Ecology & Evolution Concepts PDF
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This document presents an overview of ecology and evolution concepts, featuring definitions and examples of various ecological terms, such as adaptation, keystone species, natural selection, and succession. The document appears to be educational material, potentially lecture notes or study guide.
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Ecology & Evolution Concepts 1. Adaptation: ○ Definition: A trait that enhances an organism’s abilityto survive and reproduce in a particular environment. ○ Example: The long neck of a giraffe, which...
Ecology & Evolution Concepts 1. Adaptation: ○ Definition: A trait that enhances an organism’s abilityto survive and reproduce in a particular environment. ○ Example: The long neck of a giraffe, which allowsit to reach higher leaves for food, is an adaptation to living in areas where food is scarce on the ground. 2. Keystone Species: ○ Definition: A species whose presence and role in anecosystem has a disproportionate impact on the structure and functioning of the community. ○ Example: Sea otters are a keystone species becausethey control the population of sea urchins, which would otherwise overgraze kelp forests. Their presence supports biodiversity in kelp ecosystems. 3. Natural Selection: ○ Definition: The process by which traits that increasean organism’s chances of survival and reproduction become more common in a population over generations. ○ Example: In a population of moths, darker moths maysurvive better in polluted areas, where lighter moths are more visible to predators. 4. Pioneer Species: ○ Definition: The first organisms to colonize a barrenor disturbed environment, such as bare rock after a volcanic eruption or an area after a forest fire. ○ Example: Lichens and mosses are common pioneer speciesin primary succession, as they can survive with little soil. 5. Selective Force: ○ Definition: An environmental factor that influencesan organism’s ability to survive and reproduce, driving natural selection. ○ Example: Predation is a selective force that favorsorganisms with effective camouflage. 6. Primary Succession: ○ Definition: The process of ecological succession thatoccurs in an environment with no soil or previous life, such as on bare rock or after a volcanic eruption. ○ Example: After a volcanic eruption, mosses and lichensare among the first organisms to establish themselves on the new rock surface. 7. Secondary Succession: ○ Definition: The process of succession that occursin an area where a disturbance has altered an existing community, but soil and some organisms remain. ○ Example: A forest recovering after a wildfire undergoessecondary succession. 8. Late Successional Species: ○ Definition: Species that dominate an ecosystem laterin the process of ecological succession, usually characterized by slower growth, greater competitive ability, and longer lifespans. ○ E xample: Oak trees are a late successional species in temperate forests, replacing pioneer species over time. 9. Climax Community: ○ Definition: The final, stable community in an ecologicalsuccession, where species composition remains relatively unchanged over time unless disturbed. ○ Example: A mature oak forest might be a climax communityin a temperate climate. 10.Carrying Capacity: Definition: The maximum number of individuals of aspecies that an environment can support over time, based on available resources. Example: A lake may have a carrying capacity of 500fish, beyond which competition for food and space reduces survival. 11.Limiting Resources: Definition: Resources that are in limited supply andconstrain the growth, distribution, or abundance of organisms. Example: In a desert, water is often the limitingresource for plant life. 12.Overshoot/Dieoff: Definition:Overshootoccurs when a population exceedsthe environment's carrying capacity.Dieoffis the rapid decrease in populationsize when the resources are exhausted. Example: Deer populations might experience overshootand dieoff if they consume all available vegetation, leading to a food shortage. 13.Density-Dependent Factors: Definition: Factors whose effects on population growthdepend on the population’s density. These factors often intensify as the population increases. Example: Disease spread is density-dependent, as itspreads more easily in denser populations. 14.Density-Independent Factors: Definition: Factors that affect population size regardlessof the population’s density, such as natural disasters. Example: A wildfire that destroys a forest will reducethe population size of species in that forest, regardless of their density. 15.Fecundity: Definition: The reproductive capacity of an organismor population, typically measured by the number of offspring produced. Example: A rabbit’s high fecundity means it can producemany offspring each year. 16.Mortality: Definition: The death rate in a population, typicallyexpressed as the number of deaths per 1,000 individuals per year. Example: Mortality rates can be influenced by factorslike disease, predation, or resource scarcity. 17.Population Momentum: Definition: The tendency for a population to continuegrowing even after fertility rates have declined, due to a large proportion of the population being in reproductive age. E xample: A country that has a high proportion of young people may experience continued population growth even if its birth rate drops. 