Unit 2: Natural resources and ecosystem - Subjective Questions

Natural resources are the materials and components (both biotic and abiotic) that occur in nature and can be utilized by humans to satisfy their needs. Examples include air, water, soil, minerals, forests, and sunlight.

Classification of Natural Resources:

• On the basis of origin:

  • Biotic resources – Obtained from the biosphere and having life, e.g., forests, animals, fossil fuels (formed from decayed organic matter).
  • Abiotic resources – Non-living resources, e.g., land, water, air, minerals.

• On the basis of renewability:

  • Renewable resources – Can be replenished naturally over time, e.g., solar energy, wind, water, forests.
  • Non-renewable resources – Exist in fixed quantity and cannot be replenished within a human timescale, e.g., coal, petroleum, natural gas, minerals.

• On the basis of availability/development:

  • Potential resources – Exist but not yet utilized, e.g., solar energy in remote deserts.
  • Actual/Developed resources – Currently in use.
  • Reserve resources – Part of actual resources kept for future use.

Proper management and conservation of these resources is essential for sustainable development.

Renewable and non-renewable resources differ as follows:

Key points:

• Renewable resources such as solar and wind are considered clean energy sources.
• Non-renewable resources need careful conservation as they deplete permanently.
• Even renewable resources like forests can become non-renewable if exploited faster than their regeneration rate.

Land resources provide the base for agriculture, forestry, industry, and settlements. However, they face several problems:

Problems associated with land resources:

• Soil erosion – Removal of top fertile soil by wind and water.
• Desertification – Conversion of fertile land into desert due to overgrazing and deforestation.
• Waterlogging and salinity – Caused by over-irrigation.
• Land degradation – Loss of soil fertility due to overuse of chemicals.
• Landslides – Due to deforestation and construction in hilly regions.
• Soil pollution – From industrial waste, pesticides, and fertilizers.

Remedial measures:

• Afforestation and reforestation to bind the soil.
• Contour bunding and terracing on slopes to reduce erosion.
• Crop rotation and mixed cropping to maintain fertility.
• Controlled grazing to prevent overgrazing.
• Proper drainage to prevent waterlogging.
• Use of organic manure instead of excessive chemical fertilizers.
• Shelterbelts and windbreaks to control wind erosion.

Sustainable land management ensures long-term productivity and ecological balance.

Water is a vital renewable resource, but its availability and quality are increasingly threatened.

Problems associated with water resources:

• Overexploitation of groundwater leading to falling water tables.
• Water pollution from industrial, agricultural, and domestic waste.
• Floods due to deforestation and poor drainage.
• Droughts due to erratic rainfall and mismanagement.
• Conflicts over water sharing between states and countries.
• Waterlogging and salinity from over-irrigation.

Remedial measures:

• Rainwater harvesting to recharge groundwater.
• Watershed management for efficient water use.
• Drip and sprinkler irrigation to reduce wastage.
• Treatment of sewage and industrial effluents before discharge.
• Construction of check dams to control runoff.
• Public awareness about water conservation.
• Reuse and recycling of water.

Individual efforts such as fixing leaks, using water-efficient appliances, and avoiding wastage play a major role in conservation.

Forest resources are among the most valuable renewable natural resources providing both ecological and economic benefits.

Importance of forests:

• Ecological functions – Maintain climate, regulate the water cycle, prevent soil erosion, and act as carbon sinks.
• Economic functions – Provide timber, fuelwood, medicines, gums, resins, and raw materials.
• Habitat – Support biodiversity and wildlife.

Problems associated with forests:

• Deforestation for agriculture, urbanization, and industry.
• Overgrazing and shifting cultivation.
• Forest fires (natural and man-made).
• Construction of dams submerging forest areas.
• Illegal logging and mining.

Effects: Loss of biodiversity, soil erosion, floods, climate change, and disturbed water cycle.

Remedial measures:

• Afforestation and reforestation programs.
• Social forestry and agroforestry.
• Strict laws against illegal logging (e.g., Forest Conservation Act).
• Community participation such as the Chipko Movement.
• Controlled and sustainable harvesting of forest products.
• Forest fire management systems.

Conservation of forests is essential for ecological balance and sustainable development.

Energy resources are broadly classified into two categories:

1. Conventional (Non-renewable) energy resources:

• Coal, petroleum, natural gas, and nuclear energy.
• Limited in quantity and cause pollution.

