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The Carbon Cycle

• It is a biogeochemical cycle where carbon is exchanged within the biosphere, atmosphere, hydrosphere, and geosphere.
• The carbon cycle regulates the availability of carbon, which is essential for life.
• The carbon cycle regulates Earth's climate by controlling atmospheric carbon dioxide.

Photosynthesis

• Plants, algae, and cyanobacteria remove CO2 from the atmosphere.
• They convert CO2 into glucose (C6H12O6) using sunlight.
• The equation representing this process is: 6CO2 + 6H2O + light → C6H12O6 + 6O2

Respiration

• Organisms break down glucose to release stored energy.
• This process emits CO2 back into the atmosphere.
• The pertinent equation is: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

Decomposition

• Decomposers like bacteria and fungi break down dead organisms.
• This releases carbon into the soil and atmosphere.

Combustion

• The burning of fossil fuels and biomass releases stored carbon as CO2 into the atmosphere.

Carbon Sequestration

• It involves the long-term storage of carbon.
• Carbon is stored in reservoirs like forests, soil, and oceans.

Ocean Uptake

• Oceans absorb CO2 and store it as dissolved carbon.
• CO2 also gets stored in the shells and skeletons of marine organisms.

Fossil Fuels

• Carbon is stored underground in coal, oil, and natural gas.
• This storage occurs over millions of years.

Volcanic Activity

• Releases carbon from the geosphere into the atmosphere.

Carbon Reservoirs

• These are places where carbon is stored.
• Examples include the atmosphere, biosphere, geosphere, and hydrosphere.

Carbon Sink

• It refers to systems that absorb more carbon than they release.
• Examples include forests and oceans.

Carbon Source

• It includes systems that release more carbon than they absorb.
• Examples include combustion and respiration.

Anthropogenic Effects

• These are human activities that disrupt the carbon cycle.
• Examples include fossil fuel combustion and deforestation.

Greenhouse Gas

• CO2 is a greenhouse gas that traps heat in the atmosphere.
• Trapping heat contributes to global warming.

Nitrogen Fixation

• Conversion of atmospheric nitrogen (N2) into ammonia (NH3) or ammonium (NH4+).
• It's done by nitrogen-fixing bacteria or lightning.

Nitrification

• Conversion of ammonia (NH3) into nitrites (NO2-) and then into nitrates (NO3-.)
• Performed by nitrifying bacteria.

Assimilation

• Plants uptake nitrates (NO3-) or ammonium (NH4+).
• This synthesizes proteins and nucleic acids.

Ammonification

• Decomposition of organic nitrogen from dead organisms and waste.
• Releases ammonia (NH3) is released by decomposers.

Denitrification

• Conversion of nitrates (NO3-) back into nitrogen gas (N2).
• performed by denitrifying bacteria, releasing it into the atmosphere.
• Human activities disrupt the nitrogen cycle by using synthetic fertilizers, burning fossil fuels, and livestock farming.
• These activities can result in eutrophication, soil acidification, and groundwater contamination.

The Phosphorus Cycle

• Transports phosphorus through the biosphere, geosphere, and hydrosphere.
• Unlike the nitrogen and carbon cycles, it does not have a significant atmospheric component.
• Primarily cycles through rock weathering, soil, water, and living organisms.

Weathering & Erosion

• Phosphorus is released from rocks as phosphate (PO43-) through weathering.
• Enters soil and water.

Assimilation

• Plants absorb phosphate from soil.
• Phosphorus incorporates it into DNA, ATP, and cell membranes.

Consumption

• Animals obtain phosphorus by eating plants or other organisms

Decomposition & Mineralization

• Decomposers break down organic material.
• Phosphorus returns to soil as inorganic phosphate.

Sedimentation & Geological Uplift

• Excess phosphorus in water bodies settles into sediments.
• Remains there for extended periods until tectonic activity uplifts rocks, restarting the cycle.

Human Impacts on Phosphorus

• Fertilizer use leads to eutrophication in water bodies, causing algal blooms and dead zones.
• Deforestation & soil erosion reduces phosphorus available for plant growth.
• Mining for phosphate rock accelerates phosphorus cycling and can lead to environmental degradation.

