Environmental Science Essentials

Cheatsheet Content

Introduction to Environment Environment: Everything around us (water, air, land, living organisms). Components: Biotic Factors: Living organisms (humans, plants, animals, microorganisms). Abiotic Factors: Non-living factors (light, air, water, soil). Relationship: Mutual and interconnected between biotic and abiotic factors. Characteristics of Environment: Complete system (chemical, biological, physical). Affects and is affected by living organisms. Ecosystem: Unit of environment; specific area ($e.g.$, a lake, forest, desert). Composed of biotic and abiotic factors interacting together within a community. Earth's Spheres Earth consists of four interconnected spheres: Atmosphere: Air (mixture of gases like $N_2, O_2, CO_2$, water vapor). Hydrosphere: Water bodies ($H_2O$ in liquid and solid forms). Lithosphere: Land (rocks, minerals, petroleum). Biosphere: All living organisms on Earth. Hydrosphere Details Total water: 70% of Earth's surface. Distribution: 97% Saltwater (oceans, seas, salty lakes). 3% Freshwater: 1% Liquid Freshwater (rivers, freshwater lakes, groundwater). 2% Frozen Water (polar ice caps, glaciers). Potable Water: Liquid freshwater is suitable for human consumption. Water Vapor: Part of the atmosphere, not the hydrosphere. Water Cycle (Hydrological Cycle) Continuous movement of water on, above, and below Earth's surface. Key Processes: Evaporation: Liquid water to water vapor (gas). Direct evaporation from water bodies (sunlight). Biological processes: Respiration & Excretion: Living organisms release $H_2O$ vapor (and $CO_2$, nitrogenous waste). Transpiration: Plants release $H_2O$ vapor through stomata in leaves. Pulls water up from roots ($cohesion$). Cools the plant (like sweating). Condensation: Water vapor to liquid water droplets, forming clouds. Precipitation: Water falling from clouds ($e.g.$, rain, snow, hail). Percolation (Infiltration): Water seeping into soil and rocks to form groundwater. Melting: Solid to liquid (ice to water); requires temperature increase. Freezing: Liquid to solid (water to ice); requires temperature decrease. Living Organisms & Cells Organic Molecules: Found only in living organisms and food ($e.g.$, carbohydrates, proteins, lipids). Inorganic Molecules: Found in living organisms and environment ($e.g.$, water, mineral salts). Water in Body: ~70% of body weight. 47% Intracellular water (cytoplasm). 23% Extracellular water (blood plasma, other body fluids). Cell: Basic structural and functional unit of life. Cells $\rightarrow$ Tissues $\rightarrow$ Organs $\rightarrow$ Systems $\rightarrow$ Organism. Cell Types - Prokaryotes vs. Eukaryotes Prokaryotes: No true nucleus (genetic material free in cytoplasm). $E.g.$, Bacteria (unicellular). Cell wall made of peptidoglycan. Eukaryotes: True nucleus (genetic material enclosed). $E.g.$, Plants, Animals, Fungi, Protists. Can be unicellular ($e.g.$, Amoeba, Paramecium) or multicellular. Plant Cell vs. Animal Cell Plant Cell: Cell Wall (cellulose). Large central vacuole. Chloroplasts (for photosynthesis). Animal Cell: No cell wall. Small, numerous vacuoles. No chloroplasts. Both: Nucleus, Cytoplasm, Cell Membrane, Mitochondria, Endoplasmic Reticulum. Cell Organelles & Functions Cell Wall: (Plant, Fungi, Prokaryotes) Provides shape and protection; permeable. Plant: Cellulose. Fungi: Chitin. Bacteria: Peptidoglycan. Cytoplasm: Watery matrix where chemical reactions (metabolic reactions) occur. Nucleus: Contains genetic material (DNA) that controls cell activities. Chloroplasts: (Plant) Site of photosynthesis; contains chlorophyll. Vacuole: Storage (water, food, waste). Large in plants, small/numerous in animals. Mitochondria: Powerhouse of the cell; site of cellular respiration. Cellular Respiration: Glucose + Oxygen $\rightarrow CO_2 + H_2O + Energy (ATP)$. Endoplasmic Reticulum: Transports materials within the cell. Water Functions in Cell Universal Solvent: Dissolves molecules for chemical reactions, helps in excretion of waste. Main Component of Cytoplasm: Enables cell functions and maintains structure. Temperature Regulation: High specific heat helps stabilize body temperature. Homeostasis: Maintains internal balance ($e.g.