📖 Chapter BN08 · NDA Class 11–12 Level🎯 NDA Level : High Priority
This chapter covers four high-yield areas for NDA: ecosystem structure and energy flow, India's biodiversity conservation framework (national parks, biosphere reserves), environmental pollution with specific pollutants and their effects, and basic biotechnology including genetic engineering and GM crops. Questions are factual, India-centric, and reward systematic memorisation of examples and definitions.
📌 What to expect in NDA (2022–2025 pattern): (1) Food chain and food web — producer/consumer/decomposer roles; 10% energy law; (2) Ecological pyramids — types, which pyramid is always upright; (3) India's biodiversity hotspots, major national parks and their flagship species; (4) Pollution types — specific pollutant → disease/effect linkages (CO, lead, mercury, BOD); (5) Biotechnology — recombinant DNA technology basics, Bt cotton, Golden Rice, insulin production.
Topics at a Glance
① Ecosystem
Components, food chains, energy flow, ecological pyramids
② Biodiversity & Conservation
Hotspots, national parks, wildlife sanctuaries, biosphere reserves
③ Pollution
Air, water, soil pollution — causes, effects, control
④ Biotechnology
rDNA, insulin, GM crops, applications
1. Ecosystem
1.1
Components of an Ecosystem
Biotic + Abiotic — both components must be defined with examples for NDA
An ecosystem is a functional unit of nature where living organisms interact with each other and with their non-living environment. Term coined by A.G. Tansley (1935). The largest ecosystem on Earth is the Biosphere (also called Ecosphere).
🌿 Biotic Components (Living)
Producers (Autotrophs): make their own food by photosynthesis — green plants, phytoplankton, cyanobacteria
Decomposers (Saprotrophs): break down dead organic matter; recycle nutrients — bacteria, fungi, earthworms
🌍 Abiotic Components (Non-living)
Climatic factors: sunlight (primary energy source), temperature, rainfall, humidity, wind
Edaphic factors: soil composition, pH, mineral content, texture
Chemical factors: CO₂, O₂, N₂, water, minerals (N, P, K)
Topographic factors: altitude, slope, aspect of land
Abiotic factors determine which biotic communities can live in an ecosystem
1.2
Food Chain, Food Web & Energy Flow
10% law of energy transfer — the single most tested ecology concept in NDA
Fig. 1 — Food chain with Lindeman's 10% Law. Starting with 10,000 J in producers (grass), only 1,000 J reaches primary consumers (rabbit), 100 J reaches secondary consumers (fox), and just 10 J reaches tertiary consumers (hawk). 90% is lost as heat at each step. This explains why longer food chains are energetically inefficient.
🌿 Food Chain vs Food Web
Food chain: linear sequence of organisms where each is eaten by the next; e.g. Grass → Rabbit → Fox → Hawk
Food web: interconnected network of multiple food chains in an ecosystem; more realistic; more stable (if one organism disappears, alternatives exist)
Energy flows in ONE direction (unidirectional): producer → consumers
Nutrients cycle (are recycled); energy is NOT recycled
Grazing food chain: starts from green plants (most common)
Detritus food chain: starts from dead organic matter; decomposers play key role
📚 Trophic Levels & Key Terms
Trophic level: position of organism in food chain (T1 = producers; T2 = herbivores etc.)
Biomass: total dry weight of organisms at a trophic level
Standing crop: amount of living matter at a given time
Productivity: rate of production of organic matter; GPP (Gross Primary Productivity) − Respiration = NPP (Net Primary Productivity)
Bioaccumulation: increase of toxic substance in organism over lifetime
Biomagnification: increase of toxic substance concentration up the food chain (e.g. DDT, mercury)
1.3
Ecological Pyramids
Three types — which are always upright and which can be inverted is the key NDA distinction
Fig. 2 — Three types of ecological pyramids. Pyramid of Numbers: usually upright (grassland) but can be inverted (e.g. one large tree supporting many insects). Pyramid of Biomass: upright on land but inverted in aquatic ecosystems (phytoplankton biomass < zooplankton). Pyramid of Energy: ALWAYS upright — energy can never increase up the food chain (10% law ensures this).
