Unit 2: Natural resources and ecosystem - Subjective Questions

Natural resources are materials, organisms, and environmental conditions obtained from nature and used by living organisms, especially humans, for survival and development.

Examples include:

• Air, water, soil, and sunlight.
• Forests, wildlife, minerals, and fossil fuels.
• Land, fisheries, and biodiversity.

Importance:

• They provide food, water, shelter, clothing, and medicines.
• They supply raw materials for agriculture, industries, and construction.
• They support energy production and economic development.
• They regulate climate, purify air and water, conserve soil, and maintain nutrient cycles.
• They provide habitats for plants, animals, and microorganisms.

Uncontrolled exploitation can cause resource depletion, pollution, biodiversity loss, and ecological imbalance. Therefore, natural resources must be used efficiently and conserved for future generations.

Renewable resources are resources that can be naturally replenished within a relatively short period when they are properly managed. Examples include solar energy, wind energy, water, forests, and biomass.

Non-renewable resources are resources that exist in limited quantities and require millions of years to form. Their consumption is much faster than their natural replacement. Examples include coal, petroleum, natural gas, and metallic minerals.

Renewable resources are generally more suitable for sustainable development, but they must also be managed carefully.

Major problems associated with land resources:

• Soil erosion: Removal of fertile topsoil by water or wind.
• Deforestation: Clearing of forests for agriculture, roads, industries, and settlements.
• Desertification: Conversion of productive land into desert-like land due to climatic and human factors.
• Land degradation: Decline in soil fertility caused by overgrazing, mining, salinity, and excessive use of chemicals.
• Urbanization: Conversion of agricultural and natural land into built-up areas.
• Waterlogging and salinity: Excess irrigation may reduce soil productivity.

Remedial measures:

• Practice contour ploughing, terracing, and strip cropping.
• Plant trees and grasses through afforestation and shelterbelts.
• Control overgrazing and adopt rotational grazing.
• Use organic manure, compost, and balanced fertilizers.
• Promote rainwater harvesting and efficient irrigation.
• Reclaim mined, saline, and degraded land.
• Follow proper land-use planning and reduce unnecessary urban expansion.

These measures conserve soil, maintain fertility, and support sustainable land use.

Soil erosion is the removal of the upper fertile layer of soil by agents such as water, wind, and human activities.

Causes:

• Deforestation and removal of vegetation.
• Overgrazing and improper agricultural practices.
• Heavy rainfall, floods, and strong winds.
• Construction, mining, and road development.
• Ploughing along the slope instead of across it.

Effects:

• Loss of fertile topsoil and agricultural productivity.
• Siltation of rivers, reservoirs, and irrigation channels.
• Increased floods and reduced groundwater recharge.
• Desertification and loss of soil biodiversity.
• Nutrient depletion and food insecurity.

Control measures:

• Afforestation and maintenance of grass cover.
• Contour ploughing and terracing on slopes.
• Strip cropping and shelterbelt plantation.
• Mulching and conservation tillage.
• Check dams, bunds, and gully plugging.
• Controlled grazing and appropriate land-use planning.

Effective soil conservation combines vegetation management, engineering methods, and responsible farming.

Problems related to water resources:

• Water scarcity: Caused by population growth, overuse, drought, and unequal distribution.
• Water pollution: Results from domestic sewage, industrial effluents, agricultural chemicals, and solid waste.
• Groundwater depletion: Caused by excessive pumping for irrigation and urban use.
• Floods and droughts: Arise from climatic variation, deforestation, poor drainage, and mismanagement.
• Salinity and waterlogging: Often result from improper irrigation.
• Conflicts: Competition may occur among domestic, agricultural, industrial, and ecological users.

Conservation measures:

• Construct rainwater harvesting systems and recharge pits.
• Use drip and sprinkler irrigation.
• Reuse and recycle treated wastewater.
• Prevent discharge of untreated sewage and industrial waste.
• Protect wetlands, watersheds, rivers, and catchment areas.
• Promote water-efficient appliances and public awareness.
• Adopt integrated water-resource management.

