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Saturday, 13 January 2018

SBI Probationary Officer (PO) Pre. Exam

SBI Probationary Officer (PO) Pre. Exam 

Quantitative Aptitude Solved Questions

1. At present, Pia is 6 years older to Ray. The respective ratio between the present ages of Pia and Mini is 3 : 4. At present Ray is 14 years younger to Mini. What. is Ray's present age? 
(a) 16 years (b) 20 years (c) 14 years (d) 18 years (e) 24 years (Ans : d)

Directions (2-6) : In these questions, two equations numbered I and II are given. You have to solve both the equations and mark the appropriate answer. 

Give answer : (a) If ≥ y 
(b) If x ≤ y 
(c) If x > y 
(d) If x < y
(e) If relationship between x and y cannot be established 

2. I. 4x2 + 17+ 15 = 0
II. 3+ 19+ 28 = 0 (Ans : e)

3. I. 3x2 –17x + 22 = 0 
II. 5y – 21y + 22 = 0 (Ans : a)

4. I. 3x2 + 11x + 10 = 0 
II. 2y + 13+ 21 = 0 (Ans : c)

5. I. 3x2 + 13x+ 14 = 0 
II. 8+ 26+ 21 = 0 (Ans : d)

6. I. 3x– 14+ 15 = 0 
II. 15– 34+ 15 = 0 (Ans : a)

Directions (7-11) : Study the table to answer the given questions. 

(Note: Other than the mentioned expenses under the given heads, there may also be some other expense. For calculation purposes, please consider the given expense heads only.) 

7. What is the respective ratio between the marketing expenses of company A and the marketing expenses of company C ? 
(a) 34 : 35 (b) 32 : 33 (c) 35 : 36 (d) 36 : 37 (e) 37 : 38 (Ans : d)

8. Total expenses of company E in October 2012 was 20% more than the total given expenses of the same company in April 2012. How much was the Marketing expenses of the same company in October 2012, if it was 25% of the total expenses of the same month? (in Rs. lakh) 
(a) 27 (b) 24 (c) 26 (d) 21 (e) 18 (Ans : d)

9. Marketing expenses of company D is less than marketing expenses of Company B, by approximately what percent? 
(a) 20% (b) 40% (c) 39% (d) 59% (e) 29% (Ans : e)

10. What is the average total expense of all the companies? (in Rs. lakh) 
(a) 75.25 (b) 75.8 (c) 75 (d) 72.8 (e) 72.25 (Ans : b)

11. What is the difference between the total expenses made by company C in legal and marketing together and the total expenses made by company E in legal and marketing together? (in Rs. lakh) 
(a) 24.5 (b) 23.5 (c) 22.9 (d) 23 (e) 23.9 (Ans : e)

Directions (12-16) : What approximate value will come in place of the question mark (?) in the given questions? (You are not expected to calculate the exact value.) 
12. 6399  × l 5/8 + 353 » ? = 10444 
(a) 14 (b) 22 (c) 2 (d) 16 (e) 8 (Ans : e)

13 (624) × 14.02 + (404) × 15.97 = ? 
(a) 670 (b) 570 (c) 710 (d) 510 (e) 610 (Ans : a)

14. 8461 » 11.99 – 24.01 » 5/100 = ? 
(a) 625 (b) 400 (c) 25 (d) 900 (e) 225 (Ans : e)

15. 14.85% of 679 + 19.9% of 219.89 = ? 
(a) 115 (b) 145 (c) 65 (d) 105 (e) 85 (Ans : b)

16. 1441 » ? + 149.98 × 14.99 = 3006 – 254.91 
(a) 35 (b) 15 (c) 25 (d) 45 (e) 3 (Ans : e)

Directions (17-21) : What will come in place of the question mark (?) in the following number series? 
17. 19 30 44 67 117 ? 
(a) 236 (b) 272 (c) 264 (d) 248 (e) 254 (Ans : d)

18. 7 9 18 46 111 ? 
(a) 245 (b) 229 (c) 233 (d) 248 (e) 237 (Ans : e)