PYQTopic-Wise PYQs — Ecosystem
Q1. Which ecological pyramid is always upright and can never be inverted?
A. Pyramid of numbers
B. Pyramid of biomass
C. Pyramid of energy
D. Both A and B
Answer: C — Pyramid of energy. Energy always decreases as it moves up trophic levels (10% law — 90% is lost as heat). Therefore, the pyramid of energy is always upright in every ecosystem without exception. Pyramids of numbers and biomass can be inverted (e.g. a tree with many insects = inverted numbers; aquatic ecosystem = inverted biomass).
Q2. Lindeman's 10% law states that the energy transferred from one trophic level to the next is:
A. 1%
B. 10%
C. 50%
D. 90%
Answer: B — 10%. R.L. Lindeman (1942) proposed that only about 10% of energy at any trophic level is passed to the next level. The remaining 90% is lost as heat during respiration, metabolic activities, and waste. This limits food chains to 4–5 trophic levels. If 10,000 J at producers → 1,000 J at herbivores → 100 J at primary carnivores → 10 J at secondary carnivores.
Q3. The term "ecosystem" was coined by:
A. Ernst Haeckel
B. A.G. Tansley
C. Charles Darwin
D. R.L. Lindeman
Answer: B — A.G. Tansley (1935). British ecologist Arthur George Tansley coined the term "ecosystem" in 1935, emphasising the interaction between living organisms and their physical environment as a unified system. Haeckel coined "ecology" (1866); Lindeman proposed the 10% energy law (1942); Darwin proposed natural selection (1859).
TRICKY🧐 Ecology Traps
⚠️ "Energy flows in a cycle in ecosystems, just like nutrients." True or False?
False. Energy flows in one direction only (unidirectional) — from sun to producers to consumers — and is NOT recycled. Once energy is lost as heat (90% at each trophic level), it cannot be recovered by the ecosystem. In contrast, nutrients (matter) DO cycle — nitrogen cycle, carbon cycle, phosphorus cycle, water cycle — these are biogeochemical cycles. NDA has tested this distinction: "Which is cyclic in an ecosystem — energy or matter?" → Matter/Nutrients cycle; Energy flows unidirectionally.
⚠️ "Biomagnification and bioaccumulation mean the same thing." True or False?
False — they are related but different.Bioaccumulation = buildup of a toxic substance within an individual organism over its lifetime (e.g. a fish accumulating mercury from water). Biomagnification = progressive increase in concentration of a toxic substance as it moves up the food chain (e.g. phytoplankton 0.025 ppm DDT → small fish 0.5 ppm → large fish 2 ppm → birds 25 ppm). Classic NDA example: DDT causes eggshell thinning in birds of prey (osprey, bald eagle) due to biomagnification.
