10th Science Unit 14 Transportation in Plants and Circulation in Animals Book Back Answers
10th Science Unit 14 Transportation in Plants and Circulation in Animals book back answers for all 63 questions in the 2026-27 Samacheer Kalvi (Tamil Nadu) textbook.
This unit looks at how water, minerals and food move inside plants, and how blood travels around the animal body. You will study diffusion, osmosis, active transport, root hairs, apoplast and symplast pathways, transpiration, blood composition, the heart, circulation, blood pressure, blood groups and lymph. Book-back questions include multiple choice, fill-ups, matching, short answers, differences and diagram-based questions.
Answers at a glance
I. Choose the correct answer
III. Match the following
IV. State whether True or False. If false write the correct statement
- Q1True
- Q2True
- Q3False – The form of sugar transported through the phloem is sucrose.
- Q4False – In apoplastic movement, water travels through the intercellular spaces and cell walls without crossing the cell membrane.
- Q5False – When guard cells lose water the stoma closes.
- Q7False – All veins carry deoxygenated blood except the pulmonary veins.
- Q8True
- Q9True
I. Choose the correct answer
Active transport uses energy (ATP) to pump molecules against the concentration gradient, from low to high concentration.
This 'uphill' transport is done by membrane bound proteins called pumps.
So all three statements given are true of active transport.
d) all of the above
Water which is absorbed by roots is transported to aerial parts of the plant through
Water and mineral salts absorbed by the roots reach all parts of the plant through the xylem.
Phloem carries food, not water; cortex and epidermis are only tissues the water passes through.
d) xylem
Transpiration is the evaporation of water from the aerial parts of the plant, especially through the stomata of leaves.
Hence the substance lost is water.
c) water
Root hairs are thin walled, slender extensions of epidermal cells.
Each root hair is a single-celled (unicellular) projection that increases the surface area for absorption.
So both b and c are correct.
d) both b and c
Diffusion and osmosis are passive processes that need no energy.
Only active transport uses energy to pump molecules against the concentration gradient.
a) active transport
The heart wall is made of three layers — the outer epicardium, the middle cardiac muscle layer myocardium and the inner endocardium.
Since all three form the wall, the answer is all of the above.
d) All of the above
Veins bring blood to the atrium, the atrium pumps it into the ventricle, and the ventricle pumps it out through the arteries.
Among the options, the sequence atrium → ventricle → arteries → vein follows this correct direction of flow.
c) atrium ventricle arteries vein
A patient with blood group O was injured in an accident and has blood loss. Which group of blood should be used by doctor for transfusion?
'O' group plasma contains both antibodies anti-a and anti-b, so A, B or AB blood would be agglutinated.
An O group person can receive blood only from an O group donor.
a) O group
The sino-atrial (SA) node, in the wall of the right atrium near the opening of the superior vena cava, initiates the impulse for contraction.
As it sets the rhythm of the heart it is called the pacemaker or 'heart of heart'.
a) SA node
Blood has two main components — the fluid plasma and the formed elements suspended in it.
The formed elements are RBC, WBC and platelets, so Blood = Plasma + RBC + WBC + Platelets.
d) Blood - Plasma + RBC+ WBC +Platelets
II. Fill in the blanks
Transpiration is the evaporation of water from the aerial parts of the plant, especially through the stomata in leaves.
Transpiration
Water moves into the root hair cell by osmosis, which takes place through a semi-permeable membrane.
semi-permeable
Millions of root hairs at the tip of the root absorb water and minerals from the soil; they are thin-walled extensions of epidermal cells that increase the surface area of absorption.
root hair
In a healthy adult at rest, systolic and diastolic blood pressure is expressed as 120 mm / 80 mm Hg.
120 mm / 80 mm Hg
One complete systole and diastole of atria and ventricles is a heartbeat; the heart normally beats 72–75 times per minute.
72 – 75
III. Match the following
Section I
| 1. Symplastic pathway | Leaf |
| 2. Transpiration | Plasmodesmata |
| 3. Osmosis | Pressure in xylem |
| 4. Root Pressure | Pressure gradient |
- Symplastic pathway – Plasmodesmata: water moves into adjacent cells through the plasma membrane, cytoplasm and plasmodesmata.