19. 7 24 58 109 ? 262 
(a) 183 (b) 189 (c) 171 (d) 163 (e) 177 (Ans : e)

20. 19 20 16 25 9 ? 
(a) 32 (b) 38 (c) 34 (d) 42 (e) 48 (Ans : c)

21. 7.4 9.2 11.4 14 17 ? 
(a) 19.8 (b) 22.6 (c) 23 (d) 21 (e) 20.4 (Ans : e)

22. A bag contains 5 red balls, 6 yellow balls and 3 green balls. If two balls are picked at random, what is the probability that either both are red or both are green in colour ? 
(a) 3/7 (b) 5/14 (c) 1/7 (d) 2/7 (e) 3/14 (Ans : c)

23. In a 140 litre of mixture of milk and water, percentage of water is only 30%. The milkman gave 20 litre of this mixture to a customer. Then he added equal quantities of pure milk and water to the remaining mixture. As a result the respective ratio of milk and water in the mixture became 2 : 1. What was the quantity of milk added? (in litres) 
(a) 12 (b) 16 (c) 18 (d) 8 (e) 10 (Ans : a)

24. A boat can travel 4.2 km upstream in 14 min. If the respective ratio of speed of the boat in still water and speed of the stream is 7 : 1. How much time will the boat take to cover 17.6 km downstream? (in min) 
(a) 52 (b) 44 (c) 48 (d) 36 (e) 54 (Ans : b)

25. A starts a business with a capital of Rs. 1,500/-. B joins the business 6 months later from the start of the business and C joins the business 8 months later from the start of the business. In the end of the year their respective share in profit was in ratio of 5 : 3 : 3. What is the sum of amount put in the business by Band C together? 
(a) Rs. 3,300/- (b) Rs. 3,500/- (c) Rs. 4,200/- (d) Rs. 4,800/- (e) Rs. 4,500/- (Ans : e)

26. The length of a rectangle is 4m more than the side of a square and the breadth of the rectangle is 4m less than side of the same square. If the area of the square is 567 sq m, what is the area of the rectangle? (in sq m) 
(a) 549 (b) 545 (c) 557 (d) 560 (e) 551 (Ans : d)

27. A sells an item at 20% profit to B. B sells it to C at 10% profit. C sells it to D at Rs. 116/- profit. Difference between the cost price of D and cost price of A was Rs. 500/-. How much did B pay to A for the item? 
(a) Rs. 1,240/- (b) Rs. 1,250/- (c) Rs. 1,440/- (d) Rs. 1,450/- (e) Rs. 1,400/- (Ans : c)

28. 10 men can finish a piece of work in 15 days. 8 women can finish the same piece of work in 25 days. Only 10 women started working and in few days completed certain amount of work. After that 3 men joined them. The remaining work was completed by 10 women and 3 men together in 5 days. After how many days 3 men joined 10 women? 
(a) 11 (b) 13 (c) 15 (d) 10 (e) 12 (Ans : b)

29. Rs. 16,000/- was invested for three years, partly in Scheme A at the rate of 5% simple interest per annum and partly in Scheme B at the rate of 8% simple interest per annum. Total interest received at the end was Rs. 3,480/-. How much sum of money was invested in Scheme A ? 
(a) Rs. 6,000/- (b) Rs. 6,500/- (c) Rs. 4,500/- (d) Rs. 4,000/- (e) Rs. 8,000/- (Ans : d)

Directions (30-34) : Refer to the graph and answer the given questions. 

