Elaborate Notes
INTRODUCTION TO THE SUBJECT AND APPROACH
The study of Environment and Ecology holds significant importance within the UPSC Civil Services Examination framework, reflecting the growing global and national focus on environmental issues. Its weightage in the Preliminary examination has been consistently high, often ranging between 15 to 20 questions, making it a decisive component. The subject is interdisciplinary, drawing concepts from biology, geography, chemistry, and social sciences. A successful approach necessitates not only rote learning of facts but also a deep conceptual understanding and a genuine curiosity about the natural world. This involves observing environmental phenomena, understanding their underlying scientific principles, and connecting them to contemporary issues like climate change, biodiversity loss, and sustainable development. The core of the preparation should revolve around building a strong foundation of basic concepts, which enables a candidate to tackle both direct factual questions and complex analytical ones.
ECOLOGY
- Definition and Etymology: The term “Ecology” was coined by the German biologist Ernst Haeckel in 1866. It is derived from two Greek words: ‘oikos’ meaning house or dwelling place, and ‘logos’ meaning study. Therefore, ecology is literally the “study of the household of nature.” It is the scientific study of the interactions among organisms and between organisms and their physical (abiotic) environment.
- Gaia Hypothesis: This influential concept was proposed by chemist James Lovelock and co-developed with microbiologist Lynn Margulis in the 1970s (formalised in Lovelock’s 1979 book Gaia: A New Look at Life on Earth).
- The hypothesis posits that the Earth’s biosphere, atmosphere, oceans, and soil constitute a complex, self-regulating system, much like a living organism.
- This system, named ‘Gaia’ after the Greek goddess of the Earth, actively maintains the planetary conditions necessary for life, such as temperature, atmospheric composition, and ocean salinity, in a state of homeostasis.
- An example often cited is the regulation of atmospheric oxygen, which has been maintained at approximately 21% for millions of years, a level optimal for complex life but also highly flammable. The Gaia hypothesis suggests this is not a coincidence but an actively maintained state.
- It remains a subject of scientific debate, with some critics arguing it is teleological (implying purpose) and inconsistent with principles of natural selection acting on individuals. However, it has profoundly influenced Earth System Science.
- Ecosystem: The term “ecosystem” was coined by the British botanist Arthur Tansley in 1935.
- An ecosystem is defined as a community of living organisms (biotic components) interacting with each other and with their non-living environment (abiotic components) as a functional unit.
- Biotic components include:
- Producers (Autotrophs): Organisms that produce their own food, primarily through photosynthesis (e.g., plants, algae, phytoplankton).
- Consumers (Heterotrophs): Organisms that obtain energy by feeding on other organisms (e.g., herbivores, carnivores, omnivores).
- Decomposers (Saprotrophs): Organisms that break down dead organic matter, returning nutrients to the soil (e.g., bacteria, fungi).
- Abiotic components include all non-living factors, such as sunlight, temperature, water, soil composition, and atmospheric gases.
- Branches of Ecology: Ecology is broadly divided into two main branches:
- Autecology (Population Ecology): This branch focuses on the study of a single species or a single population and its relationship with its environment. It examines aspects like the species’ life history, population dynamics, and adaptation to environmental conditions.
- Example: A study of the habitat requirements, diet, and reproductive behaviour of the Snow Leopard (Panthera uncia) in the Himalayas.
- Synecology (Community Ecology): This branch deals with the study of groups of different species living together in a community. It investigates the composition and structure of communities and the interactions between different species, such as competition, predation, and symbiosis.
- Example: A study of the interactions between various species—mangrove trees, Bengal tigers, spotted deer, crocodiles, and microbes—within the Sundarbans mangrove forest ecosystem.
- Autecology (Population Ecology): This branch focuses on the study of a single species or a single population and its relationship with its environment. It examines aspects like the species’ life history, population dynamics, and adaptation to environmental conditions.
LEVELS OF ORGANISM (Levels of Ecological Organisation)
Ecology is studied at various levels of organisation, each level building upon the one below it.
- Organism (Individual): The most basic level. It is a single living being. The study at this level focuses on the individual’s morphology, physiology, behaviour, and its adaptation to the environment.
- Population: A group of individuals of the same species living and interbreeding within a given area. Population ecology studies factors that affect population size and distribution, such as birth rates (natality), death rates (mortality), immigration, and emigration.
