Class 10 — Notes 📙

404 = 96×4 + 20 → 96 = 20×4 + 16 → 20 = 16×1 + 4 → 16 = 4×4 + 0. HCF = 4

Assume √2 = p/q (lowest terms). Then 2 = p²/q² → p² = 2q² → p² is even → p is even → p = 2k → 4k² = 2q² → q² = 2k² → q is even. But p and q both even contradicts our assumption that p/q is in lowest terms. So √2 is irrational.

Adding both: 2x = 6 → x = 3. Substituting: 3 + y = 5 → y = 2. Solution: x = 3, y = 2

When the lines are parallel — they never meet. Condition: a₁/a₂ = b₁/b₂ ≠ c₁/c₂. The system is called inconsistent.

In right triangle ABC, AB² + BC² = AC² (Pythagoras). Dividing by AC²: (AB/AC)² + (BC/AC)² = 1 → sin²θ + cos²θ = 1 ✓

= (√3/2)(√3/2) + (1/2)(1/2) = 3/4 + 1/4 = 1 (= sin 90°)

A reaction where a more reactive element displaces a less reactive element from its compound. Example: Fe + CuSO₄ → FeSO₄ + Cu. Iron displaces copper because iron is more reactive than copper.

3Fe + 4H₂O → Fe₃O₄ + 4H₂

Corrosion is the slow oxidation of metals in presence of air and moisture. Example: rusting of iron (Fe → Fe₂O₃). Prevention: painting, galvanizing (zinc coating), oiling, alloying.

At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across it. V = IR. The ratio V/I is constant and is called resistance.

In parallel: 1) Each appliance gets the same voltage (220V). 2) Each appliance works independently — if one fails others keep working. 3) Total resistance decreases allowing more current.

P = V²/R = 200²/100 = 40000/100 = 400 W

Napoleon's conquests spread ideas of liberty, equality and fraternity from French Revolution to Europe. He introduced the Civil Code (1804) abolishing feudal privileges. Though he was a conqueror, his administrative reforms inspired nationalism in conquered territories.

1. Giuseppe Mazzini — gave vision and ideology of unified Italy. 2. Count Cavour — used diplomacy and war. 3. Giuseppe Garibaldi — led armed movement in southern Italy with his Red Shirts.

The students are taught by the teacher.

"Yours faithfully" is used when you do NOT know the name of the person (Dear Sir/Madam). "Yours sincerely" is used when you know and use the name of the person (Dear Mr. Sharma).

Transcription is the process of RNA synthesis using DNA as a template. Only one strand of DNA is used. mRNA is produced with a nucleotide sequence complementary to the DNA strand. RNA has Uracil instead of Thymine. The mRNA carries the genetic code from nucleus to cytoplasm for protein synthesis.

Darwin proposed: (1) All organisms reproduce in large numbers. (2) There is competition among organisms for survival. (3) Only those with useful modifications survive (survival of the fittest). (4) Nature selects fit organisms, which reproduce and pass characters to offspring. (5) Over time, new species form. Objections: Natural selection alone doesn't explain all evolution; no explanation for abrupt changes.

Vestigial organs are degenerated or underdeveloped organs that are non-functional in a particular organism but may be functional in related organisms. Examples in humans: (1) Appendix (functional in ruminants), (2) Ear muscles (functional in monkeys), (3) Tail bone/Coccyx (functional as tail in other vertebrates), (4) Wisdom teeth (used for chewing in ancestors).

Carbon dating is a method to determine the age of fossils based on radioactive decay of C-14. After death, C-14 keeps decaying while C-12 remains constant. By measuring ratio of C-14 to C-12, the time since death can be calculated. It is used in palaeontology and anthropology for dating fossils and ancient manuscripts. Developed by Willard Libby (Nobel Prize 1960).

Connecting links are organisms that show characteristics of two different groups, proving evolutionary relationships. Examples: (1) Peripatus — between Annelida and Arthropoda (segmented body + tracheal respiration). (2) Duckbill Platypus — between Reptilia and Mammalia (lays eggs + has mammary glands). (3) Lungfish — between Pisces and Amphibia (breathes with lungs despite being a fish).