2. Biodiversity & Conservation
2.1
Biodiversity Hotspots in India
India has 4 biodiversity hotspots out of 36 global hotspots — names and locations are NDA-tested
Biodiversity hotspot criteria (Norman Myers, 1988): region must have ≥1,500 endemic plant species AND have lost ≥70% of original vegetation. India has 4 biodiversity hotspots: 1. Western Ghats (+ Sri Lanka) — one of world's richest; endemic amphibians, plants 2. Eastern Himalayas (Himalayan biodiversity hotspot) — includes NE India; orchids, large mammals 3. Indo-Burma region — NE India; freshwater turtles, birds 4. Sundaland (Nicobar Islands are part) — extremely high endemism
📚 Types of Biodiversity
Genetic diversity: variation in genes within a species (e.g. different rice varieties)
Species diversity: variety of species in a region (e.g. number of bird species in a forest)
Ecosystem diversity: variety of different ecosystems (e.g. forests, wetlands, coral reefs)
India ranks 7th in global plant diversity and 8th in mammal species
India = 2.4% land area but 7–8% of world's species
Invasive/alien species: water hyacinth (Eichhornia crassipes) in India; Nile perch in Lake Victoria
Pollution: pesticides, industrial waste, plastics
Population growth: over-exploitation of resources
Climate change: disrupts habitats and breeding cycles
Over-exploitation: hunting, poaching, overfishing
Water hyacinth is the worst aquatic weed in India (exotic invasive)
2.2
Conservation Areas — National Parks, Sanctuaries & Biosphere Reserves
Flagship species of India's major national parks + differences between PA types = NDA direct MCQs
🏛️ National Parks
Strictly protected; no human activity or grazing allowed inside
Buffer zones around may allow limited activity
First NP in India: Jim Corbett NP (Uttarakhand, 1936) — tigers
Kaziranga NP (Assam) — one-horned rhino; UNESCO WH
Sundarbans NP (WB) — Royal Bengal Tiger; mangrove
Gir NP (Gujarat) — Asiatic lion (only wild population)
Kanha NP (MP) — Barasingha (swamp deer)
Ranthambore NP (Rajasthan) — tigers
Sariska NP (Rajasthan) — tigers; leopards
Periyar NP (Kerala) — elephants, tigers
India has 106 National Parks (as of 2024)
🌈 Wildlife Sanctuaries
Less strict than NP; human activities (grazing, collection of forest produce) may be permitted
Managed for specific species conservation
Bharatpur (Keoladeo Ghana) WS (Rajasthan) — migratory birds; now NP
Chilika Lake WS (Odisha) — flamingoes, Irrawaddy dolphins
Vedanthangal WS (Tamil Nadu) — water birds; oldest bird sanctuary in India
Mudumalai WS (TN) — elephants, tigers
India has 544+ Wildlife Sanctuaries
🏘️ Biosphere Reserves
Largest and most comprehensive conservation units
Have 3 zones: Core zone (fully protected), Buffer zone (limited research), Transition zone (human settlements)
India has 18 Biosphere Reserves
Nilgiri BR (TN/Kerala/Karnataka) — first BR in India (1986)
Sundarbans BR (WB) — UNESCO WH; mangrove; tiger
Nanda Devi BR (Uttarakhand) — snow leopard
Gulf of Mannar BR (TN) — dugong; coral reefs
Pachmarhi BR (MP)
📌 Ex-situ vs In-situ Conservation — NDA Key Distinction: In-situ conservation: protecting species in their natural habitat — national parks, wildlife sanctuaries, biosphere reserves, sacred groves (most effective method) Ex-situ conservation: protecting species outside their natural habitat — zoos, botanical gardens, seed banks, gene banks, cryopreservation
National Botanical Gardens: Kolkata, Lucknow | Zoological parks: Arignar Anna (Chennai), National Zoological Park (Delhi) Seed bank: National Bureau of Plant Genetic Resources (NBPGR), New Delhi
PYQTopic-Wise PYQs — Biodiversity & Conservation
Q4. Which National Park in India is associated with the one-horned rhinoceros?
A. Jim Corbett NP
B. Gir NP
C. Kaziranga NP
D. Kanha NP
Answer: C — Kaziranga National Park (Assam). Kaziranga is home to the world's largest population of Indian one-horned rhinoceros (Rhinoceros unicornis). It is also a UNESCO World Heritage Site. Gir NP has the Asiatic Lion; Jim Corbett NP has tigers (Project Tiger was launched here in 1973); Kanha NP has Barasingha (swamp deer).
Q5. Which of the following is the correct difference between a National Park and a Wildlife Sanctuary?
A. NP allows human activities; WS does not
B. NP is strictly protected; WS allows limited human activities
C. NP is larger than WS always
D. WS is for plants; NP is for animals
Answer: B. In a National Park, no human activities (grazing, collection of forest produce, cultivation) are permitted inside the core area. In a Wildlife Sanctuary, some human activities may be allowed under regulation. Both are Protected Areas (PAs) under the Wildlife Protection Act 1972. Biosphere Reserves are the largest, with 3 zones (core, buffer, transition).