Water conservation requires both technological solutions and responsible individual behavior.

Rainwater harvesting is the collection, storage, and use of rainwater before it flows away as surface runoff.

Major methods:

• Rooftop harvesting: Rainwater from roofs is collected through gutters and stored in tanks.
• Groundwater recharge: Water is directed into recharge pits, wells, trenches, or percolation tanks.
• Surface runoff harvesting: Small dams, farm ponds, check dams, and reservoirs store runoff.
• Watershed management: Vegetation, contour bunds, and trenches slow runoff and improve infiltration.

Significance:

• Increases the availability of water during dry periods.
• Recharges depleted groundwater reserves.
• Reduces dependence on municipal and surface-water supplies.
• Controls soil erosion, flooding, and runoff.
• Improves water security in rural and urban areas.
• Reduces energy used for pumping water from distant sources.

Rainwater harvesting is a simple, decentralized, and sustainable water-management practice.

Forests are renewable biological resources that provide ecological, economic, and social benefits.

Importance of forests:

• Produce timber, fuelwood, bamboo, fibers, fruits, medicines, and other products.
• Absorb carbon dioxide and release oxygen through photosynthesis.
• Regulate temperature, rainfall, humidity, and the water cycle.
• Prevent soil erosion, floods, landslides, and desertification.
• Provide habitats for wildlife and conserve biodiversity.
• Support the livelihoods and cultures of forest-dependent communities.

Problems caused by deforestation:

• Loss of biodiversity and wildlife habitat.
• Soil erosion, land degradation, and desertification.
• Increase in atmospheric carbon dioxide and climate change.
• Disturbance of rainfall patterns and groundwater recharge.
• Increased floods, droughts, and landslides.
• Displacement of indigenous and forest-dependent communities.

Sustainable forest management and restoration are necessary to maintain these benefits.

Causes of deforestation:

• Expansion of agriculture, plantations, and cattle grazing.
• Logging for timber, paper, and fuelwood.
• Mining, industries, roads, dams, and urban development.
• Forest fires, shifting cultivation, and illegal encroachment.
• Overpopulation and excessive dependence on forest products.

Remedial measures:

• Undertake afforestation and reforestation using native species.
• Implement social forestry, agroforestry, and community forestry.
• Control illegal logging and enforce forest-protection laws.
• Promote sustainable harvesting and certification of forest products.
• Reduce fuelwood consumption through improved cookstoves and alternative energy.
• Prevent and manage forest fires.
• Involve local communities in planning and forest management.
• Establish protected areas and wildlife corridors.
• Rehabilitate mined and degraded forest land.

Forest conservation is most successful when ecological protection is combined with the livelihood needs of local communities.

Energy resources may be classified as renewable and non-renewable resources.

Renewable energy resources:

• Solar, wind, hydropower, geothermal, tidal, and biomass energy.
• These resources are naturally replenished and generally produce fewer emissions.

Non-renewable or conventional resources:

• Coal, petroleum, natural gas, and nuclear fuels.
• They are finite and are widely used for electricity, transportation, and industry.

Environmental problems of conventional energy:

• Burning coal, oil, and gas releases carbon dioxide, causing global warming.
• Sulfur and nitrogen oxides contribute to acid rain and respiratory illness.
• Particulate matter causes air pollution and health problems.
• Mining damages land, destroys habitats, and may contaminate water.
• Oil extraction and transport can cause spills and marine pollution.
• Thermal power plants generate fly ash and heated wastewater.
• Nuclear energy produces radioactive waste and involves accident risks.

Energy efficiency and a transition to cleaner renewable sources can reduce these impacts.

Renewable energy resources are naturally replenished, whereas non-renewable energy resources are finite and take very long periods to form.

Renewable energy is important because it reduces greenhouse-gas emissions, improves energy security, decreases dependence on imported fuels, creates employment, and supports decentralized electricity generation. However, renewable systems must be carefully planned because they may require land, storage, transmission infrastructure, and responsible management of ecological impacts.

Individuals can significantly support conservation through responsible choices and daily practices.

