Unit 2: Natural resources and ecosystem - Subjective Questions

Natural resources are the materials and components that can be found within the environment and are used by living organisms, especially humans, to satisfy their needs and support life.

Classification of Natural Resources:

1. On the basis of origin:

   • Biotic resources – Obtained from living organisms (e.g., forests, wildlife, fossil fuels like coal and petroleum).
   • Abiotic resources – Obtained from non-living things (e.g., land, water, air, minerals).

2. On the basis of renewability:

   • Renewable resources – Can be replenished naturally (e.g., solar energy, wind, water, forests).
   • Non-renewable resources – Cannot be replenished within a human timescale (e.g., coal, petroleum, natural gas, minerals).

3. On the basis of development:

   • Potential resources – Exist but not yet utilised (e.g., unexplored petroleum reserves).
   • Actual/Developed resources – Currently being used.

Importance: Natural resources form the foundation of economic development, provide raw materials, energy, food, and maintain ecological balance.

Renewable vs Non-renewable Resources:

Key Points:

• Renewable resources must still be used wisely; over-exploitation (e.g., deforestation) can make them non-renewable in practice.
• Non-renewable resources should be conserved and replaced with renewable alternatives wherever possible.

Land Resources include soil, minerals, and the land surface used for agriculture, forestry, industry, and habitation.

Major Problems:

• Soil Erosion – Removal of topsoil by wind and water, reducing fertility.
• Desertification – Conversion of fertile land into desert due to over-grazing, deforestation, and climate change.
• Waterlogging and Salinity – Excess irrigation raises water table and salt content.
• Landslides – Mass movement of soil/rock on slopes due to deforestation and mining.
• Soil Pollution – From fertilizers, pesticides, and industrial waste.
• Land degradation – Due to mining, urbanization, and improper farming.

Remedial Measures:

• Afforestation and reforestation to bind soil.
• Contour ploughing and terrace farming on slopes.
• Crop rotation and organic farming to maintain fertility.
• Construction of check dams and shelter belts.
• Proper drainage to prevent waterlogging.
• Regulation of mining and reclamation of degraded land.
• Reduced use of chemicals and promotion of biofertilizers.

Water resources include surface water (rivers, lakes) and groundwater essential for life and development.

Problems Associated with Water Resources:

• Over-utilisation of groundwater – Leading to falling water tables.
• Floods – Due to heavy rainfall, deforestation, and poor drainage.
• Droughts – Scarcity of water due to low rainfall and mismanagement.
• Water pollution – From industrial effluents, sewage, and agricultural runoff.
• Conflicts over water – Inter-state and international disputes over river sharing.
• Dam-related problems – Displacement of people, submergence of forests.

Remedial Measures:

• Rainwater harvesting to recharge groundwater.
• Watershed management for efficient use.
• Water conservation through drip and sprinkler irrigation.
• Recycling and reuse of wastewater.
• Afforestation to prevent floods and droughts.
• Treatment of effluents before discharge.
• Public awareness for judicious use of water.

Forest Resources are among the most important renewable resources providing ecological, economic, and social benefits.

Importance of Forests:

• Provide timber, fuelwood, medicines, and raw materials.
• Maintain oxygen-carbon dioxide balance.
• Conserve soil and prevent erosion.
• Regulate water cycle and climate.
• Provide habitat for wildlife and maintain biodiversity.

Problems Due to Deforestation:

• Soil erosion and reduced fertility.
• Loss of biodiversity and wildlife habitat.
• Climate change due to increased .
• Disturbed water cycle leading to floods and droughts.
• Global warming and desertification.

Causes of Deforestation:

• Agriculture expansion, urbanization, mining, timber logging, forest fires, and construction of dams.

Remedial Measures:

• Afforestation and reforestation programmes.
• Social and agroforestry initiatives.
• Regulation of logging through laws.
• Fire prevention and control measures.
• Public participation (e.g., Chipko Movement).
• Use of alternative fuels to reduce fuelwood dependence.

Energy Resources are sources that provide energy for various needs.

Advantages of Conventional Sources: High energy output, established technology, easy to store and transport.

Disadvantages: Cause pollution, contribute to global warming, will be exhausted.