- Transpiration – Leaf: transpiration is the evaporation of water from aerial parts, especially through the stomata of leaves.
- Osmosis – Pressure gradient: solvent (water) molecules move from a region of higher concentration to lower concentration through a semi-permeable membrane, i.e. along a pressure/concentration gradient.
- Root Pressure – Pressure in xylem: mineral ions are actively pumped into the xylem of the root, water follows and raises the pressure inside the xylem.
1 - b, 2 - a, 3 - d, 4 - c
Section II
| 1. Leukemia | Thrombocytes |
| 2. Platelets | Phagocyte |
| 3. Monocytes | Decrease in leucocytes |
| 4. Leucopenia | Blood Cancer |
| 5. AB blood group | Allergic condition |
| 6. O blood group | Inflammation |
| 7. Eosinophil | Absence of antigen |
| 8. Neutrophils | Absence of antibody |
Show steps (8)
- Leukemia – Blood Cancer.
- Platelets – Thrombocytes: blood platelets are also called thrombocytes and help in clotting.
- Monocytes – Phagocyte: they are the largest leucocytes and engulf bacteria.
- Leucopenia – Decrease in leucocytes.
- AB blood group – Absence of antibody: RBC carries antigens A and B, but plasma has no antibodies (universal recipient).
- O blood group – Absence of antigen: no antigen on RBC, but both antibodies a and b in plasma (universal donor).
- Eosinophil – Allergic condition: their number increases during allergy and parasitic infections.
- Neutrophils – Inflammation: their number increases during infection and inflammation.
1 - d, 2 - a, 3 - b, 4 - c, 5 - h, 6 - g, 7 - e, 8 - f
IV. State whether True or False. If false write the correct statement
The food synthesised by the leaves is carried to all parts of the plant through the phloem.
Phloem transports food (sucrose) from a source (leaf) to a sink (part that uses or stores food).
True
Transpiration is the evaporation of water from the aerial parts of the plant, especially through the stomata in leaves.
This loss of water creates the transpiration pull that draws water up from the roots.
True
Glucose prepared at the source by photosynthesis is first converted into sucrose.
It is this sucrose that moves into the companion cells and then into the sieve tubes by active transport.
False – The form of sugar transported through the phloem is sucrose.
In apoplastic movement the water travels through the cell membrane and enter the cell.
Apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells.
It does not involve crossing the cell membrane; movement through the plasma membrane and cytoplasm is the symplast pathway.
False – In apoplastic movement, water travels through the intercellular spaces and cell walls without crossing the cell membrane.
Opening and closing of the stoma depends on the turgidity of the guard cells.
When water enters the guard cells they become turgid and the stoma opens; when they lose water they become flaccid and the stoma closes.
False – When guard cells lose water the stoma closes.
The human heart is myogenic in nature.
Contraction is initiated by the sino-atrial (SA) node, a specialised portion of heart muscle in the wall of the right atrium, which acts as the pacemaker.
Heart beat initiated by a nerve impulse (neurogenic) is seen in annelids and most arthropods, not in humans.
False – Initiation and stimulation of heart beat take place by the SA node (specialised heart muscle fibres), so the human heart is myogenic.
Veins are collecting vessels that bring blood back to the heart from the organs.
But the pulmonary vein carries oxygenated blood from the lungs to the left atrium.
False – All veins carry deoxygenated blood except the pulmonary veins.
White blood corpuscles are nucleated, colourless cells capable of amoeboid movement.
Lymphocytes produce antibodies during bacterial and viral infections, and monocytes and neutrophils engulf bacteria.
Thus blood is involved in protection of the body and defence against diseases.
True
The closure of the mitral and tricuspid valves at the start of the ventricular systole produces the first sound 'LUBB'.
Heart sounds are produced by the rhythmic closure and opening of the valves.
The first sound LUBB, of longer duration, is produced by the closure of the tricuspid and bicuspid (mitral) valves after the beginning of ventricular systole.
The second sound DUPP is produced by closure of the semilunar valves at the end of ventricular systole.
True
V. Answer in a word or sentence
The heart is enclosed in a double walled sac.
It contains lubricating pericardial fluid that reduces friction during heart beat and protects the heart from mechanical injuries.
Pericardium (the double walled sac covering the heart).
Mature mammalian RBCs have no nucleus or cell organelles.
