10th Science - Book Back Answers - Biology Unit 14 - English Medium Guides

 

SSLC / 10th - Science - Book Back Answers - Biology Unit 14 - English Medium

Tamil Nadu Board 10th Standard  Science - Biology Unit 14: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 14 – Biology from the Tamil Nadu State Board 10th Standard  Science textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Biology Unit 14 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 10 students! Prepare well and aim for top scores. Thank you!

Topic: Transportation in Plants and Circulation in Animals

I. Choose the correct Answer

1. Active transport involves:
(a) movement of molecules from lower to higher concentration
(b) expenditure of energy
(c) it is an uphill task
(d) all of the above
Answer Key:
(d) all of the above

2. Water which is absorbed by roots is transported to aerial parts of the plant through ______.
(a) cortex
(b) epidermis
(c) phloem
(d) xylem.
Answer Key:
(d) xylem.

3. During transpiration there is loss of:
(a) carbon dioxide
(b) oxygen
(c) water
(d) none of the above
Answer Key:
(c) water
 

4. Root hairs are ______.
(a) cortical cell
(b) projection of the epidermal cell
(c) unicellular
(d) both b and c.
Answer Key:
(b) projection of the epidermal cell

5. Which of the following process requires energy?
(a) active transport
(b) diffusion
(c) osmosis
(d) all of them
Answer Key:
(a) active transport

6. The wall of the human heart is made of ______.
(a) Endocardium
(b) Epicardium
(c) Myocardium
(d) All of the above.
Answer Key:
(d) All of the above.

7. Which is the sequence of correct blood flow?
(a) ventricle – atrium – vein – arteries
(b) atrium – ventricle – veins – arteries
(c) atrium – ventricle – arteries – vein
(d) ventricles – vein – atrium – arteries
Answer Key:
(c) atrium – ventricle – arteries – vein

8. A patient with blood group O was injured in an accident and has blood loss. Which blood group the doctor should effectively use for transfusion in this condition?
(a) O group
(b) AB group
(c) A or B group
(d) all blood group.
Answer Key:
(d) all blood group.

9. ‘Heart of heart’ is called:
(a) SA node
(b) AV node
(c) Purkinje fibres
(d) Bundle of His
Answer Key:
(a) SA node

10. Which one of the following regarding blood composition is correct?

(a) Plasma – Blood + Lymphocyte

(b) Serum – Blood + Fibrinogen

(c) Lymph – Plasma + RBC + WBC

(d) Blood – Plasma + RBC + WBC + Platelets.

Answer Key:

(d) Blood – Plasma + RBC+ WBG + Platelets.

 

II. Fill in the blanks

1. ……….. involves evaporative loss of water from aerial parts.
2. Water enters the root cell through a ………. plasma membrane.
3. Structures in roots that help to absorb water are …………
4. Normal blood pressure is …………
5. The normal human heartbeat rate is about ……….. time per minute.
Answer Key:
1. Transpiration
2. Semipermeable
3. Root hairs
4. 120 mm / 80 mm Hg
5. 72 – 75 times

 

III. Match the following

1. Match the following

Column I		Column II
1	Symplastic pathway	i	Leaf
2	Transpiration	ii	Plasmodesmata
3	Osmosis	iii	Pressure in xylem
4	Root Pressure	iv	Pressure gradient

Answer Key:

Column I		Column II
1	Symplastic pathway	ii	Plasmodesmata
2	Transpiration	i	Leaf
3	Osmosis	iv	Pressure gradient
4	Root Pressure	iii	Pressure in xylem

2. Match the following

Column I		Column II
1	Leukemia	i	Thrombocytes
2	Platelets	ii	Phagocyte
3	Monocytes	iii	Decrease in leucocyte
4	Leucopenia	iv	Blood Cancer
5	AB blood group	v	Allergic condition
6	O blood group	vi	Inflammation
7	Eosinophil	vii	Absence of antigen
8	Neutrophils	viii	Absence of body

Answer Key:

Column I		Column II
1	Leukemia	iv	Blood Cancer
2	Platelets	i	Thrombocytes
3	Monocytes	ii	Phagocyte
4	Leucopenia	iii	Decrease in leucocyte
5	AB blood group	viii	Absence of body
6	O blood group	vii	Absence of antigen
7	Eosinophil	v	Allergic condition
8	Neutrophils	vi	Inflammation

 