$, body temperature). Metabolism & Enzymes Metabolism: All chemical reactions in an organism. Catabolic Reactions (Catabolism): Break down large molecules into smaller ones, releasing energy ($e.g.$, cellular respiration). Anabolic Reactions (Anabolism): Build large molecules from smaller ones, consuming energy ($e.g.$, photosynthesis, protein synthesis). Enzymes: Biological catalysts (proteins) that speed up chemical reactions. Specific (lock and key model). Lower activation energy. Affected by temperature and pH (optimum conditions). Water Properties: Polarity, Universal Solvent, Acid-Base Balance Water Molecule ($H_2O$): One oxygen, two hydrogen atoms. Oxygen is more electronegative than hydrogen. Results in partial negative charge on oxygen and partial positive charges on hydrogen (polarity). Hydrogen Bonds: Weak electrostatic attractions between water molecules (between partial positive H and partial negative O of another molecule). Gives water unique properties ($e.g.$, high boiling point, cohesion). Universal Solvent: Hydration: Water surrounds ions ($e.g.$, $Na^+$ and $Cl^-$ in $NaCl$) to dissolve them. Hydrolysis: Water molecule itself breaks ($H_2O \rightleftharpoons H^+ + OH^-$) to break down other molecules. Acid-Base Balance (Ionic Equilibrium): Water's ability to dissociate into $H^+$ (acidity) and $OH^-$ (alkalinity). pH Scale: 0-14. 7 alkaline. Salts: Can be acidic, basic, or neutral when dissolved in water, depending on their parent acid and base strength. Physical Properties of Solutions Solution: Mixture of solute (dissolved substance) and solvent (dissolving medium). Concentration: Amount of solute per unit volume of solvent ($g/L$). Colligative Properties (depend on concentration): Vapor Pressure: Pressure exerted by vapor above a liquid. Lower in solutions than pure water. Boiling Point: Temperature at which vapor pressure equals atmospheric pressure. Higher in solutions than pure water. Affected by atmospheric pressure (higher altitude $\rightarrow$ lower BP). Freezing Point: Temperature at which liquid becomes solid. Lower in solutions than pure water. Solutes interfere with ice crystal formation. Osmotic Pressure: Pressure needed to prevent osmosis. Higher in solutions than pure water. Osmosis: Movement of water across a semipermeable membrane from low solute concentration to high solute concentration. Density of Water Density: Mass per unit volume ($g/cm^3$ or $kg/m^3$). Unique Property: Maximum density at $4^\circ C$. As water cools from $4^\circ C$ to $0^\circ C$, it expands, and density decreases. Ice is less dense than liquid water, so it floats. Importance of Ice Floating: Insulates aquatic life in cold regions. Salinity: Higher salinity (more dissolved salts) increases water density. Hydrometer: Device used to measure liquid density. Ocean Currents: Driven by differences in water density (due to temperature and salinity), and water pressure. Temperature Heat: Form of energy (measured in Joules). Temperature: Measure of hotness or coldness (measured in $^\circ C$, K, $^\circ F$). $K = ^\circ C + 273$. $^\circ F = (1.8 \times ^\circ C) + 32$. Specific Heat: Amount of heat energy required to raise the temperature of 1 kg of a substance by 1 Kelvin. Water has a high specific heat, enabling it to regulate temperature slowly. Latent Heat of Vaporization: Energy required to change a substance from liquid to gas without changing temperature. Heat Transfer Mechanisms: Conduction: Heat transfer through direct contact (solids). Convection: Heat transfer through fluid movement (liquids and gases). Radiation: Heat transfer via electromagnetic waves (can occur through vacuum). Adaptations of Aquatic Organisms Organisms adapt to challenges like high water pressure, low oxygen, and osmotic pressure. Types of Adaptations: Physiological (Functional): Changes in body functions ($e.g.$, adjusting blood pressure, kidney function, specialized proteins). Behavioral: Changes in actions ($e.g.$, migration, communication). Structural: Changes in body parts ($e.g.