2. Non-conventional (Renewable) energy resources:

• Solar, wind, tidal, geothermal, biomass, and hydro energy.
• Clean, inexhaustible, and eco-friendly.

Problems associated with conventional energy resources:

• Depletion of fossil fuel reserves at a rapid rate.
• Air pollution – Release of , , and causing global warming and acid rain.
• Global warming due to greenhouse gas emissions.
• Nuclear hazards – Radiation and radioactive waste disposal problems.
• Oil spills damaging marine ecosystems.
• Mining hazards affecting land and health.

Remedial measures:

• Shift towards renewable energy sources.
• Energy conservation and efficient use.
• Use of energy-efficient appliances and public transport.
• Adoption of green and clean technologies.

A transition to renewable energy is crucial for a sustainable future.

Every individual can significantly contribute to conserving natural resources through small, conscious efforts in daily life.

Role of an individual in conservation:

• Water conservation:

  • Turn off taps when not in use.
  • Repair leaking pipes and taps.
  • Practice rainwater harvesting.
  • Reuse and recycle water.

• Energy conservation:

  • Switch off lights and appliances when not needed.
  • Use energy-efficient devices (LEDs, star-rated appliances).
  • Use public transport, carpool, or cycle.
  • Use solar energy where possible.

• Forest and soil conservation:

  • Plant trees and support afforestation.
  • Avoid using products causing deforestation.
  • Use paper judiciously and recycle it.

• Reduce, Reuse, Recycle (3 R's):

  • Minimize waste generation.
  • Reuse materials and recycle products.

• Spread awareness:

  • Educate family and community about conservation.
  • Participate in environmental programs.

Collective individual efforts lead to large-scale conservation and sustainable development.

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

Structure of an ecosystem:

1. Abiotic components (non-living):

• Climatic factors – Sunlight, temperature, rainfall, humidity.
• Inorganic substances – Carbon, nitrogen, phosphorus, water.
• Organic substances – Proteins, carbohydrates, lipids.

2. Biotic components (living):

• Producers (Autotrophs) – Green plants that make food through photosynthesis.
• Consumers (Heterotrophs) – Primary (herbivores), secondary and tertiary (carnivores).
• Decomposers (Saprotrophs) – Bacteria and fungi that break down dead matter.

Functions of an ecosystem:

• Energy flow – Unidirectional flow of energy from the sun through various trophic levels.
• Nutrient cycling – Circulation of nutrients (biogeochemical cycles) between biotic and abiotic components.
• Ecological succession – Gradual development and change in community structure.
• Regulation – Maintains balance through feedback mechanisms.

Thus, an ecosystem is a self-sustaining and self-regulating unit of nature.

Ecosystems are broadly classified into two major types based on their habitat:

1. Natural Ecosystems – Operate under natural conditions without human interference.

• Terrestrial Ecosystems (land-based):

  • Forest ecosystem – Tropical, temperate, and coniferous forests.
  • Grassland ecosystem – Prairies, savannas.
  • Desert ecosystem – Hot and cold deserts with low rainfall.

• Aquatic Ecosystems (water-based):

  • Freshwater ecosystem – Lakes, ponds, rivers, streams.
  • Marine ecosystem – Oceans and seas with high salinity.

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

• Examples: Croplands, aquariums, gardens, dams, and cities.

Key features:

• Natural ecosystems are self-regulating and stable.
• Artificial ecosystems require human input (energy, fertilizers) to sustain.

Each ecosystem has its own characteristic flora, fauna, and climatic conditions, contributing to the overall biodiversity of the planet.

Energy flow refers to 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 primary source of energy.
• Producers capture solar energy and convert it into chemical energy through photosynthesis.
• This energy passes to primary consumers (herbivores), then to secondary and tertiary consumers (carnivores).
• Decomposers release energy from dead organic matter back into the system.

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 as heat.

Ten Percent Law (Lindeman):

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

Why energy flow is unidirectional:

• Energy flows in a single direction from the sun → producers → consumers → decomposers.
• It cannot flow back to the sun or to previous trophic levels.
• At each level, energy is lost as heat and cannot be reused.

Thus, a constant supply of solar energy is required to sustain the ecosystem.