Advantages of Non-Conventional Sources: Renewable, clean, environment-friendly, reduce dependence on fossil fuels.

Disadvantages: High initial cost, weather dependent, require large area.

Conclusion: A shift toward non-conventional (renewable) energy is essential for sustainable development.

Every individual can significantly contribute to conserving natural resources through responsible actions in daily life.

Role of Individual in Conservation:

1. Conservation of Water:

• Turn off taps when not in use.
• Adopt rainwater harvesting.
• Reuse and recycle water.

2. Conservation of Energy:

• Use energy-efficient appliances (LED bulbs, star-rated devices).
• Switch off lights/fans when not needed.
• Use public transport, carpooling, or cycling.
• Use solar energy at home.

3. Conservation of Forests and Land:

• Plant trees (afforestation).
• Avoid wastage of paper.
• Use eco-friendly products.

4. Reduce, Reuse, Recycle (3Rs):

• Minimise waste generation.
• Segregate and recycle waste.

5. Spreading Awareness:

• Educate family and society.
• Participate in environmental campaigns.

Conclusion: Individual efforts, when multiplied across society, lead to large-scale conservation and sustainable development.

An ecosystem is a functional unit of nature where living organisms (biotic components) interact with each other and their physical environment (abiotic components), exchanging energy and matter.

Structure of Ecosystem:

The structure refers to the components and their arrangement.

1. Abiotic Components (Non-living):

• Climatic factors – light, temperature, humidity, rainfall.
• Edaphic factors – soil, minerals, water.
• Inorganic substances – , , , water.
• Organic substances – proteins, carbohydrates, lipids.

2. Biotic Components (Living):

• Producers (Autotrophs) – Green plants that synthesise food via photosynthesis.
• Consumers (Heterotrophs) – Primary (herbivores), Secondary (carnivores), Tertiary (top carnivores).
• Decomposers – Bacteria and fungi that break down dead organic matter.

Functions of Ecosystem:

• Energy flow – Flow of energy from sun → producers → consumers.
• Nutrient cycling – Circulation of nutrients (biogeochemical cycles).
• Ecological succession – Development of community over time.
• Homeostasis – Self-regulation and stability of the system.

An ecosystem can be classified based on its habitat and origin.

Types of Ecosystems:

1. Natural Ecosystems – Operate naturally without human intervention.

(a) Terrestrial Ecosystems (land-based):

• Forest ecosystem – tropical, temperate, coniferous forests.
• Grassland ecosystem – savanna, prairie.
• Desert ecosystem – hot and cold deserts.

(b) Aquatic Ecosystems (water-based):

• Freshwater ecosystem – ponds, lakes, rivers (lentic and lotic).
• Marine ecosystem – oceans, seas (high salinity).
• Estuarine ecosystem – where rivers meet the sea.

2. Artificial (Man-made) Ecosystems – Created and maintained by humans.

• Examples: Croplands, aquariums, gardens, dams.

Key Features:

• Each ecosystem has characteristic flora and fauna adapted to its conditions.
• Ecosystems vary in size from a small pond to the entire biosphere.

Energy flow is the transfer of energy from one trophic level to another in an ecosystem, originating from the sun.

Process of Energy Flow:

• The sun is the ultimate source of energy.
• Producers capture solar energy and convert it into chemical energy through photosynthesis.
• Energy passes to primary consumers (herbivores), then to secondary and tertiary consumers.
• Decomposers release energy by breaking down dead matter.

Laws Governing Energy Flow:

• First Law of Thermodynamics – Energy can neither be created nor destroyed, only transformed.
• Second Law of Thermodynamics – Energy transfer is accompanied by loss of energy as heat.

10% Law (Lindeman's Law):

• Only about 10% of energy is transferred from one trophic level to the next; the rest (~90%) is lost as heat and in metabolic activities.

Why Unidirectional?

• Energy flows in one direction only: Sun → Producers → Consumers → Decomposers.
• It cannot be reused or flow back because energy is progressively lost as heat at each level and cannot return to the sun.
• This is why a continuous supply of solar energy is required.

A food chain is a linear sequence of organisms through which energy and nutrients pass as one organism eats another.

