Biota and Environment (Zoology): animal adaptation, behaviour and migration, pollution

Consequences of overuse of pesticides in the locality (any three):

1. Soil and water pollution — Pesticides that are not absorbed by crops leach into the soil and are washed into ponds, streams and wells. This contaminates drinking water and kills useful soil organisms such as earthworms and nitrogen-fixing bacteria, reducing soil fertility.

2. Harm to non-target organisms and biodiversity loss — Pesticides kill beneficial insects (bees, butterflies, ladybirds) along with the pests. Loss of pollinators reduces crop yield, and birds and fish that feed on poisoned insects also die, disturbing the food chain.

3. Bioaccumulation and health hazards in humans — Pesticide residues accumulate in crops, vegetables, milk and meat. People consuming these suffer from acute poisoning, skin and eye irritation, respiratory problems, and long-term effects such as cancer, infertility and damage to the liver and kidney. Farmers handling pesticides without safety measures are at greatest risk.

4. Development of pesticide-resistant pests — Continuous overuse allows resistant varieties of pests to survive and multiply, so stronger and more toxic pesticides become necessary, worsening the problem.

Awareness campaign to be followed (any two):

1. Organise community awareness programmes — Conduct door-to-door campaigns, street dramas, posters, pamphlets and local radio/FM programmes to inform farmers about the harmful effects of excessive pesticides and the safe handling practices (wearing masks, gloves, full-sleeve clothes, and never eating or smoking while spraying).

2. Promote eco-friendly alternatives through training and demonstration — Train farmers in Integrated Pest Management (IPM), use of bio-pesticides, neem-based preparations, crop rotation, and biological control by natural predators. Demonstrate organic farming in a model plot so that farmers can see that good yields are possible without heavy pesticide use.

(b) Chlorofluorocarbons (CFCs)

In the stratosphere, UV radiation breaks CFCs and releases chlorine atoms. Each chlorine atom catalytically destroys many ozone molecules, thinning the ozone layer.

(c) Behavioral adaptation

Hibernation (winter sleep) is a change in behaviour, in which the animal hides in a burrow or shelter and stays inactive to survive cold and food scarcity. It is therefore classed as a behavioral adaptation.

(b) Hibernation

Ectotherms such as frogs, snakes and lizards cannot keep their body temperature constant, so in severe cold they retreat to burrows or mud and become inactive (hibernation). Estivation is the corresponding summer dormancy, migration is seasonal movement and mimicry is resemblance to another organism.

(c) Aves (Birds)

Birds have light, hollow bones with air cavities connected to the air sacs of the respiratory system. These pneumatic bones reduce body weight and make flight easier.

Causes of environmental pollution in Nepal and management strategies (2+3 marks)

Major causes of pollution in Nepal (2 marks)

1. Rapid urbanisation and vehicles: old vehicles and heavy traffic emit smoke, dust and carbon monoxide, which cause severe air pollution in the Kathmandu Valley.
2. Industries and brick kilns: factories and brick kilns release smoke, $\text{SO}_2$ and particulate matter, and discharge effluents into rivers.
3. Solid waste and sewage: untreated household waste and sewage are dumped in rivers (the Bagmati), polluting water.
4. Agricultural chemicals: excess chemical fertilisers and pesticides contaminate soil and water.
5. Deforestation, burning of biomass and construction dust also add to pollution.

Management strategies (3 marks)

1. Waste management: segregate waste (the 3 Rs: reduce, reuse, recycle), compost organic waste and treat sewage before release.
2. Control of air pollution: introduce emission standards, ban old vehicles, promote electric vehicles and public transport, use cleaner fuels, and plant trees.
3. Laws and awareness: enforce environment protection laws (the Environment Protection Act), the "polluter pays" principle, and teach communities about pollution and its effects.
4. Safe agriculture: promote organic farming and integrated pest management.

Water pollution is the contamination of water bodies (rivers, lakes, ponds, wetlands, groundwater) by substances that make the water unfit for its normal use and harm living organisms.

