Science and Technology Part 2 विज्ञान भाग 2

Quick summary

Genes on DNA decide our traits by making proteins. Over millions of years, small changes in living things added up — this is evolution.

Key points

• A gene is a piece of DNA that holds the code for one protein.
• Flow of information: DNA → mRNA → protein (Central Dogma).
• Transcription (in nucleus): mRNA is made from DNA. Translation (at ribosome): tRNA brings amino acids as per mRNA code.
• Translocation: the ribosome slides along mRNA one codon (3 bases) at a time.
• Mutation is a sudden change in a gene, e.g. sickle-cell anaemia.
• Evidences of evolution: morphological, anatomical, vestigial organs, fossils, connecting links, embryological.
• Lamarck: use and disuse of organs. Darwin: natural selection — "survival of the fittest".
• Speciation: a new species forms when groups are isolated and changes pile up.

Important terms

• Codon – set of 3 bases on mRNA that codes for one amino acid.
• Homologous organs – same bone plan, different work (human hand, whale flipper, bat wing).
• Vestigial organs – useless leftovers in humans, e.g. appendix, tail bone (coccyx), wisdom teeth.
• Connecting link – organism with features of two groups, e.g. Peripatus (annelids–arthropods), Duck-billed platypus (reptiles–mammals), Lungfish (fishes–amphibians).
• Carbon dating – finds age of fossils using C-14.

Diagram in words

• Draw forelimbs of human, cat, whale and bat side by side.
• Label the same bones: humerus, radius-ulna, carpals, metacarpals, phalanges.

Example

Giraffe: Lamarck said necks grew by stretching and the change was passed on. Darwin said giraffes born with longer necks got more food, survived and had more young.

Quick revision

• RNA has uracil (U) in place of thymine (T).
• Transcription needs the enzyme RNA polymerase.
• Darwin's book: "On the Origin of Species".
• Earliest life appeared about 3.5 billion years ago.
• Homologous organs prove a common ancestor.

Quick summary

Cells break food to release energy (ATP) through respiration. Cells also divide — mitosis for growth and repair, meiosis for making gametes.

Key points

• Food (carbohydrates, fats, proteins) is oxidised in cells to give energy stored as ATP.
• Aerobic respiration uses oxygen: glycolysis (cytoplasm) → Krebs cycle → electron transfer (mitochondria).
• One glucose gives 38 ATP in aerobic respiration.
• Anaerobic respiration (no oxygen) gives only 2 ATP; yeast makes ethanol + CO₂, muscles make lactic acid.
• Proteins and lipids are also used for energy when needed; proteins mainly build the body.
• Mitosis: one cell → 2 identical cells; chromosome number stays same (2n → 2n).
• Meiosis: one cell → 4 cells with half chromosomes (2n → n); happens in germ cells.

Important terms

• ATP – energy currency of the cell.
• Glycolysis – glucose → 2 pyruvic acid, in cytoplasm.
• Krebs cycle – tricarboxylic acid cycle in mitochondria; pyruvate fully oxidised.
• Fermentation – anaerobic breakdown of glucose by microbes.
• Crossing over – exchange of parts between paired chromosomes in meiosis I; gives variation.

Formulas

• Aerobic: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP
• Anaerobic (yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2 ATP

Diagram in words

• Mitosis stages in order: prophase → metaphase (chromosomes in the middle) → anaphase (chromatids pulled to poles) → telophase → cytokinesis.

Example

After a fast run, legs ache. Muscles got too little oxygen, so they respired anaerobically and lactic acid built up.

Quick revision

• Mitochondria = powerhouse of the cell.
• Mitosis in body (somatic) cells; meiosis in reproductive cells.
• Meiosis has two divisions: meiosis I and meiosis II.
• Plants form a cell plate; animal cells pinch in during cytokinesis.
• 1 gram of fat gives more energy than 1 gram of carbohydrate.

Quick summary

Reproduction makes new individuals of the same kind. It can be asexual (one parent) or sexual (two parents, gametes fuse).

