The Class 8 is an important year in a student’s life and Maharashtra State Board Science is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 8 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 8 Science Book syllabus.
Question 1: Find out my partner.
| Group ‘A ’ | Group ‘B ’ |
| 1. Heart beats | a. 350 ml |
| 2. RBC | b. 7.4 |
| 3. WBC | c. 37 °C |
| 4. Blood donation | d. 72 |
| 5. Normal body temperature | e. 50 –60 lakh/mm3 |
| 6. pH of oxygenated blood | f. 5000-6000 per mm3 |
Answer:
| Group ‘A ’ | Group ‘B ’ |
| 1. Heart beats | d. 72 |
| 2. RBC | e. 50 –60 lakh/mm3 |
| 3. WBC | f. 5000-6000 per mm3 |
| 4. Blood donation | a. 350 ml |
| 5. Normal body temperature | c. 37 °C |
| 6. pH of oxygenated blood | b. 7.4 |
Question 2: Complete the following table.
| Organ system | Organs | Functions |
| 1. Respiratory | ||
| 2. Circulatory system |
Answer:
| Organ system | Organs | Functions |
| 1. Respiratory | Nose
Pharynx Windpipe Lungs | This organ traps the dust particles and microbes like a filter and prevents their entry into the respiratory system.
It acts as a passage or medium through which air enters into the windpipe. This organ acts as a passage or channel through which air passes into or reaches the lungs. An exchange of gases occurs in it. |
| 2. Circulatory system | Heart
Blood vessels | The main organ from where blood circulation occurs to different parts of the body.
This consists of a closed system of vessels that help in blood circulation to different body parts. |
Question 3: Draw neat and labeled diagrams.
a. Respiratory system
b. Internal structure of heart
Answer:
a. Respiratory system
b. Internal structure of heart
Question 4: Explain with reasons.
a. Human blood is red coloured.
b. Upward and downward movement of diaphragm occurs consecutively.
c. Blood donation is considered to be superior of all donations.
d. Person with ‘O ’blood group is considered as ‘universal donor ’
e. Food must have a limited amount of salts.
Answer: a. Human blood is red in colour due to the presence of haemoglobin which is a respiratory pigment. Haemoglobin is a red colour pigment, which gives red colour to the blood.
b. Diaphragm is a partition comprising muscles that is present between the thoracic cavity and abdominal cavity. When a person breathes, there is upward and downward movement of diaphragm that occurs simultaneously. When we inhale, the ribs rise up while the diaphragm lowers down at the same time causing a pressure decrease on lungs. This promotes free movement of air into lungs through the nostrils. Likewise when the ribs return to their normal position, the diaphragm rises up leading to an increase in pressure inside the lungs. This helps in movement of the air outside the nostrils.
c. Blood donation is considered superior of all donations because it can save a person’s life who is in need of it. Most lives are often lost due to blood loss during operations, surgeries, accidents or whenever regular blood transfusion is required. Many lives can be saved, if sufficient blood is available to inject to the patient who is in need of it.
d. Person with an ‘O ’blood group is considered a ‘universal donor ’because such an individual can give or donate blood to a person who has any other blood group.
e. Food must have a limited amount of salts as too much mineral salts are harmful to the body. As a matter of fact, we require limited amounts of salts in our body. Excessive salts in food can lead to water retention in different parts of the body such as arms, legs etc. and might also lead to edema. Too much salt however also leads to increase in the blood pressure and may cause hypertension.
Question 5: Answer the following questions in your own words.
a. Explain the functional correlation of the circulatory system with respiratory, digestive and excretory systems.
b. Explain the structure and function of human blood.
c. Explain the importance and need of blood donation.
Answer: a. The functional correlation between circulatory system with respiratory, digestive and excretory system are listed as follows:
We are all aware that during respiration there is exchange of gases that occurs in the lungs. The respiratory system causes the diffusion of oxygen into the blood and the diffusion of carbon dioxide from the blood. This oxygen is then transported to different body cells through the circulatory system.
