NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation

Irshad AnwarUpdated on 25 Oct 2025, 12:17 PM IST

The NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation explores how blood and lymph function in the body. This chapter also explains the mechanism of blood clotting and the importance of various blood groups, such as A, B, and O. The structure of blood and the anatomy of the heart are described clearly, along with labelled diagrams. The NCERT Solutions provide detailed and easy-to-understand explanations for all the questions.

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Download Body Fluids and Circulation Class 11 Questions and Answers PDF
Access Class 11 Biology Chapter 15 Body Fluids and Circulation Question Answer (Exercise Questions)
Approach to Solve Body Fluids and Circulation Class 11 Question Answer
Important Questions of NCERT Chapter 15 Body Fluids and Circulation
What Students Learn from Body Fluids and Circulation NCERT Solutions
Why Class 11 Biology Chapter 15 Body Fluids and Circulation NCERT Solutions are Important?
What Extra Should Students Study Beyond the NCERT for NEET?
NCERT Solutions for Class 11 Biology - Chapter Wise

NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation

Body Fluids and Circulation Class 11 question answer describes the heart's structure and function, as well as the concept of double circulation. The regulation of cardiac activity gives students a detailed knowledge of the transportation of nutrients around the body. By studying the Body Fluids and Circulation Class 11 Questions and Answers PDF, they can understand how oxygen and waste are transported in the body. To make learning easier and build a strong foundation, students can make the most of the NCERT Class 11 Solutions.

Download Body Fluids and Circulation Class 11 Questions and Answers PDF

Students can download the solutions of this chapter in a PDF format for better learning. The Body Fluids and Circulation Class 11 Questions and Answers PDF can be used offline anytime and anywhere, making it ideal for quick revision and self-study.

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Access Class 11 Biology Chapter 15 Body Fluids and Circulation Question Answer (Exercise Questions)

The detailed answers to all the questions are given below. Students can use the Class 11 Biology Chapter 15 Body Fluids and Circulation question answer to strengthen their revision and score better in exams. Each solution is explained step by step and follows the NCERT guidelines which makes concepts clear.

Question 1. Name the components of the formed elements in the blood and mention one major function of each of them.

Answer:

The following formed elements were discovered in the blood:

(1) Erythrocytes: The most prevalent type of red blood cells, erythrocytes are coloured red by the red pigment known as haemoglobin. Every part of the body receives oxygen from erythrocytes. Some body parts, like the marrow of long bones, ribs, etc., continuously produce these. Each cubic millimetre of blood contains roughly 4–6 million red blood cells.

(2) Leukocytes: These are colourless cells devoid of haemoglobin. They are the largest cells in blood (larger than RBCs) .

(a) Granulocytes- These leukocytes have granules in their cytoplasm and include neutrophils, eosinophils, and basophils. Neutrophils are phagocytic cells that protect the body against various infecting agents. Eosinophils are associated with allergic reactions, while basophils are involved in inflammatory responses.

(b) Agranulocytes- Lymphocytes and monocytes are agranulocytes. Lymphocytes generate immune responses against infecting agents, while monocytes are phagocytic in nature.

(3) Platelets- These are small, irregular bodies present in the blood. They contain essential chemicals that help in clotting. The main function of platelets is to promote clotting.

Question 2. What is the importance of plasma proteins?

Answer:

About 55% of blood is made up of plasma, the colourless fluid. It facilitates the transportation of waste materials, salts, food, and carbon dioxide, among other things. Proteins like albumins, globulins, and fibrinogens make up around 6.8% of plasma. The liver produces the plasma glycoprotein fibrinogen. It contributes to blood coagulation. One of the main proteins in plasma, globulin, shields the body from pathogens. One of the main proteins in plasma that keeps the fluid volume in the vascular space constant is albumin.

Question 3. Match Column I with Column II :

Column I	Column II
(a) Eosinophils	(i) Coagulation
(b) RBC	(ii) Universal Recipient
(c) AB Group	(iii) Resist Infections
(d) Platelets	(iv) Contraction of the Heart
(e) Systole	(v) Gas transport

Answer:

The correct matching is a-iii, b-v, c-ii, d-i, e-iv

Column I	Column II
(a) Eosinophils	(iii) Resist Infections
(b) RBC	(v) Gas transport
(c) AB Group	(ii) Universal Recipient
(d) Platelets	(i) Coagulation
(e) Systole	(iv) Contraction of Heart

Question 4. Why do we consider blood as a connective tissue?