The Water Cycle

• Describes the continuous movement of water between the atmosphere, biosphere, geosphere, and hydrosphere.
• The cycle is driven by solar energy and gravity.

Evaporation

• Water changes from liquid to vapor with heat from the sun.

Transpiration

• Water evaporates from plant surfaces into the atmosphere.

Condensation

• Water vapor cools and forms clouds.

Precipitation

• Water falls to the Earth's surface as rain, snow, sleet, or hail.

Infiltration

• Water seeps into the soil and replenishes groundwater.

Percolation

• Water moves deeper into soil layers, recharging aquifers.

Runoff

• Excess water flows over land into rivers, lakes, and oceans.
• Deforestation reduces transpiration, altering local precipitation patterns.
• Urbanization increases runoff and decreases infiltration, leading to flooding.
• Overdrawing groundwater depletes aquifers and causes land subsidence.
• Pollution from agriculture and industry contaminates water sources.

Net Primary Productivity (NPP)

• Measures the rate at which plants in an ecosystem produce usable energy (biomass).
• Accounts for the energy they use for their metabolic processes (respiration).
• Formula: NPP = GPP - R, where GPP is Gross Primary Productivity and R is Respiration.
• Sunlight drives photosynthesis, so ecosystems closer to the equator typically have higher NPP.
• Essential for photosynthesis; ecosystems with ample water (e.g., rainforests) have high NPP.
• Fertile soils rich in nitrogen and phosphorus support higher NPP.
• Warmer temperatures increase photosynthesis but may limit productivity if too extreme.
• High NPP Ecosystems: Tropical rainforests, estuaries, wetlands.
• Low NPP Ecosystems: Deserts, tundra, open oceans.
• Important to know that deforestation reduces NPP by removing forests, which are major carbon sinks.
• Agriculture alters NPP by converting natural ecosystems into monocultures, which may have lower biodiversity and resilience.
• Climate change reduces NPP in sensitive ecosystems.
• Supports ecosystems by NPP determining the energy available to herbivores and higher trophic levels.
• Carbon Sequestration: Ecosystems with high NPP store large amounts of carbon, helping to mitigate climate change.
• Resource Availability: Human activities often rely on high-NPP ecosystems for food, timber, and other resources.

The Green Revolution

• Period of agricultural innovation that increased food production worldwide.
• Achieved through high-yield crop varieties, synthetic fertilizers, pesticides, advanced irrigation, and mechanization.
• High-Yield Crop Varieties: Crops (wheat, rice, etc) were genetically improved to produce higher yields.
• Synthetic Fertilizers: Provided nutrients (N, P, K) to enhance soil fertility.
• Irrigation: Farming in arid regions became possible, increasing water use efficiency.
• Mechanization: Tractors, harvesters, and other machinery reduced labor needs.
• Benefits: Reduced global hunger, supported population growth, economic growth, reduced famine risks, and global trade expansion.
• Soil Degradation: Overuse of chemical fertilizers reduced soil health and productivity. water.
• Water Resource Depletion: Irrigation systems overexploited groundwater and surface water.
• Loss of Biodiversity: Monoculture farming made crops more vulnerable to pests and diseases.
• Pesticide Pollution: Widespread use of chemical pesticides polluted air, soil, and water and harmed non-target species.
• Climate Change: Increased greenhouse gas emissions.
• Includes economic inequality, dependency (on seeds, fertilizers, and machinery), and rural displacement.