TRICKY🧐 Biodiversity Traps
⚠️ "The first national park in India is Gir National Park." True or False?
False. The first national park in India is Jim Corbett National Park (originally called Hailey National Park), established in 1936 in Uttarakhand. It was renamed in 1956 after the famous hunter-turned-conservationist Jim Corbett. It also became the first park under Project Tiger in 1973. Gir NP (1965) is famous for being the only home of the Asiatic Lion.
3. Environmental Pollution
3.1
Air, Water & Soil Pollution — Causes, Effects & Control
Specific pollutant → specific disease/effect — the NDA format; know each pairing
💨 Air Pollution
Major pollutants & effects:
● CO (Carbon monoxide): from incomplete combustion (vehicles); combines with Hb 210× more than O₂ → carboxyhaemoglobin → suffocation; most dangerous air pollutant
● SO₂ + NO₂: from power plants, vehicles → acid rain (pH<5.6); damages forests, monuments (Taj Mahal)
● Ozone (O₂ at ground level): photochemical smog; from vehicle exhaust + sunlight; respiratory damage; stratospheric ozone (good) → absorbs UV
● SPM (Suspended Particulate Matter): dust, smoke → silicosis (miners), asthma, lung cancer
● Lead (Pb): old leaded petrol → neurotoxin; affects brain in children
● Greenhouse gases: CO₂, CH₄, N₂O, CFCs → global warming; CO₂ is the primary GHG by volume
● CFCs: from refrigerants, aerosols → destroy ozone layer (O₂ + Cl → ClO + O₂); Montreal Protocol (1987) banned CFCs Control: Catalytic converters in vehicles; CNG over diesel; Green buildings; Clean energy (solar, wind)
💧 Water Pollution
Major pollutants & effects:
● BOD (Biochemical Oxygen Demand): oxygen needed by microbes to decompose organic matter; high BOD = high pollution; clean water BOD <1 mg/L; severely polluted >10 mg/L
● Mercury (Hg): industrial waste → Minamata disease (Japan, 1956); neurological damage; methylmercury in fish
● Fluoride: excess in groundwater → fluorosis (Rajasthan, Gujarat)
● Arsenic: groundwater contamination → arsenicosis; skin cancer; West Bengal, Bangladesh
● Nitrates & Phosphates: from fertiliser runoff → Eutrophication (algal bloom → O₂ depletion → fish kill)
● Sewage: pathogens → cholera, typhoid, hepatitis A
● Oil spill: coats feathers/fur of wildlife; kills marine life Control: Sewage treatment plants (primary/secondary/tertiary); phytoremediation; constructed wetlands
🌍 Soil Pollution
Major pollutants & effects:
● Pesticides (DDT, BHC): bioaccumulation & biomagnification; DDT banned in many countries; chlorinated hydrocarbons persist in soil for decades
● Heavy metals (Cd, Pb, Cr): from industrial waste → Itai-Itai disease (Cadmium; Japan) → bone softening
● Plastic waste: non-biodegradable; microplastics enter food chain
● Desertification: soil degradation due to deforestation, overgrazing, climate change
● Salinity: excess irrigation → waterlogging + salinisation → loss of fertility Control: Bioremediation (using bacteria to break down pollutants); Phytoremediation (using plants like sunflower to absorb heavy metals); Organic farming; Composting
🔊 Noise Pollution
Sources & effects: Vehicles, industry, aircraft, loudspeakers, construction
● Measured in decibels (dB); threshold of pain = 120 dB; safe level = <45 dB (residential night)
● Prolonged exposure >85 dB → NIHL (Noise-Induced Hearing Loss); permanent
● Other effects: hypertension, sleep disturbance, stress, reduced productivity Control: Sound barriers; noise standards; green belts around urban areas; ear protection
📌 Key Pollution-Disease Pairs (NDA Direct Questions):
CO → Carboxyhaemoglobin (suffocation) | Mercury → Minamata disease | Cadmium → Itai-Itai disease
Silica dust → Silicosis (miners) | Asbestos → Asbestosis, mesothelioma | Fluoride excess → Fluorosis
Eutrophication → algal bloom → O₂ depletion → fish kill | High BOD = high pollution | Low BOD = clean water
PYQTopic-Wise PYQs — Pollution
Q6. Minamata disease is caused by pollution of water by:
A. Lead
B. Cadmium
C. Mercury
D. Arsenic
Answer: C — Mercury. Minamata disease (1956, Japan) was caused by methylmercury discharged into Minamata Bay by a chemical factory. The mercury biomagnified in fish, which were then eaten by local people, causing severe neurological damage (numbness, tremors, hearing/vision loss, paralysis). Itai-Itai disease = Cadmium; Arsenicosis = Arsenic; Lead = neurotoxin in children.