Answer:

For the following reasons, we view blood as connective tissue:

The body's other organs are held together, connected, or supported by connective tissues.
They are the body's most prevalent and plentiful tissue.
Gases, nutrients, and hormones are all transported by blood between the body's organs.
It circulates throughout the body.
Blood is, therefore, regarded as connective tissue.

Question 5. What is the difference between lymph and blood?

Answer:

Blood

Blood is a red colour connective tissue.
It consists of haemoglobin, red blood cells, white blood cells, and platelets. It circulates via arteries, veins, and capillaries.
Blood transports gases and nutrients to various parts of the body.

Lymph

Lymph is a white-coloured fluid in the body.
It has white blood cells known as lymphocytes and flows through vessels called lymph.
The lymph system facilitates the interchange of gases and nutrients between the body's cells and blood.

Question 6. What is meant by double circulation? What is its significance?

Answer:

Double circulation occurs when blood flows through the heart twice in a single cycle. Although it can be found in birds, mammals, amphibians, and reptiles, it is most noticeable in birds and mammals because of their four-chambered hearts:

Atrium on the right
The right ventricle
Atrium on the left
The left ventricle

The circulation of blood is separated into:
Systemic circulation: Blood that has been oxygenated leaves the left ventricle and travels to the aorta, then passes through arteries to reach bodily tissues before returning to the right atrium as deoxygenated blood.
Pulmonary circulation: Blood that has lost oxygen travels from the right ventricle to the lungs for oxygenation before returning to the left atrium.
By separating oxygenated and deoxygenated blood, double circulation guarantees an effective oxygen supply.

Question 7. (a) Write the differences between Blood and Lymph

Answer:

Blood	Lymph
Red liquid connective tissue that circulates in blood vessels.	White tissue fluid that circulates in lymphatic vessels.
Red due to the presence of haemoglobin.	Colourless or pale yellow due to the absence of haemoglobin.
Contains red blood cells (RBCs), white blood cells (WBCs), platelets, plasma, and haemoglobin.	Contains white blood cells (mainly lymphocytes), proteins, and plasma but lacks RBCs and platelets.
Transports oxygen, nutrients, hormones, and waste products throughout the body.	Helps in immunity, removal of waste, and exchange of nutrients and gases between blood and cells.
Travels through arteries, veins, and capillaries.	Travels through lymphatic vessels.
Circulated by the heart.	Moves slowly without a central pump, relying on muscle movement and valves.

Question 7. (b) Write the differences between the Open and Closed systems of Circulation

Answer:

Open circulatory system:

The blood vessels open into spaces and not into capillaries.
Blood comes in direct contact with tissues.

Closed circulatory system:

Blood flows through capillaries.
It is connected by arteries and veins.

Question 7. (c) Write the differences between Systole and Diastole

Answer:

Systole:

It is the heart's chambers contracting.
It raises the heart's internal blood pressure.
When the chambers are in systole, blood is pumped out.

Diastole:

It is the heart's chambers relaxing.
The heart's blood pressure drops.
The chambers in diastole receive blood.

Question 7. (d) Write the differences between the P-wave and the T-wave

Answer:

P-Wave:

P-wave represents the depolarisation or electrical excitation of the atria.
Blood is pumped into the ventricles.

T-Wave

The T-wave represents the repolarisation of the ventricles.
Blood is received by the atria.

Question 8. Describe the evolutionary change in the pattern of heart among the vertebrates.

Answer:

In vertebrates, the heart has changed from having two chambers in fish to having four chambers in mammals and birds.
In fish, deoxygenated blood is pumped to the gills for oxygenation by the heart's two chambers.
Amphibians have three chambers, a ventricle, two atria, and a mixture of oxygenated and deoxygenated blood in the ventricle.
In reptiles, blood mixing is decreased by an incomplete septum.
The four-chambered hearts of crocodiles, birds, and mammals guarantee that oxygenated and deoxygenated blood are completely separated.

This development increases the availability of oxygen and effectively controls blood flow.

Question 9. Why do we call our hearts myogenic?

Answer:

Because the cardiac impulse starts in the heart's muscles, the organ is known as myogenic. The heart beats as a result of impulses produced by the SA node, a specialised cardiac tissue, spreading throughout the heart walls.

"Genic" means coming from, and "myo" means muscle.

Question 10. The sino-atrial node is called the pacemaker of the heart. Why?

