Science: Biology Revision Notes

Science enables us to study both physical and natural world through various observations, experimentation, etc. This article deals with the Biology section which has various Questions and their explanations with the help of diagram for better understanding and clarity of the concept in the form of revision notes.
Created On: May 11, 2017 13:14 IST
Modified On: May 12, 2017 12:55 IST

Science enables us to study both physical and natural world through various observations, experimentation, etc. Science consists of Biology, Physics and Chemistry. This article deals with the Biology section which has various Questions and their explanations with the help of diagram for better understanding and clarity of the concept in the form of revision notes. We all know biology is the study of living organisms i.e. life, their adaptations, environment, etc. These revision notes on Biology will help you with the academic as well as competitive preparations.

1. What is the main difference between autotrophic and heterotrophic mode of nutrition?
Ans. Autotrophic nutrition is in which an organism synthesises its own organic food from simple inorganic materials like carbon dioxide, water and minerals with the help of sunlight. It takes place in green plants and some bacteria which carry out photosynthesis.

Heterotrophic nutrition is in which an organism don’t synthesise its own food and depends on others. It occurs in all animals and non-green plants which does not carry photosynthesis.
2. What is the role of acid and enzymes in the digestion process?
Ans. The role of acid is to make the gastric juice acidic during the digestion of food in the stomach, due to which enzyme pepsin becomes active and break down proteins of the food. It is so pepsin digests protein in the presence of acid only. Also,acid kills bacteria which enter in the stomach through food.

Source: www.
On the other hand enzyme plays very important role in the digestion of food in our body. They act as catalysts which help in breaking down the complex food into simpler ones which can be absorbed from the alimentary canal into blood stream and provides energy.

Organ Systems of Human Body
3. How lungs help in the exchange of gases during respiration?
Ans. Exchange of gases is the main function of respiratory System. The blood in the capillaries surrounding the alveoli has a lower concentration of Oxygen than the air in the alveoli which has just inhaled. Both alveoli and capillaries have walls which are only one cell thick and allow gases to diffuse across them.

Similarly it happens with Carbon dioxide. It diffuses from the capillaries into the alveoli where it can be exhaled. Alveoli present in the lungs provide a large area for the exchange of gases.
4. Why Nephron is known as unit of Kidney?
Ans. Nephron is the structural and functional unit of kidney. Its main function is to regulate the concentration of water and soluble substances in the body by filtering the blood by removing excess of waste salts, reabsorb what is needed and excrete the waste product in the form of urine. Both Kidneys contain millions of nephrons.

Source: www.

Excretory System in Humans
5. Which hormone in our body is released during emergency situations?
Ans. Adrenal gland is an endocrine gland located above the kidneys and is two in number. It releases hormones like adrenaline, steroids, aldosterone and cortisol. In an emergency situation adrenaline hormone is released which prepares our body to function at maximum efficiency like danger, anger, excitement etc.

For better understanding when we face a dangerous situation, then our nervous system stimulates the adrenal glands to secrete adrenaline hormone into our body. With the help of this hormone our heart beat, breathing rate increases, blood flow into muscles and causes liver to put more glucose into our blood. In our body due to these actions of adrenaline hormone lot of energy is released that too very quickly. This energy helps us to fight in an emergency situation.
6. Why diabetic patients are given the injections of insulin?
Ans. Pancreas is a leaf like gland located behind the stomach and secretes enzymes as well as hormones which help in the digestion of food. So, it has exocrine function for digestion and endocrine function that regulates blood sugar.

Insulin is a hormone produced by pancreas gland which helps to lower the blood sugar level. If deficiency of insulin occurs in the body, level of blood sugar increases and leads to diabetes. If the sugar level is very high then patient is treated by giving injection of insulin because addition of insulin hormone to blood lowers the blood sugar level.

Various Glands and Hormones in Human Body
7. Explain the function of neuron and its working?
Ans. The structural and functional unit of nervous system is neuron. It is the largest cell in the body. It carries messages in the form of electrical signals called electric impulses or nerve impulses. A neuron has three components: cell body, Dendrites and Axon. A cell body consists of cytoplasm like other cell and a number of long and thin fibres are stretching out of the cell body of neuron. Shorter fibres are known as Dendrites and longest fibre is known as Axon. The dendrites pick up the nerve impulse or messages from the receptors and pass it to the cell body and then axon. Further the message is passed by axon to another neuron through a junction called synapse.


Neurons are of three types: Sensory, motor and relay neurons. Sensory neuron transmits impulses from the receptors towards the central nervous system i.e. spinal cord and brain. Motor neurons transmit impulses from the central nervous system towards the muscle cells or effectors and relay neurons occur in the central nervous system where they serve links between other neurons.
8. Why DNA plays an important role in the process of reproduction?
Ans. DNA is a double helical structure present in the chromosomes in the cell which contain information for the inheritance of characteristics from the parents to the next generation.

So, it plays an important role in the reproduction because copying or replication of DNA makes possible the transmissions of characteristics of the parents to the offsprings in the next generation. And also due to the copying of DNA some variations are produced in the offsprings during reproduction which form the basis for evolution.

What is the difference between DNA and RNA
9. How you will determine the sex of a child?
Ans. With the help of genetics you can determine the sex of a child. Mainly, Sex chromosomes determine the sex of a child. X and Y are two types of sex chromosomes. We know that in humans 23 pairs of chromosomes are present. 22 pairs are known as autosomes which are same in male and female. The 23rd pair is the sex chromosome, in female it is XX and in male XY. So Y chromosome is responsible for the mail child. During the process of fertilisation in the reproduction when male chromosome fuses with the female zygote is formed. But when Male X chromosome fuses with female X then girl child will be born and if Male Y chromosome fuses with female X chromosome then Male child will be born.

10. Deficiency of Haemoglobin leads to:
Ans. Haemoglobin is present in our blood and due to it only blood is red in colour. During the process of respiration and breathing, oxygen is carried by haemoglobin to all parts of the body through blood. If deficiency of Haemoglobin occurs then in a person oxygen carrying capacity will be reduced which results into tiredness, breathing problem or lack of energy. Person will look pale and loses wait. Become anaemic also. Because of anaemia RBC in the blood will be reduced which further causes deficiency of iron and due to this body will not be able to generate a protein called haemoglobin.


Human Circulatory System and Control and Coordination

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