Key points

• Asexual: one parent, no gametes, young are exact copies.
• Types: binary fission (Amoeba, bacteria), multiple fission (Plasmodium), budding (yeast, Hydra), fragmentation (Spirogyra), regeneration (Planaria), spore formation, vegetative propagation (potato, Bryophyllum).
• Sexual: male and female gametes (n) fuse to form a zygote (2n); gives variation.
• Flower: stamen (male – anther, filament) and carpel (female – stigma, style, ovary).
• Pollination: transfer of pollen to stigma — self or cross (by wind, water, insects).
• Flowering plants show double fertilization.
• Human male: testes make sperms and testosterone. Female: ovaries make ova, oestrogen and progesterone.
• Fertilization happens in the oviduct (fallopian tube); the embryo grows in the uterus.

Important terms

• Zygote – first cell formed after fertilization.
• Double fertilization – one male gamete + egg → zygote; other + secondary nucleus → endosperm.
• Menstrual cycle – about 28-day cycle in females; ovulation around day 14.
• Identical twins – one zygote splits into two; same sex, look alike.
• IVF – fertilization outside the body (test-tube baby).

Diagram in words

• Draw a flower in vertical section; label sepal, petal, anther, filament, stigma, style, ovary, ovule.

Example

A Bryophyllum leaf kept on moist soil grows small plants from buds on its edge — vegetative propagation.

Quick revision

• Puberty in humans: about 10–14 years.
• Placenta joins the foetus to the mother.
• Fraternal twins come from two different ova.
• Sexually transmitted diseases: syphilis, gonorrhoea, AIDS.
• Asexual reproduction is fast; sexual reproduction brings variation.

Quick summary

Living and non-living parts of nature work together as an ecosystem. Pollution and loss of biodiversity harm it, so we must manage and conserve the environment.

Key points

• Ecosystem = biotic (plants, animals, microbes) + abiotic (air, water, soil, light) parts.
• Energy flows: producers → herbivores → carnivores → top carnivores; decomposers recycle nutrients.
• Pollution of air, water, soil, noise and radiation damages health and ecosystems.
• Radioactive pollution (nuclear waste, accidents) can cause cancer and genetic defects.
• Laws: Wildlife Protection Act 1972, Forest Conservation Act 1980, Environment Protection Act 1986.
• Biodiversity has three levels: genetic, species and ecosystem diversity.
• Conserve by national parks, sanctuaries, biosphere reserves, sacred groves (devrai) and special projects like Project Tiger.
• India has 4 of the world's biodiversity hotspots: Himalaya, Western Ghats, Indo-Burma, Sundaland (Nicobar).

Important terms

• Trophic level – each step in a food chain.
• Hotspot – area very rich in species that is under threat.
• Sacred grove (देवराई) – forest patch protected by local people for religious reasons.
• Endangered species – may vanish soon if not protected, e.g. tiger.
• Vulnerable species – numbers falling, may become endangered.

Example

Jadav Payeng of Assam planted trees alone for about 30 years on a sandbar of the Brahmaputra. That forest (Molai forest) now shelters elephants, tigers and deer. He is called the "Forest Man of India".

Quick revision

• Producers are autotrophs; decomposers are bacteria and fungi.
• Energy decreases at each higher trophic level.
• Chipko movement – people hugged trees to save forests.
• Threatened species are listed in the Red Data Book (IUCN).
• Reduce, Reuse, Recycle saves resources.

Quick summary

Most power plants spin a turbine that turns a generator to make electricity. Green energy comes from sources that cause little or no pollution, like sun, wind and water.

Key points

• Generator works on electromagnetic induction: a coil turning in a magnetic field makes current.
• Thermal plant: coal burns → water becomes steam → steam turns turbine → generator.
• Nuclear plant: fission of uranium-235 gives heat → steam → turbine → generator.
• Hydro plant: water stored in a dam falls and turns the turbine.
• Wind plant: wind turns the blades of a windmill joined to a generator.
• Solar photovoltaic cell turns sunlight directly into electricity (DC); no turbine needed.
• Coal and gas plants give CO₂, smoke and ash; nuclear plants leave radioactive waste.
• Solar, wind and hydro are renewable and eco-friendly (green energy).

Important terms

• Turbine – wheel with blades that spins due to steam, water or wind.
• Nuclear fission – a heavy nucleus splits into smaller ones and gives huge energy.
• Solar panel – many solar cells joined together.
• Green energy – energy obtained without harming the environment.

Formulas

• Energy chain (thermal): chemical energy → heat → kinetic energy of turbine → electrical energy.
• Energy chain (hydro): potential energy of water → kinetic energy → electrical energy.