Answer:

The sino-atrial node is referred to as the heart's pacemaker due to its ability to generate a cardiac impulse. The cardiac impulse and action potential are produced by the sinoatrial node. The atria and ventricles then contract or relax as a result of this cardiac impulse spreading throughout them.

The maximum number of action potentials that the SA node can produce is roughly 70–75 per minute. It also regulates the heart's rhythmic contractions.

Question 11. What is the significance of the atrio-ventricular node and the atrio-ventricular bundle in the functioning of the heart?

Answer:

The atrioventricular node and atrioventricular bundle are important for the heart's operation because:

The SA node sends the cardiac impulse to the atrioventricular node.
The cardiac impulse is sent farther toward the ventricular walls by the atrioventricular bundle, which emerges from the AV node.

Question 12. Define the cardiac cycle and the cardiac output.

Answer:

Cardiac cycle

The alternating contraction and relaxation of the heart chambers, which is also referred to as diastole and systole, is what causes the blood to circulate in the heart.
There is a relaxation or expansion phase (diastole) after each contraction phase (systole).
The cardiac cycle, which lasts 0.8 seconds, is the sequence of events that take place during a single heartbeat.

Cardiac Output

The cardiac output is the volume of blood pumped by each ventricle in a minute.

Question 13. Explain heart sounds.

Answer:

Every heartbeat is followed by a series of heart sounds.

Every cardiac cycle produces the sounds "lub" and "dub."
The first low-pitched sound, "lub," is produced when the tricuspid and bicuspid valves close.
The second high-pitched sound, "dub," is produced when the semi-lunar valves close.
For the diagnosis of heart-related conditions, these sounds are important.

Question 14. Draw a standard ECG and explain the different segments in it.

Answer:

The heart's activity during a cardiac cycle is represented graphically by an ECG. Electrocardiograph, or ECG. Assume that a patient has three electrical leads attached to the device—one to the left ankle and one to each wrist—and that the device is continuously monitoring the patient's heart activity. Several leads are connected to the chest area for a thorough assessment of the heart's performance.

Every ECG peak is denoted by a letter, ranging from P to T, which represents a distinct electrical activity of the heart.

ECG diagram

The P-wave is a representation of the electrical excitation (or depolarisation) of the atria, which causes both atria to contract.

The QRS complex stands for the ventricles' depolarisation, which starts the ventricular contraction. Shortly after, the contraction begins.
The
T-wave symbolises the ventricles' repolarisation or transition from an excited to a normal state.

The systole ends when the T-wave ends. Naturally, one can calculate a person's heartbeat rate by counting the number of QRS complexes that occur in a specific amount of time. For a given lead configuration, the ECGs from different people have a similar shape, so any deviation from this shape suggests a potential abnormality or illness. It is, therefore, very important from a clinical standpoint.

NCERT Solutions for Class 11: Subject-wise

Approach to Solve Body Fluids and Circulation Class 11 Question Answer

Listed below are some important tips that students must follow to solve the questions skillfully:

Firstly, it's important to understand the basics of this chapter. This includes plasma, RBCs, WBCs, platelets, and double circulation, before going towards the questions.
Read the NCERT textbook carefully, line by line, and try to understand and visualise how the circulatory system works.
After reading, it's important to make notes that can be used in the future, too. Students can refer to the Class 11 Biology Chapter 15 Body Fluids and Circulation question answer to prepare notes.
Practice the diagrams like the heart, blood vessels, and circulatory routes given in the Class 11 Biology Chapter 15 Body Fluids and Circulation Solutions.
Try to revise the chapter regularly, and if you have any doubts, students can refer to the NCERT Solutions for Class 11 Biology.

Check the NCERT Books and NCERT Syllabus here:

Important Questions of NCERT Chapter 15 Body Fluids and Circulation

The chapter explores the mechanisms by which substances like oxygen and nutrients are transported, and the function of the Human Circulatory System. Doing practice of the questions given in the NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation improves understanding.

Question 1: Arrange the following blood vessels in descending order of their average pressure.

Aorta, artery, arteriole, capillary, venule, vein.

Choose the correct option:

A. Aorta > arteriole > venule > artery > vein > capillary.

B. Aorta > artery > arteriole > capillary > venule > vein.

C. Capillary > arteriole > venule > artery > vein > aorta.

D. Capillary > vein > venule > arteriole > artery > aorta.

Answer: The correct answer is option (B) Aorta > artery > arteriole > capillary > venule > vein.

