the biosphere and ecosystems

Dynamic Earth: The Biosphere and Ecosystems

Overview

• Course Title: Dynamic Earth GY4741
• Main Topics:
  1. The Biosphere
  2. Ecosystems and Humans

Lecture Outline

1. Components of the Biosphere
2. Plant and Animal Distributions
3. Biogeochemical Cycles

Biological Organization on Earth

• Hierarchy of Biological Organization:
  1. Biosphere - global sum of all ecosystems.
  2. Ecosystems - communities of organisms interacting with their environment.
  3. Community - various populations of different species living together.
  4. Population - group of individuals of the same species living in the same area.
  5. Organism - an individual living entity.
  6. Cells - basic unit of life; sum of all biological organization.

Components of the Biosphere

• Lithosphere: Earth's solid outer shell.
• Atmosphere: Layer of gases surrounding Earth.
  • Precipitation: Rain, snow, sleet, and hail falling from the atmosphere.
  • Insolation: Incoming solar radiation.
• Hydrosphere: All water parts of Earth (oceans, rivers, lakes).

Key Habitat Types

• Biogeochemical Cycles: Movement of elements through biological and geological systems.
  • Evaporation and Transpiration: Movement of water through evaporation and plant transpiration.
  • Albedo Changes: Earth's reflectivity affecting temperature regulation.
  • Burrowing Organisms: Contribute to soil aeration and nutrient cycling.
  • Soil Nutrients: Essential nutrients (C, N, P) added to soil from various processes.

Carbon Cycle and Its Efforts

• Pathways: Conversion of CO₂ to living matter through photosynthesis; cycling through death and decay processes.
• Status of Carbon:
  • Algae referred as the foundational element of life.
  • Carbon: Fourth most abundant element in life forms.

Photosynthesis and Atmospheric Composition

• Role of Photosynthetic Organisms: They are crucial for creating the Earth's atmosphere by producing oxygen (O₂) and consuming carbon dioxide (CO₂).
• Seasonal Atmospheric Changes:
  • Summer: Higher O₂ levels, lower CO₂ levels due to photosynthesis.
  • Winter: Lower O₂ levels, higher CO₂ levels due to dormancy.
• Climate Change Influence: Increase in CO₂ from 275 ppm in the 1700s to 415 ppm in 2022.
• Growing Season Effects: Length and productivity of growing seasons directly impact CO₂ concentrations.

Gaia Hypothesis

• Concept Introduced by James Lovelock in 1965:
  • The Earth as a self-regulating organism (Gaia = Mother Earth).
  • The temperature and composition of Earth’s surface are actively controlled by life.
  • Biological factors like natural greenhouse gases (e.g., CO₂) regulate climate.

Forests and Their Ecosystem Services

Benefits of Trees

• Regulation of Temperature: Trees provide shade, reducing heat.
• Filtration: Trees filter out air pollutants, improving air quality.
• Carbon Sequestration: Trees absorb CO₂ from the atmosphere.
• Water Management: Trees manage and filter rainwater, preventing erosion.
• Soil Stabilization: Roots stabilize soils and prevent degradation.
• Health Benefits: Access to trees improves mental and physical well-being.
• Recreational Opportunities: Trees provide spaces for recreation.

Human Impact on Trees

• Exploitation Trends:
  • Trees often treated as disposable resources, used for fuel and as commodities.
  • Human development leads to deforestation and loss of ecosystem services.

The Biosphere and Biomes

• Definition of the Biosphere: The biologically inhabited part of Earth, where life exists.
• Biomes: Major global zones characterized by different life forms of plants and animals.
• Human Impact: Activities like domestication, deforestation, and agricultural practices influence the biosphere.
• Ecological Studies:
  • Focus on ecology, evolution, extinction, biodiversity, and biogeography.
  • Understand natural distribution patterns in historical and current contexts.
• Control Factors: Climate, latitude, and oceanic temperature impacts govern biome distribution.