30. Number of hats sold by store M during January is what per cent of the total number of hats sold by the store N during March and April together? 
(a) 51 % (b) 55 ⅔% (c) 47 % (d) 53 % (e) 57 ⅔% (Ans : d)

31. What is the average number of hats sold by store N during January, March, May and June? 
(a) 535 (b) 525 (c) 515 (d) 500 (e) 530 (Ans : b)

32. Stores M and N sell only two types of hats : Fedora Hats and Trilby Hats. If the respective ratio of total number of Fedora hats to total number of Trilby hats sold by stores M and N together during March is 9 : 5, what is the total number of Fedora hats sold by stores M and N together during March? 
(a) 990 (b) 900 (c) 720 (d) 630 (e) 810 (Ans : e)

33. If the total number of hats sold by stores M and N together in July is 15% more than the total number of hats sold by the same stores together during June, what is the total number of hats sold by the same stores together during July? 
(a) 1298 (b) 1316 (c) 1356 (d) 1284 (e) 1334 (Ans : e)

34. Number of hats sold by store M increased by what percent from February to May? 
(a) 75 (b) 55 (c) 65 (d) 70 (e) 60 (Ans : c)

35. Monthly salary of Dex is 1/4th of his father's monthly salary. Dex's sister's monthly salary is 2/5th of their father's monthly salary. Dex's sister pays Rs. 12,800/- which is 1/4th of her monthly salary as study loan. Savings and expenses made out of the monthly salary, by Dex is in the respective ratio 3 : 5. How much does Dex save each month? 
(a) Rs. 12,000/- (b) Rs. 10,600/- (c) Rs. 10,400/- (d) Rs. 12,600/- (e) Rs. 12,400/- 

(Ans : a) - 
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Thermodynamics Revision Sheet

              Thermodynamics Revision Sheet

TF=9/5 TC + 32°
TC = TK - 273.15 K
The pressure,volume and temperature in kelvin of such gases obey the equation
PV=nRT ----(1)
Thermal expansion


Specific Heat Capacity=ΔQ/mΔT

Gas Laws
Boyles Law: PV=constant
Charles Law : V/T=constant
Dalton Law of Partial Pressure: P=P1 + P2 +P3
Root mean Square Velocity
Mean  Velocity
Most Probable Velocity
Vrms > Vm > V

Average kinetic Energy of Gas=3/2nRT

First law of Thermodynamics


Gas Processes

Isothermal Process : PV=constant ,ΔU=0,Q=W,Molar Specific Heat=infinity
Adaibatic Process : PVy=constant,Q=0,ΔU=-W,Molar Specific Heat=zero
Polytropic Process : PVn=constant,Molar Specific Heat=[R/(y-1) + R/(1-n)]
Volume Constant : P/T=constant W=0,ΔU=Q,Molar Specific Heat=Cv
Pressure Constant : V/T=constant ΔU=Q-W ,Molar Specific Heat=CP

Internal energy depends on Temperature.
So for same temperature change ΔT

Molar Specfic Heat Capacity of any process is given by

C=Cv + Pdv/ndT where n is no of moles of the gas

Workdone by Gas= ∫PdV

Heat Conduction


Wein displacement lawλT4=Constant

Stefan's Law

Newton law of Cooling


Problem Solving tips
1.     Net Heat flow at a junction is Zero
2.     Internal Energy does not depend on the path
3.     Internal Energy in a cyclic  Process is zero
4.     Heat is positive when given to the system and negative when taken out of the system
5.     Workdone by the system on the surrounding is positive while the workdone on the system by the surrounding is megative

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Laws of chemical combinations

Laws of chemical combinations

      1)      Law of conservation of mass:- According to this law “matter can neither be created nor destroyed” Given by Antone Lovoisin in 1789.
    2)      Law of definite proportion:- According to this law “A given compound always contains exactly the same proportion of elements by weight known as law of definite proportion or law of definite composition” given by Joseph Proust in 1754-1826
     3)      Law of multiple proportion:- According to this law “if two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of small whole number” given by Dalton in 1803.
    4)      Gay lussac’s law of gaseous volume:- According to this law “gases combine or are produced in chemical reactions they do so in a simple ratio by volume provided to all gases are at the  same temperature and pressure” given by Gay Lussac’s in 1808.
    5)      Avogadro’s law:- According to this law “Equal volume of gases at same temperature & pressure should contain equal no. of molecules” given by Avogadro in 1811.