IV.  State whether True or False .if false write the correct statement

1. The phloem is responsible for the translocation of food.
2. Plants lose water by the process of transpiration.
3. The form of sugar transported through the phloem is glucose.
4. In apoplastic movement the water travels through the cell membrane and enter the cell.
5. When the guard cells lose water the stoma opens.
6. Initiation and stimulation of heart beat take place by nerves.
7. All veins carry deoxygenated blood.
8. WBC defend the body from bacterial and viral infections.
9. The closure of the mitral and tricuspid valves at the start of the ventricular systole produces the first sound ‘LUBB’.
Answer Key:
1. True
2. True
3. False – The form of sugar transported through the phloem is sucrose.
4. False – Apoplastic movement does not involve crossing the cell membrane.
5. False – When the guard cells lose water the stoma closes.
6. False – Initiation and stimulation of heart beat take place by Sino-atrial node.
7. False – All veins carry deoxygenated blood except the pulmonary veins,
8. True
9. True.

V.  Answer in a word or sentence

1. Name two layered protective covering of human heart.
Answer Key:
Pericardium is the two layered protective covering of human heart.
 
2. What is the shape of RBC in human blood?
Answer Key:
The shape of RBC in human blood is biconcave and disc – shaped.
 
3. Why is the colour of the blood red?
Answer Key:
The blood is red in colour due to the presence of respiratory pigment – haemoglobin.
 
4. Which kind of cells are found in the lymph?
Answer Key:
Lymphocytes in the lymph, which defend the body from infection.
 
5. Name the heart valve associated with the major arteries leaving the ventricles.
Answer Key:
Aortic valve present at the base of aorta.
 
6. Mention the artery which supplies blood to the heart muscle.
Answer Key:
Coronary arteries.

 

VI. Short answer question

1. What causes the opening and closing of guard cells of stomata during transpiration?
Answer Key:
The general mechanism of stomatal movement is based on entry and exit of water molecules in guard cells. When the turgidity increases within the guard cells the stomata open. When the guard cells lose water it becomes flaccid and the stomata closes.

2. What is cohesion?
Answer Key:
The force of attraction between molecules of water is called Cohesion.
 
3. Trace the pathway followed by water molecules from the time it enters a plant root to the time it escapes into the atmosphere from a leaf.
Answer Key:
Soil → root hair → cortex → endodermis → Pericycle → xylem → stem → leaves.
 
4. What would happen to the leaves of a plant that transpires more water than its absorption in the roots?
Answer Key:
When transpiration exceeds than water absorption by roots, the plant dehydrates. It affects plant processes such as growth, Photosynthesis and transpiration.
 
5. Describe the structure and working of the human heart.
Answer Key:
The heart is thick muscular organ located in the thoracic cavity. It is covered by a two layered sac called pericardium. The heart is four chambered with two auricles and two ventricles. Right Auricle receives deoxygenated blood from superior and inferior vena cava and passes to right ventricles from right ventricles impure blood passes to pulmonary artery and reaches the lungs.
 
6. Why is the circulation in man referred to as double circulation?
Answer Key:
The blood circulates twice, through the heart in one complete cycle, in the circulation of blood in man. So it is called double circulation.
 
7. What are heart sounds? How are they produced?
Answer Key:
‘Lubb’ and ‘Dupp’ are the sounds of the heart. ‘Lubb’ sound is produced by the ventricle- contraction. It arises due to closing of mitral and tricuspid valve.
‘Dupp’ is produced by ventricular diastole. This arises due to the closing of the semi-lunar valves of two auricles.
 
8. What is the importance of valves in the heart?
Answer Key:
The valves are the muscular flaps, that regulate the flow of blood in a single direction and prevent backflow of blood.
 
9. Who discovered Rh factor? Why was it named so?
Answer Key:
Landsteiner and Wiener discovered Rh factor of blood in 1940. Rh factor is a protein CD antigen present on the surface of the red blood cells in majority of humans. This protein is similar to the protein present in Rhesus monkey, hence the term Rh.
 
10. How are arteries and veins structurally different from one another?
Answer Key:

Arteries	Veins
Wall of artery is strong, thick and elastic	Wall of vein is weak, thin and non-elastic
All arteries carry oxygenated blood except pulmonary arteries	All veins carry deoxygenated blood except pulmonary veins
Distributing vessel	Collecting vessel
Internal valves are absent	Internal valves are present

 
11. Why is the Sinoatrial node called the pacemaker of the heart?
Answer Key:
Sinoatrial node is called the pacemaker of the heart because it is capable of initiating impulse, which can stimulate the heart muscles to contract.
 