This gives them a biconcave, disc shape which increases the surface area for oxygen binding.
Human RBCs are biconcave and disc-shaped.
RBCs contain the respiratory pigment haemoglobin.
Haemoglobin imparts the red colour to blood and carries oxygen from the lungs to the tissues.
Because the RBCs contain the red respiratory pigment haemoglobin.
Lymph is a colourless fluid similar to plasma but with less protein.
It contains white blood cells, mainly lymphocytes.
These lymphocytes defend the body against infections.
Lymph contains WBCs, mainly lymphocytes.
The pulmonary artery and the aorta leave the ventricles.
They have semilunar valves — the pulmonary and aortic semilunar valves.
These valves prevent the backward flow of blood into the ventricles.
Semilunar valves (pulmonary and aortic semilunar valves).
The cardiac muscles get oxygenated blood through the coronary arteries, which arise from the aortic arch.
Deoxygenated blood from cardiac muscles drains into the right atrium through the coronary sinuses.
This supply of blood to the heart muscle is called coronary circulation.
The coronary arteries supply blood to the heart muscle.
VI. Short answer questions
What causes the opening and closing of guard cells of stomata during transpiration?
The opening and closing of stomata is due to the change in turgidity of the guard cells.
When water enters the guard cells, they become turgid (swollen) and the stoma opens.
When the guard cells lose water, they become flaccid (shrunken) and the stoma closes.
Change in turgidity of the guard cells — turgid guard cells open the stoma, flaccid guard cells close it.
Cohesion is the force of attraction between molecules of water.
Because of cohesion (along with adhesion), water molecules form a continuous, unbroken column in the xylem.
This continuous column helps the transpiration pull to draw water up to great heights.
Cohesion is the force of attraction between water molecules, which keeps the water column in the xylem continuous.
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.
Show steps (6)
Soil to root hair: water enters the root hairs from the soil by osmosis.
Root hair to cortex: water moves from root hair cells to cortical cells by osmosis, through the apoplast pathway (cell walls and intercellular spaces) or the symplast pathway (plasma membrane, cytoplasm and plasmodesmata).
Cortex to xylem: water reaches the xylem of the root; root pressure pushes it up to the base of the stem.
Xylem of stem: water rises through the xylem as a continuous column due to capillary action, adhesion-cohesion and transpiration pull (ascent of sap).
Xylem to mesophyll: from the xylem in the veins of the leaf, water enters the mesophyll cells by osmosis.
Mesophyll to atmosphere: water evaporates from the mesophyll cells and escapes into the air through the open stomata as transpiration.
Soil → root hair → cortex (apoplast/symplast) → root xylem → stem xylem → leaf veins → mesophyll cells → stomata → atmosphere.
What would happen to the leaves of a plant that transpires more water than its absorption in the roots?
Transpiration is the loss of water from the aerial parts, mainly through the stomata.
If the loss of water is more than the water absorbed by the roots, the cells lose more water than they gain.
The mesophyll and guard cells become flaccid, so the leaves lose turgidity and their shape.
The leaves will wilt (droop and dry up); the stomata close, reducing photosynthesis, and the plant may finally die.
The leaves lose turgidity and wilt, since transpiration is keeping the cells turgid and maintaining their shape.
Show steps (7)
Position: The heart is a muscular pumping organ made of cardiac muscle, situated between the lungs, slightly tilted to the left and above the diaphragm in the thoracic cavity.
Covering: It is enclosed in a double walled sac, the pericardium, which contains pericardial fluid that reduces friction and protects the heart from mechanical injuries.
Chambers: It is four chambered — two upper thin walled auricles (atria) and two lower thick walled ventricles, separated by interatrial and interventricular septa which prevent mixing of oxygenated and deoxygenated blood.
Valves: The tricuspid valve lies between right atrium and right ventricle, the bicuspid (mitral) valve between left atrium and left ventricle, and semilunar valves guard the pulmonary artery and aorta; they allow blood to flow in one direction only.
Working (right side): Deoxygenated blood from the body enters the right atrium through the superior and inferior vena cava and coronary sinus; the right atrium pumps it into the right ventricle, which sends it through the pulmonary artery to the lungs.
