Unit 2: Natural resources and ecosystem - Subjective Questions

Natural resources are materials, substances, and environmental conditions obtained from nature and used by living organisms, especially humans, to satisfy their needs. Examples include air, water, soil, forests, minerals, wildlife, and energy resources.

Importance of natural resources:

• They provide essential requirements such as food, water, oxygen, and shelter.
• Soil, water, and sunlight support agriculture and food production.
• Forests provide timber, fuelwood, medicinal plants, fruits, and fibres.
• Minerals and fossil fuels support industries, transport, and construction.
• Natural ecosystems regulate climate, purify water, control floods, and maintain biodiversity.
• They provide employment and support economic development.

However, excessive exploitation, pollution, and population growth can lead to resource depletion and ecological imbalance. Therefore, natural resources must be used judiciously 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, forests, freshwater, and wildlife.

Non-renewable resources are resources available in limited quantities and formed over geological periods. Their rate of formation is much slower than their rate of consumption. Examples include coal, petroleum, natural gas, metallic minerals, and nuclear fuels.

Renewable resources are not always unlimited. For example, groundwater and forests can become depleted if their rate of use exceeds their rate of regeneration.

Land is required for agriculture, forests, settlements, industries, transport, and wildlife habitats. Unsustainable land use creates several environmental problems.

Major problems:

• Soil erosion: Removal of fertile topsoil by wind and water.
• Deforestation: Conversion of forest land for agriculture, mining, and construction.
• Desertification: Decline in land productivity in dry areas due to climatic and human factors.
• Land degradation: Loss of soil fertility because of salinity, waterlogging, overgrazing, and excessive chemical use.
• Urbanization and encroachment: Conversion of agricultural and natural land into built-up areas.
• Mining and industrial activities: Destruction of vegetation and contamination of soil.

Remedial measures:

• Adopt contour ploughing, terracing, strip cropping, and plantation of shelterbelts.
• Promote afforestation, reforestation, and social forestry.
• Control overgrazing and encourage rotational grazing.
• Use organic manure, crop rotation, and integrated nutrient management.
• Reclaim saline and waterlogged soils through proper drainage.
• Restore mined land and regulate mining activities.
• Follow scientific land-use planning and prevent unnecessary conversion of fertile land.

Soil erosion is the detachment and transport of the upper fertile layer of soil by agents such as water and wind.

Causes:

• Deforestation and removal of vegetation cover.
• Overgrazing by livestock.
• Intensive agriculture and improper ploughing.
• Construction, mining, and road development.
• Heavy rainfall, floods, and strong winds.

Effects:

• Loss of fertile topsoil and soil nutrients.
• Reduction in agricultural productivity.
• Siltation of rivers, reservoirs, and canals.
• Increased flooding and reduced groundwater recharge.
• Expansion of barren and desert-like areas.

Control measures:

• Plant trees and grasses to bind the soil.
• Use contour farming and terrace cultivation on slopes.
• Construct check dams, bunds, and gully plugs.
• Practice strip cropping and maintain crop residues.
• Develop shelterbelts to reduce wind velocity.
• Control overgrazing and regulate construction activities.

Effective soil conservation combines vegetation restoration, engineering methods, and proper land management.

Water resources include surface water from rivers, lakes, and reservoirs, as well as groundwater. Increasing demand and poor management have created serious problems.

Major problems:

• Water scarcity caused by population growth, urbanization, and overuse.
• Groundwater depletion due to excessive pumping.
• Pollution from domestic sewage, industrial effluents, fertilizers, pesticides, and plastics.
• Eutrophication caused by excess nutrients in water bodies.
• Floods due to deforestation, encroachment, and poor drainage.
• Droughts resulting from low rainfall, climate variability, and inefficient water use.
• Salinity intrusion in coastal groundwater.

Remedial measures:

• Harvest rainwater and recharge groundwater.
• Treat domestic sewage and industrial wastewater before discharge.
• Promote drip and sprinkler irrigation.
• Reuse and recycle water wherever possible.
• Protect wetlands, lakes, rivers, and catchment areas.
• Prevent dumping and regulate agricultural chemicals.
• Adopt watershed management and efficient irrigation practices.
• Encourage public participation and water conservation at the household level.

