Environmental Biology BZO1T02

Syllabus topics (RTMNU)

• 1.1 Atmosphere: Major zones, importance, composition of air.
• 1.2 Hydrosphere: Global distribution of water, Physico-chemical characteristics of water.
• 1.3 Lithosphere: formation of soil, Causes of soil erosion.
• 1.4 Renewable and non-renewable energy sources.

1.1 Atmosphere: Major zones, importance and composition of air

The atmosphere is the layer of gases surrounding the Earth, held by gravity. It extends to about 500–1000 km, but about 99% of its mass lies within 30–32 km of the surface.

Composition of dry air (by volume)

Air also contains variable amounts of water vapour (0–4%) and suspended particles (dust, pollen, smoke).

Major zones (based on temperature)

Importance of atmosphere

• Provides O₂ for respiration and CO₂ for photosynthesis.
• The ozone layer filters harmful ultraviolet (UV-B, UV-C) rays.
• Keeps the Earth warm (natural greenhouse effect, average ≈ 15 °C instead of about −18 °C).
• Controls weather and climate; distributes heat and moisture; part of the water cycle.
• Protects from meteors; reservoir of nitrogen for the nitrogen cycle.

1.2 Hydrosphere: Global distribution of water and its physico-chemical characteristics

The hydrosphere includes all water on Earth – oceans, seas, rivers, lakes, ground water, ice and water vapour. About 71% of the Earth’s surface is covered by water.

Global distribution

So less than 1% of all water is easily available for human use.

Physical characteristics

• Temperature: affects dissolved oxygen and metabolism; water has high specific heat, so water bodies change temperature slowly.
• Density: maximum at 4 °C, so ice floats and aquatic life survives below the ice in winter.
• Colour, turbidity and transparency: suspended particles reduce light penetration (measured by Secchi disc).
• Taste and odour; total solids (dissolved and suspended); electrical conductivity (indicates dissolved salts).

Chemical characteristics

• pH: natural fresh water 6.5–8.5 is suitable for life.
• Dissolved oxygen (DO): 5–8 mg/L in clean water; below 4 mg/L harms fish.
• Free CO₂: from respiration and decay; high CO₂ means pollution.
• Hardness: due to Ca²⁺ and Mg²⁺ salts – temporary (bicarbonates, removed by boiling) and permanent (sulphates, chlorides).
• Alkalinity, chlorides, nitrates, phosphates (excess nutrients cause eutrophication).
• BOD and COD: measure organic pollution; clean water BOD < 3 mg/L.

1.3 Lithosphere: Formation of soil and causes of soil erosion

The lithosphere is the solid outer layer of the Earth (crust and upper mantle). Soil is its thin, loose top layer made of mineral particles, organic matter (humus), water, air and living organisms.

Formation of soil (pedogenesis)

1. Weathering of parent rock:
   • Physical – temperature changes, freezing–thawing, wind and water break rock into pieces.
   • Chemical – oxidation, hydration, carbonation and solution change minerals.
   • Biological – lichens, mosses, roots and burrowing animals break and mix rock material.
2. Humification: dead plants and animals decompose into dark humus.
3. Translocation and horizon formation: water moves materials down (eluviation) and deposits them (illuviation), forming layers – O (organic), A (top soil), B (sub soil), C (weathered parent rock) and R (bed rock).

Factors of soil formation: parent material, climate, organisms, topography (relief) and time. It takes hundreds of years to form about 2.5 cm of top soil.

Soil erosion

Soil erosion is the removal of the fertile top soil by wind, water or human activity faster than it can form.

• Natural causes: heavy rain and floods (sheet, rill and gully erosion), strong winds in dry areas, landslides, waves along the coast.
• Human causes: deforestation, overgrazing, faulty farming (ploughing up and down slopes, shifting cultivation), mining, construction and road building.
• Effects: loss of fertility, siltation of rivers and dams, floods, desertification.
• Control (in brief): afforestation, contour ploughing, terrace farming, strip cropping, wind breaks (shelter belts), check dams, controlled grazing.

1.4 Renewable and non-renewable energy sources

Renewable sources – key points

• Solar energy: solar cookers, heaters, photovoltaic cells; India’s National Solar Mission.
• Wind energy: windmills/turbines; Tamil Nadu, Gujarat lead in India.
• Hydroelectric: energy of falling water; but large dams displace people and flood forests.
• Tidal and wave energy: uses the rise and fall of sea tides (Gulf of Khambhat, Gulf of Kutch have potential).
• Geothermal: heat from inside the Earth (Puga valley, Ladakh).
• Biomass and biogas: wood, crop waste, cow dung; biogas (mainly methane) from anaerobic digestion.