$, body shape, gills, swim bladder). Examples: Fishes in Freshwater: Kidneys excrete dilute urine, contractile vacuoles in unicellular organisms. Fishes in Saltwater: Drink large amounts of seawater, excrete concentrated urine/salt from gills. Sharks retain urea to match osmotic pressure. Deep-Sea Organisms: Flexible bodies (viperfish), large gills, slow metabolism, swim bladders with liquid instead of gas (or no swim bladder, $e.g.$, ray fish). Cold-Blooded Animals: Body temperature fluctuates with environment ($e.g.$, fish, reptiles, amphibians). Warm-Blooded Animals: Maintain constant body temperature ($e.g.$, mammals, birds). Wood Frog: Partially freezes body, stops heart and breathing during winter hibernation. Ice Fish: Produces antifreeze proteins, absorbs oxygen directly through skin. Devil Lizard: Collects moisture from air/sand. Dolphin: Streamlined body, lungs (mammal), fins instead of legs. Gases in Water ($O_2$ & $CO_2$) Oxygen ($O_2$): Sources: Gas exchange with atmosphere, photosynthesis by aquatic plants ($e.g.$, phytoplankton, algae). Importance: Essential for respiration, supports metabolism and activity. Effects of Excess: Increases respiration, activity. Effects of Deficiency: Reduces respiration, activity, can lead to death. Carbon Dioxide ($CO_2$): Sources: Gas exchange with atmosphere, respiration by aquatic organisms, human activities (industrial pollution), decomposition of organic matter. Effects of Excess: Acidification: $CO_2$ dissolves in water to form carbonic acid ($H_2CO_3$), lowering pH. Harms sensitive species ($e.g.$, eggs, larvae). Reduces calcification (formation of shells/skeletons from $CaCO_3$). Reduces oxygen levels, hindering respiration. Effects of Deficiency: Reduces photosynthesis, impacting food chains and overall ecosystem. Light in Water Solar Radiation: Electromagnetic waves (light energy from the sun). Electromagnetic Spectrum: Range of wavelengths; visible light is a small portion. Longer wavelength $\rightarrow$ lower frequency. Shorter wavelength $\rightarrow$ higher frequency. Light Penetration in Water: Partially reflected, partially absorbed, partially scattered. Red and orange light absorbed first; blue light penetrates deepest. Photic Zones (based on light penetration): Euphotic Zone (Sunlit Zone): Uppermost layer, sufficient light for photosynthesis. Twilight Zone (Mesopelagic Zone): Some light, but not enough for photosynthesis. Aphotic Zone (Dark Zone): No light, completely dark. Impact on Ecosystems: Influences water temperature, distribution of aquatic organisms, and ocean currents. Coral reefs thrive in warm, well-lit tropical waters due to symbiotic algae. Polar regions have low light in winter, limiting productivity. Ecosystem Balance & Human Impact Nutrient Balance: Both excess and deficiency of nutrients ($e.g.$, nitrogen, phosphorus) can disrupt ecosystems. Excess nutrients can lead to algal blooms, blocking light, reducing oxygen, and harming aquatic life. Food Chain (Energy Flow): Producers (plants) $\rightarrow$ Herbivores $\rightarrow$ Carnivores. Disruption at any level impacts the entire chain ($e.g.$, overfishing predators leads to overpopulation of prey, depleting producers). Human Activities & Negative Impacts: Pollution: Pesticides, heavy metals ($Hg, Cd, Pb$), industrial waste. Overfishing/Overhunting: Depletes species faster than they can reproduce. Habitat Destruction: Destroys living spaces, reducing biodiversity. Positive Actions for Sustainability: Preserving natural resources, sustainable development. Environmental education. Eco-friendly practices ($e.g.