- Community: An assemblage of all the populations of different species that live and interact in a particular area. Community ecology focuses on species interactions, such as predation, competition, and mutualism, which determine the structure and organisation of the community.
- Ecosystem: This level includes the biotic community and its non-living (abiotic) physical environment. Ecosystem ecology studies the flow of energy and the cycling of nutrients through the system. For example, the flow of energy from the sun to producers, then to consumers, and finally to decomposers.
- Biome: A very large ecological area on the Earth’s surface, with fauna and flora (animals and plants) adapting to their environment. Biomes are often defined by abiotic factors such as climate, relief, geology, soils, and vegetation.
- Major biomes include Tundra, Taiga (Boreal Forest), Temperate Deciduous Forest, Tropical Rainforest, Grassland, and Desert.
- The classification of biomes, particularly based on climate (temperature and precipitation), was pioneered by ecologists like R.H. Whittaker (1975).
- Biosphere: The highest level of organisation. It is the global sum of all ecosystems, representing the zone of life on Earth. It is a closed system with respect to matter but an open system with respect to energy (receiving solar radiation). The term was popularised by geochemist Vladimir Vernadsky in his 1926 book The Biosphere.
INTERACTIONS (FLOW OF ENERGY)
Energy flow in an ecosystem is a unidirectional process, typically from the sun to producers and then through various consumers.
- Food Chain: A linear sequence of organisms where nutrients and energy are transferred from one organism to another. Each step or level in the food chain is called a trophic level.
- Trophic Levels: Producers (T1), Primary Consumers (Herbivores, T2), Secondary Consumers (Carnivores, T3), Tertiary Consumers (T4), and so on.
- Types of Food Chains:
- Grazing Food Chain (GFC): This chain starts with green plants (producers) as the first trophic level. Energy is derived from photosynthesis.
- Example (Terrestrial): Grass → Grasshopper → Frog → Snake → Eagle.
- Example (Aquatic): Phytoplankton → Zooplankton → Small Fish → Large Fish.
- Detritus Food Chain (DFC): This chain begins with dead organic matter called detritus (e.g., dead leaves, remains of animals). The energy source is the dead organic matter, which is consumed by decomposers and detritivores.
- Example: Dead Mangrove Leaves → Detritivores (crabs, worms) → Small Fish → Larger Carnivorous Fish.
- In many terrestrial ecosystems, a larger fraction of energy flows through the detritus food chain than through the grazing food chain.
- Grazing Food Chain (GFC): This chain starts with green plants (producers) as the first trophic level. Energy is derived from photosynthesis.
- Food Web: In a natural ecosystem, the feeding relationships are not simple linear chains. Multiple food chains are interconnected, forming a complex network called a food web.
- A food web provides a more realistic and accurate representation of the energy flow in an ecosystem.
- It enhances ecosystem stability. If one species’ population declines, the consumer has alternative food sources, preventing the collapse of the entire chain. Ecologist Charles Elton, in his seminal 1927 book Animal Ecology, highlighted the importance of food webs in structuring communities. The greater the complexity of a food web, the more stable the ecosystem is generally considered to be.
WILDLIFE
- The IUCN Red List: The IUCN (International Union for Conservation of Nature) Red List of Threatened Species is the world’s most comprehensive inventory of the global conservation status of biological species (both plants and animals).
- Established in 1964, it is a critical indicator of the health of the world’s biodiversity.
- It uses a set of precise criteria to evaluate the extinction risk of thousands of species and subspecies.
- IUCN Status Categories: The categories classify species based on their risk of extinction. The risk increases as one moves from Least Concern to Extinct.
- Extinct (EX): No known individuals remaining. (e.g., Dodo).
- Extinct in the Wild (EW): Known only to survive in captivity or as a naturalized population outside its historic range.
- Critically Endangered (CR): Extremely high risk of extinction in the wild. (e.g., Great Indian Bustard, Malabar Civet).
- Endangered (EN): Very high risk of extinction in the wild. (e.g., Bengal Tiger, Lion-Tailed Macaque).
- Vulnerable (VU): High risk of endangerment in the wild. (e.g., Olive Ridley Turtle, Sloth Bear).
- The categories CR, EN, and VU are collectively known as ‘Threatened’ categories.
- Near Threatened (NT): Likely to become endangered in the near future.