Non-renewable sources – key points

• Coal: main source of thermal power in India (Jharia, Raniganj, and Chandrapur–Wardha fields in Vidarbha).
• Petroleum and natural gas: transport fuel, LPG, CNG (Mumbai High, Assam).
• Nuclear energy: fission of uranium-235; Tarapur (Maharashtra), Kudankulam; no CO₂ but radioactive waste and accident risk.

Conclusion: shifting from fossil fuels to renewable energy reduces pollution and global warming and gives energy security.

Likely exam questions

1. (Long, 8 marks) Describe the major zones of the atmosphere and the composition and importance of air.
2. (Long, 8 marks) Explain the formation of soil and the causes of soil erosion.
3. (Short, 4 marks) Write a note on the global distribution of water.
4. (Short, 4 marks) Describe any four physico-chemical characteristics of water.
5. (Short, 4 marks) Distinguish between renewable and non-renewable energy sources with examples.

Syllabus topics (RTMNU)

• 2.1 Ecosystem-Definition and Types- Forest, Grassland, Desert, Pond.
• 2.2 Food chain, food web.
• 2.3 Ecological pyramids- Definitions, pyramids in pond, forest and parasitic food chain.
• 2.4 Energy flow in an ecosystem, Single channel, Y –shape and Universal model.

2.1 Ecosystem: Definition and types – Forest, Grassland, Desert, Pond

Ecosystem: a structural and functional unit of nature in which living organisms (biotic components) interact with each other and with their physical surroundings (abiotic components), with exchange of materials and flow of energy. The term was coined by A. G. Tansley (1935).

Components

• Abiotic: inorganic substances (water, CO₂, O₂, N, P, minerals), organic substances (proteins, carbohydrates, humus) and climatic factors (light, temperature, rainfall, humidity).
• Biotic: (a) Producers (autotrophs – green plants, algae); (b) Consumers – primary (herbivores), secondary and tertiary (carnivores); (c) Decomposers (bacteria and fungi that break down dead matter and release minerals).

Types studied

2.2 Food chain and food web

Food chain: the sequence of organisms through which food energy is transferred by eating and being eaten. Each step is a trophic level.

• Grazing food chain: starts from green plants. Example (grassland): Grass → Grasshopper → Frog → Snake → Hawk. Example (pond): Phytoplankton → Zooplankton → Small fish → Large fish → Kingfisher.
• Detritus food chain: starts from dead organic matter. Example: Dead leaves → Earthworm/termites → Frog/bird → Snake.
• Parasitic food chain: from larger host to smaller parasites. Example: Tree → Birds → Lice → Bacteria.

Food web: a network of many interconnected food chains in an ecosystem. One organism may be eaten by several consumers and may eat several kinds of food.

• Example (grassland): grass is eaten by grasshopper, rabbit and mouse; mouse is eaten by snake and hawk; snake is eaten by hawk.
• Significance: gives alternative food routes, so the ecosystem is more stable; loss of one species does not break the system.

2.3 Ecological pyramids

Ecological pyramid: a graphic representation of the relationship between trophic levels in terms of number, biomass or energy, with producers at the base. Concept by Charles Elton (1927) – hence also called Eltonian pyramids.

Limitations: do not show the same species at two levels, ignore decomposers, and number pyramids do not consider size.

2.4 Energy flow in an ecosystem: single channel, Y-shaped and universal models

Energy enters as sunlight, is fixed by producers by photosynthesis and moves through trophic levels. Flow is unidirectional (sun → producers → herbivores → carnivores) and energy is lost as heat at every level (second law of thermodynamics). Only about 1–2% of sunlight falling on plants is fixed as gross primary production.

Lindeman’s 10% law (1942): only about 10% of the energy of one trophic level is transferred to the next; the rest is used in respiration or lost as heat and in waste. This limits food chains to 4–5 levels.

1. Single channel energy flow model

• Shows energy flowing in a straight line through one food chain: Sun → producers → herbivores → carnivores, with arrows for respiratory loss (R) and export to decomposers at each step.
• Proposed by E. P. Odum; simple but unrealistic because grazing and detritus chains work together.

2. Y-shaped energy flow model

• Given by H. T. Odum (1956) / E. P. Odum. Net primary production divides into two arms like the letter Y: one arm is the grazing food chain (living plants eaten by herbivores) and the other the detritus food chain (dead plant matter used by decomposers and detritivores).
• Shows that the two chains are separated in time and space but linked (dung and dead bodies of grazers enter the detritus arm).
• More realistic – in forests most energy goes through the detritus arm; in sea, most through the grazing arm.