Dalton’s Atomic Theory

 i.            Matter consists of indivisible atoms.
       i. All the atoms of a element have identical properties (same properties) i.e. atoms of a element have same mass while atoms of different elements have different masses.
       ii.Compounds formed when atoms of different elements combine in fixed ratio.
     iii Chemical reactions involve reorganization (rearrangement) of atoms.
Atomic mass unit = 1/12th mass of one carbon12 atom.
Molecular mass = It is the sum of atomic masses of the elements present in a molecule.
Mole :- It is the amount of substance equal to Avogadro no. (NA). = 6.022 ´ 1023 atoms/mole.
Molar mass:- Mass of one mol of a substances in gram is known as molar mass.
Mass % of an element = mass of that element in compound ´ 100/ molar mass of the compound.
Empirical formula :- It is the simplest whole no. ratio of various atoms present in a compound.
Molecular formula:- It is the exact no. of different types of atoms present in a molecule of a compound.

Concentration expression methods

                   ii.            Mole fraction :- If a substance ‘A’ is dissolved in ‘B’ and their no. of moles are nA and nB respectively.
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द्रव्य (Matter)

द्रव्य (Matter)

1. द्रव्य (Matter) क्या होता है?
– द्रव्य वह पदार्थ होता है जो स्थान घेरता है तथा जिसमें आयतन (Volume) या भार होता है

2.द्रव्यों की अवस्था (States of Matter) से क्या तात्पर्य होता है?
– द्रव्यों की अवस्था उनका वह विशिष्ट स्वरूप होता है जिसे वे प्राप्त करते हैं

3.द्रव्यों की चार मूलभूत अवस्थाएं कौन सी होती हैं?
– ठोस अवस्था (Solid), द्रव अवस्था (Liquid), गैसीय अवस्था (Gas) और प्लाज़्मा अवस्था (Plasma) – (ये चार अवस्थाएं द्रव्य की वे अवस्थाएं हैं जिन्हें हम रोजमर्रा के जीवन में देख सकते और महसूस कर सकते हैं। लेकिन इन चार आवस्थाओं के अतिरिक्त भी वैज्ञानिकों ने द्रव्यों की तमाम अन्य अवस्थाएं वर्णित की हैं जो अलग-अलग स्थितियों अथवा वैज्ञानिक प्रयोगों के दौरान सामने आती हैं)

4.द्रव्यों की वे कुछ प्रमुख अवस्थाएं कौन सी हैं जो वैज्ञानिकों ने उल्लिखित की हैं जो उनकी आम चार अवस्थाओं से भिन्न होती हैं?
– बोस-आइंस्टीन कण्डेन्सेट (Bose–Einstein condensate), फेर्मोइनिक कण्डेन्सेट (Fermionic condensate), सुपरफ्लुइड (Superfluid), क्वांटम हॉल स्टेट(Quantum Hall state), लिक्विड क्रिस्टल स्टेट (Liquid Crystal States), फोटोनिक मैटर स्टेट (Photonic matter state), आदि।

5.ठोस (solids) क्या होता है?
– पदार्थ जिसका आकार तथा आयतन (volume) निश्चित होता है

6. द्रव (liquid) क्या होता है?
– द्रव्य की वह अवस्था जिसमें उसका आयतन (volume) तो निश्चित होता है लेकिन आकार (shape) निश्चित नही होता है (उदाहरण के लिए किसी पात्र जैसे गिलास में रखा जल उस गिलास का ही आकार ले लेता है लेकिन बावजूद इसके उसका अपना आयतन होता है)

7.गैस (Gas) किस प्रकार के पदार्थ होते हैं?
– गैस वे पदार्थ होते हैं जिनका आकार (Shape) और आयतन (Volume) दोनों अनिश्चित होते हैं

