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Comparative Vertebrate Anatomy

Comparative Anatomy is to make a comparative study of the anatomy of an organ in different groups of vertebrates and try to derive the evolutionary significance from it, and to understand as to why an organ evolved the way it is present now. Genetic and environmental forces are responsible for the development of an organ, on which then natural selection operates to determine its survival or elimination. The following chapters are given here.

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Know these facts

*All mammals have 7 cervical vertebrae except 6 in manatee, 8 in ant bear (Tamandua) and 9 in sloth (Bradypus).

*Elephants can hear infrasonic sounds of 14 hertz. from hundreds of km and whales can hear ultrasonic sounds of 123,000 hertz from thousands of km.

*Each second brain receives 100 billion impulses and fires 5000 commands but we are conscious of one millionth activity of our brain.

*Human brain loses about 100,000 neurons each day but the loss is insignificant because of the presence of billions of neurons in brain.

*Snakes auditory lobes are highly enlarged to hear faint sounds received through ground as they possess no external ear.

* Other than mammals, in all vertebrates spinal cord has more control over body functions than the brain.

*In humans brain is marvelously packed as 1800 sq cm of brain surface area is packed in only 15% of skull space.

*Nerve impulse travels in our body @ 400 km per hour.

*Crab eating frog (Rana cancerivora) is the only amphibian that can survive in the intertidal marine water.

*Monotremes and marsupials do not possess a prostate gland.

*In sharks and caecilian kidney is called opisthonephros because it extends up to the posterior end of the body.

*Birds have only the left ovary and oviduct.

*Systolic blood pressure decreases in arteries from 130 mmHg in systemic arch, 30 mmHg in arterioles, 20 mmHg in capillaries, 12 mmHg in venules, 5 mmHg in smaller veins and zero mmHg in larger veins.

*Aortic blood pressure in giraffe is 260/160 to supply brain sitting on top of the long neck, but in brain it is only 120/70.

*Largest RBCs (75 microns) are found in the urodele, Amphiuma, and the smallest (2.5 microns) in the musk deer.

*Whales store air in huge nasal chambers and not in lungs.

*Elephant’s trunk has 40,000 muscles.

*No animal breathes free air. Oxygen from air must diffuse through fluid to the blood and hence a water film is necessary over the respiratory surface in all animals.

*Sharks jaws are loosely attached to the skull, so that when shark bites its jaws come out of the oral cavity to seize prey.

*Plethodont salamanders possess a tongue that is three-fourth the length of the body.

*Tongue of an elephant weighs 12 kg while that of a whale weighs 1500 kg and 50 persons can stand on it.

*Incisors of rodents and elephants continue to grow throughout life. A single tusk of an African elephant weighs about 100 kg.

*In hind gut fermenters such as horses, elephants and rabbits, large amount of food eaten goes undigested and hence they must eat large quantities to obtain enough nutrients.

*Gastric juices in snake’s stomach are so strong that they dissolve even the bones of the swallowed prey.

*In humans intestine is 28 feet long whereas in cow it is 165 feet long.

*Batrachotoxin and bufotoxin are such potent poisons secreted by frogs and toads that only 200 microgram can kill a man.

*Penguins breed in Antarctic and hatch their eggs at minus 50 degrees.

*Density of sweat glands is highest in the skin of Indians (738/sq cm) followed by Negros (709/sq cm), while in Europeans it is only 550/sq cm.

*The American pronghorn(Antilocapra americana) is the only antelope that sheds its horn annually.

*Antlers are found only in male deer and are shed after breeding season is over. Reindeers are the only deers that possess permanent antlers in both males and females.

In echidna and duckbilled platypus both male and female possess active mammary glands and feed young babies.

Sharks retain 100 times more urea in blood as compared to mammals. Their organs cannot function without such a high amount of urea in body.

Humans can sweat away as much as 3 litres of water per hour in summer. A person can collapse if loss of body fluid is 10% of body weight.

General Information About Civil Services Examinations

This site is aimed to help students and others interested in the study of zoology and preparation for various competitive examinations. Generally the information given in this website is available free for download but some information may be password protected. However, commercial use of the information is probibited.

Also see the following websites-




Indian Administrative Service

India Foreign Service

Indian Police Service 

 Group A Indian P & T Accounts & Finance Service Indian Audit and Accounts Service Indian Customs and Central Excise Service Indian Defence Accounts Service Indian Revenue Service Indian Ordnance Factories Service (Assistant Works Manager, non-technical) Indian Postal Service Indian Civil Accounts Service Indian Railway Traffic Service Indian Railway Accounts Service Indian Railway Personnel Service Posts of Assistant Security Officer in Railway Protection Force (RPF) Indian Defence Estates Service Indian Information Service (Junior Grade)  

Group – B Railway Board Secretariat Service (Section Officer’s Grade) Armed Forces Headquarters Civil Service (Section Officer’s Grade) Customs Appraisers’ Service

Delhi, Andaman & Nicobar Islands, Lakshadweep, Daman & Diu and Dadra & Nagar Haveli Civil Service and Police Service Pondicherry Civil Service 


The Preliminary Examination is meant to serve as screening test and has all objective type of questions. This examination is conducted according to the following pattern— With effect from 2011, the pattern of preliminary exam. has changed. There will be no optional subject in prelim. exam. now and the two papers will be as follows:

I General Studies/Current events 2 hrs 200
II Comprehension/Reasoning 2 hrs 200

I.General Studies paper includes Current events of national and international importance; History of India and Indian National Movement; Indian and World Geography – Physical, Social, Economic geography of India and the World. Indian Polity and Governance – Constitution, Political System. Panchayati Raj, Public Policy, Rights Issues, etc. Economic and Social Development – Sustainable Development. Poverty, Inclusion, Demographics, Social Sector Initiatives, etc.
General issues on Environmental ecology, Bio-diversity and Climate. General Science.

II. Comprehension & Reasoning paper includes Comprehension Interpersonal skills including communication skills;
Logical reasoning and analytical ability. Decision making and problem solving. General mental ability. Basic numeracy (numbers and their relations, orders of magnitude etc.) (Class X level). Data interpretation (charts, graphs, tables, data
sufficiency etc. -Class X level). English Language Comprehension skills (Class X level).

IAS Mains Examination


The Civil Services Examination, 2013 will consist of the following:

  • The Civil Services PreliminaryExamination (Objective Type) for the selection of candidates for the Main Examination
  • Civil Services Main Examination ( will consist of 7 written papers) and
  • A Final Interview for those who pass the Main Exam.

Following is a tabulated form of the papers one shall have to opt for :

Paper No.

Paper Title


Paper I

Section I : Essay


Section II: English Comprehension and English Precis, X level


Paper II

General Studies-I, Indian Heritage and Culture, History and Geography of the World and Society


Paper III

General Studies-II, Governance, Constitution, Polity, Social Justice and International relations


Paper IV

General Studies-III, Technology, Economic Development, Bio-diversity, Environment, Security and Disaster Management


Paper V

General Studies-IV, Ethics, Integrity and Aptitude 


Paper VI

Optional Subject – Paper 1


Paper VII

Optional Subject – Paper 2


Total marks in mains written exam. 1800

Personality Test (for those who clear the mains exam.) 275 marks

Grand Total: 2075 marks

Those who are declared by the Commission as qualified in the Preliminary Examination are eligible for appearing in the Mains Examination of that year, and those who clear the mains exam. will be called for interview or Personality Test.

From preliminary exams, 12-13 times the number of posts are selected as qualified to appear in the mains exam.

In 2012, 2674 candidates were selected from the mains and were called for interview.