3. Universal energy flow model

• Given by E. P. Odum (1968); applies to any living component – a plant, an animal, a population or a trophic level.
• The total energy taken in (I) is partly not used (NU); the assimilated energy (A) is divided into respiration (R) and production (P); production goes to growth and reproduction (G) and storage (S), and part is exported (E).
• Formula idea: I → A = P + R; it shows that most energy is lost in respiration.

Likely exam questions

1. (Long, 8 marks) What are ecological pyramids? Describe pyramids of number, biomass and energy in pond, forest and parasitic food chain.
2. (Long, 8 marks) Explain energy flow in an ecosystem with single channel, Y-shaped and universal models.
3. (Short, 4 marks) Define ecosystem and describe the structure of a pond ecosystem.
4. (Short, 4 marks) Distinguish between food chain and food web with examples.
5. (Short, 4 marks) Explain the 10% law of energy transfer.

Syllabus topics (RTMNU)

• 3.1 Biodiversity and its conservation, Biological Diversity Act, 2002.
• 3.2 Causes of reduction of biodiversity.
• 3.3 Salient features of Wildlife Protection Act, 1972, Zoological Survey of India: formation and role in animal conservation.
• 3.4 Hot spots of biodiversity in India, Introductory study of national parks and sanctuaries – Tadoba, Nagzira, Kanha.

3.1 Biodiversity and its conservation; Biological Diversity Act, 2002

Biodiversity (biological diversity) is the variety of all living organisms – plants, animals and microorganisms – the genes they contain and the ecosystems they form. The term was popularised by E. O. Wilson (1988).

Levels of biodiversity

• Genetic diversity: variation of genes within a species (e.g. thousands of rice and mango varieties in India).
• Species diversity: variety and number of species in a region (species richness and evenness).
• Ecosystem diversity: variety of habitats and ecosystems – forests, grasslands, deserts, wetlands, coral reefs.

India is one of the 17 mega-diverse countries, with about 2.4% of the world’s land but 7–8% of recorded species.

Conservation of biodiversity

Special projects: Project Tiger (1973), Project Elephant (1992), Crocodile Breeding Project (1975).

Biological Diversity Act, 2002

• Passed by the Parliament of India to fulfil India’s commitments under the Convention on Biological Diversity (CBD), 1992 (Rio Earth Summit).
• Three objectives: (1) conservation of biological diversity, (2) sustainable use of its components, (3) fair and equitable sharing of benefits arising from use of biological resources and traditional knowledge.
• Three-tier structure: National Biodiversity Authority (NBA) at Chennai (2003); State Biodiversity Boards (SBB); Biodiversity Management Committees (BMC) at local bodies.
• BMCs prepare People’s Biodiversity Registers (PBR) documenting local species and knowledge.
• Foreigners and foreign companies need prior approval of NBA to obtain Indian biological resources or apply for patents based on them – protects against biopiracy (e.g. neem, turmeric, basmati cases).
• Provides for declaration of Biodiversity Heritage Sites and penalties for violations.

3.2 Causes of reduction of biodiversity

The main causes can be remembered as “HIPPO”: Habitat loss, Invasive species, Pollution, Population (human), Over-exploitation – plus climate change.

• Habitat loss and fragmentation: the biggest cause – deforestation, agriculture, mining, dams, roads and urbanisation break habitats into small patches (e.g. tiger corridors cut by highways).
• Over-exploitation: overhunting and poaching (tiger skin, rhino horn, elephant ivory), overfishing, excess collection of medicinal plants. Extinct examples: dodo, passenger pigeon, Steller’s sea cow; in India, the cheetah (declared extinct in 1952).
• Invasive alien species: introduced species out-compete natives – Lantana, Parthenium (congress grass), water hyacinth (Eichhornia), African catfish (Clarias gariepinus), Nile perch in Lake Victoria.
• Pollution: pesticides (DDT reduced bird populations), industrial effluents, plastics, oil spills.
• Climate change: rising temperature, coral bleaching, shifting ranges of species.
• Co-extinction: when a host species dies out, its specific parasites or pollinators also disappear.
• Human–wildlife conflict, forest fires, shifting cultivation and grazing pressure.

