Ecosystem

Definition of Ecosystem

• An ecosystem is a structural and functional unit of the biosphere where living organisms (biotic components) interact with each other and with their physical environment (abiotic components) in a specific area.
• Coined by Arthur Tansley in 1935.

Types of Ecosystems

1. Natural Ecosystems: Exist naturally without human interference.
   • Terrestrial Ecosystems: Forests, grasslands, deserts.
   • Aquatic Ecosystems: Freshwater (rivers, lakes), Marine (oceans, estuaries).
2. Artificial Ecosystems: Created and maintained by humans, e.g., crop fields, gardens, aquariums.

Structure of Ecosystem

• Abiotic Components: Non-living factors that influence the ecosystem.
  • Physical factors: Sunlight, temperature, rainfall, wind, soil.
  • Chemical factors: Oxygen, carbon dioxide, nitrogen, water, and nutrients.
• Biotic Components: Living organisms classified into:
  1. Producers (Autotrophs): Convert solar energy into chemical energy through photosynthesis. Example: Plants, algae.
  2. Consumers (Heterotrophs):
     • Primary Consumers: Herbivores like deer, rabbits.
     • Secondary Consumers: Carnivores that feed on herbivores, e.g., foxes, frogs.
     • Tertiary Consumers: Top predators like lions, eagles.
  3. Decomposers (Saprotrophs): Break down organic matter into simpler compounds. Example: Fungi, bacteria.

Functions of Ecosystem

1. Energy Flow: Transfer of energy through trophic levels.
2. Nutrient Cycling: Movement of nutrients like nitrogen, carbon, and phosphorus within the ecosystem.
3. Support Services: Soil formation, oxygen production, water purification.
4. Homeostasis: Maintains ecological balance through interactions.

Energy Flow in an Ecosystem

• Unidirectional Flow: Energy flows from the sun to producers and then through consumers in one direction.
• Laws of Thermodynamics:
  • First Law: Energy is neither created nor destroyed but transforms.
  • Second Law: Energy transfer leads to energy loss as heat, making the flow inefficient.

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Trophic Levels in Ecosystem

• The hierarchical levels in a food chain are based on the mode of nutrition.

1. Trophic Level 1: Producers (e.g., plants, algae).
2. Trophic Level 2: Primary Consumers (herbivores, e.g., deer, grasshoppers).
3. Trophic Level 3: Secondary Consumers (carnivores, e.g., frogs, foxes).
4. Trophic Level 4: Tertiary Consumers (top predators, e.g., tigers, eagles).
5. Decomposers: Operate across all trophic levels by breaking down organic matter.

Food Chain

• A linear sequence of organisms where energy and nutrients pass from one to another.

1. Grazing Food Chain: Starts with producers (e.g., grass → grasshopper → frog → snake → eagle).
2. Detritus Food Chain: Starts with dead organic matter (e.g., fallen leaves → fungi → earthworms → predators).

Food Web

• A complex network of interconnected food chains in an ecosystem.
• Provides stability to the ecosystem by offering alternative energy sources.

Ecological Pyramids

1. Pyramid of Numbers: Depicts the number of individuals at each trophic level.
   • Example: A forest ecosystem often has a pyramid with fewer top predators than primary consumers.
2. Pyramid of Biomass: Shows the total biomass at each trophic level.
   • Example: Aquatic ecosystems often have an inverted biomass pyramid (small phytoplankton sustain larger fish populations).
3. Pyramid of Energy: Always upright as energy flow is unidirectional and diminishes at each level due to energy loss as heat.

Trophic Level	Example (Terrestrial)	Example (Aquatic)
Producers	Plants	Phytoplankton
Primary Consumers	Herbivores (e.g., deer)	Zooplankton
Secondary Consumers	Carnivores (e.g., fox)	Small fish
Tertiary Consumers	Top predators (e.g., lion)	Large fish (e.g., shark)

Ecological Efficiency

• The ratio of energy transferred from one trophic level to the next.
• Typically, only 10% of the energy is passed on, with the remaining 90% lost as heat, respiration, or other forms.

Biogeochemical Cycles (Overview)

• Biogeochemical cycles help in recycling nutrients.

1. Carbon Cycle: Circulates carbon through the atmosphere, organisms, and Earth.
2. Nitrogen Cycle: Converts atmospheric nitrogen into usable forms like nitrates.
3. Phosphorus Cycle: Moves phosphorus through soil, water, and organisms.
4. Water Cycle: Maintains the Earth's water balance through evaporation, condensation, and precipitation.

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Types of Ecosystem Services

Ecosystem services are the benefits that humans derive from ecosystems. These can be classified into four categories:

1. Provisioning Services:

   • Products obtained from ecosystems.
   • Examples:
     • Food (crops, fish, livestock).
     • Water (freshwater from rivers, lakes).
     • Raw materials (timber, minerals).
     • Medicinal resources (plants for drugs).

2. Regulating Services:

   • Benefits obtained from the regulation of ecosystem processes.
   • Examples:
     • Climate regulation (forests absorb CO₂).
     • Air quality maintenance.
     • Water purification (wetlands filter pollutants).
     • Disease control (natural predators regulate pests).

3. Cultural Services:

   • Non-material benefits.
   • Examples:
     • Recreation and tourism.
     • Spiritual and religious values.
     • Aesthetic inspiration.

4. Supporting Services:

   • Fundamental processes that support other ecosystem services.
   • Examples:
     • Soil formation.
     • Photosynthesis.
     • Nutrient cycling.

Ecological Succession

• Definition: The natural process by which ecosystems evolve over time, leading to a stable climax community.
• Types of Succession:
  1. Primary Succession: Occurs in areas with no prior life, e.g., volcanic eruptions, bare rocks.
     • Pioneer species like lichens initiate the process.
  2. Secondary Succession: Occurs in areas where life existed but was disturbed, e.g., after forest fires or floods.
• Stages of Succession:
  1. Pioneer Stage: Early colonizers (lichens, mosses).
  2. Intermediate Stage: Shrubs, grasses, and small trees dominate.
  3. Climax Stage: Stable and mature community with maximum biodiversity.

Biodiversity and Ecosystem Stability

• Definition: Biodiversity refers to the variety of life forms in an ecosystem.
• Importance:
  • Enhances productivity and resilience.
  • Maintains ecosystem services.
  • Promotes adaptation to changes and disturbances.
• Threats to Biodiversity:
  • Habitat destruction.
  • Pollution.
  • Overexploitation.
  • Climate change.

Human Impact on Ecosystems

• Positive Impacts:
  • Afforestation and conservation efforts.
  • Sustainable resource management.
  • Development of national parks and wildlife sanctuaries.
• Negative Impacts:
  • Deforestation and habitat loss.
  • Pollution (air, water, and soil).
  • Overexploitation of natural resources.
  • Introduction of invasive species.

Conservation of Ecosystems

1. In-Situ Conservation: Protecting ecosystems within their natural habitats.
   • Examples: National parks, wildlife sanctuaries, biosphere reserves.
2. Ex-Situ Conservation: Protecting ecosystems outside their natural habitats.
   • Examples: Zoos, seed banks, botanical gardens.
3. Sustainable Practices:
   • Reducing pollution.
   • Promoting renewable energy sources.
   • Educating communities about conservation.

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