Step 1 — Glycolysis (cytoplasm): Glucose (6C) → 2 Pyruvic acid (3C) + 2 ATP + 2 NADH₂
Step 2 — Krebs Cycle (mitochondria): Pyruvic acid → Acetyl CoA (enters TCA cycle) → CO₂ + H₂O + NADH₂ + FADH₂
Step 3 — Electron Transfer Chain (mitochondria): Each NADH₂ → 3 ATP; each FADH₂ → 2 ATP; water formed
Complete oxidation of 1 glucose → 38 ATP molecules

Mitosis: Occurs in somatic/stem cells; 1 division; 2 daughter cells formed; daughter cells are diploid (2n); no crossing over; daughter cells genetically identical to parent. Purpose: growth, repair, wound healing.
Meiosis: Occurs in germ cells; 2 divisions; 4 daughter cells formed; daughter cells are haploid (n); crossing over occurs in Prophase-I; all 4 cells genetically different. Purpose: gamete/spore formation.

ATP (Adenosine Triphosphate) is called the energy currency of the cell because: (1) Energy produced in respiration is stored in the phosphate bonds of ATP. (2) This energy is released when needed by breaking the bond between second and third phosphate (ATP → ADP + P + Energy). (3) Just like money is used for different purposes, ATP provides energy for all cellular activities like movement, synthesis of proteins, active transport, etc.

During heavy exercise, oxygen supply becomes insufficient. Muscle cells switch to anaerobic respiration: Glucose → Pyruvic acid (glycolysis) → Lactic acid (fermentation). Less energy (only 2 ATP) is produced compared to aerobic respiration (38 ATP). Also, lactic acid accumulates in the muscles, causing the feeling of tiredness and muscle cramps.

Double fertilization is unique to angiosperms (flowering plants). Two male gametes enter the embryo sac: (1) First male gamete + Egg cell → Zygote (which develops into embryo). (2) Second male gamete + 2 Polar nuclei → Endosperm nucleus (which develops into endosperm, storing food for the seed). Since two fusions occur, it is called double fertilization. Ovule → Seed, Ovary → Fruit after fertilization.

Menstrual cycle: 28–30 day repeating cycle in females from puberty to menopause.
Hormones: FSH → stimulates follicle growth + estrogen secretion → endometrium regenerates. LH surge → ovulation (follicle bursts, oocyte released) → corpus luteum forms → secretes progesterone → endometrium ready for implantation. If no fertilization: corpus luteum degenerates → estrogen and progesterone drop → endometrium breaks down → menstruation (5 days bleeding). Cycle repeats.

Sex is determined at fertilization. Father produces two types of sperms: (22+X) and (22+Y). Mother produces only one type of oocyte: (22+X). If X-sperm fertilizes oocyte: (44+XX) → Girl. If Y-sperm fertilizes oocyte: (44+XY) → Boy. Therefore, the father's sperm determines the sex of the child, NOT the mother. It is completely wrong and unscientific to blame the mother for having a girl child.

Monozygotic twins (Identical twins): Formed from a single zygote that splits into two groups within 8 days. Genetically identical. Always same gender (both boys or both girls).
Dizygotic twins (Fraternal twins): Formed when two oocytes are released and fertilized by two separate sperms. Two zygotes form. Genetically different. Can be same or different gender.

IVF (In Vitro Fertilization) is a technique where fertilization occurs outside the body (in a test tube/laboratory). The embryo formed is then implanted in the uterus at the right time. IVF is used for: (1) Less sperm count in males, (2) Blocked oviducts in females, (3) Irregular menstrual cycle or difficulty in oocyte production. It helps childless couples to have children using advanced medical technology.

Biodiversity: The richness of living organisms in nature due to presence of varieties of organisms, ecosystems and genetic variations within a species.