Climate Classification of Biomes

• Classification Based on Temperature and Precipitation:
  • Hot Biomes: Characterized by high temperatures and distinct precipitation patterns (e.g., Tropical Rainforests, Deserts, Savannas).
  • Cold Biomes: Defined by lower temperatures and specific moisture levels (e.g., Tundra, Taiga).

Examples of Biomes and Their Climates

• Mediterranean Biome: Example location - Adana, Turkey.
  • Mean Monthly Temperature Range: 35°C to 10°C.
  • Mean Monthly Precipitation Range: Variable, peaking in April.
• Desert Biome: Example location - Riyadh, Saudi Arabia.
  • Temperature fluctuations with low rainfall.
• Tropical Biome: Example location - Iquitos, Peru.
  • Consistently high temperatures and substantial rainfall throughout the year.
• Savanna Biome: Example location - Kano, Nigeria.
  • Notable annual precipitation changes affecting biodiversity.
• Tundra Biome: Example location - Baker Lake, Canada.
  • Characterized by extreme cold temperatures and minimal precipitation.

Population Dynamics and Feedback Systems

• Trophic Interactions:
  • Increase in plant growth leads to an increase in herbivore populations.
  • Further increase in herbivores leads to predator population growth.
  • An eventual predator population decrease results in a reduction of herbivores and subsequently affects plant supply.
• Feedback Mechanism: Structure representing self-regulation and population dynamics.

Biodiversity and Ecosystem Productivity

• Biodiversity Indicators: High biodiversity contributes to ecosystem resilience.
• Net Primary Productivity Statistics:
  • Tropical Rainforest: 9000 kilocal/m²/yr
  • Deciduous Temperate Forest: 6000 kilocal/m²/yr
  • Boreal Forest: 3500 kilocal/m²/yr
  • Temperate Grassland: 2000 kilocal/m²/yr
  • Polar Tundra: 600 kilocal/m²/yr
  • Desert: <200 kilocal/m²/yr

Biogeochemical Cycles Overview

• Definition: These cycles involve the transportation and transformation of matter between organisms and the environment.
• Components:
  • Gaseous Cycles: Carbon (C) and Nitrogen (N).
  • Sedimentary Cycles: Phosphorus (P).
• Processes:
  • Biotic Components: Photosynthesis and respiration.
  • Abiotic Components: Weathering processes, volcanic eruptions.
• Life Sustenance: Limited supply of nutrients must be recycled within ecosystems.

The Carbon Cycle

• Key Processes in the Carbon Cycle:
  • Fixation: Conversion of atmospheric carbon into organic forms.
  • Sink: Storage of carbon in various reservoirs (e.g., forests, oceans).
  • Source: Release of carbon back into the atmosphere (e.g., through respiration, combustion).
• Carbon Dioxide Levels Changes:
  • Historical Data:
  • 1750: 280 ppm
  • 2018: 408 ppm
  • 2022: 427 ppm
• Atmospheric Composition: Current atmosphere composition includes approximately 0.04% CO₂.

The Nitrogen Cycle

• Stages in the Nitrogen Cycle:
  • Fixation: Conversion of atmospheric nitrogen gas (N₂) into usable forms (e.g., NH₄⁺) by bacteria.
  • Consumption: Plants absorb fixed nitrogen.
  • Denitrification: Conversion of nitrates back into nitrogen gas by bacteria.
  • Gaseous Losses: Loss of nitrogen to the atmosphere through various processes.

Feedback Mechanism in Nitrogen Cycle

• Understanding nitrogen interactions and their influence on environmental health.

Environmental Effects of Nitrogen Compounds

Phosphorus Cycle

• Pathway of Phosphorus:
  • Found in rocks and soil; primary source is phosphate mining.
  • Nutrient cycle influenced by organic matter from agricultural fertilizers and runoff.
  • Essential for plant uptake and growth; excess causes algae blooms.

Learning Objectives

1. Define and explain the important terms: biosphere, biome, and biogeography.
2. Understand the main influences leading to global plant and animal distributions.
3. Describe an example of biome structure, feedback cycles, and processes.
4. Outline the importance of biogeochemical cycles in maintaining life on Earth.