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

General representation:

Types of food chains:

1. Grazing Food Chain (GFC):

• Starts with green plants (producers).
• Energy flows from producers to herbivores to carnivores.
• Example:

2. Detritus Food Chain (DFC):

• Starts with dead organic matter (detritus).
• Involves decomposers and detritivores.
• Example:

Key points:

• Each step in a food chain is called a trophic level.
• Energy decreases at each successive trophic level (10% law).
• The grazing food chain depends on solar energy, while the detritus food chain depends on dead organic matter.
• In nature, food chains are interconnected to form food webs.

Food chains help in understanding energy flow and nutrient cycling in ecosystems.

A food web is a network of interconnected food chains in an ecosystem, showing the complex feeding relationships among various organisms.

Difference between food chain and food web:

Significance of food web:

• Ecological stability – Provides alternative food sources; if one species declines, organisms can feed on others.
• Maintains balance – Prevents overpopulation of any species.
• Energy flow – Shows realistic energy transfer among organisms.
• Biodiversity – Reflects the interdependence of species.
• Adaptability – Helps species survive environmental changes.

A food web represents the realistic picture of feeding relationships in nature, unlike the simplistic food chain.

An ecological pyramid is a graphical representation of the relationship between different trophic levels of an ecosystem in terms of number, biomass, or energy.

The concept was introduced by Charles Elton.

Types of Ecological Pyramids:

1. Pyramid of Numbers:

• Represents the number of organisms at each trophic level.
• Can be upright (grassland ecosystem) or inverted (tree/parasite ecosystem).
• Example: In a grassland, producers are most numerous; top carnivores are least.

2. Pyramid of Biomass:

• Represents the total dry weight (biomass) of organisms at each trophic level.
• Usually upright in terrestrial ecosystems.
• Inverted in aquatic ecosystems (phytoplankton have less biomass than fish).

3. Pyramid of Energy:

• Represents the amount of energy at each trophic level.
• Always upright because energy decreases at each level (10% law).
• The most fundamental and accurate pyramid.

Significance:

• Shows the feeding relationships and energy transfer.
• Indicates the health and stability of an ecosystem.
• Helps understand the decrease in energy across trophic levels.

The pyramid of energy is considered the best representation as it is never inverted.

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

Types of Ecological Succession:

1. Primary Succession:

• Occurs in areas where no life existed before (barren land, bare rock, newly formed volcanic island).
• Begins with pioneer species like lichens and mosses.
• Takes a very long time.

2. Secondary Succession:

• Occurs in areas where a community previously existed but was destroyed (abandoned farmland, burnt forest).
• Faster than primary succession because soil is already present.

Based on habitat:

• Hydrarch (Hydrosere) – Begins in aquatic environments.
• Xerarch (Xerosere) – Begins in dry/arid environments.

Stages of Succession:

1. Nudation – Development of a bare area.
2. Invasion – Arrival of pioneer species.
3. Competition and Coaction – Struggle for resources among species.
4. Reaction – Organisms modify the environment.
5. Stabilization (Climax) – A stable, self-sustaining climax community is formed.

Significance:

• Restores ecological balance.
• Increases biodiversity and stability.

Succession demonstrates how ecosystems develop and mature over time.

Deforestation is the large-scale removal or clearing of forests for various human activities.

Causes of deforestation:

• Agricultural expansion – Clearing forests for farmland.
• Urbanization and industrialization.
• Timber and fuelwood extraction.
• Mining activities.
• Construction of dams and roads.
• Shifting cultivation (slash and burn).
• Forest fires and overgrazing.

Effects of deforestation:

• Loss of biodiversity – Destruction of wildlife habitats.
• Soil erosion and loss of fertility.
• Climate change – Increased and global warming.
• Disruption of the water cycle – Reduced rainfall.
• Floods and droughts.
• Desertification.

Control measures:

• Afforestation and reforestation.
• Social forestry and agroforestry.
• Strict enforcement of forest laws.
• Public awareness and community participation (e.g., Chipko Movement).
• Promoting alternative fuels to reduce fuelwood dependency.
• Sustainable harvesting of forest products.

Protecting forests is vital for maintaining ecological balance and combating climate change.

Comparison of Conventional and Non-Conventional Energy Sources:

Advantages of Renewable (Non-Conventional) Energy:

• Inexhaustible – Naturally replenished and never runs out.
• Eco-friendly – Produces little or no pollution.
• Reduces greenhouse gas emissions and combats global warming.
• Reduces dependency on imported fossil fuels.
• Decentralized – Can be generated locally (solar panels, biogas).
• Low operating costs after installation.
• Sustainable for future generations.

