NEB Class 11 Science Environment Science Question Paper 2078 Nepal

Two environmental factors affecting population growth in Nepal: (1) Availability of food and water resources, and (2) Climate and natural disasters (e.g. floods, landslides). Other factors include availability of habitat/space, disease, and predation pressure.

Two examples of K-selected populations: (1) Elephants, and (2) Humans. (Other examples: tigers, whales, large trees — organisms with long lifespan, few offspring, and population near carrying capacity K.)

Two mineral resources found in Nepal: (1) Limestone, and (2) Iron ore. (Others include copper, mica, magnesite, marble, and slate.)

Subtropical forest is the type of forest found in Nepal at an altitude of about 1,000 to 2,000 metres above sea level, in a subtropical climate. It is dominated by species such as Schima-Castanopsis (Chilaune-Katus), Alnus (Utis), and pine (Chir pine).

Ex-situ conservation (off-site conservation) would be suggested — for example, conserving the species in zoos, botanical gardens, gene banks, or captive breeding centres — to protect species that are about to become extinct in the wild.

One way to minimize energy pressure in the locality is to promote the use of renewable energy sources such as solar panels, biogas plants, or improved (fuel-efficient) cooking stoves, thereby reducing dependence on firewood and conventional energy.

One importance of a hunting reserve is that it allows controlled/regulated hunting of selected wildlife species, which generates revenue and promotes tourism while still ensuring conservation and sustainable management of wildlife populations. (Nepal's only hunting reserve is Dhorpatan Hunting Reserve.)

A hazard is a potentially damaging physical event, phenomenon, or human activity that may cause loss of life, injury, property damage, social and economic disruption, or environmental degradation. Examples include earthquakes, floods, landslides, and fires.

One effect of soil erosion is the loss of fertile topsoil, which reduces soil fertility and agricultural productivity. (Other effects: siltation of rivers and reservoirs, landslides, and desertification.)

The WHO standard (guideline value) for arsenic in drinking water is 0.01 mg/L (i.e. 10 µg/L or 10 ppb).

A soil pH below 7 is acidic. Two crops/species suited to acidic soil are: (1) Tea, and (2) Potato. (Other acid-tolerant crops include blueberries, rice, and coffee.)

A closed system is one that exchanges energy but not matter with its surroundings. The Earth behaves as a closed system because:

• Energy exchange: The Earth continuously receives energy from the Sun (solar/radiant energy) and radiates heat energy back into space. Thus energy freely crosses the Earth's boundary.
• No significant matter exchange: The total amount of matter (water, gases, minerals, etc.) on Earth remains essentially constant. Matter is neither significantly gained nor lost (apart from negligible meteorite input and gas escape); it only cycles within the Earth through biogeochemical cycles (water cycle, carbon cycle, nitrogen cycle, etc.).
• Because matter is finite and recycled while energy flows through, Earth is classified as a closed system (as opposed to an open system, which exchanges both matter and energy, or an isolated system, which exchanges neither).

Interactions between species in a community can be classified as positive, negative, or neutral:

Positive interactions — one or both species benefit and none is harmed:

• Mutualism (+/+): both species benefit, e.g. bees and flowering plants.
• Commensalism (+/0): one benefits, the other is unaffected, e.g. orchids growing on tree branches.
• Protocooperation: both benefit but the association is not obligatory.

Negative interactions — at least one species is harmed:

• Predation (+/−): predator benefits, prey is harmed, e.g. tiger and deer.
• Parasitism (+/−): parasite benefits, host is harmed, e.g. tapeworm in humans.
• Competition (−/−): both species are harmed when they compete for the same limited resource.
• Amensalism (−/0): one is harmed, the other unaffected.

Neutral interaction (0/0) — neither species is affected by the presence of the other; they coexist without influencing each other.

Anthropocentric (human-centred) perspective: This view places human beings at the centre of value. Natural resources are seen mainly in terms of their usefulness to humans, and the environment is managed primarily to maximize human benefit and welfare. Example: Cutting forests to obtain timber and clearing land for agriculture or industry because they meet human economic needs.

Eco-centric (ecosystem/nature-centred) perspective: This view places value on nature and the whole ecosystem, recognizing that all living and non-living components have intrinsic worth regardless of their usefulness to humans. Resource management aims at maintaining ecological balance and the integrity of the ecosystem. Example: Conserving a forest as a habitat and for biodiversity, watershed protection, and ecological balance — not merely for timber.

Thus the anthropocentric view treats nature as a resource for human use, whereas the eco-centric view treats humans as just one part of an interconnected ecosystem that must be protected as a whole.

Rara National Park is the smallest national park of Nepal, established in 1976 (2032 BS) and located in the Mugu and Jumla districts of the Karnali Province in the high mountains of north-western Nepal. Its main feature is Rara Lake, the largest and deepest freshwater lake in Nepal, situated at about 2,990 m altitude. The park protects coniferous forests (blue pine, black juniper, spruce) and is home to wildlife such as the red panda, musk deer, Himalayan black bear, and many migratory birds. It is important for biodiversity conservation, watershed protection, and eco-tourism.

