Principles of Ecology | Geography Optional for UPSC (Notes) PDF Download

Fundamental Ecological Principles

• Evolution and Distribution: Describing the development and spread of plants and animals within ecosystems.
• Species Extinction: Understanding the factors leading to the disappearance of certain species.
• Energy Consumption and Transfer: Exploring how energy moves through different parts of biological communities.
• Substances Cycling: Examining the recycling of organic and inorganic materials within ecosystems.
• Interactions and Relationships: Studying the connections among organisms and between organisms and their physical environment.

Organisms and the Environment

• Evolution and Distribution: Detailing the evolutionary paths and geographical spread of living beings.
• Extinction Dynamics: Investigating the causes and mechanisms behind species disappearing from ecosystems.
• Energy Flow: Analyzing how energy moves and transfers across various components of biological communities.
• Substance Recycling: Understanding the cycles and reuse of both organic and inorganic substances.
• Interactions and Inter-relationships: Exploring the connections among organisms and their surroundings, including both biotic and abiotic factors.

Organisms and the Environment

Organisms' Basic Needs

• Diversity notwithstanding, all organisms share fundamental requirements: energy and matter, both acquired from their surroundings.
• Organisms operate as open systems, reliant on and impacted by their environment for sustenance and influence.

Environmental Components

• Abiotic Factors: Nonliving elements encompassing sunlight, soil, temperature, and water constitute the abiotic factors within an environment.
• Biotic Factors: The living facets of an environment involve other organisms, spanning within and across species, forming the biotic factors.

Niche

Ecosystem's Crucial Concept: Niche

• Niche defines a species' role within its ecosystem, encompassing all interactions with both living (biotic) and non-living (abiotic) factors.
• It encapsulates how a species engages with the environment, notably through its food preferences and the methods employed to acquire that food.

Aspects of a Species' Niche

• Dietary Habits: Each species has a distinct diet, consuming specific types of food unique to its niche.
• Feeding Methods: Species vary in how they procure their food, showcasing diverse approaches to obtaining their dietary requirements within the ecosystem.

Habitat

Niche Component: Habitat

• Habitat signifies the physical surroundings where a species resides and to which it has adapted.
• It represents the environment where a species is naturally suited to exist, based on its adaptations and characteristics.

Features of a Habitat

• Determining Factors: The traits of a habitat primarily stem from abiotic elements like temperature and rainfall.
• Influence on Organisms: These abiotic factors play a significant role in shaping the characteristics and attributes of the organisms that inhabit the habitat.

Competitive Exclusion Principle

Unique Niches in a Habitat

• Despite multiple species within a habitat, each species occupies a distinct niche.
• The principle dictates that two distinct species cannot sustainably occupy identical niches within the same location.

Competitive Exclusion Principle

• Reasoning Behind Principle: If two species attempt to occupy the same niche, competition for shared resources, such as food, emerges.
• Outcome of Competition: Eventually, one species tends to surpass and replace the other due to superior adaptation and competitive advantage in acquiring resources.

The Ecosystem

Definition and Scope of Ecosystems

• Ecosystems, the focal point of ecological studies, encompass all biotic and abiotic elements in an area and their interactions.
• They vary in size, ranging from a lake to a decomposing log, housing diverse species interacting with both biotic and abiotic factors.

Energy and Matter in Ecosystems

• Energy Input: Ecosystems require continual energy inputs, primarily sourced from sunlight or in rare cases, from chemical compounds.
• Matter Recycling: Unlike energy, matter isn't continuously added to ecosystems but rather recycled, with water, carbon, nitrogen, and other elements reused repeatedly.

Ecosystem Characteristics and Origin of the Term:

• Coined Term: A.G. Tansley introduced the term "ecosystem" in 1935 to represent self-sustaining units in nature.
• Functional Unit: Ecosystems exhibit intricate interactions between their living (biotic) and non-living (abiotic) components, illustrated by entities like ponds exemplifying an ecosystem.

Global and Categorized Ecosystems

• Global Perspective: Some ecologists view the biosphere as a global ecosystem, aggregating all local ecosystems on Earth.
• Terrestrial and Aquatic Ecosystems: Ecosystems are broadly categorized into terrestrial (e.g., forests, deserts) and aquatic (e.g., ponds, oceans) types.
• Man-made Examples: Manmade ecosystems include crop lands and aquariums, showcasing human-constructed ecological systems.

Study and Common Characteristics

• Study Scope: Ecosystem studies can focus on tiny systems like water puddles or tree holes, as well as extensive ecosystems like forests or oceans.
• Shared Traits: Despite varying sizes, all ecosystems exhibit common characteristics in the interactions between organisms and their environment.