Conclusion: Shifting to renewable energy sources is essential for energy security and environmental sustainability.

The Ten Percent Law was proposed by Raymond Lindeman (1942). It states that during the transfer of energy from one trophic level to the next, only about 10% of the energy is stored and passed on, while the remaining 90% is lost.

Explanation:

• Energy enters the ecosystem through producers capturing solar energy.
• At each trophic level, energy is lost as:
  • Heat through respiration.
  • Metabolic activities.
  • Undigested/unused material.

Example:

Suppose producers capture 10,000 J of energy:

• Producers → 10,000 J
• Primary consumers (herbivores) → 1,000 J (10%)
• Secondary consumers (carnivores) → 100 J (10%)
• Tertiary consumers → 10 J (10%)

Significance:

• Explains why food chains usually have only 4–5 trophic levels.
• Shows why the number of top carnivores is small.
• Explains the upright pyramid of energy.
• Highlights the inefficiency of energy transfer in ecosystems.

Thus, energy diminishes at each successive trophic level, limiting the length of food chains.

A forest ecosystem is a natural terrestrial ecosystem dominated by trees and other vegetation, supporting a rich variety of flora and fauna.

Structure of Forest Ecosystem:

1. Abiotic components:

• Sunlight, temperature, soil, water, humidity, and inorganic/organic nutrients.

2. Biotic components:

• Producers:

  • Trees (dominant), shrubs, herbs, mosses, and lichens.
  • Carry out photosynthesis.

• Consumers:

  • Primary consumers (herbivores) – Deer, insects, elephants, rodents.
  • Secondary consumers (carnivores) – Snakes, birds, foxes.
  • Tertiary consumers (top carnivores) – Lions, tigers.

• Decomposers:

  • Fungi, bacteria, and actinomycetes that break down dead matter.

Functions of Forest Ecosystem:

• Energy flow – From sun → producers → consumers → decomposers.
• Nutrient cycling – Recycling of nutrients through decomposition.
• Regulation of climate – Maintains temperature, rainfall, and balance.
• Habitat – Provides shelter and food to diverse organisms.
• Ecological balance – Prevents soil erosion and maintains biodiversity.

Forest ecosystems are vital for oxygen production, carbon sequestration, and overall environmental stability.

Overexploitation refers to the excessive use of natural resources beyond their capacity to regenerate, leading to depletion and environmental degradation.

Problems caused by overexploitation:

• Resource depletion – Exhaustion of minerals, fossil fuels, and groundwater.
• Deforestation – Loss of forests and biodiversity.
• Soil degradation – Erosion, desertification, and loss of fertility.
• Water scarcity – Falling water tables and drying rivers.
• Extinction of species – Overhunting and overfishing.
• Pollution – Accumulation of industrial and agricultural waste.
• Climate change – Increased greenhouse gases.

Concept of Sustainable Use:

Sustainable development means "meeting the needs of the present generation without compromising the ability of future generations to meet their own needs."

Principles of sustainable use:

• Use resources within their regeneration capacity.
• Promote reduce, reuse, and recycle (3 R's).
• Adopt renewable energy sources.
• Practice conservation of water, soil, and forests.
• Encourage eco-friendly technologies.
• Maintain ecological balance.

Sustainable use ensures long-term availability of resources and a healthy environment for future generations.

A pond ecosystem is a small, self-sustaining freshwater aquatic ecosystem that is an excellent example of interaction between biotic and abiotic components.

Structure of Pond Ecosystem:

1. Abiotic components:

• Water, sunlight, temperature, dissolved oxygen, , and inorganic nutrients (nitrates, phosphates).

2. Biotic components:

• Producers:

  • Phytoplankton – Microscopic algae.
  • Macrophytes – Rooted and floating plants (lotus, hydrilla).

• Consumers:

  • Primary consumers – Zooplankton, small insects (herbivores).
  • Secondary consumers – Small fish, frogs (carnivores feeding on herbivores).
  • Tertiary consumers – Big fish, birds.

• Decomposers:

  • Bacteria and fungi at the bottom that decompose dead matter.

Functions of Pond Ecosystem:

• Energy flow – Solar energy captured by producers flows through trophic levels.
• Nutrient cycling – Decomposers recycle nutrients back into the water.
• Food chains and food webs operate within the pond.
• Self-regulation – Maintains balance among organisms.

A pond ecosystem, though small, demonstrates all the essential features and functions of a complete ecosystem.