Annapurna Conservation Area (ACA) is the largest protected area of Nepal, established in 1986 and managed by the National Trust for Nature Conservation (NTNC). It covers about 7,629 sq km across the Annapurna massif in central-western Nepal. It includes diverse ecosystems ranging from subtropical forests to alpine meadows and high Himalayan zones, and harbours species such as the snow leopard, blue sheep, and many bird species. ACA is notable for its participatory, community-based conservation approach that integrates local people into the management of natural resources, while also being a major destination for trekking and eco-tourism.

Major air pollutants include particulate matter (PM2.5, PM10), carbon monoxide (CO), sulphur dioxide (SO₂), nitrogen oxides (NOx), ground-level ozone, and lead.

Consequences on human beings:

• Respiratory diseases such as asthma, bronchitis, and lung cancer due to inhalation of particulates and toxic gases.
• Cardiovascular problems and reduced lung function.
• Eye, nose, and throat irritation; headaches and reduced immunity.
• CO reduces oxygen-carrying capacity of blood, causing suffocation; lead causes neurological damage.

Consequences on other organisms and the environment:

• Damage to plants — reduced photosynthesis, leaf damage (chlorosis/necrosis) and reduced crop yields.
• Acid rain (from SO₂ and NOx) harms forests, soils, aquatic life, and corrodes buildings.
• Disturbance of ecosystems and reduction of biodiversity.
• Global warming and ozone-layer depletion from greenhouse gases and ozone-depleting substances.

The disaster risk management cycle is a continuous process of planning and activities carried out before, during, and after a disaster to reduce its impact. Its main phases are:

Before the disaster (Pre-disaster):

• Prevention/Mitigation: Measures to eliminate or reduce risk, e.g. constructing dams, retaining walls, and enforcing building codes.
• Preparedness: Activities to be ready to respond, e.g. early-warning systems, training, drills, and stockpiling relief materials.

During the disaster (Response):

• Response: Immediate actions to save lives and property, e.g. search and rescue, evacuation, emergency relief, first aid, and shelter.

After the disaster (Post-disaster):

• Recovery/Rehabilitation: Restoring basic services and helping affected people return to normal life.
• Reconstruction: Rebuilding infrastructure and communities in a safer, more resilient way ("build back better").

These phases form a continuous cycle, with lessons from one disaster feeding into preparedness and mitigation for the next.

Individualization refers to the trend in which people increasingly act as individuals rather than as members of cooperative communities, leading to fragmentation of farmland and weakening of traditional collective farming practices.

Urbanization is the growth of towns and cities and the movement of people from rural to urban areas.

Effects on sustainable agriculture:

• Loss of agricultural land: Urban expansion converts fertile farmland into housing, roads, and industry, reducing the land available for sustainable farming.
• Labour shortage: Migration of youth to cities for jobs leaves fewer people to farm, causing farmland to be abandoned.
• Fragmentation of holdings: Individualization divides land into small, uneconomical plots, making sustainable practices harder to apply.
• Loss of traditional knowledge: Breakdown of community cooperation erodes indigenous, eco-friendly farming techniques.
• Increased demand and intensification: Growing urban populations raise food demand, encouraging excessive use of chemical fertilizers and pesticides, which harms soil and the environment.
• Pollution and resource pressure: Urban waste and water demand reduce the quality and availability of resources for agriculture.

Overall, both individualization and urbanization tend to undermine sustainable agriculture by shrinking and fragmenting farmland, reducing rural labour and cooperation, and intensifying unsustainable practices.

Different chemicals found in the environment include:

• Air pollutants: carbon dioxide (CO₂), carbon monoxide (CO), sulphur dioxide (SO₂), nitrogen oxides (NOx), chlorofluorocarbons (CFCs), and particulate matter.
• Water pollutants: heavy metals (lead, mercury, arsenic, cadmium), nitrates, phosphates, and organic pollutants.
• Soil pollutants: pesticides, herbicides, fertilizers, and persistent organic pollutants (POPs).
• Industrial chemicals: acids, alkalis, solvents, and dyes.

How knowledge of these chemicals helps reduce industrial pollution:

• Identification and monitoring: Knowing which chemicals are released allows industries to monitor and measure their emissions and effluents against standards.
• Treatment and control: Understanding chemical properties enables proper treatment (e.g. neutralizing acidic waste, scrubbing flue gases, treating wastewater before discharge).
• Substitution: Industries can replace hazardous chemicals with safer, eco-friendly alternatives (cleaner production).
• Recycling and recovery: Knowledge of chemical behaviour helps recover and reuse valuable materials, reducing waste.
• Compliance and safety: It helps industries follow environmental regulations, design safe storage/disposal, and protect workers and communities.

Thus, scientific knowledge of environmental chemicals supports prevention, control, and management of industrial pollution.

