13th Aug-Environmental Science

Which process converts atmospheric nitrogen (N₂) into forms usable by plants?

• Photosynthesis
• Nitrogen fixation
• Respiration
• Denitrification

Answer explanation

Nitrogen fixation (by microbes or lightning) converts N₂ to bioavailable forms.

Ocean acidification results primarily from:

• Increased salinity
• Oil spills

• Higher temperatures alone
• CO₂ dissolving into seawate

Answer explanation

CO₂ forms carbonic acid when dissolved, lowering ocean pH.

The term 'albedo' refers to:

• Fraction of sunlight reflected

• Soil fertility

• Photosynthesis rate
• Water retention

Answer explanation

Albedo measures reflectivity; ice has high albedo.

Which biome stores the most carbon per unit area?

• Tropical rainforest
• Temperate grassland
• Desert
• Tundra (peatlands)

Answer explanation

Peatlands and permafrost in tundra store huge carbon in soils.

Coral bleaching is caused when:

• Corals reproduce too quickly
• Symbiotic algae are expelled due to stress
• Corals get too much plankton
• Algae overgrow reef

Answer explanation

Stress (usually warming) causes corals to expel zooxanthellae, bleaching them.

Eutrophication in lakes is principally due to:

• Excess oxygen
• High fish population

• Excess nutrients causing algal blooms

• Increased salinity

Answer explanation

Nutrient runoff spurs algal blooms which lead to oxygen depletion.

Which renewable energy has the highest energy density per unit area?

• Solar PV
• Wind
• Hydropower (large dams)
• Biomass

Answer explanation

Hydropower can generate large energy from concentrated water flows per area.

The keystone species concept means:

• Species with disproportionate ecosystem effect

• Largest biomass species

• Recently discovered species
• Dominant predator only

Answer explanation

Keystones hold ecosystems together; their removal causes major change.

Urban heat islands are primarily caused by:

• Heat retention by concrete/asphalt

• High tree cover

• Increased rainfall
• Underground minerals

Answer explanation

Built surfaces and waste heat elevate urban temperatures relative to rural areas.

'Biomagnification' refers to:

• Increase in biodiversity
• Increase in pollutant concentration up the food chain
• Growth of biomass in farms
• Genetic magnification

Answer explanation

Toxins like mercury concentrate at higher trophic levels.