3.3 Wildlife Protection Act, 1972 and Zoological Survey of India

Salient features of the Wildlife (Protection) Act, 1972

• A central law for the protection of wild animals, birds and plants; applies to the whole of India (amended several times, latest major amendment 2022).
• Schedules: species are listed in schedules according to the degree of protection. Schedule I species (e.g. tiger, lion, elephant, Great Indian Bustard, blackbuck) get the highest protection and heaviest punishment. (After the 2022 amendment the schedules were reduced to four.)
• Hunting is banned for scheduled animals except in special cases (e.g. animal dangerous to human life, with permission).
• Provides for declaration of National Parks, Wildlife Sanctuaries, Conservation Reserves and Community Reserves.
• Bans trade in wild animals, their parts and products (skins, ivory, horns) of scheduled species.
• Set up the National and State Boards for Wildlife, Chief Wildlife Warden, and later the National Tiger Conservation Authority (2006 amendment) and Wildlife Crime Control Bureau.
• Punishment: imprisonment and fine; higher for offences related to Schedule I animals and in tiger reserves.

Zoological Survey of India (ZSI)

• Formation: established on 1 July 1916; headquarters at Kolkata; works under the Ministry of Environment, Forest and Climate Change. It grew out of the zoological section of the Indian Museum.
• Has 16 regional centres; the Western Regional Centre is at Pune.
• Role in animal conservation:
  • Survey, exploration and documentation of the fauna of India (Fauna of India, State Fauna series).
  • Taxonomic identification of animals and discovery of new species.
  • Maintains the National Zoological Collection (type specimens).
  • Prepares the Red Data Book/status of threatened Indian animals and helps prepare species lists for the Wildlife Act.
  • Faunal surveys of protected areas, biodiversity hotspots and wetlands; supports wildlife crime investigation by species identification.
  • Training, publications and public awareness.

3.4 Hot spots of biodiversity in India; Tadoba, Nagzira and Kanha

Biodiversity hotspot (concept by Norman Myers, 1988): a region with at least 1500 endemic vascular plant species that has lost at least 70% of its original habitat. There are 36 hotspots in the world.

Hotspots in India (4)

National parks and sanctuaries of central India

Likely exam questions

1. (Long, 8 marks) What is biodiversity? Describe the causes of reduction of biodiversity and methods of its conservation.
2. (Long, 8 marks) Give the salient features of the Wildlife Protection Act, 1972 and the Biological Diversity Act, 2002.
3. (Short, 4 marks) Write a note on the Zoological Survey of India and its role in animal conservation.
4. (Short, 4 marks) What are biodiversity hotspots? Name the hotspots in India.
5. (Short, 4 marks) Write a short note on Tadoba-Andhari Tiger Reserve or Kanha National Park.

Syllabus topics (RTMNU)

• 4.1 Air Pollution: Sources, effect and control measures of air pollution, Acid rain, green house effect, ozone depletion and global warming.
• 4.2 Water Pollution: Sources, effect and control measures of water pollution, effect of mercury.
• 4.3 Noise pollution: Sources effect and control measures of noise pollution.
• 4.4 Biomagnification and Bioaccumulation.

4.1 Air pollution; acid rain, greenhouse effect, ozone depletion and global warming

Air pollution: presence of substances in the air (gases, particles) in amounts that harm humans, animals, plants or materials.

Sources

• Natural: volcanoes, forest fires, dust storms, pollen, marsh gas.
• Man-made: vehicles (CO, NOₓ, hydrocarbons), thermal power plants and industries (SO₂, fly ash), burning of garbage and crop residue, mining, domestic fuels, aerosol sprays (CFCs).

Major pollutants and effects

Control measures

• Electrostatic precipitators, scrubbers, cyclone separators and bag filters in industries; tall chimneys.
• Catalytic converters in vehicles, CNG/electric vehicles, BS-VI fuel standards, unleaded petrol.
• Green belts, use of renewable energy, public transport; laws – Air (Prevention and Control of Pollution) Act, 1981.

Acid rain

Rain with pH below 5.6. SO₂ and NOₓ react with water vapour: SO₂ + O₂ + H₂O → H₂SO₄; NO₂ + H₂O → HNO₃. Effects: kills fish in lakes, damages leaves and soil fertility, corrodes buildings and monuments (marble cancer of the Taj Mahal). Control: reduce SO₂/NOₓ emissions, liming of lakes.

Greenhouse effect and global warming

• Greenhouse effect: greenhouse gases (CO₂, CH₄, N₂O, CFCs, water vapour) allow sunlight in but trap the outgoing infrared (heat) radiation, keeping the Earth warm. This natural effect is useful.
• Global warming: rise in average temperature due to the extra greenhouse gases from burning fossil fuels and deforestation. Earth has already warmed about 1.1 °C since pre-industrial times.
• Effects: melting of glaciers and polar ice, rise in sea level, floods and droughts, heat waves, coral bleaching, spread of diseases, crop loss.
• Control: reduce fossil fuels, renewable energy, afforestation; Kyoto Protocol (1997), Paris Agreement (2015).