18.Total Fertility Rate (TFR): Definition: The average number of children a womanis expected to have during her lifetime, based on current birth rates. Example: In a country with a TFR of 2.5, each womanis expected to have 2.5 children on average. 19.Crude Birth Rate (CBR): Definition: The number of live births per 1,000 peoplein a given year. Example: A crude birth rate of 12 means that thereare 12 births per 1,000 people in the population each year. 20.Crude Death Rate (CDR): Definition: The number of deaths per 1,000 peoplein a given year. Example: A crude death rate of 8 means that 8 peopleper 1,000 in the population die each year. Demographic Transition & Fertility 1.Stages of Demographic Transition: 2 Stage 1 (Pre-Transition): High birth rates and highdeath rates lead to a stable or slow-growing population. This occurs in pre-industrial societies. Stage 2 (Early Transition): Death rates fall due toimprovements in healthcare, sanitation, and nutrition, but birth rates remain high, leading to rapid population growth. Stage 3 (Late Transition): Birth rates begin to decline,slowing population growth as society becomes more industrialized and urbanized. Stage 4 (Post-Transition): Both birth and death ratesare low, leading to a stable or slowly growing population. Stage 5 (Declining/Zero Growth): Birth rates fallbelow death rates, leading to population decline. Some countries, especially in Europe, are in this stage. 22.Replacement Level Fertility (RLF): Definition: The total fertility rate needed to maintaina stable population, usually about 2.1 children per woman. Why it's higher in developing nations: In developingnations, higher infant mortality rates and less access to healthcare and contraception often result in higher fertility rates. RLF for developed nations: Generally around 2.1 childrenper woman, which compensates for infant mortality and ensures population replacement. 23.Infant Mortality: Definition: The death rate of infants under one yearof age, often used as an indicator of a country's healthcare quality. Biggest Factors: Poor healthcare, malnutrition, inadequatesanitation, and lack of access to prenatal care. 24.Relationship between Total Fertility Rate and Education/Economy: Explanation: Higher levels of education, especiallyfor women, typically lead to lower fertility rates because educated individuals tend to marry later, have children later, and ay prioritize careers. Economic development and increased access to healthcare and m family planning also contribute to lower fertility rates. Why It Exists: Education provides awareness of familyplanning and contraceptive options, while economic stability offers greater opportunities outside of child-rearing, reducing the perceived need for large families. Plate Tectonics and Earth Science Concepts 1. Tectonic Plates: ○ Definition: Large, rigid pieces of Earth's lithosphere(the outermost layer of the Earth) that move and interact with one another on the semi-fluid asthenosphere beneath. These movements are responsible for many geological phenomena like earthquakes, volcanoes, and mountain formation. ○ Example: The Pacific Plate, North American Plate,and Eurasian Plate are examples of tectonic plates. 2. Divergent Plate Boundary: ○ Definition: A type of plate boundary where two tectonicplates move away from each other. This movement can create new oceanic crust as magma rises to the surface. ○ Example: The Mid-Atlantic Ridge is a divergent boundarywhere the Eurasian Plate and North American Plate are moving apart. 3. Subduction Zone: ○ Definition: A type of convergent plate boundary whereone tectonic plate is forced under another into the mantle, creating deep ocean trenches and volcanic activity. ○ Example: The Pacific Plate is subducting beneath theNorth American Plate along the coast of Japan, creating volcanic islands like the Kuril Islands. 4. Why does Seafloor Spreading Create New Lithosphere?: ○ Explanation: Seafloor spreading occurs at divergentplate boundaries where magma from the mantle rises to fill the gap between the moving plates. As the magma cools, it solidifies to form new oceanic crust (lithosphere). This process continuously adds new lithosphere while older lithosphere is pushed away from the ridge. ○ Example: The formation of new crust at the Mid-AtlanticRidge, pushing older crust outward. 5. How Do We Know Where Subduction Occurs?: ○ Explanation: Subduction zones are marked by deep oceantrenches and by earthquake activity along the subduction zone. Earthquakes at these boundaries can be measured and traced, revealing the location of the subduction zone. Additionally, geological surveys and the presence of volcanic arcs can identify areas of subduction. ○ Example: The Ring of Fire, where many subduction zonesoccur, is known for frequent earthquakes and volcanic eruptions. 