Types of Ecosystems

Ecosystem Classification

• Natural Ecosystems:
  • Solar Radiation Dependence: Examples include forests, grasslands, oceans, lakes, rivers, and deserts, reliant solely on solar radiation.
  • Energy Subsidy Inclusion: Some natural ecosystems receive energy from alternative sources like wind, rain, and tides, such as tropical rainforests, tidal estuaries, and coral reefs.
• Manmade Ecosystems:
  • Solar Energy Dependence: Ecosystems like agricultural fields and aquaculture ponds primarily rely on solar energy for sustenance.
  • Fossil Fuel Dependence: Manmade ecosystems, such as urban and industrial ecosystems, are reliant on fossil fuel sources for their functioning.

Components of an Ecosystem

Broad Grouping of Components in Ecosystems

(a) Abiotic Components (Nonliving):

• Categories:
  • Physical Factors: Sunlight, temperature, rainfall, humidity, and pressure sustain and regulate organism growth.
  • Inorganic Substances: Elements such as carbon dioxide, nitrogen, oxygen, phosphorus, sulfur, water, rock, soil, and minerals.
  • Organic Compounds: Carbohydrates, proteins, lipids, and humic substances serve as foundational components linking biotic and abiotic factors.

(b) Biotic Components (Living):

• Producers: Green plants, or autotrophs, produce food for the ecosystem via photosynthesis, absorbing water, nutrients, carbon dioxide, and solar energy.
• Consumers: Heterotrophs, categorized into herbivores (e.g., cow, deer), carnivores (e.g., lion, cat), and omnivores (e.g., human, pigs) based on their food preferences.
• Decomposers: Also known as saprotrophs, primarily bacteria and fungi, decompose dead organic matter, playing a crucial role in nutrient recycling. They're also referred to as detrivores or detritus feeders.

Ecosystem – Structure and Function

Interaction and Physical Structure

• Biotic and abiotic components interact, shaping distinct physical structures in ecosystems.
• Species Composition: Identification and enumeration of plant and animal species determine an ecosystem's species composition.
• Structural Features: Species composition and stratification (vertical and horizontal distribution) showcase the ecosystem's organization.

Structural Components and Functions

• Food Relationships: Producers and consumers form various trophic levels, defining the ecosystem's structure.
• Trophic Levels: Trees, shrubs, herbs, and grasses occupy different vertical strata in ecosystems, representing trophic levels.
• Functional Aspects: Structural components work together, impacting ecosystem aspects like productivity, energy flow, and nutrient cycles.

Species Composition and Community Stability

• Community Definition: Communities comprise various populations living together in a specific area and time, determining species composition.
• Ecosystem Variation: Different ecosystems support varying species compositions based on habitat suitability and climate.
• Stability and Balance: The number and types of species within a community contribute to its stability and overall ecosystem balance.

Stratification in Ecosystems

• Vertical and Horizontal Distribution: Ecosystem stratification involves both vertical and horizontal distribution of plant life.
• Vertical Stratification: In forest ecosystems, layers from canopy to forest floor exhibit distinct flora and fauna.
• Horizontal Stratification: Deserts display low, intermittent layers of vegetation and animals, interspersed with bare patches, showcasing a type of horizontal stratification.

Functions of Ecosystem

Ecosystem Functions

• Energy Flow: Ecosystems facilitate the flow of energy through food chains or webs.
• Nutrient Cycling: They manage biogeochemical cycles, ensuring the recycling of nutrients.
• Ecological Succession: Ecosystems exhibit ecological succession or development over time.
• Homeostasis: They maintain stability through feedback control mechanisms.

Examples of Ecosystems

• Natural Ecosystems: Ponds, lakes, meadows, marshlands, grasslands, deserts, and forests represent natural ecosystems.
• Manmade Ecosystems: Examples like aquariums, gardens, lawns, etc., found in neighborhoods, are human-created ecosystems.

Food Chains, Energy Flow, and Ecological Pyramids

Energy Flow through Ecosystem

• Defined: It's the transfer of food energy from producers (green plants) to organisms through repeated consumption.
• Trophic Levels: Each step in the chain denotes a trophic level, involving producers, herbivores, carnivores, omnivores, and decomposers.
• Energy Loss: Energy diminishes with each level due to inefficiencies, limiting chain length to 4-5 trophic levels.

• Grazing Food Chains: Start from plants, feeding herbivores, and onward to carnivores.
• Detritus Food Chains: Begin with dead organic matter, nourishing detrivore organisms, continuing up the chain.

• Interconnected Trophic Levels: Food web displays a network of linked food chains in an ecosystem.
• Realistic Model: Offers a more realistic representation of energy flow than linear food chains.