Q7. A high BOD (Biochemical Oxygen Demand) value in a water body indicates:
A. Clean, unpolluted water
B. High oxygen content
C. High level of organic pollution
D. Absence of microorganisms
Answer: C — High level of organic pollution. BOD measures the amount of dissolved oxygen consumed by microorganisms to decompose organic matter. High BOD means more organic matter (sewage, dead organisms) → more microbial activity → more O₂ consumed → less O₂ for fish and aquatic life. Clean water: BOD <1 mg/L. Severely polluted: BOD >10 mg/L.
Q8. The Montreal Protocol (1987) was signed to control the emission of:
A. Carbon dioxide
B. Sulphur dioxide
C. Chlorofluorocarbons (CFCs)
D. Nitrogen oxides
Answer: C — CFCs (Chlorofluorocarbons). The Montreal Protocol on Substances that Deplete the Ozone Layer (1987) is one of the most successful international environmental agreements. It banned the production of CFCs (used in refrigerants, aerosols) because they release chlorine radicals that catalytically destroy ozone (one Cl atom can destroy thousands of O₂ molecules). The Kyoto Protocol targets CO₂; Acid rain is caused by SO₂ and NO₂.
TRICKY🧐 Pollution Traps
⚠️ "Ozone is always harmful to living organisms." True or False?
False — it depends on location (good up high, bad nearby).Stratospheric ozone (15–35 km altitude; "ozone layer") is BENEFICIAL — it absorbs harmful UV-B and UV-C radiation from the sun, protecting living organisms from skin cancer, cataracts, and DNA damage. Tropospheric ozone (ground-level) is HARMFUL — it is a major component of photochemical smog, causes respiratory irritation, damages crops and materials. Slogan: "Good ozone up high, bad ozone nearby."
⚠️ "Carbon dioxide is the most potent (powerful) greenhouse gas." True or False?
False — it is the most ABUNDANT but NOT the most potent. CO₂ is the most abundant GHG by volume and the primary driver of current warming due to sheer quantity. However, methane (CH₄) is ~25× more potent than CO₂ per molecule over 100 years, and N₂O is ~298× more potent. CFCs are thousands of times more potent. NDA may ask: "Which is the most abundant greenhouse gas?" → CO₂ (by contribution to warming) or water vapour (by volume in atmosphere).
4. Biotechnology
4.1
Basic Principles of Genetic Engineering & Recombinant DNA Technology
Tools of rDNA technology + insulin production + GM crops = core NDA biotechnology content
Biotechnology uses living organisms or their products to make useful substances. Modern biotechnology relies on recombinant DNA (rDNA) technology — introducing foreign DNA into a host organism to produce desired proteins or traits.
Fig. 3 — Steps in Recombinant DNA Technology using insulin production as an example. Key tools: Restriction endonucleases (cut DNA at specific sites), DNA ligase (joins DNA fragments), Vectors (plasmids carry foreign gene into host), Host organism (E. coli for insulin). The resulting organism is called a genetically modified organism (GMO) or transgenic organism.