8. प्लाज़्मा (Plasma) अवस्था वाले पदार्थों की विशेषता क्या होती है?
– इन पदार्थों का आकार (Shape) और आयतन (Volume) दोनों अनिश्चित होता है और इसके साथ ही अणु तटस्थ (Neutral) होते हैं (इसका तात्पर्य हुआ कि उनमें आयन (ions) और इलेक्ट्रॉनों (electrons) की पर्याप्त संख्या होती है जोकि मुक्त स्थिति में रहते हुए आसानी से अपनी स्थिति बदल सकते हैं- प्लाज़्मा में इलेक्ट्रॉनों का एक निश्चित अनुपात किसी परमाणु या अणु के साथ बंधे होने के बजाय स्वतंत्र होता है।)
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Jawahar Navodaya Vidyalaya Exam Sample Paper

हिन्दी Questions
1. हिन्दी भाषा में लिंग कितने प्रकार के होते हैं?
(a) दो (b) तीन (c) चार (d) पाँच (Ans : a)

2. 'सार्थक' शब्द का विलोम है– 
(a) निरर्थक (b) निरार्थक (c) अर्थिक (d) परार्थी (Ans : a)

3. ​'विशिष्ट अवसर पर विशिष्ट लोगों के समक्ष दिया गया विद्वतापूर्ण भाषण' के लिए एक शब्द–
(a) सम्भाषण (b) अभिभाषण (c) अपभाषण (d) अनभाषण (Ans : b)

4. 'रमेश धीरे-धीरे जाता है।' इस वाक्य में 'अव्यय' है– 
(a) रमेश (b) धीरे-धीरे (c) जाता (d) है (Ans : b)
5. 'कान भरना' मुहावरे का सही अर्थ है–
(a) किसी की बात न सुनना (b) चुगली करना 
(c) सावधान कर देना (d) ऊब जाना (Ans : b)

6. हिन्दी भाषा में वचनों की संख्या है– 

(a) दो (b) तीन (c) चार (d) पाँच (Ans : a)

7. 'कच्चे घड़े से पानी भरना' मुहावरे का सही अर्थ है– 
(a) मूर्खतापूर्ण कार्य करना (b) पानी भरना 
(c) उपहास होना (d) गलत काम करना (Ans : a)

8. निम्नलिखित शब्दों में से किस शब्द की वर्तनी शुद्ध है?

(a) अधीवेशन (b) अधिवेषन (c) अधिवेशन (d) अधिवेश्न (Ans : c)

9. 'दर्शन के योग्य' के लिए कए शब्द होगा– 
(a) दर्शनीय (b) दार्शनिक (c) दर्शन (d) दर्शक (Ans : a)

10. 'दशानन' किस समास का उदाहरण है?
(a) तत्पुरुष (b) द्विगु (c) द्वन्द्व (d) कर्मधारय (Ans : b) 

English Questions

Directions (Q. Nos. 11-12) 
In the following questions, out of the four alternatives, choose the one which can be substituted for the given words/sentence. 

11. A disease which is spread by direct contact 
(a) Contagious (b) Infectious (c) Epidemic (d) Endemic (Ans : a)

12. The study of ancient civilizations–  
(a) History (b) Anthropology (c) Enthnology (d) Archaeology (Ans : b)

Directions (Q. Nos. 13-14) In the following questions, out of the four alternatives, choose the one which best expresses the meaning of the given word. 

13. Cajole 
(a) Insist (b) Persuade (c) Flatter (d) Recommend (Ans : b)

14. Fragrance 

(a) Taste (b) Aroma (c) Sight (d) Touch (Ans : b)

Directions (Q. Nos. 15-16) In the following questions. choose the word opposite in meaning to the given word. 

15. Strife (a) War (b) Peace (c) Anger (d) Woe (Ans : b)

16. Repulsive 
(a) Attractive (b) Reflective (c) Distinctive (d) Progressive (Ans : a)

Directions (Q. Nos. 17-18) In the following questions. sentences are given with blanks to be filled in with an appropriate word(s). Four alternatives are suggested for each question. Choose the correct alternative out of the four. 