• Types of Pyramids: Represent trophic levels in ecosystems - number, biomass, and energy pyramids.
• Pyramid of Number: Shows organism quantities at each trophic level; may sometimes be inverted in specific ecosystems.
• Pyramid of Biomass: Represents total living matter per unit area; often upright in terrestrial ecosystems, occasionally inverted in aquatic ones.
• Pyramid of Energy: Depicts total energy at each trophic level, never inverted in its shape.

Biogeochemical Cycles

Nutrient Cycling (Biogeochemical Cycles)

Definition and Overview:

• Nutrient cycling or biogeochemical cycles involve the movement of elements through ecosystems.
• Linear Energy Flow vs. Cyclical Nutrient Flow: While energy flow in ecosystems is linear, nutrient cycling involves a cyclic process.
• Closed System: Nutrients are neither imported nor exported from the biosphere, making the Earth a closed system.

Types of Nutrient Cycles:

• Gaseous and Sedimentary: Gaseous cycles (e.g., nitrogen, carbon) have their reservoir in the atmosphere, while sedimentary cycles (e.g., sulfur, phosphorus) have their reservoir in the Earth's crust.

Specific Nutrient Cycles:

Carbon Cycle:

• Importance: Essential cycle due to carbon compounds being fundamental to life.
• Flow and Human Impact: Carbon flows among storage pools in the atmosphere, ocean, and land; human activities have significantly impacted this cycle, raising atmospheric carbon dioxide levels.

Nitrogen Cycle:

• Essentiality and Cycling: Nitrogen is crucial for proteins; cycles between gaseous and solid phases through various processes like fixation, nitrification, assimilation, ammonification, and denitrification.

Water Cycle:

• Importance: Vital for all life forms; the continuous movement of water through evaporation, condensation, and precipitation; unevenly distributed across the Earth's surface.

Phosphorus Cycle:

• Significance: Essential for biological structures; cycles from rock reservoirs to soil, plants, and animals, mainly through weathering, absorption, decomposition, and minimal atmospheric involvement.

These cycles depict the crucial movement and recycling of nutrients within ecosystems, impacting life processes and environmental equilibrium.

Ecological Succession

Ecological Succession Overview

Foundational Concepts:

• Origin of the Term: Ragnar Hult introduced "Ecological Succession," referred to as orderly changes in communities, later termed as ecosystem development by Odum.
• Early Studies: Hult's comprehensive study in 1881 recognized the sequential change from pioneer to stable plant communities.

Definition and Nature of Succession:

• Dynamic Nature: Biotic communities change over time; succession refers to the replacement or alteration of plant and animal communities.
• Factors Involved: Both biotic activities and the physical environment contribute to this change, influencing its direction, rate, and extent.

Components and Changes During Succession:

• Plant and Animal Communities: Both undergo transformations; some species colonize and proliferate while others diminish or vanish.
• Sere and Seral Stages: Sequential communities forming during succession; individual transitional communities termed as seral stages or communities.

Primary and Secondary Succession:

• Primary Succession: Occurs in bare, unoccupied areas like rock outcrops, deltas, glacial moraines, and emerging volcanic islands.
• Pioneer Species: First plants to inhabit bare lands; high growth rate and short life span characterize these species.
• Climax Community: Terminal stage of succession; stable, mature, and long-lasting community in dynamic equilibrium.

Xerarch and Hydrarch Succession:

• Xerarch: Succession on land with low moisture like bare rock.
• Hydrarch: Succession in water bodies like ponds or lakes.

Secondary Succession:

• Occurrence: Community development after natural events (hurricanes, fires) or human activities (tilling, land harvesting).
• Speed: Faster due to available soil nutrients and dormant organism stages.

Causes of Ecological Succession:

• Initial Causes: Habitat destruction factors like climatic elements (wind, fire) and organismal activities.
• Continuing Causes: Population shifts due to migration for safety, industrialization, competition, etc.
• Stabilizing Cause: Factors contributing to community stability such as land fertility, climate, mineral availability.

Homeostasis of Ecosystem

Ecosystem Equilibrium and Homeostasis

Definition of Homeostasis in Ecosystems

• Homeostasis refers to an ecosystem's ability to maintain its equilibrium and regulate its species composition and functional processes.
• It signifies the ecosystem's tendency to resist changes, akin to the biological system's self-regulatory capacity.

Homeostasis Illustration - Pond Ecosystem

• Example in a Pond Ecosystem: Increased zooplankton population leads to high phytoplankton consumption, causing a shortage of zooplankton food.
• Resultant Impact: Reduced zooplankton due to starvation allows phytoplankton numbers to rise again, eventually leading to increased zooplankton populations, continuing the cycle.