Rainwater harvesting is the collection, storage, and utilization of rainwater from rooftops, open land, and other surfaces.

Important methods:

• Rooftop harvesting: Rainwater is collected through gutters and directed into storage tanks or recharge pits.
• Surface runoff harvesting: Runoff is collected in ponds, reservoirs, check dams, and farm tanks.
• Groundwater recharge: Recharge wells, percolation pits, recharge trenches, and infiltration basins allow water to enter underground aquifers.
• Watershed structures: Contour bunds and small dams slow runoff and increase infiltration.

Importance:

• Reduces dependence on municipal supplies and groundwater.
• Raises the groundwater table.
• Reduces soil erosion and urban flooding.
• Provides water during dry periods.
• Improves local water security.
• Reduces energy use associated with pumping and transporting water.

Rainwater should be filtered before storage or recharge, and storage structures should be cleaned regularly to maintain water quality.

Forests are complex ecosystems dominated by trees, shrubs, herbs, animals, microorganisms, and soil organisms.

Ecological importance:

• Absorb carbon dioxide and release oxygen through photosynthesis.
• Regulate temperature, rainfall, humidity, and the water cycle.
• Prevent soil erosion and landslides.
• Recharge groundwater and reduce floods.
• Provide habitat for wildlife and conserve biodiversity.
• Maintain nutrient cycling and ecological balance.

Economic and social importance:

• Provide timber, fuelwood, bamboo, fibres, fruits, gums, resins, and medicines.
• Support forest-dependent communities and employment.
• Provide opportunities for recreation and ecotourism.

Problems caused by deforestation:

• Habitat destruction and loss of biodiversity.
• Soil erosion, floods, and desertification.
• Increased atmospheric carbon dioxide and climate change.
• Disruption of rainfall and groundwater recharge.
• Loss of livelihood and displacement of forest communities.

Conservation requires protected areas, sustainable harvesting, afforestation, community forestry, and strict control of illegal logging.

Causes of deforestation:

• Expansion of agriculture, plantations, and cattle grazing.
• Urbanization, industrialization, mining, and infrastructure development.
• Construction of roads, dams, railways, and settlements.
• Commercial logging and illegal felling.
• Collection of fuelwood and overexploitation of forest products.
• Forest fires, shifting cultivation, and population pressure.

Measures for forest conservation:

• Promote afforestation and reforestation using suitable native species.
• Establish national parks, wildlife sanctuaries, and biosphere reserves.
• Implement sustainable forest management and selective cutting.
• Encourage agroforestry, social forestry, and farm forestry.
• Involve local communities through joint forest management.
• Reduce dependence on fuelwood by using improved cookstoves and alternative energy.
• Prevent illegal logging and control forest fires.
• Recycle paper and wood products.
• Conduct environmental impact assessments before major development projects.

Forest conservation is most successful when ecological needs and the livelihood requirements of local communities are addressed together.

Energy resources are classified according to their availability, origin, and use.

Major classifications:

• Renewable sources: Solar, wind, hydropower, biomass, tidal, and geothermal energy.
• Non-renewable sources: Coal, petroleum, natural gas, and nuclear fuels.
• Conventional sources: Coal, petroleum, natural gas, large hydropower, and firewood, which have traditionally been used on a large scale.
• Non-conventional sources: Solar, wind, tidal, wave, geothermal, biogas, and other relatively newer alternatives.

A sustainable energy system should improve energy efficiency and gradually increase the use of clean renewable sources.

Problems caused by fossil fuels:

• Burning coal, petroleum, and natural gas releases carbon dioxide, causing global warming.
• Sulfur and nitrogen oxides contribute to acid rain.
• Particulate matter causes respiratory and cardiovascular diseases.
• Mining destroys land, forests, and habitats.
• Oil spills contaminate marine and coastal ecosystems.
• Fossil fuels are finite and unequally distributed.

Problems associated with nuclear energy:

• Radioactive waste remains hazardous for long periods.
• Accidents can release radiation and contaminate large areas.
• Uranium mining damages land and may pollute water.
• Nuclear plants require strict safety and waste-management systems.