Ozone depletion

• The ozone layer (stratosphere) absorbs harmful UV radiation. Ozone is measured in Dobson Units (DU); below 220 DU is called an “ozone hole”, first seen over Antarctica (1985).
• Cause: CFCs (from refrigerators, ACs, aerosols), halons, carbon tetrachloride. UV breaks CFCs and releases chlorine: Cl + O₃ → ClO + O₂; ClO + O → Cl + O₂. One chlorine atom can destroy thousands of ozone molecules.
• Effects of more UV: skin cancer, cataract, weak immunity, damage to plankton and crops.
• Control: Montreal Protocol (1987) to phase out ozone-depleting substances. 16 September is World Ozone Day.

4.2 Water pollution and effect of mercury

Water pollution: any change in the physical, chemical or biological properties of water that makes it harmful for living beings.

Sources

• Domestic sewage: organic matter, detergents, pathogens.
• Industrial effluents: heavy metals (Hg, Pb, Cd, As), acids, dyes, oils.
• Agricultural run-off: fertilisers (nitrates, phosphates), pesticides.
• Thermal pollution from power plants; oil spills in sea; plastics.

Effects

• Water-borne diseases: cholera, typhoid, jaundice (hepatitis A), dysentery.
• Increase in BOD and fall in dissolved oxygen → fish kills.
• Eutrophication: excess nutrients cause algal bloom, oxygen loss and death of aquatic animals.
• Bioaccumulation of toxic metals and pesticides in food chains.
• Fluoride and arsenic in ground water cause fluorosis and arsenicosis.

Control measures

• Sewage treatment plants (primary, secondary, tertiary treatment); effluent treatment plants in industries.
• Reduced and correct use of fertilisers and pesticides; organic farming.
• Do not dump waste, idols or ash into rivers; oxidation ponds; Water (Prevention and Control of Pollution) Act, 1974; Namami Gange programme.

Effect of mercury

• Sources: chlor-alkali industry, paper and pulp mills, fungicides, thermometers, coal burning, gold mining.
• In water, bacteria convert inorganic mercury into methyl mercury, which is fat-soluble and gets biomagnified in fish.
• Minamata disease (Minamata Bay, Japan, 1950s): people eating mercury-contaminated fish suffered numbness, tremors, loss of vision and hearing, speech problems, paralysis, birth defects and death. Cats showed “dancing” behaviour.
• Mercury damages the nervous system and kidneys and crosses the placenta, harming the foetus.

4.3 Noise pollution: sources, effects and control

Noise is unwanted, unpleasant sound. Sound intensity is measured in decibels (dB). Normal conversation ≈ 60 dB; above 80 dB is harmful; 120 dB causes pain.

• Sources: vehicles and horns, trains and aircraft, industries and machines, construction, loudspeakers, firecrackers, DJ systems.
• Effects: temporary or permanent hearing loss, irritation, headache, sleep disturbance, high blood pressure, increased heart rate, stress, lack of concentration; animals and birds are disturbed in breeding and communication.
• Control: silencers and regular maintenance of vehicles; sound-proofing and ear plugs/muffs for workers; green belts (trees absorb sound); restrictions on loudspeakers (no use 10 pm–6 am) and horns; silence zones near hospitals and schools; Noise Pollution (Regulation and Control) Rules, 2000.
• Limits (CPCB, daytime): industrial 75 dB, commercial 65 dB, residential 55 dB, silence zone 50 dB (night limits are 10 dB lower; industrial 70 dB).

4.4 Biomagnification and bioaccumulation

Conditions for biomagnification

• The chemical must be long-lived (non-biodegradable), fat-soluble (stored in fat, not excreted in urine) and biologically active.
• Examples: DDT, other organochlorine pesticides, PCBs, methyl mercury, lead, cadmium.

Classic DDT example (Long Island estuary)

Water 0.000003 ppm → zooplankton 0.04 ppm → small fish 0.5 ppm → large fish 2 ppm → fish-eating birds (ospreys) about 25 ppm – an increase of nearly 10 million times.

Effects: in birds DDT disturbs calcium metabolism → thin eggshells that break during incubation → decline of eagles, falcons and pelicans. In man: nervous and liver damage, hormone disruption, cancer risk.

Likely exam questions

1. (Long, 8 marks) Describe the sources, effects and control measures of air pollution. Add a note on acid rain.
2. (Long, 8 marks) Describe the sources, effects and control of water pollution. Explain the effect of mercury.
3. (Short, 4 marks) What is the greenhouse effect? Explain global warming.
4. (Short, 4 marks) Write a note on noise pollution and its control.
5. (Short, 4 marks) Distinguish between bioaccumulation and biomagnification with an example.