Diagram in words

• Thermal plant: draw boiler with coal, steam pipe to turbine, turbine shaft joined to generator, condenser sending water back to boiler.

Example

A rooftop solar panel on a school makes electricity in the day, which charges batteries for use at night — no fuel, no smoke.

Quick revision

• Solar cells are mostly made of silicon.
• India's first nuclear plant: Tarapur (Maharashtra).
• Koyna is a major hydroelectric project in Maharashtra.
• Wind energy depends on place and season.
• Solar cells give DC; an inverter converts it to AC.

Quick summary

Animals are grouped by body features like symmetry, body cavity, germ layers and presence of a notochord. Two big groups: non-chordates and chordates.

Key points

• Basis: body organisation, symmetry, germ layers, body cavity (coelom), segmentation, notochord.
• Non-chordates: no notochord, nerve cord on the belly side, no gill slits.
• Chordates: notochord, dorsal hollow nerve cord and gill slits at some stage.
• Non-chordate phyla: Porifera, Cnidaria, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata.
• Arthropoda is the largest phylum (jointed legs, chitin exoskeleton).
• Chordata has 3 subphyla: Urochordata, Cephalochordata, Vertebrata.
• Vertebrate classes: Cyclostomata, Pisces, Amphibia, Reptilia, Aves, Mammalia.

Important terms

• Symmetry – radial (Hydra, starfish adult), bilateral (most animals), or none (sponges).
• Diploblastic / Triploblastic – body from 2 germ layers (Cnidaria) or 3 germ layers (flatworms onwards).
• Coelom – body cavity; acoelomate (flatworm), pseudocoelomate (roundworm), true coelom (earthworm onwards).
• Notochord – stiff rod along the back in chordates.

Example

Quick revision

• Balanoglossus (Hemichordata) links non-chordates and chordates.
• Fishes breathe by gills; amphibians by skin and lungs.
• Birds: feathers, hollow bones, warm-blooded.
• Mammals: hair, mammary glands, external ears (pinna).
• Platypus is a mammal that lays eggs.

Quick summary

Microbes like bacteria, yeast and fungi are used in industry to make food, medicines, fuels and to clean waste. This is industrial microbiology.

Key points

• Curd and yoghurt: Lactobacillus turns milk sugar (lactose) into lactic acid, so milk thickens.
• Cheese is made by curdling milk and ripening it with microbes.
• Probiotics are live helpful bacteria (e.g. in yoghurt) that keep the gut healthy.
• Bread: yeast (Saccharomyces cerevisiae) ferments sugar and gives CO₂, so dough rises.
• Vinegar: Acetobacter turns ethanol into acetic acid.
• Antibiotics kill or stop harmful bacteria; penicillin came from the fungus Penicillium.
• Microbes make fuels: biogas (methane), ethanol and hydrogen.
• Microbes clean waste in sewage plants and landfills; using them to remove pollutants is bioremediation.

Important terms

• Fermentation – breakdown of sugar by microbes without oxygen.
• Probiotics – useful live microbes taken with food.
• Antibiotic – substance made by a microbe that acts against other microbes.
• Bioremediation – cleaning soil or water pollution using microbes.
• Xanthan gum – thickener made by the bacterium Xanthomonas campestris.

Example

Idli batter left overnight becomes fluffy and sour. Bacteria and yeast ferment it, release CO₂ and make acids.

Quick revision

• Penicillin was discovered by Alexander Fleming (1928).
• Citric acid is made using the fungus Aspergillus niger.
• Methane-producing bacteria work without oxygen in biogas plants.
• Antibiotics do not work against viruses.
• Microbes also spoil food, so we use cooling, drying, salting to preserve it.

Quick summary

Stem cells can become any kind of cell, so they help treat diseases. Biotechnology uses living cells and their genes to make useful products in farming, medicine and industry.

Key points

• Stem cells are unspecialised cells that can divide and turn into special cells.
• Embryonic stem cells (from early embryo) can form any cell; adult stem cells (bone marrow, fat, umbilical cord blood) form only some types.
• Uses: regenerative (cell) therapy, making blood cells, repairing damaged tissues.
• Organ donation: kidney, liver, heart, eyes, skin can be donated; one donor can save many lives.
• Biotechnology changes genes using recombinant DNA (genetic engineering).
• GM crops: Bt cotton (resists pests), Golden rice (vitamin A).
• Medicine: human insulin, vaccines, interferon, gene therapy and DNA fingerprinting.
• Cloning makes a genetically identical copy; Dolly the sheep (1996) was the first cloned mammal.