17. The sparrows took no the bread. 
(a) notice of (b) notice about (c) notice from (d) notice to (Ans : a)

18. He shows great ability Mathematics. 
(a) at (b) for (c) about (d) in (Ans : a)

Directions (Q. Nos. 19-20) In the following questions. groups of four words are given. In each group. one word is correctly spelt. Find the correctly spelt word. 
19. (a) Definitely (b) Definately (c) Definitley (d) Definitly (Ans : a)

20. (a) Cemetary (b) Semetary (c) Cemetery (d) Cemetry (Ans : c)

Physics Questions

21. Which type of mirror is used in the head lights of vehicles? 
(a) Plane mirror (b) Concave mirror 
(c) Convex mirror (d) Parabolic mirror (Ans : b)

22. The height of a geo-stationary satellite from the Earth's surface is approximately–  
(a) 36000 km (b) 42000 km (c) 30000 km (d) None of these (Ans : a)

23. An electric iron has a heating element made of–  
(a) Copper (b) Tungsten (c) Nichrome (d) Zinc (Ans : c)

24. Moving electric charge produces–  

(a) magnetic field (b) sound waves (c) light rays (d) heat waves (Ans : a)

25. The SI unit of electric charge is–  

(a) ampere (b) coulomb (c) e.s.u. (d) kelvin (Ans : b)

26. Which colour of light shows maximum deviation when passed through a prism? 
(a) White (b) Red (c) Violet (d) Green (Ans : c)

27. The best material for the core of a transformer is–  
(a) stainless steel (b) mild steel (c) hard steel (d) soft iron (Ans : d)

28. Decibel is a term connected with–  
(a) air (b) water (c) sound (d) soil (Ans : c)

29. The colour of the eye depends upon the pigment present in–  
(a) Cornea (b) Iris (c) Rods (d) Cones (Ans : b)

30. Optical fibres are mainly used for which of the following? 
(a) Communication (b) Weaving (c) Musical instruments (d) Food industry (Ans : a)

31. Magnets are stored in–  
(a) thin papers (b) thin clothes (c) electromagnets (d) keepers (Ans : d)

32. Electric current is measured by–  
(a) resistor (b) voltmeter (c) galvanometer (d) ammeter (Ans : d)

Chemistry Questions

33. Washing soda is the common name for–  
(a) calcium carbonate (b) calcium bicarbonate 
(c) sodium carbonate (d) sodium bicarbonate (Ans : c)

34. The chemical behaviour of an atom depends upon–  
(a) the number of protons in its nucleus 
(b) the number of neutrons in the nucleus 
(c) the number of electrons orbiting around the nucleus 
(d) the number of nucleons in the nucleus (Ans : c)

35. Iodine can be separated from a mixture of Iodine and Potassium Chloride by–  
(a) sedimentation (b) filtration (c) sublimation (d) distillation (Ans : c)

36. The gas that usually causes explosions in coal mines is–  
(a) Hydrogen (b) Carbon monoxide (c) Air (d) Methane (Ans : d)

37. Identify the metal which is non-toxic in nature. 
(a) Chromium (b) Gold (c) Cadmium (d) Cobalt (Ans : b)

38. Soda ash is–  
(a) NaHCO3 (b) Na2CO3 (c) CaCO3 (d) Ca(HCO3)2 (Ans : b)

39. PbCO3 is the formula of–  
(a) cinnabar (b) cerruside (c) corundum (d) chromite (Ans : d)

40. In the flame, which part of it is called the black zone? 
(a) Outer zone (b) Inner zone (c) Middle zone (d) Top of the flame (Ans : b)

Biology Questions

41. The vitamin which helps in the clotting of blood is–  
(a) A (b) D (c) B (d) K (Ans : d)

42. What is the chromosome number in a human ovum? 
(a) 24 (b) 46 (c) 48 (d) None of these (Ans : b)

43. Which is the gland that holds the body thermostat? 

(a) Pineal (b) Pituitary (c) Thyroid (d) Hypothalamus (Ans : d)

44. Insulin was discovered by–  
(a) F Banting (b) Edward Jenner (c) Ronald Ross (d) SA Wakesman (Ans : a)

45. The total number of bones in the human body is–  

(a) 206 (b) 260 (c) 306 (d) 360 (Ans : a)