Explanation:

In terms of average pressure, the correct arrangement is as follows: Aorta > artery > arteriole > capillary > venule > vein. The aorta, being the largest artery, experiences the highest pressure as it receives blood directly from the left ventricle. The pressure gradually decreases as blood flows through the arteries, arterioles, and capillaries. The pressure is lowest in the venules and veins, where blood returns to the heart.

Question 2: Which of the following correctly explains a phase/ event in the cardiac cycle in a standard electrocardiogram?

A. QRS complex indicates atrial contraction.

B. The QRS complex indicates ventricular contraction.

C. The time between S and T represents atrial systole.

D. P-wave indicates the beginning of ventricular contraction.

Answer: The correct answer is option (B). The QRS complex indicates ventricular contraction.

Explanation:

Ventricular contraction is caused by the depolarisation of the ventricles, which is represented by the QRS complex in a normal electrocardiogram (ECG/EKG).
The electrical signal that triggers the ventricular muscles' mechanical contraction is known as depolarisation.
Because it causes blood to be pumped from the ventricles into the aorta and pulmonary artery, this stage of the cardiac cycle is crucial.

Question 3: The second heart sound (dubb) is associated with the closure of

A. Tricuspid valve

B. Semilunar valves

C. Bicuspid valve

D. Tricuspid and bicuspid valves.

Answer: The correct answer is option (B) Semilunar valves

Explanation:

The bicuspid valve, and tricuspid valve and both together are associated with the first heart sound, and the semilunar valve is associated with the second. The first heart sound ("lub") occurs when the bicuspid and tricuspid valves close during ventricular contraction (systole). The second heart sound ("dub") is produced by the closure of the semilunar valves as the ventricles relax during diastole.

Question 4: Which one of the following blood cells is involved in antibody production?

A. B-Lymphocytes

B. T-Lymphocytes

C. RBC

D. Neutrophils

Answer: The correct answer is option (A) B-Lymphocytes

Explanation:

The main role of B-lymphocytes is in the humoral immune response, mainly producing antibodies. Upon activation, the B-lymphocytes undergo differentiation into the plasma cells, which release specific antibodies to destroy antigens. Apart from this, some of the B-lymphocytes differentiate into memory cells too, to help the immune system respond rapidly upon being exposed to the same antigen next time.

Question 5: Which one of the following types of cells lacks a nucleus in humans?

A. RBC

B. Neutrophils

C. Eosinophils

D. Erythrocytes

Answer: The correct answer is option (A) RBC

Explanation:

Because they don't have a nucleus or mitochondria, red blood cells (RBCs) are different from other mammalian cells. Because of this adaptation, RBCs can make the most of the space that haemoglobin, the protein that carries oxygen, has available.

What Students Learn from Body Fluids and Circulation NCERT Solutions

Students get to explore how blood and other body fluids help in maintaining life processes and how the circulatory system transports different substances in the body.

Students will understand the composition and functions of blood and lymph in transporting materials.
Through Body Fluids and Circulation Class 11 question answer, learners explore different types of blood vessels and how they regulate blood flow in the body.
They learn about the structure of the human heart and the process of blood circulation through its chambers.
Class 11 Biology Body Fluids and Circulation question answers help students know about common circulatory disorders and their impact on human health.

Why Class 11 Biology Chapter 15 Body Fluids and Circulation NCERT Solutions are Important?

Students will understand how blood and lymph present in the body transport nutrients, gases, and hormones through the Blood and Circulation chapter. It also explains the structure and function of the human heart, types of blood vessels, and the mechanism of blood circulation.

Class 11 Biology Chapter 15 Body Fluids and Circulation NCERT Solutions make students understand topics like double circulation, cardiac cycle, and the working of the human heart.
The solutions also include concepts like blood pressure, ECG, and the regulation of cardiac activity, with well-labelled diagrams.
Difficult topics such as the origin of the heartbeat and conduction of impulses are explained in a systematic way, making the solutions an important resource.
Students can strengthen their understanding of circulatory processes and perform well in competitive exams like NEET.

What Extra Should Students Study Beyond the NCERT for NEET?

NCERT is the most important book for NEET, but to score higher, students should also study some extra topics. Regular revision of the NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation helps students in effective learning.