The digestive system is responsible for producing and supplying nutrients to the human body by breaking complex molecules into simpler ones. The circulatory system transports the energy derived from these nutrients to different cells and tissues of the body.
The excretory system is responsible for eliminating the waste products from the body. These waste products are transported to the excretory system by blood in the body.
b. Blood is a red colour fluid connective tissue that flows in blood vessels. It consists of two components –blood cells and plasma.
Plasma is a pale yellow colour fluid that is slightly alkaline and made up of water (~90-92%) and some 8% of dissolved nutrients, proteins, hormones and waste products.
Blood consists of three types of blood cells. These are
i. Red Blood Cells: These are small, circular, enucleated cells that contain a red pigment called haemoglobin, which helps in transporting oxygen to different cells of the body.
ii. White Blood Cells: These are large, nucleated and colorless cells that fight against germs from entering into our body and protect us from harmful diseases.
iii. Platelets: These are extremely small and disc-shaped units of blood. For example, when we get injured, the bleeding stops after some time due to the activity of platelets that helps in the clotting of blood.
Functions of blood:
c. Blood donation is considered one of the biggest donations of an individual towards the society. We are all aware that a lot of blood is lost under various circumstances such as accidents, surgeries or in cases of blood-related diseases which require transfusion of blood. If an adequate amount of blood is available in blood banks, it can save many lives in need. Donating blood does not harm or affect the body of the donor. In fact, whenever a donor donates blood, he/she recovers it in his/her body within 24 hrs. However, this donated blood can be stored by blood banks in refrigerators and used as and when required.
Question 6: Explain the differences.
a. Arteries and veins.
b. External and internal respiration
Answer:
a. Difference between arteries and veins:
| Arteries | Veins |
| 1. Arteries carry blood to different body organs and away from the heart. | Veins carry blood towards the heart and away from other organs. |
| 2. Carries blood full of oxygen. | Carries carbon dioxide enriched and deoxygenated blood. |
| 3. Blood flows with extreme pressure and gives jerks. | Blood flows with low pressure in a smooth manner. |
| 4. Arteries do not have any valves. | Veins have valves which help to prevent backflow of blood. |
| 5. Walls of arteries are elastic. | Walls of veins are non-elastic. |
| 6. Arteries are deeply placed. | Veins are superficial in nature. |
| 7. They are branched and decrease in size. | They unite and increase in size |
| 8. Arteries are capable of constricting and dilating. | Veins cannot constrict. |
| 9. They have thick and muscular walls. | Veins have less muscular and thin walls. |
| 10. The smallest artery is known as Arteriole. | The smallest vein is called Venules. |
b. Difference between external and internal respiration:
| External respiration | Internal respiration |
| 1. It occurs between the body and the outside or external environment. | It occurs internally at the cellular level. |
| 2. External respiration follows a mechanical process. | Internal respiration is a chemical process. |
| 3. It includes both –voluntary and involuntary action. | It includes only an involuntary action. |
Question 8: Which health parameters of blood donors should be checked?
Answer: The following parameters of blood donors have to be checked prior blood donation:
1. Age – It is important to check the age of an individual before he/she donates blood. This is because there is a set age before which and after which blood donation can be done or not, respectively.
2. Weight – Weight of individuals is a key parameter of blood donation as underweight individuals are not allowed to donate blood. In underweight individuals, there are chances that the donor may face unnecessary consequences or have a reaction such as dizziness and fainting, if blood donated is in higher quantity.
3. Heart, lungs and other blood disorders – Whenever a donor goes for donating blood, his/her prior history of heart, lungs or blood diseases are thoroughly enquired. People with heart valve conditions, heart disease, irregular heartbeat, anaemia, heart failure, and certain lung conditions are excluded from blood donation. Certain blood diseases such as iron deficiency or chronic leukemia or HIV +ve are also excluded from blood donation.