Water conservation:

• Repair leaking taps and use water-efficient fixtures.
• Avoid unnecessary water use and harvest rainwater.
• Reuse suitable household water for gardening and cleaning.

Energy conservation:

• Switch off lights and appliances when not in use.
• Use energy-efficient appliances and public transport.
• Prefer renewable energy where possible.

Land and forest conservation:

• Reduce paper use and choose recycled products.
• Plant and protect native trees.
• Avoid littering, burning waste, and damaging vegetation.

Waste reduction:

• Follow the principles of reduce, reuse, repair, and recycle.
• Separate biodegradable, recyclable, and hazardous waste.
• Compost kitchen waste and avoid single-use plastics.

Responsible citizenship:

• Participate in environmental campaigns and local conservation programs.
• Report illegal logging, pollution, and wildlife crimes.
• Educate others and support sustainable products and policies.

Collective individual action can reduce resource consumption and promote sustainable living.

An ecosystem is a functional unit in which living organisms interact with one another and with the non-living components of their environment.

Structure of an ecosystem:

• Abiotic components: Light, temperature, air, water, soil, minerals, and nutrients.
• Biotic components:
  • Producers: Green plants and algae that prepare food by photosynthesis.
  • Consumers: Herbivores, carnivores, omnivores, and other organisms that depend on food produced by others.
  • Decomposers: Bacteria and fungi that break down dead organic matter.
  • Detritivores: Organisms such as earthworms that fragment dead material.

Functions of an ecosystem:

• Energy capture and transfer through food chains.
• Decomposition of dead organisms and waste.
• Recycling of nutrients such as carbon, nitrogen, and phosphorus.
• Regulation of populations and ecological balance.
• Provision of services such as soil formation, water purification, climate regulation, and habitat support.

Ecosystems remain functional through continuous interaction between biotic and abiotic components.

Ecosystems may be classified into natural and artificial ecosystems.

1. Natural ecosystems

Terrestrial ecosystems: These occur on land.

• Forest ecosystem: Dominated by trees and contains several vertical layers.
• Grassland ecosystem: Dominated by grasses and supports grazing animals.
• Desert ecosystem: Has low rainfall, sparse vegetation, and organisms adapted to water scarcity.
• Tundra ecosystem: Has very low temperatures, frozen soil, and short vegetation.

Aquatic ecosystems: These occur in water.

• Freshwater ecosystems: Ponds, lakes, rivers, streams, and wetlands.
• Marine ecosystems: Oceans, estuaries, coral reefs, and coastal areas.

2. Artificial ecosystems
These are created and maintained by humans.

• Crop fields, gardens, aquariums, reservoirs, and urban parks.
• They usually require external inputs such as irrigation, fertilizers, and pest control.

Each ecosystem has characteristic abiotic conditions, organisms, food relationships, and nutrient cycles.

Energy flow is the movement of energy through an ecosystem from the Sun to producers and then to consumers and decomposers.

Sequence of energy flow:

• Green plants capture solar energy through photosynthesis.
• Herbivores obtain energy by feeding on plants.
• Carnivores obtain energy by feeding on herbivores or other carnivores.
• Decomposers obtain energy from dead organisms and organic wastes.

The flow can be represented as:

Major characteristics:

• Energy flow is unidirectional and does not cycle back to the Sun.
• At each trophic level, much energy is lost as heat through respiration and metabolism.
• Only a small fraction is transferred to the next trophic level. According to the ten-percent law, approximately of energy may be transferred between successive trophic levels.
• Energy flow supports growth, reproduction, movement, and other life processes.

Thus, energy decreases at higher trophic levels, limiting the length of food chains.

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

1. Grazing food chain:
It begins with living green plants and proceeds through herbivores and carnivores.

Example:

2. Detritus food chain:
It begins with dead organic matter or detritus and proceeds through decomposers and detritivores.

Example:

Importance:

• Shows feeding relationships among organisms.
• Explains the transfer of energy and nutrients.
• Connects different trophic levels.
• Helps identify the effects of removing or adding a species.