- Least Concern (LC): Lowest risk. Does not qualify for a more at-risk category. Widespread and abundant taxa are included in this category. (e.g., House Sparrow).
- Data Deficient (DD): Not enough data to make an assessment of its risk of extinction.
- Not Evaluated (NE): Has not yet been evaluated against the criteria.
- Relevance for UPSC: For the examination, it is crucial to know the IUCN status of important Indian fauna and flora, their geographical distribution (which states they are found in), the specific protected areas they inhabit (National Parks, Wildlife Sanctuaries), and the threats they face.
Prelims Pointers
- Ecology: Term coined by Ernst Haeckel in 1866.
- Gaia Hypothesis: Proposed by James Lovelock in the 1970s. States that Earth is a self-regulating system.
- Ecosystem: Term coined by Arthur Tansley in 1935. It is a system of biotic and abiotic components.
- Autecology: Study of a single species and its environment (Population Ecology).
- Synecology: Study of a community of different species and its environment (Community Ecology).
- Levels of Ecological Organisation (in increasing order of complexity):
- Organism
- Population
- Community
- Ecosystem
- Biome
- Biosphere
- Biosphere: Term popularised by Vladimir Vernadsky in 1926.
- Food Chain: Linear flow of energy. Each level is a trophic level.
- 10% Energy Transfer Rule: Only about 10% of the energy from one trophic level is transferred to the next. Proposed by Raymond Lindeman (1942).
- Two types of food chains: Grazing Food Chain (starts with producers) and Detritus Food Chain (starts with dead organic matter).
- Food Web: Network of interconnected food chains. Provides stability to the ecosystem.
- IUCN: International Union for Conservation of Nature.
- IUCN Red List: Established in 1964. Provides global conservation status of species.
- Threatened Categories (IUCN):
- Critically Endangered (CR)
- Endangered (EN)
- Vulnerable (VU)
- Other IUCN Categories: Extinct (EX), Extinct in the Wild (EW), Near Threatened (NT), Least Concern (LC), Data Deficient (DD), Not Evaluated (NE).
Mains Insights
GS Paper I (Geography & Society)
- Human-Environment Interaction: The concept of biomes is central to understanding how climate shapes vegetation, fauna, and consequently, human lifestyles, cultures, and economies across different regions of the world.
- Levels of Organisation and Human Impact: Human activities impact ecology at all levels. Deforestation affects biomes, pollution degrades ecosystems, poaching threatens populations, and climate change poses a risk to the entire biosphere.
GS Paper III (Environment & Biodiversity, Economy)
- Ecosystem Stability and Economic Resilience: The concept of a food web illustrates that biodiversity is not just a matter of conservation but a prerequisite for ecosystem stability. A stable ecosystem provides consistent ecosystem services (e.g., pollination, clean water, pest control) which are fundamental to economic activities like agriculture and tourism. The collapse of a food web can have cascading economic consequences.
- Gaia Hypothesis and Anthropocene: The Gaia hypothesis offers a powerful analytical framework for understanding the Anthropocene. It suggests that human activities (e.g., greenhouse gas emissions, large-scale deforestation) are disrupting Earth’s self-regulating mechanisms, pushing the planetary system out of its stable state (Holocene) and into a new, potentially less hospitable one. This perspective strengthens the case for urgent climate action and respecting planetary boundaries.
- IUCN Red List as a Policy Tool:
- Cause-Effect: The IUCN listing acts as a critical first step (cause) that triggers conservation action (effect) at national and international levels. For example, the listing of the tiger as ‘Endangered’ was a major impetus for the launch of Project Tiger in 1973 in India.
- Debate/Challenges: While invaluable, the Red List faces challenges. The ‘Data Deficient’ category highlights gaps in our ecological knowledge. Furthermore, the process of listing can be influenced by political considerations, and its effectiveness depends on the will and capacity of nations to implement conservation measures on the ground.
- Conservation Approaches (Autecology vs. Synecology):
- Early conservation efforts were often autecological, focusing on a single flagship species (e.g., the tiger). This is a species-centric approach.
- Modern conservation thinking is increasingly synecological, emphasizing the protection of entire ecosystems or habitats (e.g., protecting a whole forest corridor or a wetland). This ecosystem-based approach is considered more holistic as it conserves not just one species but the entire community and the ecological processes that sustain it. Project Elephant, with its focus on elephant corridors, is an example of a more ecosystem-based approach.