4. Other medical conditions – Extreme medical conditions such as hypotension, diabetes, hypertension, fever etc. are also checked before blood donation to prevent it from transfusing the blood to a person in need.
5. Recent surgery – People with recent surgery history are also not allowed to donate blood. However, after a year of surgery they can donate blood if they wish but only if they’ve recovered or healed completely and they are capable of resuming full activity like a healthy human being.
6. Pregnancy – Pregnant women are not permitted to donate blood during pregnancy and for at least six weeks after the pregnancy ends.
Question 8: Fill in the blanks using appropriate words given in the bracket.
(haemoglobin, alkaline, diaphragm, red bone marrow, acidic, voluntary, involuntary.)
a. RBCs of the blood contain _________, an iron compound.
b. ____________ is present between the thoracic and abdominal cavity.
c. Cardiac muscles are_______
d. pH of oxygenated blood is________
e. Production of RBCs occurs in__________
Answer: a. RBCs of the blood contain haemoglobin , an iron compound.
b. Diaphragm is present between the thoracic and abdominal cavity.
c. Cardiac muscles are involuntary .
d. pH of oxygenated blood is alkaline .
e. Production of RBCs occurs in red bone marrow .
Question 9: Find an odd one out.
a. A, O, K, AB, B.
b. Blood plasma, platelets, blood transfusion, blood corpuscles.
c. Trachea, alveoli, diaphragm, capillaries.
d. Neutrophils, globulins, albumins, prothrombin.
Answer: a. A, O, K, AB, B – K is the odd one out because it is an inorganic ion. The rest of the four A, O, AB, B are types of blood groups.
b. Blood plasma, platelets, blood transfusion, blood corpuscles – Blood transfusion is the odd one out because it is a technique for transferring blood from a donor to the recipient. Rest of the three blood plasma, platelets and blood corpuscles are components of blood.
c. Trachea, alveoli, diaphragm, capillaries – Capillaries are the odd one out because they are a part of the circulatory system while the rest of the three trachea, alveoli and diaphragm are parts of the respiratory system.
d. Neutrophils, globulins, albumins, prothrombin – Neutrophils are the odd one out because they are a type of blood cell. Rest of the three globulins, albumins, and prothrombin are components of the plasma.
Question 10: Read the following paragraph and identify the disease.
Today, her child became one and half years old. However, that child does not seem to be healthy and happy. It was continuously crying and gradually becoming weak. It has shortness of breath. Its nails have become blue.
Answer: From the symptoms mentioned above, it appears like the child is suffering from some kind of respiratory or circulatory disorder. He has difficulty in breathing and his nails have become blue which indicates that there is low/lack of oxygen circulating in the red blood cells. It is known as Cyanosis . This disorder occurs when enough oxygen is not present in the blood, thus making the skin or membrane below the skin turn into purplish-blue.
Question 11: Your neighbouring uncle has been diagnosed with hypertension. What should he do to keep his blood pressure within normal range?
Answer: The following methods can be adopted to keep the blood pressure within the normal range:
Question 1: Define organ system. Name some organ systems.
Answer: The group of organs which work together to perform a specific function is called an organ system. Various organ systems include respiratory, digestive, nervous, circulatory, reproductive, muscular, excretory, skeletal, etc. which are essential for normal functioning in our body.
Question 2: Where is body energy produced? Why is it essential?
Answer: Energy is essential for operating all the life processes in the human body. Energy production occurs within the cells of the human body. Cells need the supply of soluble nutrients and oxygen to complete energy production. This supply takes place with the help of essential organs such as respiratory and circulatory systems.
Question 3: What are the different steps of respiration?
Answer: The different steps of respiration are listed below:
1. External Respiration
2. Internal Respiration
3. Cellular Respiration
Question 4: Define Cellular Respiration.
Answer: Dissolved nutrients such as glucose slowly burn (oxidized) with the help of oxygen and energy is released in the form of ATP. Waste materials like carbon dioxide and water vapour are produced during this process.