Food chains are usually short because considerable energy is lost at each trophic level.

A food chain is a single, linear pathway of energy transfer, whereas a food web is a network of interconnected food chains.

Importance of food webs:

• Represent the complex feeding relationships in an ecosystem.
• Provide alternative pathways for energy transfer.
• Increase ecosystem stability because a consumer may shift to another food source if one species declines.
• Help explain population regulation and predator-prey interactions.
• Show how changes in one species can affect many other species.

Food webs therefore provide a more realistic description of ecosystem feeding relationships than simple food chains.

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

1. Pyramid of numbers:

• Represents the number of organisms at each trophic level.
• It may be upright, inverted, or spindle-shaped.
• For example, one large tree may support many insects, producing an inverted pyramid of numbers.

2. Pyramid of biomass:

• Represents the total mass of living organisms at each trophic level.
• It is generally upright in terrestrial ecosystems.
• It may be inverted in some aquatic ecosystems because phytoplankton have a low standing biomass but reproduce rapidly.

3. Pyramid of energy:

• Represents the energy available at each trophic level over a given period.
• It is always upright because energy is lost as heat at every transfer.
• Its units may be expressed as energy per area per time, such as .

Ecological pyramids help compare trophic levels and demonstrate the decreasing availability of energy toward higher consumers.

Ecological succession is the gradual, predictable, and usually natural change in the species composition and structure of a community over time, leading toward a relatively stable community.

General stages:

• Nudation: Formation of a bare area due to erosion, fire, volcanic activity, floods, or human disturbance.
• Invasion: Arrival of propagules such as seeds, spores, or organisms.
• Ecesis: Successful establishment and growth of pioneer species.
• Competition and coaction: Organisms compete and interact with one another.
• Reaction: The community modifies the environment, making it suitable for other species.
• Stabilization: A relatively stable climax community develops.

Types:

• Primary succession: Begins on a previously lifeless surface without soil, such as bare rock. It is slow because soil must first develop.
• Secondary succession: Begins in an area where a previous community has been disturbed but soil remains, such as an abandoned field. It is faster than primary succession.

Succession increases soil development, biodiversity, biomass, and ecosystem complexity.

Primary succession on bare rock occurs in an area where no soil, organic matter, or established organisms are initially present.

Stages:

• Bare rock: The surface is exposed and lacks soil.
• Pioneer stage: Lichens colonize the rock. They secrete acids and physically break down the surface.
• Moss stage: Weathered rock particles combine with dead organic matter to form a thin layer of soil. Mosses become established.
• Herb and grass stage: Herbs and grasses grow as soil depth and nutrient availability increase.
• Shrub stage: Shrubs develop and further improve soil conditions.
• Forest stage: Trees establish where climate and soil permit.
• Climax community: A relatively stable and self-maintaining community develops.

At each stage, organisms modify the environment through weathering, organic-matter accumulation, shading, and nutrient cycling. The process may take hundreds or thousands of years and is influenced by climate, soil, disturbance, and species interactions.

Biodiversity includes the variety of genes, species, and ecosystems in a region. Its conservation is closely connected with sustainable management of natural resources.

Relationship:

• Diverse ecosystems are generally more resilient to drought, disease, climate change, and disturbances.
• Forests, wetlands, grasslands, and oceans provide food, medicines, pollination, soil formation, water purification, and climate regulation.
• Genetic diversity improves the ability of crops, livestock, and wild species to adapt to environmental changes.
• Sustainable harvesting maintains resource availability while preventing depletion.
• Conserving habitats protects species and maintains food webs and nutrient cycles.

Management approaches:

• Establish protected areas and wildlife corridors.
• Promote sustainable forestry, fisheries, and agriculture.
• Prevent overexploitation, pollution, invasive species, and habitat destruction.
• Restore degraded ecosystems using native species.
• Involve local and indigenous communities in conservation.
• Apply the principles of reduce, reuse, recycle, and efficient resource use.

Thus, biodiversity conservation supports ecological stability, human welfare, and the long-term availability of natural resources.