Working (left side): Oxygenated blood from the lungs enters the left atrium through the pulmonary veins, passes into the left ventricle, and is pumped through the aorta to all organs of the body.
The heart beats 72–75 times per minute by rhythmic systole and diastole, the beat being initiated by the SA node.
The human heart is a four chambered, pericardium covered muscular pump whose atria receive blood and ventricles pump it, with valves ensuring one-way flow to the lungs and body.
In man the blood passes through the heart twice in one complete cycle of the body.
Pulmonary circulation: deoxygenated blood goes from right ventricle → lungs → left atrium (first passage through the heart).
Systemic circulation: oxygenated blood goes from left ventricle → body organs → right atrium (second passage through the heart).
Since the blood circulates twice through the heart in one complete cycle, and oxygenated blood never mixes with deoxygenated blood, it is called double circulation.
Because the blood passes through the heart twice in one complete cycle — once in pulmonary and once in systemic circulation.
Heart sounds are the sounds produced by the rhythmic closure and opening of the valves of the heart; they can be heard with a stethoscope.
The first sound LUBB is of longer duration; it is produced by the closure of the tricuspid and bicuspid valves at the beginning of ventricular systole.
The second sound DUPP is of shorter duration; it is produced by the closure of the semilunar valves at the end of ventricular systole.
Heart sounds LUBB and DUPP are produced by the closure of the atrioventricular valves and the semilunar valves respectively.
Valves are the muscular flaps found in the heart.
They regulate the flow of blood in a single direction.
They prevent the back flow of blood — the tricuspid and bicuspid valves stop blood returning to the atria, and the semilunar valves stop blood returning from the aorta and pulmonary artery into the ventricles.
Thus they keep blood moving in the correct path during the cardiac cycle.
Valves keep the blood flowing in one direction only and prevent its back flow.
Rh factor was discovered by Landsteiner and Wiener in 1940.
They found this antigen on the surface of the RBC of the Rhesus monkey.
Since it was first discovered in the Rhesus monkey, it was named the Rh factor.
Persons having this antigen are Rh positive (Rh+) and those without it are Rh negative (Rh–).
Landsteiner and Wiener discovered it in 1940 in the Rhesus monkey, hence the name Rh factor.
Wall: The wall of an artery is strong, thick and elastic, while the wall of a vein is weak, thin and non-elastic.
Valves: Internal valves are absent in arteries but present in veins.
Location: Arteries are deeply located; veins are superficial in location.
Function and flow: Arteries are distributing vessels carrying blood away from the heart with high pressure; veins are collecting vessels carrying blood to the heart with low pressure.
Arteries have thick, strong, elastic walls without internal valves and lie deep, whereas veins have thin, weak, non-elastic walls with internal valves and lie superficially.
The human heart is myogenic — the beat is initiated by a specialized group of heart muscle fibres.
The sino-atrial (SA) node lies in the wall of the right atrium near the opening of the superior vena cava.
It is capable of initiating the impulse which stimulates the heart muscles to contract, and it sets the rhythm and rate of the heart beat.
The impulse then spreads over the atria to the AV node, the bundle of His and the Purkinje fibres.
Since it starts and paces every heart beat, the SA node is called the pacemaker of the heart.
Because the SA node itself initiates the impulse that makes the heart muscles contract and sets the rate of the heart beat.
Systemic circulation: circulation of oxygenated blood from the left ventricle through the aorta to all the organs of the body and the return of deoxygenated blood to the right atrium.
Pulmonary circulation: it starts in the right ventricle; the pulmonary artery carries deoxygenated blood to the lungs, and the pulmonary veins bring the oxygenated blood from the lungs to the left atrium.
Thus systemic circulation is between the heart and the body organs, while pulmonary circulation is between the heart and the lungs.
In systemic circulation the artery (aorta) carries oxygenated blood; in pulmonary circulation the artery carries deoxygenated blood.
Systemic circulation is left ventricle → body organs → right atrium, while pulmonary circulation is right ventricle → lungs → left atrium.
The complete events of cardiac cycle last for 0.8 sec. What is the timing for each event?
The cardiac cycle is the sequence of events from the beginning to the completion of one heart beat, lasting about 0.8 second.
Atrial systole (contraction of the auricles) – 0.1 second.
Ventricular systole (contraction of the ventricles) – 0.3 second.
