Environmental Systems and Societies Lecture Notes

Topic 2.1: Fundamental Building Blocks of Ecosystems

Biosphere

• Largest ecological system on Earth.
• Encompasses all parts where life exists (oceans’ trenches to mountain tops).
• Composed of interconnected systems vital for ecological balance.

Individual Organisms

• Species defined by ability to interbreed and produce fertile offspring.
• Example: Dogs (same species), Mules and Ligers (sterile hybrids).

Classification Systems

• Taxonomists classify life on Earth for identification and biodiversity understanding.
• Tools include dichotomous keys and DNA surveys.
• Importance of classification in biodiversity and species relationships.

Populations

• Group of same species, living, and interbreeding in the same location.
• Example: African elephants divided by geographical barriers.

Distribution Influences

• Abiotic Factors: Temperature, light, pH, soil characteristics.
• Biotic Factors: Interactions with other organisms.

Ecological Niches

• Specific conditions and resources required by a species.
• Example: African Savannah herbivores occupying different niches.

Population Interactions

• Herbivory: Plants consumption affecting productivity.
• Predation: Consumers eating other consumers, e.g., ladybugs eating aphids.
• Parasitism: Parasites harm host, e.g., mistletoe on trees.
• Mutualism: Relationships where both species benefit, e.g., clownfish and sea anemones.
• Disease: Can alter ecosystem composition, e.g., chestnut blight.

Carrying Capacity and Regulation

• Maximum sustainable population size an environment can support.
• Factors include density-dependent (competition, predation) and density-independent (natural disasters) factors.

Fundamental vs. Realized Niches

Concepts

• Fundamental Niche: Theoretical potential habitat of a species.
• Realized Niche: Actual habitat considering real-world limitations.

Examples

• Barnacles: Different niches based on tidal zones.
• Foxes: Red and arctic foxes in different Arctic regions.
• Mangroves: Specific zones based on salinity and competition.
• Andean Condors: Limited to Andes due to competition.
• Giant Panda: Limited mountain ranges due to human competition.

Topic 2.2: Energy and Biomass in Ecosystems

Energy Flow and Matter Cycles

• Open systems with one-way energy flow and matter cycling.
• Governed by first (energy conservation) and second (entropy) laws of thermodynamics.

Photosynthesis and Respiration

• Photosynthesis: Converts light energy to chemical energy.
• Cellular respiration: Releases stored energy in glucose.

Trophic Levels

• Producers (autotrophs) form energy base.
• Consumers (herbivores, omnivores, carnivores) obtain energy by feeding on others.
• Energy transfer is inefficient; much lost as heat.

Productivity

• Gross Productivity: Total biomass gain.
• Net Productivity: Biomass after accounting for respiration losses.

Human Impacts on Energy Flow

• Activities like fossil fuel burning, deforestation, and urbanization affect ecosystems.

Topic 2.3: Biogeochemical Cycles

Carbon Cycle

• Key stores: Atmosphere, plants, soil, oceans.
• Human impacts: Industrial emissions, deforestation.

Nitrogen Cycle

• Essential for proteins and DNA; involves nitrogen-fixing bacteria.
• Human impacts: Agriculture and industrial practices.

Water Cycle

• Water movement between atmosphere, land, and oceans.
• Dams and infrastructure impact natural flow.

Methanogenic Bacteria

• Produce methane (short-life) under anaerobic conditions.

Human Activities

• Affect nitrogen cycle through agriculture, urbanization, deforestation.
• Haber process industrially fixes nitrogen.

Topic 2.4: Climate and Biomes

Climate vs. Weather

• Climate: Long-term atmospheric conditions.
• Weather: Short-term atmospheric conditions.

Biome Distribution

• Influenced by precipitation, temperature, and insolation.
• Whitaker diagram explains biome types based on temperature and precipitation.

Biome Types

• Include freshwater, marine, forest, grassland, desert, and tundra.

Climate Change

• Shifts biome boundaries and ecosystem functions.

Topic 2.5: Zonation, Succession, and Change in Ecosystems

Zonation

• Change in communities along an environmental gradient.
• Examples: Mountain zones, coastal mangroves.

Succession

• Temporal change in communities over time.
• Primary Succession: Begins on bare rock.
• Secondary Succession: On pre-existing soil.

Ecosystem Characteristics

• Changes in energy flow, productivity, diversity, and resilience over succession.

Human Impact

• Activities often revert ecosystems to earlier stages of succession, reducing diversity and resilience.