1. Genetic Diversity: Diversity among organisms of the same species due to genetic variation. Ex: Every human being is different from other.
2. Species Diversity: Innumerable species of organisms (plants, animals, microbes) present in nature.
3. Ecosystem Diversity: Many different types of ecosystems in each region. Each ecosystem has characteristic plants, animals, microbes and abiotic factors. Types: Natural (forest, pond) and Artificial (crop field, garden).

Environmental pollution: Direct or indirect changes in physical, chemical and biological properties of air, water and soil due to natural events or human activities, which are harmful to humans and other living beings.

Causes: (1) Population explosion, (2) Fast industrialization, (3) Indiscriminate use of natural resources, (4) Deforestation, (5) Unplanned urbanization.

(1) Forest Conservation Act, 1980: Land reserved for forest cannot be used for any other purpose. Permission of central govt. compulsory for mining. Violation: 15 days imprisonment.
(2) Environmental Protection Act, 1986: Controls pollution; prohibits releasing pollutants beyond permissible limits. Violation: 5 years imprisonment or ₹1 lakh fine.
(3) Wildlife Protection Act, 1972: Trading of rare animals banned (Clause 49A). Use of articles from wild animals banned (49B).
(4) National Green Tribunal, 2010: Effective implementation of environment laws.

Endangered Species: Number has declined so much that they can become extinct in near future if conservation not done. Ex: Lion-tailed monkey, Lesser florican.
Rare Species: Number considerably declined; endemic species may become extinct very fast. Ex: Red panda, Musk deer.
Vulnerable Species: Number is extremely less and continuously declining. Ex: Tiger, Lion.
Indeterminate Species: Appear to be endangered but no definite information due to their behaviour (shyness). Ex: Giant squirrel (Shekru).

(1) Protecting rare species of organisms, (2) Establishing national parks and sanctuaries, (3) Declaring some regions as 'bioreserves', (4) Projects for conservation of special species, (5) Conserving all plants and animals, (6) Observing the rules and laws, (7) Maintaining record of traditional knowledge.

Jadav Molai Payeng from Assam started planting trees at age 16. Over 30 years of continuous work, he converted barren land of 1360 acres into a dense forest in Kokilamukh, Jorhat district. He was awarded the Padmashree. The lesson: "Many people come together to destroy the forest, but a single person, if determined, can establish a new forest!" — Individual dedication and determination can bring great environmental change.

Most electric power plants work on Michael Faraday's principle of Electromagnetic Induction: Whenever the magnetic field around a conductor changes, a potential difference (EMF) is generated across it.

A turbine is used to rotate a magnet inside the generator. When any fluid (steam, water, gas, wind) strikes the turbine blades, they rotate. The rotating magnet creates changing magnetic field around the coil, generating electricity.

Flow chart: Energy source → Turbine → Generator → Electrical energy

Green Energy: Electricity generated from environment-friendly, renewable (perpetual/never-ending) sources that do not cause air pollution or environmental degradation.

Green energy sources:
(1) Hydroelectric — uses flowing water, no fuel burnt
(2) Wind energy — uses kinetic energy of wind, clean and renewable
(3) Solar energy — uses sunlight, no combustion
(4) Biofuels — made from organic matter, renewable

These are called green energy sources because: they never deplete (perpetual), do not emit harmful gases, do not cause global warming or acid rain, and are environment-friendly.

Nuclear Fission: When a neutron is bombarded on Uranium-235, it absorbs the neutron and forms Uranium-236. U-236 is extremely unstable and splits into Barium + Krypton + 3 neutrons + 200 MeV energy.

Chain Reaction: The 3 neutrons released each cause fission of 3 more U-235 atoms, releasing more neutrons and energy. This self-sustaining process is the chain reaction. In nuclear power plants, the chain reaction is controlled to release thermal energy gradually for electricity generation.

(1) Burning fossil fuels (coal, natural gas) emits CO₂, SO₂, NOx, soot particles → Air pollution, global warming, acid rain, respiratory diseases.
(2) Fossil fuels took millions of years to form and have limited reserves — coal may last ~200 years, natural gas ~200–300 years. They will deplete.
(3) They are not renewable — once used, cannot be replenished.
Therefore, fossil fuels cause environmental damage and are non-renewable — opposite of green energy criteria.