6. How Do We Know Where a Plate Moves Over a Hotspot?: ○ E xplanation: A hotspot is a location where a mantle plume rises from deep within the Earth to create volcanic activity. As a plate moves over this stationary hotspot, a chain of volcanoes forms, with the youngest volcano being located directly above the hotspot. The age progression of these volcanoes shows the direction and speed of plate movement. ○ Example: The Hawaiian Islands, which form a volcanicchain as the Pacific Plate moves over a hotspot. Soil Layers and Soil Composition 1. Soil Layers: ○ O Horizon(Organic Layer): Composed of organic materiallike decomposed leaves, plants, and animal matter. It is rich in nutrients. ○ A Horizon(Topsoil): The uppermost layer containinga mix of organic matter and minerals. It’s where most plant roots are found. ○ E Horizon(Eluviation Layer): Found in some soils,this layer is where minerals are leached or washed away by water, leaving behind lighter materials. ○ B Horizon(Subsoil): Contains minerals leached fromthe above layers (illuviation) and may also contain clay and other materials. ○ C Horizon(Parent Material): The unweathered layerof rock or unconsolidated material from which the soil develops. ○ R Horizon(Bedrock): The layer of solid rock beneaththe soil profile. 2. Parent Material: ○ Definition: The underlying geological material (oftenbedrock or unconsolidated sediment) from which soil develops. It provides the mineral content for soil formation. 3. Darkest Layers of Soil: ○ Explanation: The darkest layers of soil are typicallythe O and A horizons, rich in organic matter and decomposed material, giving them a darker color compared to mineral-rich layers. ○ Why They Are Dark: These layers have a high concentrationof organic material, which contains carbon and gives soil a darker appearance. 4. Layers with Most Nutrients and Why: ○ Explanation: The A horizon (topsoil) typically containsthe highest concentration of nutrients because it is rich in organic matter and minerals leached from the overlying layers. This is where most plant roots are located. ○ Why: Organic matter in the A horizon decomposes intohumus, which retains and releases nutrients needed by plants. 5. Layer with Most Parent Material: ○ Explanation: The C Horizon, which consists of unweatheredparent material, contains the bulk of the rock or mineral content. This is the source of the minerals in soil as it slowly breaks down over time. 6. How Parent Material Becomes Soil: ○ Explanation: Parent material undergoes weathering,which breaks it down physically (e.g., through freezing and thawing) and chemically (e.g., through reactions with water and air). Over time, weathered material is mixed with organic material, forming soil. 7. Groundwater Location Relative to Soil Layers: ○ Explanation: Groundwater typically occurs below theA and B horizons, often in the C horizon or in an underlying layer of bedrock. It can accumulate in the spaces between particles in the soil or in rock fractures. Soil Water Filtration and Ecosystem Services 8. How Soil Filters Water: ○ Explanation: Soil acts as a natural filter for waterthrough its texture and structure. Water passes through the soil, where particles like sand, silt, and clay trap pollutants and contaminants. The organic matter in the soil also helps to bind and filter chemicals. ○ Example: In areas with healthy, well-structured soil,water percolates slowly and cleanly through the soil profile. 9. Why Organic Matter is Important to Soil: ○ Explanation: Organic matter improves soil structure,water retention, nutrient holding capacity, and provides a habitat for soil organisms. It also decomposes into humus, which helps retain nutrients and maintain soil fertility. ○ Example: Composting adds organic matter to soil, improvingits ability to retain moisture and nutrients. 10.Four Ecosystem Services Intact Soil Provides: Soil Fertility: Nutrient cycling supports plant growth. Water Filtration: It cleans and purifies water asit passes through the soil. Carbon Sequestration: Soil captures and stores carbon,helping mitigate climate change. Habitat: Soil provides a habitat for organisms, frommicrobes to larger animals. 11.How Soil Filters Groundwater: Explanation: Soil filters groundwater by trappingcontaminants and pollutants as water moves through the soil layers. Organic material in the soil helps break down harmful substances and can retain heavy metals or chemicals in its structure. Soil Texture, Porosity, and Water Holding Capacity 2.Soil Texture: 1 Definition: The relative proportion of sand, silt,and clay particles in soil. It is measured using a soil texture triangle, which classifies soils into types like sandy, loamy, or clayey. H ow It's Measured: Soil texture can be measured through laboratory analysis or the "feel method" by feeling the soil and determining its relative proportions of sand, silt, and clay. 13.Soil Texture and Porosity, Permeability, and Water Holding Capacity: Porosity: Refers to the space between soil particlesthat holds water and air. Sandy soils have larger pores, making them less porous but more permeable, while clay soils have smaller pores, making them more porous but less permeable. Permeability: The ability of soil to transmit waterand air. Sandy soil has high permeability, while clay has low permeability. Water Holding Capacity: The amount of water soil canretain. Clay soil has the highest water holding capacity due to small particles and high surface area, while sandy soil holds less water. 14.Soil Types and Their Water Retention: Largest Pore Size: Sandy soil has the largest pores,allowing water to drain quickly, but it also retains less water. Most Water Retained: Clay soil retains the most waterbecause it has small particles and high surface area, which trap water in the pores. 