Important terms

• Stem cell – unspecialised cell that can form many cell types.
• Recombinant DNA – DNA made by joining genes from two different sources.
• Transgenic organism – organism with a gene from another species.
• Cloning – producing identical copies of a cell or organism.
• Biofertilizer – microbes that add nutrients to soil, e.g. Rhizobium.

Example

Diabetic patients need insulin. The human insulin gene is put into bacteria; the bacteria multiply and make large amounts of human insulin cheaply.

Quick revision

• Umbilical cord blood is a good source of stem cells (stem cell banking).
• Bt cotton carries a gene from the bacterium Bacillus thuringiensis.
• DNA fingerprinting helps identify criminals and parents.
• Eyes are donated after death; kidney can be donated by a living donor.
• Biotechnology also helps in cleaning pollution (bioremediation).

Quick summary

Social health is our ability to get along well with family, friends and society. Stress, addictions and misuse of technology disturb it; good habits and support restore it.

Key points

• Health (WHO) = physical + mental + social well-being, not just absence of disease.
• Social health depends on family, surroundings, friends, economic condition and culture.
• Disturbing factors: mental stress, addictions (tobacco, alcohol, drugs), chronic illness, isolation.
• Tobacco has nicotine; it causes mouth, lung and throat cancer.
• Alcohol damages the liver and nerves and breaks families.
• Overuse of mobile, internet and games causes addiction, poor sleep and loneliness.
• Cyber crimes: hacking, phishing, identity theft, online bullying; India's IT Act was passed in 2000.
• Stress is reduced by exercise, yoga, meditation, hobbies, talking to people and counselling.

Important terms

• Social health – ability to form good relations and adjust in society.
• Addiction – strong habit one cannot stop despite harm.
• Cyber crime – crime done using a computer, phone or internet.
• Stress – mental pressure due to difficult situations.
• Counselling – guidance by a trained expert to solve personal problems.

Example

A student plays mobile games till 2 a.m. daily, misses school and stops talking to family. Fixing screen-time limits, outdoor sports and family time can bring back social health.

Quick revision

• Never share OTP or passwords online.
• Salaam Mumbai Foundation works for tobacco-free schools and children.
• Smoking is banned in public places in India.
• Chronic diseases (diabetes, heart disease) also affect social life.
• Report cyber crime to the cyber police cell.

Quick summary

A disaster is a sudden event that causes heavy loss of life and property. Planning before it and quick help after it reduce the damage — this is disaster management.

Key points

• Natural disasters: earthquake, flood, cyclone, landslide, drought, tsunami, volcanic eruption.
• Biological disasters: epidemics (cholera, COVID-19), pest attacks on crops.
• Man-made disasters: fire, gas leak, industrial accidents, bomb blasts, stampede.
• Effects: deaths, injuries, homelessness, disease, loss of crops, money and jobs, mental shock.
• Phases after a disaster: emergency (rescue, relief) → rehabilitation → reconstruction.
• Pre-disaster: prevention, mitigation, preparedness (warning systems, drills, safe buildings).
• Post-disaster: rescue, first aid, relief camps, rebuilding.
• India passed the Disaster Management Act in 2005; NDMA is headed by the Prime Minister.

Important terms

• Disaster – sudden event causing large loss that the local people cannot handle alone.
• Mitigation – steps to reduce the impact of a disaster.
• First aid – immediate help given to an injured person before a doctor comes.
• Mock drill – practice of what to do during a disaster.
• Rehabilitation – helping victims return to normal life.

Example

During an earthquake in school: Drop under a desk, Cover your head, Hold on till shaking stops. Then walk out calmly to an open ground, away from walls and wires.

Quick revision

• Emergency numbers: 112 (all emergencies), 108 (ambulance), 101 (fire), 100 (police).
• First aid basics: check Airway, Breathing, Circulation (ABC).
• For a burn, pour clean cool water on it; do not burst blisters.
• Never use a lift during a fire or earthquake.
• NDRF is the special force for disaster rescue.