A solar photovoltaic cell converts solar radiation energy directly into DC electrical energy through the photovoltaic effect. It is made of semiconductor material (silicon). A 1 cm² silicon cell gives ~30 mA current and 0.5 V. Potential difference is independent of cell area.

Series connection: Voltage adds (V₁+V₂), current stays same. Used to increase voltage.
Parallel connection: Current adds (I₁+I₂), voltage stays same. Used to increase current.
Solar cell → Module (cells in series) → String (modules in series) → Array (strings in parallel). DC output is converted to AC using an inverter.

Advantages: (1) No fuel burnt — no air pollution from combustion. (2) Can generate electricity as and when needed (if water available). (3) Water reservoir replenished in rainy season — uninterrupted supply.

Problems: (1) Back-water submerges villages, towns, forests, fertile land — displacement of communities. (2) Obstruction of river flow harms aquatic life. Due to these issues, debate exists on whether hydroelectric is truly environment-friendly.

Thermal: Fuel = coal; Energy chain = Chemical→Thermal→Kinetic(steam)→Kinetic(turbine)→Electrical; Pollution = high; Renewable = No
Nuclear: Fuel = Uranium/Plutonium; Energy chain = Nuclear→Thermal→Kinetic(steam)→Kinetic(turbine)→Electrical; Pollution = nuclear waste; Renewable = No
Hydroelectric: Fuel = none; Energy chain = Potential(water)→Kinetic(water)→Kinetic(turbine)→Electrical; Pollution = none; Renewable = Yes
Solar PV: Fuel = sunlight; Energy chain = Solar→DC Electrical (direct); Pollution = none; Renewable = Yes (day only)

(A) Grades of organization: Protoplasmic (unicellular-Amoeba) → Cellular (Porifera) → Cell-Tissue (Cnidaria) → Tissue-Organ (Platyhelminthes) → Organ-System (all higher animals)
(B) Body symmetry: Asymmetrical (sponges), Radial (starfish — any plane gives two equal halves), Bilateral (one plane only — humans, frogs)
(C) Germ layers: Diploblastic = 2 layers (Cnidarians). Triploblastic = 3 layers (all others — mesoderm added)
(D) Body cavity (Coelom): Acoelomate = absent (Porifera, Cnidaria, Platyhelminthes). Pseudocoelomate = false cavity (Aschelminthes). Eucoelomate = true cavity from mesoderm (Annelida onwards)
(E) Segmentation: Body divided into similar units (segments). Ex: Earthworm (Annelida)

Chordates: (1) Notochord present in body (at least some stage). (2) Pharyngeal gill slits present. (3) Nerve cord on dorsal side — hollow, single. (4) Heart on ventral side.
Non-Chordates: (1) No notochord. (2) No pharyngeal gill slits. (3) Nerve cord (if present) on ventral side — solid and paired. (4) Heart (if present) on dorsal side.

(1) Largest phylum in animal kingdom — highest number of animals on Earth. (2) Found in all habitats from deep ocean to highest mountains. (3) Jointed appendages — hence called arthropods. (4) Body is triploblastic, eucoelomate, bilaterally symmetrical, segmented. (5) Chitinous exoskeleton present. (6) Unisexual. Examples: Crab, Spider, Scorpion, Millipede, Centipede, Cockroach, Butterfly, Honey bee.

Vertebrates are animals in which the notochord is replaced by a vertebral column. They belong to Subphylum Vertebrata of Phylum Chordata. Phylum Chordata also includes Urochordata (Herdmania) and Cephalochordata (Amphioxus) which have notochord but no vertebral column. So all vertebrates have chordate characteristics (notochord, gill slits, dorsal nerve cord), making them chordates. But Urochordata and Cephalochordata are chordates without vertebrae — so not all chordates are vertebrates.

