Abiotic Drivers

• Temperature & precipitation patterns (latitude, altitude, continentality, rain-shadow, ocean currents) define desert, grassland, forest, tundra, Mediterranean.

• Deserts: Subtropical, rain-shadow, coastal, temperate, polar — lowest NPP.

• Grasslands: Savanna (tropical wet–dry), Prairie (temperate), Tundra (polar permafrost).

• Forests: Tropical rain, Temperate rain/deciduous, Boreal (taiga, conifers), Mediterranean shrublands.

Ecosystem Succession

• Primary: colonisation on new substrate (bare rock → lichens → grasses → climax forest).

• Secondary: recovery after disturbance (fire, flood) — faster as soil present.

Evolutionary Principles & Biodiversity

• Hierarchy: Cell → Tissue → Organ → System; Organism → Population → Community → Ecosystem → Biosphere.

• Adaptations: physical, behavioural, physiological; define habitat tolerance ranges.

• Natural selection pressures: physiological stress, predation, competition, sexual selection.

• Speciation: Divergent (allopatric e.g., chimp vs bonobo); Convergent (mantis vs mantis-fly); Artificial selection (domestic dog).

• Taxonomy: 3-Domain (Archaea, Bacteria, Eukarya); 5-Kingdom; binomial nomenclature ($Genus\ species$).

• Global species estimates $\approx8.7$ million; insects largest share.

Population Dynamics & Community Interactions

• Growth models: Logistic (S-curve, carrying capacity $K$) vs Exponential (J-curve, overshoot & dieback).

• Density-dependent vs independent resistance.

• Interactions: Predator–prey, competition (intra/inter-specific), resource partitioning, symbiosis (mutualism, commensalism, parasitism).

Aquatic Ecosystems

Freshwater

• Lakes/Ponds zones: Littoral (emergent plants), Limnetic (photic open water), Profundal (aphotic), Benthic.
  • Trophic state: Oligotrophic (nutrient-poor, clear) ↔ Eutrophic (nutrient-rich, algal blooms).

• Rivers: Source (cold, high $O_2$, low nutrients) → Transition → Floodplain → Mouth (brackish, warm, nutrient-rich).

• Inland wetlands: Marsh (no trees), Swamp (trees), Bog (sphagnum). Services: biodiversity, flood buffering, filtration.

Marine

• Coastal wetlands: Deltas, estuaries, lagoons, tidal flats, salt marshes, mangroves, sea-grass beds.

• Intertidal zone: alternates submersion/exposure; shaped by lunar–solar tides (Bay of Fundy $\Delta h\approx16.3\,m$).

• Coastal zone (continental shelf, $\le200\,m$): $\approx90\%$ ocean biodiversity; rocky vs sandy shores.

• Coral reefs: symbiosis coral–algae; high productivity in oligotrophic tropics.

• Open ocean: Photic, Dysphotic, Aphotic; nutrient-poor “marine desert”; bioluminescence common.

• Abyssal plain: detritus-based (“marine snow”); chemosynthesis at hydrothermal vents.

Ecosystem Services of Wetlands & Coastal Systems

• Biodiversity support, storm & flood protection, water purification, carbon storage.

These bullet-point notes integrate all major and minor concepts, examples, data, equations, and interdisciplinary links from the provided transcript, offering a comprehensive standalone study guide for environmental science topics.