15.Identifying Sand, Silt, and Clay Proportions: Method: You can use the soil texture triangle or asedimentation method. The sedimentation method involves mixing soil with water and letting it settle; sand will settle first, followed by silt, and clay will settle last. Soil Types, Pore Size, and Water Retention 1. Soil Type with Largest Pore Size: ○ Sandy Soilhas the largest pore size. Reason: Sandy soils have relatively large particlesthat create larger gaps between them, allowing air and water to pass through quickly. Effect on Water: While sandy soil has large pores,it does not retain water well. Water drains quickly through it because there is less surface area for water to adhere to. 2. Soil Type that Retains the Most Water: ○ Clay Soilretains the most water. Reason: Clay particles are small and tightly packed,creating a large surface area that holds water effectively. The water moves slowly through clay soils, as the small pores do not allow for rapid drainage. Effect on Water: While clay soils hold water well,they can become waterlogged if there is too much rainfall or irrigation. 3. Soil Type that Retains the Least Water: ○ Sandy Soilretains the least water. Reason: Sandy soils drain very quickly because thelarge particles and spaces between them don't hold water well. The water flows through too fast to be absorbed or retained effectively. nalyzing and Identifying Proportions of Sand, Silt, and Clay (Soil Texture A Chart) To analyze soil texture and identify proportions of sand, silt, and clay, you can use two methods: 1. Feel Method: ○ Sandy soilfeels gritty, coarse, and rough. ○ Silt soilfeels soft, smooth, and floury. ○ Clay soilfeels sticky, smooth, and moldable whenwet. 2. Sedimentation Method(Lab or DIY): ○ Step-by-Step: 1. Take a sample of soil and place it in a clear jar. 2. Add water to the jar and shake it to mix the soil. 3. Let the soil settle for a few hours or overnight. 4. Observe the layers: Sand will settle at the bottom, followed by silt, and then clay. 5. Measure the proportions of each layer and refer to a soil texture chart (or triangle) to identify the soil type (loam, clay, sandy, etc.). Five Essential Nutrients for Plant Growth 1. Nitrogen (N): ○ Function: Vital for vegetative growth (leaf and stemdevelopment). ○ Charge: Generally negatively charged (anions). 2. Phosphorus (P): ○ Function: Crucial for energy transfer, root development,and flower/fruit production. ○ Charge: Negatively charged (anions). 3. Potassium (K): ○ Function: Important for disease resistance, waterregulation, and overall plant health. ○ Charge: Positively charged (cations). 4. Calcium (Ca): ○ Function: Strengthens cell walls and helps in nutrientuptake. ○ Charge: Positively charged (cations). 5. Magnesium (Mg): ○ Function: Central component of chlorophyll, importantfor photosynthesis. ○ Charge: Positively charged (cations). Soil Particle Most Critical for Nutrient Retention Clay Particlesare the most critical for nutrientretention. ○ Reason: Clay particles are small and have a high surfacearea, which allows them to hold onto nutrients, particularly positively charged ions (cations). Clay also has the ability to retain water and nutrients, preventing leaching. High Soil Acidity and Its Effects on Nutrient Leaching and Toxicity 1. How High Soil Acidity Leaches Nutrients: ○ Explanation: In acidic soils (low pH), positivelycharged nutrients (cations) such as calcium, magnesium, and potassium tend to be displaced from the soil particles and leached away by water. This happens because the hydrogen ions in the soil compete with these nutrients for binding sites on soil particles, leading to nutrient loss. 2. Why High Soil Acidity Can Be Toxic to Plants: ○ Explanation: Acidic soils can make certain elements,like aluminum and manganese, more soluble. In excess, these elements can be toxic to plants, inhibiting root growth and nutrient uptake. ○ Result: Plants may suffer from nutrient deficienciesor root damage, which can stunt their growth. Relationship Between Particle Size (Soil Texture) and Porosity E xplanation: Porosity refers to the amount of spacebetween soil particles where air and water can be stored. ○ Sandy Soilhas large particles and thus large pores.It isless porousbut allows for faster water drainage. ○ Clay Soilhas fine particles and smaller pores, whichmakes itmore porousin terms of total space but limits water movement. ○ Loam Soil(a mix of sand, silt, and clay) tends tohave the best balance of porosity, allowing for good water retention and drainage. Soil Texture and Water Holding Capacity E xplanation: The texture of the soil affects its waterholding capacity because it determines how much water the soil can retain and how easily water moves through it. ○ Clay soilscan hold more water due to the small particlesize and high surface area, but they tend to retain too much water, which can lead to waterlogging. ○ S andy soilshave low water holding capacity because of their larger pores and quick drainage. How Water Holding Capacity Affects Plant Growth E xplanation: Water holding capacity affects how plantsreceive water. Soils withlow water holding capacity(e.g., sandy soils) dry outquickly, requiring more frequent watering for plants to survive. Clay soils, while holding more water, can lead topoor oxygen availability for roots due to excess water. Plants need oxygen for proper root function, sobalanced water retentionis important. Optimal water holding capacityensures that plantsget enough water without the risk of suffocation or water stress. Chemical Measures of Soil Quality and Their Relationship to Plant Growth 1. Soil pH: ○ Measure: Indicates the acidity or alkalinity of thesoil. Most plants thrive in a pH range of 6-7 (neutral). ○ Relation to Growth: Soils that are too acidic or tooalkaline can limit nutrient availability, making it harder for plants to absorb essential nutrients. 