Remedial measures:

• Improve energy efficiency and reduce unnecessary consumption.
• Shift toward solar, wind, small hydropower, and other renewable sources.
• Use cleaner fuels and pollution-control devices.
• Enforce emission standards and monitor air quality.
• Reclaim mined land and prevent oil spills.
• Store and dispose of radioactive waste in secure, scientifically designed facilities.
• Maintain strict safety regulations and emergency preparedness for nuclear installations.

Individuals play an important role because daily choices influence the demand for natural resources.

Ways to conserve resources:

• Follow the principles of refuse, reduce, reuse, repair, and recycle.
• Save electricity by using efficient appliances and switching off unused devices.
• Use public transport, walking, cycling, and carpooling whenever possible.
• Avoid wastage of water, repair leaking taps, and use water-efficient fixtures.
• Harvest rainwater and reuse greywater where safe.
• Plant and protect native trees.
• Avoid single-use plastics and carry reusable bags and bottles.
• Purchase durable, energy-efficient, and locally produced goods.
• Segregate waste at source and compost biodegradable waste.
• Use paper carefully and support recycled products.
• Prevent littering and participate in local clean-up drives.
• Report illegal logging, wildlife trade, pollution, and water wastage.
• Educate family and community members about conservation.

Individual action becomes more effective when supported by community participation, environmental laws, and sustainable public policies.

An ecosystem is a functional unit of nature 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, nutrients, and organic matter.
• Biotic components:
  • Producers: Green plants and algae that prepare food through photosynthesis.
  • Consumers: Herbivores, carnivores, omnivores, and other organisms that depend on producers or other consumers.
  • Decomposers: Bacteria and fungi that break down dead organic matter.

Functions of an ecosystem:

• Capture and transfer energy through food chains and food webs.
• Recycle nutrients such as carbon, nitrogen, phosphorus, and water.
• Decompose dead matter and return nutrients to the environment.
• Maintain population interactions and ecological balance.
• Provide ecosystem services such as soil formation, water purification, climate regulation, and habitat provision.

An ecosystem remains stable when energy flow and material cycling operate effectively.

Ecosystems may be classified into natural and artificial ecosystems.

1. Natural ecosystems

• Terrestrial ecosystems: These occur on land.
  • Forest ecosystems contain trees, diverse animals, microorganisms, and layered vegetation.
  • Grassland ecosystems are dominated by grasses and support herbivores and grazing food chains.
  • Desert ecosystems receive very little rainfall and contain organisms adapted to water scarcity.
  • Tundra ecosystems have low temperatures, frozen soils, and short growing seasons.
• Aquatic ecosystems: These occur in water.
  • Freshwater ecosystems include ponds, lakes, rivers, streams, and wetlands.
  • Marine ecosystems include oceans, estuaries, coral reefs, and mangroves.

2. Artificial ecosystems
These are created or strongly managed by humans. Examples include crop fields, gardens, aquariums, reservoirs, and urban ecosystems.

Natural ecosystems generally have greater biodiversity and self-regulation, whereas artificial ecosystems often require continuous human inputs such as irrigation, fertilizers, pesticides, or feed.

Energy enters most ecosystems as sunlight. Green plants capture a portion of solar energy through photosynthesis and convert it into chemical energy stored in organic food.

The general pathway is:

At every trophic level, much energy is used in respiration, movement, growth, and reproduction. A large part is released as heat, so only a small fraction is transferred to the next trophic level. According to the approximate ten-percent law, about of the energy at one trophic level may be transferred to the next level, although the actual value varies.

Characteristics:

• Energy flow is unidirectional.
• Energy enters mainly as solar radiation and is eventually lost as heat.
• Energy decreases at successive trophic levels.
• Decomposers obtain energy from dead organic matter but do not return energy to the Sun.
• Unlike nutrients, energy is not recycled within the ecosystem.

This explains why food chains are usually short and why top consumers are fewer in number.

A food chain is a linear sequence in which food and energy pass from one organism to another.

Types of food chains:

• Grazing food chain: Begins with living green plants, followed by herbivores and carnivores. Example: grass → grasshopper → frog → snake → hawk.
• Detritus food chain: Begins with dead organic matter and proceeds through decomposers and detritivores. Example: leaf litter → earthworm → bird.