Role of Negative Feedback

• In Homeostatic Systems: Negative feedback mechanisms maintain stability within ecosystems by counteracting changes and restoring balance.
• Limitations: While ecosystems exhibit homeostasis, their capacity isn't limitless, and not all aspects are uniformly regulated.

Human Disturbance to Ecosystems:

• Greatest Disruption: Human activities significantly disrupt ecosystems, often exceeding the ecosystem's self-regulating capabilities.
• Impact on Homeostasis: Human interference poses challenges to maintaining equilibrium and disrupts the balance within ecosystems.

Productivity of Ecosystem

Types of Productivity in Ecosystems

Primary Productivity:

• Definition: Primary productivity is the rate at which radiant energy is stored by photosynthetic or chemosynthetic organisms (producers) in an ecosystem.
• Categories:
  • Gross primary productivity: Total photosynthesis rate, including organic matter used up in plant respiration during the measurement period.
  • Net primary productivity: Rate of organic matter storage in plant tissues, exceeding respiratory utilization by plants during the measurement period.

Secondary Productivity:

• Description: Secondary productivity signifies the energy storage rate at consumer levels, encompassing herbivores, carnivores, and decomposers.
• Utilization: Consumers use already produced food materials in respiration and transform food into various tissues. Some ecologists prefer using the term 'assimilation' at this level.

Net Productivity:

• Definition: Net productivity indicates the rate of organic matter storage not utilized by heterotrophs or consumers.
• Calculation: Derived from subtracting consumption by heterotrophs from net primary production during a specified period like a season or year.
• Outcome: Reflects the rate of biomass increase of primary producers remaining unconsumed by consumers.

Principles of Ecology

Key Principles of Ecology in Ecosystems

Ecosystem Framework:

• Ecosystems unite physical environments and living organisms, allowing the study of interactions between biotic and abiotic components. They consist of autotrophic and heterotrophic components.

Interconnected Components:

• Biotic and abiotic components are linked through cyclic mechanisms, enabling the transfer of energy, water, chemicals, and sediments in the biosphere.

Sustained Life in Ecosystems:

• The ecosystem, not individual organisms or populations, supports sustained life on Earth.

Environmental Principles (M.J. Holliman):

• Nothing disappears; materials cycle in the natural environment.
• Systems and problems are interrelated; solving them individually is obsolete.
• Earth's resources are finite.
• Nature has refined stable ecosystems over millions of years.

Uniformitarianism Principle (D.B. Botkin and E.A. Keller):

• Processes operating in the past and present will continue but at varying rates influenced by human activities.

Natural Hazards and Biological Communities:

• Natural hazards impact biological communities and humans. Sometimes, biological processes contribute to creating severe hazards.

Mutual Reactivity:

• Living organisms and the physical environment interact positively, negatively, or neutrally at inter and intraspecific levels.

Solar Radiation and Ecosystem Energy Flow:

• Solar energy, trapped by plants via photosynthesis, drives ecosystem processes. Energy flow is unidirectional, following thermodynamic laws.

Energy Transfer and Trophic Levels:

• Energy transfers from lower to higher trophic levels. Organisms at higher levels receive energy from multiple sources.

Trophic Level Relationships (R.L. Linderman):

• Relationships between trophic levels dictate energy dependence, loss due to respiration, efficiency, and food chain length.

Biogeochemical Cycles:

• Inorganic and organic substances circulate through closed systems known as biogeochemical cycles.

Ecosystem Productivity Factors:

• Ecosystem productivity relies on solar radiation availability and plant efficiency in converting solar energy.

Homeostatic Mechanism and Stability:

• Self-regulating mechanisms maintain stability in ecosystems by countering external changes. Ecological diversity and complexity enhance stability.

Ecosystem Instability:

• Ecosystems become unstable when unable to adapt to environmental changes.

Dynamic Nature of Ecosystems (Charles Darwin):

• The evolution of species reflects the inherently dynamic nature of ecosystems.

Mutation and Evolution (T. Dobzhansky):

• Mutation introduces inheritable variations. Natural selection favors advantageous gene patterns in species.

Ecological Succession:

• Sequential transition stages from one vegetation community to another lead to a climax community.

Successional Changes in Ecosystems:

• Succession leads to increased complexity, productivity, soil maturity, stability, and regularity of populations in an ecosystem.

Human Impact on Ecosystems:

• Human activities, including resource exploitation, reduce ecological diversity and complexity.

Ecological Knowledge for Resource Preservation:

• Prompt and universal ecological knowledge application is vital for preserving diversity amid depleting resources.