Butterfly: Phylum Arthropoda; body has head+thorax+abdomen; 3 pairs of legs + 2 pairs of wings; chitinous exoskeleton; cold blooded; lays eggs.
Bat: Class Mammalia; body has head+neck+trunk+tail; forelimbs modified into patagium (wing membrane); hairs on body; warm blooded; gives birth to young ones; mammary glands present.

Amphibia characteristics: moist soft skin (no scales), digits without claws, no neck, larva is aquatic only. Tortoise has dry scaly skin, digits with claws, neck is present, no larval aquatic stage. Also tortoise breathes with lungs on land AND in water — not with gills in water like amphibian larvae. These are characters of Class Reptilia, not Amphibia.

Applied Microbiology: Branch of biology that studies enzymes, proteins, applied genetics and molecular biology of prokaryotes and eukaryotic microbes for producing food and medicines on large scale for society.

Industrial Microbiology: Science related to commercial use of microbes for various economic, social and environmental processes and products.

Main features: (A) Various productions through fermentation — bread, cheese, wine, raw material for chemicals, enzymes, nutrients, medicines. (B) Use of microbes for garbage management and pollution control.

Yoghurt is produced with help of lactobacilli (inoculants). Milk is boiled, then cooled to warm temperature. Two bacterial strains are added in 1:1 proportion — Streptococcus thermophilus and Lactobacillus delbrueckii.
Streptococcus produces lactic acid → proteins gel out → gives dense consistency to yoghurt.
Lactobacilli produce acetaldehyde compounds → gives characteristic taste.
Condensed milk powder is added to maintain protein content. Pasteurization improves shelf life and probiotic properties.

Baker's yeast (Saccharomyces cerevisiae) is mixed with flour, water, salt and other materials to form dough. Yeast performs fermentation of carbohydrates: Sugar → CO₂ + Ethanol. The CO₂ gas produced gets trapped in the dough and makes it rise. During baking, gas expands further and ethanol evaporates. This gives the bread its spongy, porous texture. Yeast also makes bread nutritious as it contains carbohydrates, fats, proteins, vitamins and minerals.

Probiotics: Milk products containing active live bacteria like Lactobacillus Acidophilus, Lactobacillus casei, Bifidobacterium bifidum. Available as yoghurt, kefir, sauerkraut, dark chocolate, pickles, etc.

Importance: (1) Maintain balance of intestinal microorganisms — increase helpful microbes and decrease harmful ones (Clostridium). (2) Improve resistance and lower ill-effects of harmful metabolic substances. (3) Reactivate useful microbes made inactive by antibiotics. (4) Used for treatment of diarrhoea and in poultry treatment. (5) Form colonies of useful microbes in alimentary canal.

(1) Active at low temperature, pH and pressure — saves energy and no need for erosion-proof instruments. (2) Enzymes carry out specific processes — no unnecessary by-products formed, reducing purification costs. (3) Waste material elimination and decomposition avoided — enzymes can be reused. (4) Eco-friendly — do not cause pollution. These advantages make microbial enzymes preferred over chemical catalysts in chemical, cheese, textile, leather and paper industries.

Petroleum oil spilling in ocean is toxic and fatal to aquatic organisms. It cannot be easily removed by mechanical methods. Hydrocarbonoclastic bacteria (HCB) like Pseudomonas spp. and Alcanovorax borkumensis can destroy pyridines and other hydrocarbons. They decompose the hydrocarbons and react carbon with oxygen, forming CO₂ and water. These bacteria are used to clean oil spills in oceans.

Bioremediation: Absorption or destruction of toxic chemicals and harmful pollutants using microorganisms or plants (phyto-remediation). Dr. Anand Mohan Chakravarti (India-born American scientist) first suggested use of such microbes for oil spill cleaning.

Biofuel: Renewable fuel obtained from biological sources. Available in solid (coal, dung, crop residue), liquid (vegetable oils, alcohol) and gaseous (biogas, coal gas) forms.