Impacts of Agriculture

• Agriculture has environmental, social, and economic impacts.
• Soil Erosion occurs because overplowing and lack of ground cover lead to topsoil loss.
• Desertification will occur if arable land is turned into desert because of overuse and poor management.
• Nutrient Depletion will occur if excessive cropping and monoculture farming strips essential nutrients.
• Water Resource Issues:
  • Overuse of Water for Irrigation depletes aquifers and surface water sources.
  • Fertilizer and pesticide runoff leads to eutrophication and contamination of freshwater supplies.
• Habitat Destruction: Clearing forests and wetlands for farmland reduces habitat availability and leads to Biodiversity Loss.
• Monoculture Farming reduces genetic diversity, making crops more susceptible to pests and diseases.
• Agriculture contributes methane and nitrous oxide to global warming by Greenhouse Gas Emissions
• Antibiotic Resistance and Health Issues include overuse of antibiotics in CAFOs leads to resistant bacterial strains.
• Reliance on large-scale farming and mechanization has increased food supply but displaced small-scale farmers.
• Unequal access to agricultural resources leads to disparities in food availability which causes Food Insecurity.
• Pesticide exposure and nutrient-poor diets from highly processed foods affect human health.
• Sustainable Agriculture Practices include:
  • Crop Rotation which prevents nutrient depletion and reduces pest infestations.
  • Agroforestry: Combines trees with crops or livestock to conserve biodiversity and improve soil.
  • No-Till Farming reduces soil erosion and maintains organic matter.
  • Integrated Pest Management (IPM) minimizes pesticide use through biological and mechanical controls.
  • Efficient Irrigation Techniques conserve water and reduces runoff.
  • Organic Farming avoids synthetic chemicals, promoting healthier ecosystems.

Soil Formation and Erosion

• Soil provides the foundation for plant growth, water filtration, and habitat.
• Physical, chemical, and biological factors influence soil formation.
• Wind, water, and gravity contribute to soil erosion over time.
• Agriculture, deforestation, overgrazing, and urbanization accelerate erosion by removing vegetation and disturbing the soil.
• Loss of fertile land and agricultural productivity is a consequence of Human Activities.
• Sedimentation in waterways, which can harm aquatic ecosystems, is a consequence of Human Activities.
• Techniques to reduce soil erosion and preserve soil health include:
  • Terracing which reduces water runoff on steep slopes.
  • Contour Plowing that aligns plowing with natural land contours to prevent erosion.
  • Cover Crops protect the soil from erosion and improve fertility.
  • Windbreaks: Rows of trees or shrubs that reduce wind erosion.
  • No-Till Farming reduces soil disturbance, preserving organic matter and preventing erosion.

Soil Properties

• Soil Texture: The relative proportions of sand, silt, and clay which affect permeability, water-holding capacity, and aeration.
• Soil Structure: How soil particles are arranged into aggregates which influences water infiltration and root penetration.
• Influences water infiltration and root penetration. - Permeability is the rate at which water moves through soil. - Porosity: The amount of pore space between soil particles, which affects water retention and drainage.
• Water-Holding Capacity dictates that sandy soils drain quickly but retain less water while clay soils hold more water but may impede drainage and root growth.
• Chemical Properties: -A pH between 6 and 7.5 is ideal. -Cation Exchange Capacity determines nutrient availability.
• Decomposition -Bacteria, fungi, earthworms, and other organisms are key components of soil. -Organic matter is important to enrich soil fertility and improve water retention.

Soil Degradation

• Soil Degradation: -Is defined as the loss of topsoil due to water or wind which reduces fertility and disrupts ecosystems. -Compaction reduces porosity and permeability, hindering root growth and water infiltration. -Salinization occurs with an accumulation of salts in soil from improper irrigation practices.
• Nutrient Depletion occurs because of overcropping and overuse of synthetic fertilizers which reduces soil fertility over time.

Pest Control Methods

• Chemical Pest Control: -chemical substances such as herbicides, insecticides, and fungicides are used to kill or control pests. -The Benefits include quick and effective eliminating pests, leading to increased agricultural yields. -Can cause pesticide resistance, bioaccumulation, and environmental contamination.

• Biological Pest Control: -Natural predators are introduced to control pest populations.

• Advantages: Environmentally friendly and sustainable. -Challenges: Requires careful management to avoid disrupting local ecosystems.

• Crop Rotation can be used to manage pests.

• Intercropping: Growing different crops together to deter pests can be used to manage pests.

• Barriers and Traps can be used to prevent pest access.

• A combination of chemical, biological, and cultural methods can be used to minimize harm while reducing pests.

• The use of least-toxic methods should be a priority before using chemical controls.