Cellular respiration can be summarized as follows:
C6 H12 O6 +6O2 → 6CO2 +6H2 O+ Energy (38 ATP)
Question 5: Who discovered the mechanism of heart valves of the human body?
Answer: In 1628, William Harvey discovered the working mechanism of valves of the heart. He described the working of circulation in the human body. He proposed a theory that our heart is a muscular pump through which blood circulates in the body.
Question 6: Define capillaries.
Answer: Arteries that gradually divide with the decrease in their diameter as they spread in the body and finally form fine hair-like vessels are called capillaries. The walls of capillaries are extremely lean and thin and composed of a single layer of cells.
Question 7: Who is a blood donor?
Answer: A person who donates blood to other people or to the blood bank is referred to as a blood donor.
Question 8: What are the different groups of human blood?
Answer: There are four main groups of human blood namely A, B, AB and O. Besides, there are two more types as ‘Rh ’negative and ‘Rh ’positive of each of those four groups. Thus, in all eight blood groups are formed. (Examples: A Rh +ve &A Rh -ve).
Question 9: What are veins?
Answer: The capillaries unite together in the entire body to form blood vessels of bigger diameter which are known as veins. The network of capillaries is present in each organ.
Question 10: Define a blood recipient.
Answer: A person who receives blood from other people or from the blood bank is referred to as a blood recipient.
Question 11: What is the function of a blood bank?
Answer: Blood is collected in blood banks by following specific procedures from healthy persons and supplied to the people who are in need of it. If the collected blood is not to be used instantly, it is stored by the blood banks for some days in the refrigerator.
Question 12: Define hypertension.
Answer: When the blood pressure is higher than normal it is referred to as hypertension. Hypertension is usually considered a hereditary disorder. In hypertension, the arteries of the person develop unnecessary tension. The heart does not perform its functions properly in case of hypertension. Both the systolic and diastolic pressures stay high in hypertension.
Question 13: Define blood pressure.
Answer: Blood continuously flows through the blood vessels of the human body due to contraction and relaxation of the heart. This exerts pressure on the walls of the arteries of the heart due to contraction and it is known as blood pressure.
Question 14: What is systolic pressure?
Answer: The pressure that is recorded during the contraction of heart is known as systolic pressure.
Question 15: Define diastolic pressure.
Answer: The pressure that is recorded during relaxation is known as diastolic pressure.
Question 16: What is the normal blood pressure of a healthy person?
Answer: The blood pressure of a healthy person is about 120/80 mm to 139/89 mm of Hg. It is measured with the help of a sphygmomanometer.
Question 17: What is the minimum age requirement for blood donation?
Answer: A healthy person of age more than 18 years can donate blood for 3 –4 times a year. However, his/her health history should be thoroughly checked before he/she donates blood. Proper care should be taken so that there is no trouble during or after the blood donation.
Question 18: What are the scenarios where blood is required for transfusion?
Answer: Blood is required by the needful persons in various situations such as accidents, excess bleeding, surgical operations, childbirth, etc. Sometimes people suffering from blood disorders such as leukemia or Thalassemia or even anaemia are required to opt for blood transfusion.
Question 19: When is National Voluntary Blood Donation Day observed?
Answer: 1st October is observed as National Voluntary Blood Donation Day every year. Healthy people are encouraged to donate blood so that it can be transfused into the bodies of people who are in urgent need of it.
Question 20: Who discovered the blood groups –A, B, O and AB?
Answer: In 1900, the blood groups –A, B, O were discovered by Carl Landsteiner. He won the Nobel Prize in 1930 for this discovery. In 1902, the blood group AB was discovered by Decastello and Sturli.
Question 21: Define Hematology.
Answer: Hematology is a branch of medical science that deals with the study of hematopoietic organs, blood and blood diseases. In this branch, research of diagnosis and remedies of blood diseases are performed.