2. Cation Exchange Capacity (CEC): ○ Measure: The ability of the soil to hold onto andexchange cations (positive ions like calcium, magnesium, and potassium). ○ Relation to Growth: Soils with a high CEC can retainmore nutrients, improving soil fertility and supporting plant growth. 3. Soil Organic Matter: ○ Measure: The amount of decayed plant and animal materialin the soil. ○ Relation to Growth: Organic matter improves soil structure,enhances nutrient availability, and promotes microbial activity, all of which benefit plant growth. Let's break this down step by step: 1. Relationship Between Altitude and Temperature in Atmospheric Layers T roposphere: The temperature decreases with altitudeat an average rate of about 6.5°C per kilometer (known as the lapse rate). This is because the troposphere is heated from below by the Earth's surface, so as you go higher, there is less heat. S tratosphere: In this layer, temperatureincreaseswith altitude. This happens because the ozone layer absorbs ultraviolet (UV) radiation from the Sun, which warms the stratosphere as you go higher. Mesosphere: Temperaturedecreaseswith altitude inthe mesosphere. This is the coldest layer of the atmosphere. Thermosphere: Temperatureincreaseswith altitudein the thermosphere. In this layer, solar radiation is absorbed directly by the few gas particles that are present, causing them to heat up dramatically. Exosphere: Temperature alsoincreaseswith altitude,but the temperature is difficult to define because the air density is so low. The few particles that exist absorb solar radiation, but they are too sparse for the temperature to have a consistent measure. 2. Atmospheric Gas Abundance (in Percentages) itrogen (N₂): ~78% N Oxygen (O₂): ~21% Water vapor (H₂O): 0-4% (varies with location andweather conditions) Carbon Dioxide (CO₂): ~0.04% (0.038% is the currentconcentration, but it has been increasing) 3. Relationship Between Altitude and Atmospheric Pressure Atmospheric pressuredecreaseswith altitude. ○ As altitude increases, the weight of the air above you decreases, and air molecules become more spread out. ○ This leads to lower pressure at higher altitudes. ○ For instance, at sea level, the atmospheric pressure is about 1013 hPa, but it drops significantly as you ascend. At 5,000 meters, pressure is about half that at sea level. 4. Layers of the Atmosphere (From Least Dense to Most Dense) xosphere(least dense) E Thermosphere Mesosphere Stratosphere Troposphere(most dense) he density of gases in each layer decreases as you move higher in the atmosphere. The T troposphereis the densest because it contains most of the Earth's mass and is closest to the Earth's surface. 5. Layer with the Most Ozone S tratosphere: The ozone layer is located within thelower stratosphere, between about 15 and 35 kilometers above Earth's surface. The highest concentration of ozone is here, where it absorbs and scatters ultraviolet solar radiation. 6. Layer that Receives the Most Intense Solar Radiation T hermosphere: This layer receives the most intensesolar radiation, especially from high-energy ultraviolet and X-rays. The thermosphere absorbs solar radiation directly, leading to a significant increase in temperature. 7. Definitions of Atmospheric Layers 1. T roposphere: The lowest layer (up to about 8-15 km),where weather, clouds, and most of the Earth's atmosphere are found. Temperature decreases with altitude. 2. Stratosphere: Extends from 15 km to about 50 km. Containsthe ozone layer. Temperature increases with altitude due to ozone absorbing UV radiation. 3. Mesosphere: Extends from about 50 km to 85 km. Thislayer is where meteors burn up. Temperature decreases with altitude and is the coldest layer. 4. Thermosphere: Extends from 85 km to about 500 km.Solar radiation causes this layer to heat up significantly. It's where the Northern and Southern Lights (auroras) occur. 5. Exosphere: The outermost layer, above 500 km, wherethe atmosphere transitions into space. It contains very sparse particles that are affected by solar radiation. 8. Energy that Drives Global Wind Patterns T heSunis the primary energy source driving globalwind patterns. It heats the Earth's surface unevenly due to the curvature of the Earth and the angle at which sunlight strikes the surface. Theuneven heatingof the Earth causes temperaturedifferences between regions, creatingpressure differences. These pressure differencesresult in air movement (wind) from high-pressure areas to low-pressure areas. T heCoriolis effect(due to Earth's rotation) deflects wind patterns, creating large-scale wind systems like the trade winds, westerlies, and polar easterlies. 9. Relationship Between Air Temperature and Density Air temperatureis inversely related todensity. ○ Warmer airis less dense because its molecules movefaster and spread out more. ○ Colder airis denser because the molecules move moreslowly and are closer together. This relationship is important in creating convection currents, as warm air rises (because it is less dense), and cooler air sinks (because it is denser). 