Environmental Concerns due to Pesticides

• Pesticide runoff contaminates water bodies, harming aquatic life.
• Non-target Species: Non-target species, including beneficial pollinators like bees, are often affected.
• Persistent organic pollutants (POPs) can accumulate in food chains (bioaccumulation and biomagnification).
• Long-term pesticide exposure has been linked to health issues such as respiratory problems, neurological disorders, and cancer.

Alternatives to Pesticides

• Organic Farming avoids synthetic pesticides and relies on natural alternatives like compost and beneficial insects.
• Agroecology has been shown to design agricultural systems that work with natural ecological processes.
• Genetic Engineering develops pest-resistant crop varieties through genetic modification.

Integrated Pest Management (IPM)

• Combines multiple control strategies to minimize environmental and economic harm.
• Emphasizse biological, cultural, mechanical, and chemical methods in a coordinated way.
• IPM is based on Prevention, Monitoring, Control Strategies, and Evaluation.
• Environmental benefits include reduced pesticide use, lower risk of water contamination, and biodiversity.
• Can result in enhanced crop yields and quality as well as economic benefits.
• Lowers human exposure to harmful chemicals, reducing risks of pesticide-related illnesses.
• Requires extensive knowledge of pest life cycles and ecosystem interactions although initial costs and labor can be higher.
• Requires ongoing monitoring and adaptation of strategies.

Meat Production Methods

• Concentrated Animal Feeding Operations (CAFOs): High-density livestock operations where animals are confined and fed grain-based diets.

• Advantages include efficient meat production, lower costs, and increased supply.

• Disadvantages: High waste production, antibiotic use, ethical concerns, and significant environmental impact.

• Free-Range and Pasture-Raised Livestock: Animals graze on open land with natural diets.

• Meat production includes deforestation, water consumption, and pollution.

• Meat production contributes to greenhouse gas emissions, high incidents of antibiotic resistance adn health issues,

• Ways to lower environmental impacts are shown to be related to the reduction of meat consumption.

Sustainable Agriculture

• Focuses on producing food while maintaining environmental health, economic profitability, and social equity.
• Agriculture can ensure long-term food production while minimizing environmental harm.
• By adopting soil conservation, efficient water use, and sustainable livestock management, agriculture can support ecosystems in a changing climate. -Soil Conversation = prevent erosion and maintain soil fertility. -Water Management includes practices such as efficient irrigation techniques. -Integrated Pest Management (IPM) helps reduce chemical pesticides.

Human Threats to Biodiversity

• Habitat Destruction, overexploitation, pollution, and climate change are negatively impacting our systems.
• Deforestation which happens because of agriculture, urbanization, and resource extraction causes Habitat Destruction,
• Overfishing, hunting, poaching, and illegal wildlife trade are contributing to overexploitation of keystone species leading ti ecosystem imbalances.
• Air pollution has damaging effects as does water and soil pollution.
• Sustainable conservation efforts, including protected areas, habitat restoration, and policy initiatives, are essential to mitigating biodiversity loss and preserving ecosystems.

Bioaccumulation and Biomagnification

• Describe how toxic substances build up in organisms and increase in concentration at higher trophic levels.
• Heavy Metals: Mercury (Hg), Lead (Pb), Cadmium (Cd)
• Persistent Organic Pollutants (POPs): -Pesticides (e.g., DDT) -Industrial Chemicals (e.g., PCBs, dioxins)
• The decline in predator populations due to high toxin levels is an example of Ecosystem Effects.
• Human health is affected because of an increased cancer risks from long-term exposure to POPs.
• Legislation such as The Clean Water Act (CWA) and Stockholm Convention regulate harmful chemicals.
• Advisories on seafood consumption help reduce people from ingesting mercury.

Lethal Dose 50 (LD50)

• Key tools used to assess the toxicity of substances.

• Lethal Dose 50 (LD50) is the dose required to kill 50% of a test population.

• Linear: The response increases directly with dose.

• Nonlinear/Threshold: No response at low doses, then effects increase rapidly.

• Hormesis: Small doses have beneficial effects, but large doses are toxic. -Acute exposure, short-term high dose. -Chronic exposure, long term low dose.

• Certain toxins increase in concentration as they move-up the food chain.

• Certain toxins increase in conce