12. Differentiate between systemic circulation and pulmonary circulation.
Answer Key:

Systemic circulation:	Pulmonary circulation
In Systemic circulation, the oxygenated blood entering the aorta from the left ventricles is carried by a network of arteries to the issues.	In pulmonary circulation, the blood from the heart(right ventricle) is taken to the lungs by pulmonary artery.
The deoxygenated blood from the tissue is collected by veins and vena cava, emptied into the right atrium.	The oxygenated blood from lungs is emptied into the left auricle by the pulmonary veins.

 

13. The complete events of the cardiac cycle last for 0.8 sec. What is the timing for each event?
Answer Key:
1. Atrial Systole: Contraction of auricles (0.1 sec)
2. Ventricular Systole: Contraction of ventricles (0.3 sec)
3. Ventricular diastole: Relaxation of Ventricles (0.4 sec).

VII. Give reasons for the following statements

1. Minerals cannot be passively absorbed by the roots.
Answer Key:
All minerals cannot be passively absorbed by the roots because, minerals are present in the soil as charged particles that cannot move across the cell membranes and the concentration of minerals in the soil is usually lower than the. concentration of minerals in the root. So, the minerals enter the root by active absorption through the cytoplasm of epidermal cells which needs energy.
 
2. Guard cells are responsible for opening and closing of stomata.
Answer Key:
Guard cells are responsible for the opening and closing of stomata because, during transpiration, the movement of ions (Potassium) in and out of the guard cells causes the opening and closing of Stomata. When the water moves inside the guard cells, causing them to swell up and become turgid making the stomata open. When guard cells cause water to move out of the cell and make guard cells shrunk and stomata pores close.
 
3. The movement of substances in the phloem can be in any direction.
Answer Key:
Phloem transports food from the source to sink. The source is part in which plant synthesize food, sink is the part that needs or stores food. Since the source-sink relationship is variable, the direction of movement in the Phloem can be upwards or downwards, i.e., bidirectional.
 
4. Minerals in the  plants are not lost when the leaf falls.
Answer Key:
Minerals like Phosphorus, Sulphur, Nitrogen and Potassium are remobilised in the soil from older dying leaves to younger leaves. This phenomenon is seen in deciduous plants. So minerals in the plants are not lost, when the leaf falls.
 
5. The walls of the right ventricle are thicker than the right auricles.
Answer Key:
Because the right ventricle have to pump out the deoxygenated blood with force away from the heart through pulmonary artery to lungs.

6. Mature RBC in mammals does not have cell organelles.
Answer Key:
Mature RBC in mammals does not have cell organelles because
• The lack of Nucleus in RBC makes the cells, biconcave and disc – shaped. RBC involved in the transport of oxygen from lungs to tissues.
• They do not have cell organelles in order to accommodate maximum space for haemoglobin.
• The loss of endoplasmic reticulum allows more flexibility, for RBC to move through narrow capillaries.

VIII. Long answer questions

1. How do plants absorb water? Explain.
Answer Key:
Water present in the soil must reach the xylem of roots. Root hair is in contact with soil water. Their cell wall is thin and water easily diffuses in the passage of water from the soil to leaf is
Soil water → Root hair → Epidermis → Cortex → Endodermis → Pericycle → Xylem → Stem and leaf.
Once water is absorbed by the root hairs, it can move deepers into root layers by two pathways. Apoplast and Symplast.
1. Apoplast: This is the non living path in plants. It occurs through the intercellular spaces and walls of the cells. This movement dependent on the gradient.
2. Symplast: This is the living passage. The movement of water from cell to cell through plasmodesmato and cytoplasm, Movement is again down a potential gradient.
 
2. What is transpiration? Give the importance of transpiration.
Answer Key:
Transpiration is the evaporation of water in plants through stomata in the leaves.
Importance of Transpiration
• Creates transpirational pull for the transport of water.
• Supplies water for photosynthesis.
• Transports minerals from the soil to all parts of the plant.
• Cools the surface of the leaves by evaporation.
• Keeps the cells turgid; hence, maintains their shape.
 