46. Bile is secreted by–  
(a) Gall bladder (b) Liver (c) Bile duct (d) Pancreas (Ans : a)

47. The largest organ of human body is–  
(a) Heart (b) Brain (c) Liver (d) Kidney (Ans : c)

48. Which one of the following organs excretes water, fat and various catabolic wastes? 

(a) Kidney (b) Skin (c) Spleen (d) Salivary glands (Ans : a)

49. Which one of the following gives energy to our body? 

(a) Vitamins (b) Water (c) Carbohydrates (d) Proteins (Ans : c)

50. The abnormal constituent of urine is–  
(a) urea (b) creatinine (c) albumin (d) sodium (Ans : c)

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Theories of Evolution


Origin of Life

Big Bang theory
The universe expanded from explosion of a primordial, hot substance.
1924 − 1929
Oparin and Haldane
Chemical evolution preceded organic evolution
Simple organic molecules originated from inorganic precursors.
Stanley Miller and Urey
Synthesis of bio molecules by creation of similar conditions as primitive atmosphere on laboratory scale
Amino acids were synthesised from ammonia, oxygen, and carbon dioxide inside specialised apparatus.

Urey and Miller experiment

  • Primitive atmosphere had high temperature, volcanic storms, and reducing atmosphere, containing CH4, NH3, H2, etc.
  • Urey and Miller took the same compounds in a closed flask along with water vapour at 800ºC and created an electric discharge.
  • Formation of biomolecules such as amino acids, simple sugars, fats, etc. was observed in the flask.
Theories of Evolution
  • The theory of special creation or divine intervention was challenged by Charles Darwin.
  • He made observations on his sea-trip around the world aboard H.M.S.
Beagle and concluded that all existing living forms share similarities among themselves and also with other life forms, which existed millions of years ago of which many are extinct.
  • The evolution of life forms has been gradual and those life forms better fit in environments that leave more progeny. This is called natural selection and is a mechanism of evolution.
  • Alfred Wallace working in the Malay Archepelago also came to the same conclusion.
Evidences of Evolution

  • Fossils − They represent plants and animals that lived millions of years ago and are now extinct. Different aged rock sediments contain fossils of different life-forms, which probably died during the formation of the particular sediment.
  • Comparative anatomy and morphology − It shows evidences of the similarities and differences between living forms of today and that of the prehistoric times. Some of the examples of comparative anatomy and morphology are:
  • Homologous organs − All mammals share the same pattern of forelimbs. Though they perform different functions, they are anatomically similar. This is called divergent evolution and the structures are called homologous structures (common ancestors).
  • Analogous organs − The pair of organs is not anatomically similar, but performs the same function (e.g., the wings of butterflies and birds). This is called convergent evolution.
  • Adaptive melanism − In England, it was noted that before industrial revolution, the number of white-winged moths was more than that of dark melanised moth. However, after industrialisation, there were more of dark melanised moths. The explanation was that after industrialization, the tree trunks became darker with deposits of soot and smoke and hence, the number of dark moths increased in order to protect themselves from predators while the white-winged ones were easily picked up by the predators.
  • Similarly, the herbicide and pesticide resistant plants and animals and antibiotic resistant bacteria are some of the evidences that point towards evolution.
Adaptive Radiation
  • During his exploration of the Galapagos Islands, Darwin noticed that there were many varieties of finches in the same island.
  • They varied from normal seed eating varieties to those that ate insects.
  • This process of evolution starting from a single point and radiating in different directions is called adaptive radiation.
  • The other example for this is the evolution of the Australian marsupials from a single ancestor. Placental mammals also exhibit similarities to their corresponding marsupial. Example: placental wolf and the Tasmanian wolf
  • When more than one adaptive radiation occurs in an isolated geographical area, the phenomenon is called convergent evolution.