$, reducing water use, recycling, public transport, cycling). Atmosphere & Its Chemical Reactions Atmosphere: Layer of gases surrounding Earth, held by gravity. Components: Primarily Nitrogen (78%), Oxygen (21%), Argon (0.93%), Carbon Dioxide (0.04%). Composition changes due to biological processes (respiration, photosynthesis) and volcanic eruptions. Importance: Thermal insulator, protects from harmful solar radiation ($UV, X-rays, gamma rays$), retains heat, aids water cycle. Layers of Atmosphere (from bottom up): Troposphere (0-10 km): Contains most living organisms. Highest density, most weather phenomena. Temperature decreases with altitude ($6.5^\circ C$ per km). Stratosphere (10-50 km): Contains the ozone layer. Temperature increases with altitude (due to ozone absorbing UV). Horizontal air movement, good for aircraft. Mesosphere (50-80 km): Coldest layer (temperature decreases with altitude). Burns up meteors. Thermosphere (80-700 km): Hottest layer (temperature increases with altitude). Contains Ionosphere (80-550 km), where UV, X-rays, gamma rays ionize gases. Ionosphere reflects radio waves (long-distance communication). Auroras occur here (interaction of solar wind with Earth's magnetic field). Exosphere (700-10,000 km): Outermost layer, very thin. Molecules escape into space (escape velocity). Ideal for satellites and spacecraft. Ozone Layer & Depletion Ozone ($O_3$): Three oxygen atoms. Formation: UV radiation breaks $O_2$ into $O$ atoms ($photodissociation$). $O$ then combines with $O_2$ to form $O_3$. Location: Primarily in the stratosphere. Function: Absorbs harmful UV radiation. UV Radiation Types: UVA (315-400 nm): Least harmful. UVB (280-315 nm): Moderate harm. UVC (100-280 nm): Most harmful, completely absorbed by atmosphere. Ozone Depletion: Gradual destruction of ozone layer. Cause: Release of chlorine and bromine-containing compounds ($e.g.$, Chlorofluorocarbons (CFCs) from refrigerants, halon gases from fire extinguishers). Effects of Increased UV: Skin Damage: DNA damage, skin cancer (melanoma). Immune System: Weakens immune response. Eye Damage: Cataracts. Ecosystem damage. Solutions: Use ozone-friendly products, avoid CFCs, Montreal Protocol. Ozone in Troposphere: Harmful ground-level ozone, formed from nitrogen oxides and hydrocarbons. Causes smog, damages plants, harms human respiratory system. Atmospheric Physical Factors Heat/Temperature: Solar radiation heats Earth's surface, which then heats the atmosphere. Temperature decreases with altitude in troposphere, increases in stratosphere, decreases in mesosphere, increases in thermosphere. Conversion between $^\circ C$, K, $^\circ F$. Heat transfer by conduction, convection, and radiation. Air Pressure: Weight of air column above a unit area. Decreases with altitude. Measured by barometer (units: $N/m^2$, Pascal, atm, mmHg, cmHg, bar, millibar). Affects organisms ($e.g.$, climbers need oxygen, can experience nosebleeds). Blood Components: Plasma, red blood cells (hemoglobin for $O_2$ transport), white blood cells (immunity), platelets (clotting). Blood Pressure: Force exerted by blood on vessel walls. Systolic (max, contraction), Diastolic (min, relaxation). Wind: Movement of air from high-pressure to low-pressure areas. Measured by anemometer. Polar winds are cold and dry. Plant Tissues: Parenchyma (photosynthesis, storage), Collenchyma (support, flexibility), Sclerenchyma (strong support, non-living). Humidity: Amount of water vapor in the air. Measured by hygrometer. High humidity affects weather (heavy rainfall), animals (difficulty cooling), plants (reduced transpiration), and humans (discomfort, skin issues). Global Warming & Climate Change Global Warming: Increase in Earth's average temperature. Cause: Increased concentration of greenhouse gases ($e.g., CO_2, CH_4, N_2O$, water vapor, CFCs) from burning fossil fuels. Greenhouse gases trap heat in the atmosphere. Effects: Melting of polar ice caps $\rightarrow$ rising sea levels, coastal flooding. Extinction of polar species. Severe climate changes ($e.g.$, hurricanes, floods, droughts). Mitigation: Reduce greenhouse gas emissions, use clean energy, afforestation (planting trees), monitoring and forecasting. Air Pollutants: Carbon Monoxide ($CO$): Odorless, colorless, binds to hemoglobin 200-250 times more strongly than oxygen, causing hypoxia and brain damage. Sulfur Oxides ($SO_2, SO_3$): From burning fossil fuels with sulfur, industrial processes. Nitrogen Oxides ($NO_x$): From high-temperature combustion in engines, power plants. Acid Rain: Formed when sulfur and nitrogen oxides react with water in atmosphere ($H_2SO_4, HNO_3$). Damages human respiratory system, plants, infrastructure ($e.g.$, monuments made of $CaCO_3$).