⚙️ Key Tools of Genetic Engineering
Restriction endonucleases: "molecular scissors"; cut DNA at specific palindromic sequences (restriction sites); produce sticky ends or blunt ends; named after source bacteria (e.g. EcoRI from E. coli)
DNA ligase: "molecular glue"; joins DNA fragments; seals sticky ends to form recombinant DNA
Vectors: carry foreign gene into host; plasmids (most common), bacteriophages, Ti plasmid of Agrobacterium tumefaciens (for plants)
PCR (Polymerase Chain Reaction): amplifies specific DNA sequences millions of times; invented by Kary Mullis (Nobel Prize 1993)
Gel electrophoresis: separates DNA fragments by size
💊 Insulin Production — First Commercial rDNA Product
Before 1982: insulin extracted from pig/cattle pancreas (bovine/porcine insulin; some patients had allergic reactions)
1982: Humulin = first recombinant human insulin approved (by Eli Lilly); produced in E. coli
Human insulin gene inserted into E. coli plasmid → bacteria express insulin → purified and used for diabetes
Two chains: A chain + B chain synthesised separately, then combined
This was the first approved genetically engineered pharmaceutical product in the world
💊 Medical Applications
Insulin (Humulin): diabetes treatment; E. coli host
Human Growth Hormone (HGH): dwarfism treatment
Erythropoietin (EPO): anaemia in kidney failure
Hepatitis B vaccine: recombinant HBsAg in yeast
Interferon: antiviral; cancer treatment
Gene therapy: ADA deficiency (SCID) was first treated by gene therapy (1990)
mRNA vaccines: COVID-19 (Pfizer, Moderna)
Monoclonal antibodies: cancer diagnosis and treatment
🌿 Agricultural Applications (GM Crops)
Bt cotton (Bacillus thuringiensis): Cry protein gene inserted → cotton plant produces its own insecticide against bollworm; approved in India 2002; most planted GM crop in India
Bt brinjal: insect resistance; controversial in India
Golden Rice: rice engineered to produce beta-carotene (provitamin A); developed to address Vitamin A deficiency in developing countries
Flavr Savr tomato: first approved GM food (1994, USA); delayed ripening by antisense gene
Tissue culture: rapid propagation of disease-free plants
💿 Gene Technology Terms
GMO: Genetically Modified Organism; organism with altered genome
Transgenic: organism containing gene from another species
Knockout mice: mice with specific gene deactivated for research
CRISPR-Cas9: "gene editing scissors"; latest precision gene editing tool (Nobel 2020 to Doudna and Charpentier)
Dolly (1996): first mammal cloned from adult somatic cell (sheep; Roslin Institute, Scotland)
Bioinformatics: use of computers to analyse biological data (genome sequences)
🌿 Environmental & Other Applications
Bioremediation: using microbes (GMOs) to clean up pollution; Pseudomonas putida ("Superbug" by Ananda Chakraborty) degrades hydrocarbons
Biofuels: ethanol from sugarcane (GM yeast); biodiesel from Jatropha
DNA fingerprinting: Alec Jeffreys (1984); forensics, paternity testing
Human Genome Project (HGP): 1990–2003; mapped all ~20,000–25,000 human genes; completed in 2003
Biopiracy: commercial exploitation of biological resources without benefit-sharing
PYQTopic-Wise PYQs — Biotechnology
Q9. Bt cotton is resistant to insects because it produces:
A. Herbicide
B. Antibiotic
C. Cry protein (crystal toxin) from Bacillus thuringiensis
D. Extra nitrogen
Answer: C — Cry protein (crystal toxin). The Bt gene from Bacillus thuringiensis encodes Cry (crystal) proteins that are toxic to specific insects (especially Lepidoptera larvae like cotton bollworm) but harmless to humans and other animals. The gene was inserted into cotton plants; when bollworm larvae eat the plant, the Cry protein disrupts their gut lining, killing them. Bt cotton was approved in India in 2002 and dramatically reduced pesticide use.