Example: Grass → Grasshopper → Frog → Snake → Eagle

Types of Food Chains:

1. Grazing Food Chain (GFC):

• Begins with green plants (producers).
• Energy flows from producers to herbivores to carnivores.
• Example: Grass → Deer → Tiger
• Depends directly on solar energy.

2. Detritus Food Chain (DFC):

• Begins with dead organic matter (detritus).
• Involves decomposers and detritivores.
• Example: Dead leaves → Earthworms → Frog → Snake
• Does not depend directly on solar energy.

Significance of Food Chains:

• Maintain energy flow in the ecosystem.
• Help in nutrient cycling.
• Maintain ecological balance and population control.
• Show biological magnification of toxins.

Food Chain vs Food Web:

Food Web:
A food web is a network of interconnected food chains in an ecosystem, showing multiple feeding relationships.

Significance of Food Webs:

• Provide alternative food sources if one species declines.
• Increase stability and resilience of the ecosystem.
• Maintain population balance among species.
• Ensure efficient energy flow and nutrient cycling.
• Greater biodiversity leads to more complex and stable food webs.

Ecological pyramids are graphical representations of the relationship between different trophic levels in an ecosystem in terms of number, biomass, or energy.

The concept was proposed by Charles Elton.

Types of Ecological Pyramids:

1. Pyramid of Numbers:

• Represents the number of organisms at each trophic level.
• Upright in grassland ecosystem (many producers, fewer consumers).
• Inverted in a tree ecosystem (one tree supports many insects/birds).

2. Pyramid of Biomass:

• Represents the total dry weight (biomass) at each trophic level.
• Upright in terrestrial (forest/grassland) ecosystems.
• Inverted in aquatic ecosystems (small phytoplankton support larger fish).

3. Pyramid of Energy:

• Represents the amount of energy at each trophic level.
• Always upright because energy decreases at each successive level (10% law).
• Most fundamental and accurate representation.

Significance:

• Show energy/matter distribution across trophic levels.
• Help understand ecosystem structure and function.

Ecological succession is the gradual and orderly process of change in the community structure of an ecosystem over time until a stable community (climax) is established.

Types of Succession:

1. Primary Succession:

• Occurs on a bare, lifeless area where no life existed before (e.g., bare rock, newly cooled lava, sand dunes).
• Very slow process; begins with pioneer species (lichens, mosses).

2. Secondary Succession:

• Occurs in an area where a community existed but was destroyed (e.g., abandoned farmland, burnt forest).
• Faster because soil and nutrients are already present.

Stages of Succession (Seral stages):

1. Nudation – Formation of a bare area.
2. Invasion – Arrival of pioneer species.
3. Competition and Coaction – Struggle for resources among species.
4. Reaction – Modification of environment by organisms.
5. Stabilisation (Climax) – Establishment of a stable climax community in equilibrium with the environment.

Types based on moisture:

• Hydrarch – begins in water.
• Xerarch – begins in dry areas.

Problems of Over-Utilisation of Groundwater:

• Lowering of water table – Excessive pumping depletes aquifers.
• Ground subsidence – Sinking of land surface due to water removal.
• Saltwater intrusion – Sea water enters coastal aquifers.
• Drying of wells and springs – Water scarcity for drinking and irrigation.
• Reduced base flow of rivers.

Problems Associated with Dam Construction:

Advantages: Irrigation, hydroelectric power, flood control, water supply.

Problems (Disadvantages):

• Displacement of people and loss of homes (e.g., Narmada, Tehri dams).
• Submergence of forests and loss of biodiversity.
• Loss of fertile land and cultural heritage.
• Waterlogging and salinity in surrounding areas.
• Downstream effects – reduced water flow and sediment.
• Seismic activity (reservoir-induced earthquakes).
• Breeding of water-borne diseases.

Remedial Measures:

• Rainwater harvesting and artificial recharge.
• Proper rehabilitation of displaced people.
• Environmental impact assessment before dam construction.

Solar Energy is the energy obtained from the sun and is the most abundant renewable energy resource.

Methods of Harnessing Solar Energy:

1. Solar Thermal Devices:

• Solar cooker – uses reflectors to cook food.
• Solar water heater – heats water for domestic use.
• Solar furnace – produces high temperatures.