Concepts	NEET	NCERT
Body fluids	✅	✅
Blood	✅	✅
Blood Groups: ABO Blood Groups	✅	✅
Rh Blood Group	✅	✅
Blood Coagulation	✅	✅
Blood Vessels	✅	✅
Functioning of the Human Heart	✅	✅
Cardiac cycle	✅	✅
Heart rate and Cardiac Output	✅	✅
Artificial Kidney	✅	✅
ECG	✅	✅
Double Circulation In Humans	✅	✅
Blood vessels and their system	✅	✅
Human lymphatic system	✅	✅
Abnormal conditions related to the Circulatory system	✅	✅

NCERT Solutions for Class 11 Biology - Chapter Wise

Below mentioned are the Chapter-wise solutions:

NCERT Solutions for Class 11 Chapter 1 Biology The Living World

NCERT Solutions for Class 11 Chapter 2 Biology Biological Classification

NCERT Solutions for Class 11 Chapter 3 Biology Plant Kingdom

NCERT Solutions for Class 11 Chapter 4 Biology Animal Kingdom

NCERT Solutions for Class 11 Chapter 5 Biology Morphology of Flowering Plants

NCERT Solutions for Class 11 Chapter 6 Biology Anatomy of Flowering Plants

NCERT Solutions for Class 11 Chapter 7 Biology Structural Organisation in Animals

NCERT Solutions for Class 11 Chapter 8 Biology Cell: The Unit of Life

NCERT Solutions for Class 11 Chapter 9 Biology Biomolecules

NCERT Solutions for Class 11 Chapter 10 Biology Cell Cycle and Cell Division

NCERT Solutions for Class 11 Chapter 11 Biology Photosynthesis in Higher Plants

NCERT Solutions for Class 11 Chapter 12 Biology Respiration in Plants

NCERT Solutions for Class 11 Chapter 13 Biology Plant Growth and Development

NCERT Solutions for Class 11 Chapter 14 Biology Breathing and Exchange of Gases

NCERT Solutions for Class 11 Chapter 15 Biology Body Fluids and Circulation

NCERT Solutions for Class 11 Chapter 16 Biology Excretory Products and their Elimination

NCERT Solutions for Class 11 Chapter 17 Biology Locomotion and Movement

NCERT Solutions for Class 11 Chapter 18 Biology Neural Control and Coordination

NCERT Solutions for Class 11 Chapter 19 Biology Chemical Coordination and Integration

Frequently Asked Questions (FAQs)

Q: What are the important topics covered in NCERT Solutions for Class 11 Biology Chapter 15?

The important topics covered in the NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation are given below:

Blood composition
Human circulatory system
Heart structure and function
Blood groups and clotting
Double circulation
Oxygen and carbon dioxide transport
Lymph and its functions
Heart disorders

Q: What is the significance of the human circulatory system in Class 11 NCERT Biology?

It delivers hormones, nutrients, and oxygen to body cells.
It eliminates waste products like urea and carbon dioxide.
It aids in preserving the pH balance and body temperature.

Q: What is double circulation, and why is it important according to NCERT?

In a single circulation cycle, the blood goes through the heart twice.
Transporting deoxygenated blood to the lungs for oxygenation is known as pulmonary circulation.
Systemic Circulation delivers blood enriched with oxygen to the body's organs.
This separation keeps oxygenated and deoxygenated blood from mixing and guarantees an effective oxygen supply.

Q: How does the heart function as per NCERT Class 11 Biology Chapter 15?

The sinoatrial (SA) node produces the electrical impulses that cause the heart to beat.
Systole, or contraction, and diastole, or relaxation, are the rhythmic contractions that it uses to pump blood.
The heart's valves guarantee that blood only flows in one direction.

Q: What are the different types of blood groups explained in NCERT Class 11 Biology?

Based on the presence of antigen on RBCs, there are four primary types A, B, AB, and O.
The O group is a universal donor, and the AB group is a universal recipient.

Q: What are the differences between open and closed circulatory systems in NCERT solutions?

Given below are the differences between open and circulatory systems. These are well-explained in the NCERT Solutions for Class 11 Biology Chapter 15 Body Fluids and Circulation.

Open Circulatory System: Blood circulates freely within bodily cavities (in insects, for example).
Closed Circulatory System: Humans and other animals can be transported efficiently because blood is contained within vessels.

Q: How is lymph different from blood as explained in NCERT Class 11 Biology?

A colourless substance called lymph aids in immunity and removes extra fluid from tissues.
Blood contains platelets, plasma, RBCs, and WBCs that transport nutrients and oxygen.

Q: What is the cardiac cycle, and how is it explained in NCERT solutions?

One heartbeat, lasting roughly 0.8 seconds, is included.