3. Why are leucocytes classified as granulocytes and agranulocytes? Name each cell and mention its functions.
Answer Key:
Depending on the presence and absence of granules, leucoytes are divided into two types Granulocytes and Agranulocytes.
Granulocytes : They are characterised by the presence of granules in cytoplasm. The granulocytes include neutrophils, eosinophils and basophils.
1. Neutrophils: They constitute about 60-65% of total WBC’s. They are large and have many lobed nucleus. They are phagocytic in nature and appear in large,number in and around the infected tissue.
2. Eosinophils: They have bilobed nucleus and constitute about 2-3% of total WBC’s. Eosinophil increase during certain types of parasitic infection and allergic reaction. It bring about detoxification of toxin.
3. Basophils: Basophil have lobed nucleus. They form 0.5 – 1.0% of the total leucocytes. They release chemicals during the process of inflammation.
Agranulocytes: They are characterised by the absence of granules in the cytoplasm. These are of two types Lymphocytes and Monocytes.
1. Lymphocytes: These are about 20-25% of the total leucocytes. They produce antibodies during bacterial and viral infections.
2. Monocytes: They are the largest leucocytes and amoeboid in shape. These cells form 5-6% of the total leucocytes. They are phagocytic and can engulf bacteria.
 
4. Differentiate between systole and diastole. Explain the conduction of the heartbeat.
Answer Key:
One complete contraction (Systole) and relaxation (diastole) of the atrium and ventricles of the heart constitutes Heartbeat. The human heart is myogenic. Contraction is initiated by the sino – atrial (SA) node, which is situated in the wall of the right atrium, near the opening of the superior vena cava. SA node is broader at the top and tapering below and made up of thin fibres.
SA node acts as the ‘pacemaker’ of the heart because it is capable of initiating impulse which can stimulate the heart muscles to contract. The impulse spreads like a wave of contraction over the right and left atrial wall, pushing the blood, through the atrioventricular valves into the ventricles and the same wave from SA node reaches the atrioventricular node (AV), to emit an impulse of contraction, spreading to the ventricular muscle, through the atrioventricular bundle and the Purkinje fibres. The expansion of the artery every time, the blood is forced into the arteries, is called pulse. Normal pulse rate ranges from 70 – 90 / min.
 
5. Enumerate the functions of blood.
Answer Key:
1. Transport of respiratory gases (Oxygen and CO₂).
2. Transport of digested food materials to the different body cells.
3. Transport of hormones.
4. Transport of nitrogenous excretory products like ammonia, urea and uric acid.
5. It is involved in protection of the body and defense against diseases.
6. It acts as buffer and also helps in regulation of pH and body temperature.
7. It maintains proper water balance in the body.

IX.  Assertion and Reasoning

Direction: In each of the following questions a statement of assertion (A) is given and a corresponding statement of reason (R) is given just below it. Mark the correct statement as.
(a) If both A and R are true and R is correct explanation of A.
(b) If both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) Both A and R are false.

1. Assertion: RBC plays an important role in the transport of respiratory gases.
Reason: RBC do not have cell organelles and nucleus.
Answer Key:
(a) If both A and R are true and R is correct explanation of A.

2. Assertion: Persons with AB blood group are called an universal recipients, because they can receive blood from all groups.
Reason: Antibodies are absent in persons with AB blood group.
Answer Key:
(a) If both A and R are true and R is correct explanation of A.

 

X.  HOTS questions

1. When any dry plant material is kept in water, they swell up. Name and define the phenomenon involved in this change.
Answer Key:
The process is imbibition’. The type of diffusion in which a solid absorbs water and gets swelled up is Imbibition.
 
2. Why are the walls of the left ventricle thicker than the other chambers of the heart?
Answer Key:
The walls of the left ventricle are about three times thicker than the right ventricle. The left ventricle gives rise to the aorta, which carries oxygenated blood, to various organs of the body. The ventricle walls are thick because they have to pump out blood with force away from the heart.
 
3. Doctors use stethoscope to hear the sound of the heart. Why?
Answer Key:
A stethoscope is an instrument used to detect the sound produced by the internal organs of human body. It is an useful diagnostic tool to identify and localize health problems and diagnose disease.
 
4. How do the pulmonary artery and pulmonary vein differ in their function when compared to a normal artery and vein?
Answer Key:
• All arteries carry oxygenated blood, except pulmonary arteries, which carry deoxygenated blood from the right ventricle to the lungs.
• All veins carry deoxygenated blood, except pulmonary veins, which carry oxygenated blood from the lungs and to the left atrium of the Heart.
 
5. Transpiration is a necessary evil in  plants. Explain.
Answer Key:
The water is lost from the leaves due to transpiration, pressure is created in, at the top to pull more water from the xylem to the leaves through the process of transpiration pull. This ensure the continuous flow of water from the roots of the leaves.