2. Solar Electric Devices (Photovoltaic):

• Solar cells (PV cells) – convert sunlight directly into electricity using semiconductors like silicon.
• Solar panels – arrays of solar cells.

Advantages:

• Renewable and inexhaustible.
• Pollution-free and eco-friendly.
• Available almost everywhere, especially in tropical regions.
• Low maintenance cost.
• Reduces dependence on fossil fuels.

Limitations:

• High initial installation cost.
• Depends on sunlight availability (not at night or on cloudy days).
• Requires large surface area for large-scale generation.
• Energy storage (batteries) is expensive.

Conclusion: Solar energy is a promising clean energy source for achieving sustainable development.

A pond ecosystem is a self-sufficient freshwater aquatic ecosystem and a good example to study ecosystem structure and function.

Structure of Pond Ecosystem:

1. Abiotic Components:

• Water, dissolved oxygen, , nutrients (nitrates, phosphates), light, temperature.

2. Biotic Components:

• Producers:
  • Phytoplankton – microscopic algae.
  • Macrophytes – rooted and floating plants (e.g., Hydrilla, Lotus).
• Consumers:
  • Primary consumers – zooplankton, small herbivores.
  • Secondary consumers – small fishes, insects.
  • Tertiary consumers – large fishes, birds.
• Decomposers:
  • Bacteria and fungi at the bottom that decompose dead matter.

Functions of Pond Ecosystem:

• Energy flow – from sun to producers to consumers.
• Food chains and food webs operate.
• Nutrient cycling between water, sediments, and organisms.
• Self-regulation maintains balance.

Zones of a Pond: Littoral (shallow), Limnetic (open water), and Profundal (deep) zones.

The use of chemical fertilizers and pesticides increases agricultural productivity but causes serious environmental problems.

Problems Due to Fertilizers:

• Eutrophication – Nutrient runoff into water bodies causes excessive algal growth and oxygen depletion.
• Soil degradation – Loss of natural fertility and soil structure.
• Groundwater contamination – Nitrates cause health hazards (blue baby syndrome).
• Micronutrient imbalance in soil.

Problems Due to Pesticides:

• Biomagnification – Accumulation of toxins along the food chain.
• Killing of non-target organisms (bees, birds, fish).
• Pesticide resistance in pests.
• Health hazards to humans (cancer, nervous disorders).
• Soil and water pollution.

Sustainable Alternatives:

• Organic farming using compost and manure.
• Biofertilizers (Rhizobium, Azotobacter, blue-green algae).
• Biopesticides and integrated pest management (IPM).
• Crop rotation and mixed cropping.
• Use of natural predators for biological control.

Conclusion: Sustainable agriculture practices maintain productivity while protecting the environment.

Mineral resources are naturally occurring non-renewable substances used as raw materials for industries and energy.

Effects of Over-Exploitation of Minerals:

• Land degradation – Mining destroys land and vegetation.
• Deforestation – Forests cleared for mining operations.
• Soil erosion and loss of fertility.
• Water pollution – Acid mine drainage contaminates water bodies.
• Air pollution – Dust and toxic gases released during mining.
• Subsidence of land – Collapse of underground mine areas.
• Displacement of communities and health hazards to miners.
• Depletion of reserves for future generations.

Measures for Conservation of Minerals:

• Recycling and reuse of metals (e.g., iron, aluminium, copper).
• Reducing wastage during extraction and processing.
• Use of substitutes and renewable alternatives.
• Efficient technology for extraction.
• Reclamation of mined land through afforestation.
• Legal regulation of mining activities.

Conclusion: Judicious use and recycling of minerals ensure their availability for future generations.

Grazing Food Chain (GFC) vs Detritus Food Chain (DFC):

Biological Magnification (Biomagnification):

Biomagnification is the progressive increase in the concentration of non-degradable toxic substances (like DDT, mercury) at successive trophic levels of a food chain.

Example (DDT):

• Water contains DDT at ppm.
• Zooplankton: ppm.
• Small fish: ppm.
• Large fish: ppm.
• Fish-eating birds: ppm.

Effects:

• Top consumers (including humans) receive the highest toxin concentration.
• Causes reproductive failure in birds (eggshell thinning), diseases, and death.

Prevention: Ban on harmful chemicals like DDT, use of biodegradable pesticides.