An ecosystem is a self-sustaining unit in which living organisms (biotic components) interact with each other and with their physical environment (abiotic components).

Structural aspects (4 marks): These describe the composition and arrangement of the ecosystem.

• Abiotic components: non-living physical and chemical factors such as sunlight, temperature, water, air, soil, and inorganic/organic nutrients.
• Biotic components:
  • Producers (autotrophs): green plants and algae that make food through photosynthesis.
  • Consumers (heterotrophs): primary (herbivores, e.g. deer), secondary (carnivores, e.g. frog), and tertiary consumers (top carnivores, e.g. tiger).
  • Decomposers (saprotrophs): bacteria and fungi that break down dead matter.
• Species composition, stratification, and trophic structure describe how organisms are organized. Example: a pond ecosystem with water and dissolved nutrients (abiotic), phytoplankton (producers), zooplankton and fish (consumers), and bacteria (decomposers).

Functional aspects (4 marks): These describe the processes that keep the ecosystem working.

• Energy flow: Solar energy is captured by producers and flows through the food chain/food web in a unidirectional manner (producers → herbivores → carnivores), with energy lost as heat at each trophic level (10% law).
• Nutrient cycling (biogeochemical cycles): Elements such as carbon, nitrogen, and water are recycled between organisms and the environment.
• Food chains, food webs, and ecological pyramids show feeding relationships.
• Productivity and decomposition maintain the balance of matter and energy.

Relating structure and function: The structural components provide the basis for functions — producers (structure) carry out energy capture (function); decomposers (structure) drive nutrient cycling (function). Thus structure and function are interdependent: a change in one (e.g. loss of producers) directly disrupts the other (energy flow and nutrient cycling), and together they maintain the stability and balance of the ecosystem.

Environmental degradation (3 marks): Environmental degradation is the deterioration of the environment through the depletion of natural resources such as air, water, soil, and biodiversity, the destruction of ecosystems, and the extinction of wildlife. It reduces the quality and capacity of the environment to support life and meet human and ecological needs. It can be natural or, more commonly, caused by human activities.

Various causes of environmental degradation (5 marks):

• Population growth: Rapid increase in population raises demand for food, land, water, and energy, increasing pressure on natural resources.
• Deforestation: Clearing forests for agriculture, settlement, and timber leads to loss of habitat, soil erosion, and reduced biodiversity.
• Pollution: Air, water, soil, and noise pollution from industries, vehicles, and waste damages ecosystems and human health.
• Unplanned urbanization and industrialization: Expansion of cities and factories destroys natural land, generates waste, and increases emissions.
• Overexploitation of resources: Excessive mining, fishing, hunting, and use of fossil fuels depletes resources faster than they can regenerate.
• Unsustainable agriculture: Overuse of chemical fertilizers and pesticides, overgrazing, and poor irrigation degrade soil and water.
• Natural causes: Floods, landslides, earthquakes, droughts, and volcanic eruptions also contribute to degradation.
• Climate change: Global warming alters ecosystems, melts glaciers, and causes extreme weather events.

Analysis: Most causes are interlinked and largely driven by human activity and population pressure; tackling environmental degradation therefore requires integrated measures such as afforestation, pollution control, sustainable resource use, and environmental education.

To analyze the water quality of a pond, I would measure physical, chemical, and biological parameters using appropriate instruments, because together they give a complete picture of the water's health.

Physical parameters and instruments:

• Temperature — thermometer; affects dissolved oxygen and aquatic life.
• Turbidity — turbidity meter / Secchi disc; indicates suspended particles and light penetration.
• Colour, odour, and total suspended solids — visual inspection and filtration; indicate pollution.

Chemical parameters and instruments:

• pH — pH meter / litmus or universal indicator; shows acidity/alkalinity, important for aquatic life (ideal range ≈ 6.5–8.5).
• Dissolved oxygen (DO) — DO meter / Winkler titration; essential for aquatic organisms; low DO indicates pollution.
• Biochemical Oxygen Demand (BOD) — BOD incubator and DO measurement; high BOD shows organic pollution.
• Chemical Oxygen Demand (COD) — titration/spectrophotometer; measures total oxidizable pollutants.
• Nitrates, phosphates, and heavy metals — spectrophotometer / colorimeter / titration; indicate nutrient loading (eutrophication) and toxic contamination.
• Total Dissolved Solids (TDS) and conductivity — TDS meter / conductivity meter; show dissolved salts.

Biological parameters and instruments:

• Coliform bacteria (e.g. E. coli) — microscope and culture media (MPN test); indicate faecal contamination and disease risk.
• Plankton and aquatic organisms — microscope; bio-indicators of water quality.

Logic: Physical parameters reveal the appearance and clarity of water; chemical parameters (especially pH, DO, BOD, nutrients, and toxins) reveal the chemical safety and pollution level; biological parameters reveal contamination by pathogens. Measuring all three classes ensures a reliable, complete assessment of whether the pond water is safe and ecologically healthy.