Fuels from microbes:
(1) Methane — microbial anaerobic decomposition of urban, agricultural and industrial waste (biogas plants).
(2) Ethanol — fermentation of molasses by Saccharomyces. Clean, smokeless fuel. Mixed with petrol/diesel to reduce pollution.
(3) Hydrogen — bio-photolysis of water in which bacteria perform photoreduction. Considered fuel of the future.

Stem cells: Special undifferentiated cells in multicellular organisms that can give rise to all other cell types and play important role in wound healing. Property of changing into any cell type = pleuripotency.

Types: (1) Embryonic stem cells — from embryo before 14th day (5th–7th day blastocyst stage). (2) Adult stem cells — from red bone marrow, adipose tissue, blood.

Sources: Umbilical cord, blastocyst, red bone marrow, adipose tissue, cord blood.

Uses: (1) Cell therapy — replace dead cells in diabetes, Alzheimer's, Parkinson's disease. (2) Blood cell production for anaemia, thalassemia, leukemia. (3) Organ transplantation — produce new kidney/liver using stem cells.

Biotechnology: Science of bringing about artificial genetic changes and hybridization in organisms for human welfare. It includes cytology, biochemistry, molecular biology, and genetic engineering.

Benefits in Agriculture:
(1) Increased per hectare yield irrespective of land limitations.
(2) Development of disease-resistant varieties — reduces expenses on disease control.
(3) Fast fruit-setting varieties increase yield per annum.
(4) Stress-resistant varieties (cold, drought, soil salinity).
(5) Bt Cotton/Brinjal — built-in pest resistance using Bacillus thuringiensis gene.
(6) Golden Rice — enriched with Vitamin A (beta carotene).
(7) Biofertilizers (Rhizobium, Azotobacter) improve nitrogen fixation — reduce chemical fertilizer use.

Cloning: Production of an exact genetic replica of any cell, organ or entire organism.

Dolly the sheep was the first mammal cloned, born on 5th July 1996 in Scotland. Method: Nucleus was taken from the udder cell of a Finn Dorset sheep and inserted into an enucleated ovum of a Scottish sheep. The ovum was then implanted in the uterus of a Scottish sheep. The lamb (Dolly) born showed characters of the Finn Dorset sheep (as per the nucleus), with no characters of the Scottish sheep.

Types of cloning: (1) Reproductive cloning — to produce a new organism. (2) Therapeutic cloning — stem cells derived from lab-made embryo for treating diseases.

DNA fingerprinting: The DNA sequence of each person is unique, just like fingerprints. Identity of any person can be established using their available DNA sample. This technique is called DNA fingerprinting.

Uses: (1) Forensic sciences — identity of criminal can be established from any body part found at crime scene. (2) Paternity testing — identity of the biological father of a child can be confirmed. (3) Center for DNA Fingerprinting and Diagnostics, Hyderabad performs this research in India.

Bioremediation: Absorption or destruction of toxic chemicals and harmful pollutants with the help of plants and microorganisms. When plants are used, it is called phyto-remediation.

Examples:
(1) Pseudomonas bacteria — clean hydrocarbon and oil pollutants from soil and water (oil spills)
(2) Pteris vitata (fern) — absorbs arsenic from soil
(3) Genetically modified Indian mustard — absorbs selenium from soil
(4) Sunflower — absorbs uranium and arsenic
(5) Geobacter — converts water-soluble uranium salts into insoluble salts, preventing groundwater contamination
(6) Deinococcus radiodurans — radiation-resistant, absorbs radiation from radioactive debris

Green Revolution: Use of dwarf varieties of wheat and rice, proper use of fertilizers and pesticides, and water management to increase food grain production. Dr. Norman Borlaug (USA) and Dr. M.S. Swaminathan (India) contributed. Saved millions from hunger.

White Revolution: Increase in dairy production through cooperative movement and use of biotechnology. Dr. Verghese Kurien established the cooperative dairy movement at Anand, Gujarat (Amul model).

Blue Revolution: Production of useful aquatic organisms (fish, shrimp, lobster) using water bodies. Government launched NKM-16 (Nil-Kranti Mission 2016) with 50–100% subsidy for pisciculture.