Causes of water pollution in local freshwater systems

1. Domestic sewage and wastewater. Untreated sewage, kitchen and washing waste are discharged directly into rivers such as the Bagmati and Bishnumati. They carry organic matter, detergents and disease-causing microbes.
2. Industrial effluents. Factories release heavy metals (lead, mercury, chromium), dyes, acids and oils into streams without treatment.
3. Agricultural runoff. Chemical fertilizers (nitrates, phosphates), pesticides and animal waste are washed from fields into ponds and rivers by rain.
4. Solid waste dumping. Plastics, household garbage and religious or cremation remains are thrown into water bodies.
5. Other sources. Soil erosion and siltation from landslides and construction, oil spills from vehicles and thermal discharge also pollute water.

Environmental consequences

1. Eutrophication. Excess nitrates and phosphates cause algal bloom. When the algae die, bacteria decompose them and use up dissolved oxygen, so fish and other aquatic animals die.
2. Fall in dissolved oxygen. Organic waste raises biochemical oxygen demand (BOD), reducing oxygen for aquatic life.
3. Loss of biodiversity. Sensitive species of fish, insects and plants disappear; only tolerant species survive.
4. Bioaccumulation and biomagnification. Heavy metals and pesticides such as DDT build up along the food chain and reach high concentrations in top consumers, including humans.
5. Water-borne diseases. Cholera, typhoid, dysentery, diarrhoea and hepatitis A spread through contaminated water.
6. Loss of water quality and use. Polluted water becomes unsafe for drinking, irrigation and fisheries, and gives foul odour and poor appearance.

Control: treating sewage and industrial waste before discharge, reducing chemical fertilizers, banning dumping, and public awareness.

Air pollution is the presence of harmful gases, particulates or other substances in the atmosphere in amounts that damage human health, living organisms and the environment.

Major causes in urban Nepal (e.g. Kathmandu Valley)

1. Vehicular emissions. The large number of old, poorly maintained petrol and diesel vehicles emits carbon monoxide, nitrogen oxides, hydrocarbons, sulphur dioxide and particulate matter (PM$_{2.5}$, PM$_{10}$).
2. Road dust and construction. Unpaved or broken roads, road widening and building construction raise large amounts of dust.
3. Brick kilns and industries. Traditional brick kilns burning coal and industries release smoke, SO$_2$ and fine particles.
4. Burning of solid waste and biomass. Open burning of garbage, plastics and crop residue, and the use of firewood and kerosene for cooking, add smoke and toxic gases.
5. Other causes. Forest fires, diesel generators and the valley's bowl-shaped topography, which traps pollutants especially in winter inversion, worsen the problem.

Preventive measures

1. Strict vehicle emission testing, phasing out old vehicles, and promoting electric vehicles and public transport.
2. Using cleaner fuel and better quality standards (low-sulphur fuel).
3. Replacing traditional brick kilns with improved technologies such as zig-zag kilns and installing filters in industries.
4. Paving roads, covering construction sites and regular water sprinkling or cleaning to control dust.
5. Banning open burning of waste and promoting waste segregation and recycling.
6. Promoting clean cooking energy (biogas, LPG, electricity).
7. Planting trees and creating green belts, along with strong laws and public awareness.

Bird migration is the regular seasonal movement of birds from one region to another and back, usually between breeding and wintering areas, in search of food, favourable climate and breeding sites.

Significance of bird migration

1. Escape from harsh climate. Birds avoid severe winter cold and food shortage by moving to warmer regions, which improves their survival.
2. Availability of food. Migration takes birds to areas with abundant insects, seeds, fruits or fish at a given season, so they can feed and build energy reserves.
3. Breeding success. Birds move to safe and suitable breeding grounds with enough food and less competition and predation, so more young are raised.
4. Reduced competition. Moving away spreads the population over a wider area and reduces competition for food and nesting sites.
5. Gene flow and genetic diversity. Mixing of populations from different regions maintains genetic variation and reduces inbreeding.
6. Ecological balance. Migratory birds control insect pests, and help in pollination and seed dispersal in the places they visit.
7. Indicators of environmental change. Changes in timing or routes show climate change and habitat loss, and so help in conservation planning.
8. Economic and scientific value. Migratory birds support bird-watching tourism (for example in Koshi Tappu and Chitwan in Nepal) and are studied by ringing and tracking.