A food web is a network of interconnected food chains. It shows that most organisms consume more than one type of food and may be eaten by several predators.

Ecological significance:

• Transfer energy between trophic levels.
• Describe feeding relationships among organisms.
• Help regulate population sizes.
• Support nutrient cycling through consumers and decomposers.
• Increase ecosystem stability because alternative food pathways may be available.
• Show the effects of removing or introducing a species.

Food webs are generally more realistic than simple food chains because natural ecosystems contain complex feeding relationships.

An ecological pyramid is a graphical representation of the trophic structure of an ecosystem. Producers form the first trophic level, followed by primary, secondary, and higher consumers.

1. Pyramid of numbers:
It represents the number of organisms at each trophic level. It is generally upright in a grassland but may be inverted in a tree ecosystem, where one tree supports many herbivores.

2. Pyramid of biomass:
It represents the total mass of living organisms at each trophic level. It is usually upright in terrestrial ecosystems but may be inverted in aquatic ecosystems because the standing biomass of phytoplankton can be lower than that of zooplankton at a particular time.

3. Pyramid of energy:
It represents the energy available at each trophic level per unit area and time. It is always upright because energy decreases as it moves upward due to respiration and heat loss.

Limitations:

• Pyramids may not show complex food webs.
• Decomposers are often excluded.
• A single organism may occupy more than one trophic level.
• Number and biomass do not always accurately represent energy transfer.

The pyramid of energy is considered the most reliable representation of ecosystem function.

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

Major stages:

• Nudation: Formation of a bare area due to volcanic activity, erosion, fire, cultivation, or other disturbances.
• Invasion: Arrival of propagules such as seeds, spores, or organisms from surrounding areas.
• Ecesis: Successful establishment and growth of pioneer species.
• Aggregation: Increase and grouping of individuals of the pioneer species.
• Competition and coaction: Organisms compete for light, water, nutrients, and space.
• Reaction: The community modifies the environment, making it more suitable for some species and less suitable for others.
• Stabilization: A relatively stable community develops, often called the climax community.

Succession may be primary, beginning on a previously lifeless surface such as bare rock, or secondary, beginning in an area where a previous community was disturbed but soil remains. Succession contributes to soil development, biodiversity, and ecosystem stability.

Both processes involve changes in species composition, competition, environmental modification, and eventual development of a relatively stable community. Secondary succession generally reaches a mature stage more quickly than primary succession.

Nutrient cycling is the movement and recycling of essential elements between the abiotic environment and living organisms. Important cycles include the carbon, nitrogen, phosphorus, and water cycles.

General process:

• Producers absorb inorganic nutrients from soil, water, or air.
• Consumers obtain nutrients by feeding on producers or other consumers.
• Decomposers break down dead organisms and wastes.
• Nutrients are released in inorganic forms and become available to producers again.

Decomposers are essential because they return nutrients to the soil and water. Human activities such as deforestation, fossil-fuel combustion, excessive fertilizer use, and pollution can disturb natural cycles.

Overexploitation occurs when natural resources are used faster than their natural regeneration or replenishment.

Effects on ecosystems:

• Depletion of forests, fisheries, minerals, fossil fuels, and groundwater.
• Habitat destruction and fragmentation.
• Decline in biodiversity and extinction of species.
• Soil erosion, desertification, and loss of fertility.
• Water scarcity and deterioration of water quality.
• Increased greenhouse gas emissions and climate change.
• Disruption of food chains, nutrient cycles, and ecosystem services.
• Conflicts and livelihood problems among resource-dependent communities.

Strategies for sustainable management:

• Determine sustainable yields and regulate extraction.
• Use renewable resources within their regeneration limits.
• Improve efficiency and reduce waste.
• Recycle metals, paper, plastics, and water.
• Promote afforestation, watershed management, and soil conservation.
• Establish protected areas and conserve biodiversity.
• Use renewable energy and cleaner technologies.
• Conduct environmental impact assessments before development projects.
• Involve local communities in planning and decision-making.
• Strengthen environmental laws, monitoring, and public awareness.

Sustainable management aims to meet present needs without reducing the ability of future generations to meet their own needs.