Human Body, Nutrition and Diseases
Human Body, Nutrition and Diseases
Biology is the largest slice of the science block, and the human body section alone can supply 2 questions. Deficiency diseases and disease vectors are the two areas that repeat most, and both can be memorised from a single table each. Treat these as guaranteed marks.
Systems of the Human Body
| System | Main job | Key organ |
|---|---|---|
| Digestive | Breaks down food | Small intestine |
| Respiratory | Gas exchange | Lungs |
| Circulatory | Transports blood | Heart |
| Excretory | Removes waste | Kidney |
| Nervous | Control and coordination | Brain |
| Skeletal | Support and protection | Bones |
Two figures get asked directly: an adult human has 206 bones, and the heart has four chambers — two atria and two ventricles. Most digestion and absorption of food happens in the small intestine, not the stomach.
Nutrients and Deficiency Diseases
Carbohydrates and fats give energy, proteins build and repair the body, and vitamins and minerals keep processes running. Deficiency questions are a fixed pattern.
| Nutrient | Deficiency disease |
|---|---|
| Vitamin A | Night blindness |
| Vitamin B1 | Beriberi |
| Vitamin C | Scurvy |
| Vitamin D | Rickets |
| Iron | Anaemia |
| Iodine | Goitre |
| Protein | Kwashiorkor, marasmus |
Vitamin D is made in the skin with the help of sunlight, which is why it is called the sunshine vitamin. Vitamins C and B are water-soluble; A, D, E and K are fat-soluble.
✗ Scurvy is caused by lack of vitamin D | ✓ Scurvy is caused by lack of vitamin C; vitamin D deficiency causes rickets
Communicable Diseases and Their Carriers
A communicable disease spreads from person to person or through a carrier. A non-communicable one, such as diabetes or hypertension, does not.
| Disease | Caused by | Spread by |
|---|---|---|
| Malaria | Protozoan (Plasmodium) | Female Anopheles mosquito |
| Dengue | Virus | Aedes aegypti mosquito |
| Kala-azar | Protozoan (Leishmania) | Sandfly |
| Tuberculosis | Bacterium | Air droplets |
| Typhoid | Bacterium | Contaminated food and water |
| Polio | Virus | Contaminated water |
Note the pattern in the carrier column: malaria comes from the female Anopheles specifically, and kala-azar from the sandfly, not a mosquito.
मलेरिया — मादा एनॉफिलीज मच्छर; कालाजार — बालू मक्खी (सैंडफ्लाई)।
TRE pointer: Kala-azar deserves special attention for a Bihar candidate: it is spread by the sandfly rather than a mosquito, and that distinction is exactly the kind of detail a state paper likes to test. The deficiency table is the most reliable scoring block in the whole science section, so revise it until the pairs are automatic. Given −1/3 for each wrong answer across five options, these are the questions you should never leave to chance.
60-Second Recap
- 206 bones in an adult; four heart chambers; small intestine absorbs most food.
- Vitamin A night blindness, B1 beriberi, C scurvy, D rickets.
- Iron deficiency causes anaemia; iodine deficiency causes goitre.
- A, D, E, K are fat-soluble; B and C are water-soluble.
- Malaria from the female Anopheles; dengue from Aedes aegypti; kala-azar from the sandfly.
- Communicable diseases spread; diabetes and hypertension do not.
Frequently Asked Questions
Which mosquito spreads malaria?
The female Anopheles mosquito, which carries the Plasmodium parasite. Dengue and chikungunya are spread by the Aedes aegypti mosquito instead. The word female matters, because only female mosquitoes feed on blood, and questions include the male option specifically to catch careless reading.
What causes kala-azar and how does it spread?
Kala-azar, or visceral leishmaniasis, is caused by the Leishmania parasite and is transmitted by the bite of an infected sandfly, not a mosquito. This distinction is worth remembering carefully for a Bihar state examination, where the disease appears more often than in national papers.
Which vitamin deficiency causes scurvy?
Vitamin C. The confusing neighbours are vitamin A, whose deficiency causes night blindness, and vitamin D, whose deficiency causes rickets in children. Learn the four pairs together as a block rather than individually, because papers usually present them as a matching question.
How many bones are there in an adult human body?
Two hundred and six. A newborn has around three hundred, and the number falls as bones fuse during growth. Both figures have appeared as options in the same question, so remember that 206 belongs to the adult and the larger figure to the infant.