  • Biological Evolution & Mechanism of Evolution 

  • According to Darwin, evolution took place by natural selection.
  • The number of life forms depends upon their ability to multiply and their life span.
  • Another aspect of natural selection is the survival of the fittest, where nature selects the individuals, which are most fit, to adapt to their environment.
  • Branching descent and natural selection are the two important concepts of Darwin’s theory of evolution.
  • The French naturalist Lamarck observed that evolution occurs due to the use or disuse of particular organs or body parts. For example, giraffe have developed long necks as a result of attempts to eat leaves high up on trees.
  • Darwin also observed that variations are inheritable and the species fit to survive the most, leaves more offsprings. Hence, the population’s characteristics change, giving rise to the evolution of new life forms.
  • Mechanism of Evolution
  • Darwin did not quite explain how evolution gave rise to different species of the same organism.
  • Mendel mentioned about inheritable factors, which influenced the phenotype of an organism.
  • Hugo de Vries based on his work on evening primrose suggested that variations occurred due to mutations.
  • Mutations are random and directionless while the variations that Darwin talked about were small and directional. Hugo de Vries gave the name saltation (single step large mutation) to the mutations which brought about speciation.
  • Hardy-Weinberg Principle 
  • The frequency of occurrence of alleles of a gene in a population remains constant through generations unless disturbances such as mutations, non-random mating, etc. are introduced.
  • Genetic equilibrium (gene pool remains constant) is a state which provides a baseline to measure genetic change.
  • Sum total of all allelic frequencies is 1.
  • Individual frequencies are represented as p and q such as in a diploid, where p and q represent the frequency of allele A and a.
  • The frequency of AA is p2, that of aa is q2, and that of Aa is 2pq.
  • Hence, p2 + 2pq + q2 = 1, which is the expansion of (p + q)2.
  • When the frequency measured is different from that expected, it is indicative of evolutionary change.
  • Hardy-Weinberg equilibrium is affected by
  • gene flow or gene migration
  • genetic drift (changes occurring by chance)
  • mutation
  • genetic recombination
  • natural selection
  • Sometimes, the change in allele frequency is so prominent in the new sample of population that they become a different species and the original drifted population becomes the founder. This effect is called founder effect.
  • The advantageous mutations that help in natural selection over the generations give rise to new phenotypes and result in speciation.
  • Evolution of Plants and Animals 
  • Evolution of Plants
  • Cellular life forms occurred on earth about 2000 million years ago.
  • Some of these cells had the ability to produce oxygen through reactions similar to photosynthesis.
  • Slowly, single-celled organisms became multicellular.
  • Seaweeds and some plants probably existed around 320 million years ago.

Evolution of Animals
  • Animals evolved about 500 million years ago. The first of them to evolve were invertebrates.
  • Jawless fishes evolved around 350 million years ago.
  • Some of the fishes could go on land, and then come back to water. These were the first amphibians. In 1938, a fish Coelacanth, which was thought to be extinct, was caught in South Africa. This variety of fish, called lobefins, is believed to have evolved into the first amphibians.
  • Amphibians evolved into reptiles. In the next 200 million years, reptiles of different sizes dominated the earth. However, about 65 million years ago, some of them such as dinosaurs disappeared.
  • The first among the mammals were small shrew-like mammals.
  • During continental drift when North America joined South America, primitive mammals suffered, but pouched mammals of Australia survived the same drift because of lack of competition from other mammals.
Origin and Evolution of Man
15 million years ago
Dryopithecus (ape-like) and Ramapithecus (man-like)
Hairy and walked similar to chimpanzees
3 − 4 million years ago
Man-like primates
Not tall, but walked straight
2 million years ago
Australopithecines, also called Homo habilis,lived in East Africa
Used stone weapons and ate fruits;
human-like with brain capacity of 650 − 800 cc; not meat eaters
1.5 million years ago
Homo erectus
Brain capacity of about 900 cc; were meat eaters
1,000 − 40, 000 years ago
Neanderthal man
Brain capacity of 1400 cc; used hides
75, 000 − 10, 000 years ago
Homo sapiens

When we compare the skulls of an adult human being, baby chimpanzee, and adult chimpanzee, we observe that skull of baby chimpanzee resembles human being more as compared to adult chimpanzee.

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