Q10. The first genetically engineered human insulin (Humulin) was produced using:
A. Saccharomyces cerevisiae (yeast)
B. Agrobacterium tumefaciens
C. Escherichia coli (bacteria)
D. Chinese hamster ovary cells
Answer: C — Escherichia coli. The human insulin gene was inserted into an E. coli plasmid vector. The bacteria expressed the insulin gene and produced human insulin, which was then purified. Marketed as Humulin by Eli Lilly (1982), it was the world's first recombinant DNA pharmaceutical product. The Hepatitis B vaccine is produced in yeast; some modern insulins use CHO cells.
Q11. Restriction endonucleases are also called "molecular scissors" because they:
A. Join DNA fragments together
B. Cut DNA at specific sequences
C. Replicate DNA
D. Transcribe DNA to RNA
Answer: B — Cut DNA at specific sequences. Restriction endonucleases recognise and cut DNA at specific short palindromic sequences (restriction sites). They are named from the bacteria they were isolated from (e.g. EcoRI from Escherichia coli strain RY13). They produce either sticky ends (staggered cuts) or blunt ends. DNA ligase (not restriction enzyme) joins DNA fragments.
Q12. Golden Rice was developed to address the deficiency of:
A. Iron
B. Vitamin C
C. Vitamin A (beta-carotene)
D. Zinc
Answer: C — Vitamin A (beta-carotene). Golden Rice was engineered by Ingo Potrykus and Peter Beyer to produce beta-carotene (provitamin A) in the rice endosperm (which normally has none). The name comes from the yellow-golden colour of the rice due to beta-carotene. It was developed to combat Vitamin A deficiency (night blindness, xerophthalmia) in developing countries where rice is the staple food.
TRICKY🧐 Biotechnology Traps
⚠️ "The first cloned mammal was a mouse." True or False?
False. The first mammal cloned from an adult somatic cell was Dolly the sheep, cloned in 1996 at the Roslin Institute, Scotland, by Ian Wilmut and colleagues. Dolly was a Finn Dorset sheep cloned using the nucleus from a mammary gland cell of an adult sheep fused with an enucleated egg cell (somatic cell nuclear transfer = SCNT). She was born in July 1996 but announced to the world in February 1997. She lived until 2003 (age 6). NDA has asked about the year and species repeatedly.
⚠️ "PCR is used to cut specific sequences of DNA." True or False?
False. PCR (Polymerase Chain Reaction) is used to amplify (make millions of copies of) specific DNA sequences — NOT to cut them. PCR was invented by Kary Mullis (Nobel Prize 1993). The enzyme used in PCR is Taq polymerase (from the thermophilic bacterium Thermus aquaticus) which is heat-stable. Restriction endonucleases are the enzymes that cut DNA at specific sequences. This distinction is directly tested in NDA MCQs.
📄 Quick-Reference Fact Sheet — BN08
🌿 Ecosystem & Energy Flow
"Ecosystem" coined by A.G. Tansley (1935)
10% law: Lindeman (1942); 10% energy reaches next trophic level
Energy = unidirectional (not recycled); Nutrients = cyclic
Pyramid of energy = ALWAYS upright (never inverted)
Pyramid of biomass = inverted in aquatic ecosystems
Pyramid of numbers = inverted in tree+insects system
Biomagnification: DDT, mercury concentrate up food chain
🏛️ Conservation Areas
First NP in India: Jim Corbett NP (1936)
Kaziranga NP → one-horned rhino; Gir NP → Asiatic lion
Sundarbans → Royal Bengal Tiger; mangrove ecosystem
India's 4 biodiversity hotspots: Western Ghats, E. Himalayas, Indo-Burma, Sundaland
First Biosphere Reserve: Nilgiri BR (1986)
In-situ: NP, WS, BR (best conservation)
Ex-situ: zoo, botanical garden, seed bank
💨 Pollution Key Facts
CO → carboxyhaemoglobin; 210× affinity vs O₂
Mercury → Minamata disease (Japan, 1956)
Cadmium → Itai-Itai disease (Japan)
High BOD = high organic pollution; Low BOD = clean water
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