10. Relationship Between Air Temperature and Moisture Warmer aircan hold more moisture (water vapor) thancooler air. ○ Warm airincreases the evaporation rate of water,and the molecules of water vapor can stay in the air because of their higher energy. ○ Cool airhas lower capacity to hold moisture, whichis why you often see condensation, clouds, and precipitation in cooler areas (like at night or higher altitudes). 11. Steps of the Hadley Cell (Tropical Circulation) heHadley Cellis the atmospheric circulation thatoccurs between the equator and 30° T latitude. It is responsible for the major tropical rainforests and desert regions. Here's how it works: 1. S tep 1:Warm airat the equator rises due to intensesolar heating. The air is warm and humid. 2. Step 2: As the warm air rises, it cools and losesmoisture (causing heavy rainfall near the equator). This is why tropical regions near the equator are wet. 3. Step 3: The air cools and spreads out towards thepoles at high altitudes (about 10-15 km high). 4. Step 4: As the air moves toward 30° latitude (subtropicalregions), it cools further and sinks back towards the Earth's surface. 5. Step 5: The descending air is dry, causing arid conditionsin desert regions (around 30° N and S). The air then moves back toward the equator at the surface, completing the loop. his creates thetrade winds(from the northeast in the northern hemisphere and from the T southeast in the southern hemisphere) that blow towards the equator. Let's break down each of these concepts and explain them in detail: Why Deserts Occur at 30° North and South eserts are commonly found at around30° latitude(both N and S)due to the atmospheric D circulation patterns, specifically theHadley cells. H adley Cell: Warm air rises at the equator, coolsas it travels toward higher latitudes, and then sinks around30° North and South. This descendingair is dry, having lost its moisture while rising and cooling near the equator. As the air sinks, it compresses and warms up, which reduces its ability to hold moisture, creating dry conditions. This is why deserts, such as the Sahara in the north and the Atacama in the south, are found around these latitudes. hy Air Moves Back to the Equator from 30° North and South (Convection W Cycle) This movement of air is part of theconvection cycle.Here's the process: W arm air risesat the equator, where it is heatedby solar radiation. The aircools and sinksaround30° latitude(bothNorth and South). Once the air sinks, it moveshorizontallyback towardsthe equator at the surface, completing the loop. This movement creates thetrade windsbetween 0° and30° latitude, blowing from the northeastin the northern hemisphere and from thesoutheastin the southern hemisphere. onvection Cycle: It refers to the vertical movementof air (or any fluid), driven by temperature C differences. Warm air rises because it is less dense, while cooler air sinks because it is denser. The process creates a circulation that helps distribute heat around the planet. Why Wind Moves from East to West Between 0° and 30° (Trade Winds) W inds in thetropics(between 0° and 30°) blow fromeast to westdue to the rotation of the Earth. This is known as theCoriolis effect. T he Earth rotates from west to east, and the movement of the atmosphere is deflected due to this rotation. As a result, thetrade windsblowfrom the easttowardsthe west in both the northern and southern hemispheres. Direction of Wind Between 30° and 60° Latitude (Westerlies) W inds in themid-latitudes(between 30° and 60°) blowfromwest to east, forming the westerlies. This direction is also influenced by theCorioliseffect, which deflects air to the right in the northern hemisphere and to the left in the southern hemisphere. These winds bring weather systems from the west towards the east. Where on Earth Solar Radiation is Most Direct S olar radiationis most direct at theequator(0°latitude), because the Sun's rays strike the Earth’s surface at a90° angle. At higher latitudes (closer to the poles), the angle of the Sun's rays is more oblique, and the energy is spread over a larger area, reducing the intensity of solar radiation. Direction of Wind Between 0° and 30°, 30° and 60°, 60° and 90° Latitudes 0 ° to 30° (Trade Winds): Wind moves fromeast to westdue to the Coriolis effect. 30° to 60° (Westerlies): Winds move fromwest to east,as air in the mid-latitudes is deflected by the Coriolis effect. 60° to 90° (Polar Easterlies): Winds move fromeastto west, but at these latitudes, the air is much colder, and the polar easterlies are weaker than the other wind belts. 90° and 120°: Beyond 90° (near the poles), winds aregenerally very weak and variable. At the poles themselves, air tends to sink, creating high-pressure zones. Coriolis Effect heCoriolis effectis the deflection of moving objects(like wind) caused by the Earth's rotation. T In thenorthern hemisphere, the deflection is to theright, and in thesouthern hemisphere, the deflection is to theleft. This effect is responsiblefor creating the wind belts and ocean currents we observe around the planet. Hadley Cell, Ferrel Cell, and Polar Cell These are the three primary atmospheric circulation cells: H adley Cell: Found between the equator and 30° latitude.Warm air rises at the equator and sinks at 30° latitude. Ferrel Cell: Found between 30° and 60° latitude. Inthis cell, air moves from 30° to 60°, where it rises at 60° and sinks around 30°. This causes the westerlies in the mid-latitudes. Polar Cell: Found between 60° and the poles. Coldair sinks at the poles and moves towards 60° latitude, where it meets warmer air from the Ferrel cell. This causes the polar easterlies. How the Coriolis Effect Determines Global Wind Patterns TheCoriolis effectmodifies the direction of winds. In theHadley cell, it causes the trade winds to blowfrom theeast(from the northeast in the Northern Hemisphere and southeast in the Southern Hemisphere). In theFerrel cell, it causes the westerlies to blowfrom thewest(from the southwest in the Northern Hemisphere and northwest in the Southern Hemisphere). In thePolar cell, the winds blow from theeast, formingthepolar easterlies. Why Precipitation Occurs Greater at the Equator A t the equator, warm air rises due to the intensesolar heating. As the air rises, it cools and condenses, forming clouds and precipitation. This is why tropical rainforests are found near the equator. The rising air also leads to low pressure, encouraging more moisture-laden air to move in from surrounding areas, enhancing rainfall. Insolation and Units of Measurement Insolationrefers to the amount of solar radiationreaching a given area. It is influenced by factors like latitude, time of year, and cloud cover. Units of measurement: Insolation is typically measuredinwatts per square meter (W/m²). Relationship Between Albedo and Surface Temperature A lbedois the reflectivity of a surface. Light-coloredsurfaces (like ice and snow) have high albedo, meaning they reflect most of the solarradiation, keeping temperatures lower. Darker surfaces (like forests or oceans) havelowalbedo, meaning they absorb more solar radiation, leading to higher temperatures. Relationship Between Latitude and Insolation A t the equator(0° latitude),insolationis the mostdirect because the Sun’s rays hit the surface at a90° angle. At higher latitudes(towards the poles), the Sun'srays hit the surface at a more oblique angle, spreading the energy over a largerarea, which reduces the intensity of the energy reaching the surface. hen the Northern and Southern Hemispheres Are Most Tilted Towards the W Sun T heNorthern Hemisphereis most tilted towards theSun during theJune solstice (around June 21st), and theSouthern Hemisphereismost tilted towards the Sun during theDecember solstice(around December 21st). These tilts result in thesummer solsticesfor eachhemisphere, where the Sun is at its highest point in the sky and the days are longest. Earth's Tilt and Its Relationship to Solar Intensity T hetilt of the Earth(about 23.5°) is responsiblefor the changing seasons. The tilt causes different areas of the Earth to receive varying amounts of solar radiation throughout the year. During summerin each hemisphere, the Sun's rays hitthat hemisphere more directly, resulting inhigher solar intensityand longer days.During winter, the rays are more oblique, resulting inlower solar intensityand shorterdays. hen the Northern and Southern Hemispheres Receive 12 Hours of W Daylight and Why E quinoxes: On thespring equinox(around March 21st) andfall equinox(around September 21st), both hemispheres receive12 hoursof daylightand12 hours of night. This happens because the Earth's axis is not tilted towards or away from the Sun during these times, so the Sun is directly over the equator, leading to equal day and night lengths across the globe. Point That Receives 24 Hours of Daylight on the December Solstice N orth Pole: During theDecember solstice(around December21st), theNorth Pole experiences24 hours of daylight. This occurs because the Northern Hemisphere is tilted away from the Sun, and the North Pole is oriented toward the Sun at this time of year. The South Pole, on the other hand, is in complete darkness during this solstice. Where on the Globe Receives Direct Insolation on the June Solstice D uring theJune solstice(around June 21st), theTropicof Cancer(23.5°N latitude) receives direct solar radiation. This is the time when the Northern Hemisphere is tiltedtowardsthe Sun, and it experiences thelongest dayof the year. Mountain Effects on Microclimate M ountainsinfluence local weather patterns, creatingmicroclimates. The temperature generally decreases as elevation increases, causing cooler and wetter conditions at higher altitudes compared to lower elevations. Windward side: The side facing the prevailing windstends to be cooler and wetter because moist air is forced upward by the mountain, leading toprecipitation (orographic lift). Leeward side: The opposite side, sheltered from thewind, is drier and warmer, often experiencing arain shadoweffect. Ocean Temperature Effect on Climate O cean temperatureplays a significant role in regulating climate by absorbing and releasing heat. Warm oceans (such as near the equator) provide more moisture to the atmosphere, leading to warmer and more humid conditions. Cold oceans(near the poles) can cool the air, leadingto cooler temperatures. Ocean currents transfer heat from the equator towards the poles, impacting regional climates. Rain Shadow/Rainshadow Effect R ain Shadow: A dry area on the leeward side of a mountainrange, caused by the blocking of moist air by the mountains. As moist air rises on the windward side, it cools and releases moisture as rain or snow. By the time it reaches the leeward side, the air is dry, creating desert-like conditions. Leeward and Windward W indward: The side of a mountain range that facesthe prevailing winds and receives the moist air. This side is typically cooler and wetter due to orographic lift. Leeward: The side of the mountain range opposite tothe windward side, which is sheltered from the prevailing winds. This side is typically drier, warmer, and often has a rain shadow. Rain Shadow Effect on Mountain Vegetation and Andes Climate In theAndes Mountainsof South America, thewindwardside(on the eastern side) receives significant rainfall, supporting dense tropical rainforests. On theleeward side, the air is much drier, contributingto theAtacama Desert, one of the driest places on Earth. The rain shadow effect on the vegetation in the Andes causes dramatic differences in ecosystems on each side of the mountain range. Why Water is Warmest at the Equator S olar radiationis most direct at theequator, causingthe water to warm up. The Sun's rays hit the surface at a near90-degree angleatthe equator, transferring more energy and raising the temperature of the water. Why Water Moves Away from the Equator W arm waternear the equator is displaced towards thepoles byocean currents. As warm water moves away from the equator, it is replaced by colder water rising from the deep ocean (a process known asupwelling). The movement of surface waters is primarily driven bywind patterns, such as the trade winds and westerlies. Why Water Sinks and Spreads Across the Ocean Floor at the Poles C old waterat the poles becomesdenserand sinks dueto its lower temperature and higher salinity (from the formation of sea ice). This sinking water helps drive theglobal thermohaline circulation, which circulates ocean waterthroughout the globe. Thisdeep waterthen spreads across the ocean floor,eventually returning to the surface in other regions throughupwelling. Upwelling U pwellingis the process wherecold, nutrient-richwaterrises from the deep ocean to the surface. This occurs when surface water is pushed away by wind or ocean currents, and deeper water rises to replace it. Upwelling is important for supporting marine life because it brings nutrients from the ocean floor, supporting the growth of phytoplankton and, consequently, the entire marine food web. El Niño and Its Characteristics E l Niñois a climate phenomenon that occurs when thetrade windsweaken or reverse, leading to warmer-than-average sea surface temperatures in the central and eastern Pacific Ocean. Characteristics of El Niño include: ○ Warmer ocean temperatures in the central and eastern Pacific. ○ Disruption of weather patterns around the world, including wetter conditions in some regions and droughts in others. ○ Decreased upwelling off the coast of South America, reducing nutrients and harming marine life. El Niño Weather In South America: El Niño often leads towetter conditionsalong the west coast (e.g., floods in Peru and Ecuador). In Southeast Asia and Australia: El Niño bringsdrierconditions, often leading to droughts and increased risk of wildfires. In North America: It can bringwarmer and wetter wintersto the northern United States anddrier conditionsto the southwest. El Niño Effect on Fishing in South America E l Niñodisrupts theupwellingprocess off the coastof South America, leading to a decrease in nutrients that support marine life. As a result, thefish catchin countries like Peru and Ecuador declines, impacting local fishing industries. El Niño Effect on Global Temperatures E l Niñotypically causes an increase inglobal temperatures,as the warming of the Pacific Ocean affects atmospheric circulation patterns, leading to aglobal heat increase. Normal Direction of Currents at the Equator (Not During El Niño Year) N ormally, thetrade windsblow fromeast to westacrossthe equator, pushing warm water towards the western Pacific. This creates atemperature gradientwhere the western Pacific is warmer, and the eastern Pacific is cooler. During El Niño, these winds weaken, and warm waterspreads across the central and eastern Pacific. Weather in Southeast Asia and Australia During a Normal Year (Not El Niño) S outheast Asia and Australiatypically experiencewet conditionsduring thesummer monsoonanddry conditionsduring the winter. El Niñodisrupts this pattern, making the region drierand leading to more frequent droughts and wildfires. La Niña and Its Characteristics L a Niñais the opposite ofEl Niño. It occurs whenthetrade windsstrengthen, pushing warm water even further westward across the Pacific. Characteristics of La Niña: ○ Cooler-than-average sea surface temperaturesin thecentral and eastern Pacific. ○ Stronger upwellingoff the coast of South America,leading to higher productivity in the oceans. ○ Moreactive hurricane seasonsin the Atlantic anddrier conditionsin the southern U.S. Direction of Currents at the Equator During La Niña D uringLa Niña, thetrade windsare stronger thanusual, and warm water is pushed more strongly toward the western Pacific, enhancing upwelling in the eastern Pacific. Weather in Southeast Asia and Australia During La Niña S outheast Asia and Australiaexperiencewetter-than-usualconditions, especially in Southeast Asia and northern Australia, which can lead to floods and a more active monsoon season. Weather in the Americas During La Niña In theAmericas,La Niñatends to bringdrier conditionsto the southern U.S. and wetter conditionsto the Pacific Northwest. Change in Upwelling During La Niña L a Niñaenhancesupwellingoff the coast of SouthAmerica, bringing cold, nutrient-rich water to the surface, supporting marine life and increasing fish populations.