Ventricular diastole (relaxation of the ventricles) – 0.4 second.
Total: second.
Atrial systole 0.1 sec, ventricular systole 0.3 sec and ventricular diastole 0.4 sec, totalling 0.8 sec.
VII. Give reasons for the following statements
Minerals are present in the soil as charged particles (ions), and ions cannot move freely across cell membranes.
The concentration of minerals in the soil is usually lower than the concentration inside the root cells, so passive movement along a gradient is not possible.
Hence minerals enter the root by active absorption through the cytoplasm of epidermal cells, using energy in the form of ATP.
From there they are carried to all parts of the plant by transpiration pull.
Minerals occur as ions and are less concentrated in soil than in the root, so they must be taken in by active transport using ATP, not passively.
Each stoma is bounded by two guard cells whose turgidity controls the pore.
When water enters the guard cells they become turgid and swollen, so the stoma opens.
When the guard cells lose water they become flaccid and shrunken, so the stoma closes.
Thus the change in turgidity of the guard cells decides whether the stoma is open (day) or closed (night).
Change in the turgidity of guard cells opens the stoma when they are turgid and closes it when they are flaccid.
Phloem transports food (sucrose) from a source (the food-making part, the leaf) to a sink (the part that uses or stores food).
The source and sink may be reversed depending on the season or the plant's need.
Since this source–sink relationship is variable, the phloem sap can move upwards or downwards, i.e. it is bidirectional.
In contrast, movement in the xylem is always unidirectional (upwards).
Because the source–sink relationship is variable, phloem transport is bidirectional — upwards or downwards.
Before old leaves die and fall, the minerals in them are remobilised to the younger leaves.
This phenomenon is clearly seen in deciduous plants that shed their leaves.
Elements like phosphorus, sulphur, nitrogen and potassium are easily mobilised; elements like calcium are not remobilised.
So most of the useful minerals are withdrawn and reused by the plant instead of being lost with the fallen leaf.
Mobile minerals are remobilised from older dying leaves to younger leaves before leaf fall, so they are not lost.
The auricles are the upper thin walled chambers; they only receive blood and push it a short distance into the ventricles below.
The ventricles are the lower chambers and must pump blood out of the heart with great force.
The right ventricle pumps deoxygenated blood through the pulmonary trunk to the lungs, which needs strong muscular contraction.
Therefore the ventricular wall is thick and muscular while the auricular wall is thin.
Ventricles pump blood out of the heart with force, so their walls are thicker than those of the receiving auricles.
Mature mammalian RBCs lose the nucleus, which makes the cell biconcave and increases the surface area for oxygen binding.
Loss of mitochondria means the RBC does not use up the oxygen it carries, so all the oxygen is delivered to the tissues.
Loss of endoplasmic reticulum gives the cell more flexibility to squeeze through narrow capillaries.
Thus the absence of organelles suits the RBC for its main work — transport of oxygen from lungs to tissues.
Loss of nucleus and other organelles gives RBCs a biconcave shape, more space and flexibility, so they carry and deliver oxygen efficiently.
VIII. Long answer questions
Show steps (8)
Root hairs – the absorbing unit: Millions of thin walled, slender root hairs are present at the tip of the root. They are extensions of epidermal cells and increase the surface area for absorption of water and minerals.
Absorption by diffusion and osmosis: Water from the soil enters the root hairs by diffusion and osmosis, because the soil water is at a higher concentration than the cell sap of the root hair.
Movement to the cortex: Once water enters the root hair, the concentration of water molecules in the root hair cell becomes more than that of the cortex. So water moves from the root hair into the cortical cells by osmosis and finally reaches the xylem.
Apoplast pathway: Water moves exclusively through the intercellular spaces and the walls of the cells. It does not involve crossing the cell membrane and depends on the gradient.
Symplast pathway: Water molecules move to the adjacent cells through the plasma membrane, cytoplasm and plasmodesmata. This transport is slow as water crosses the plasma membrane; it follows the concentration gradient.
Uptake of minerals: Most minerals are present as charged ions and their concentration in soil is lower than in the root, so they enter by active absorption through the cytoplasm of epidermal cells using energy (ATP).
Root pressure: As mineral ions are actively pumped into the xylem, water follows and increases the pressure inside the xylem. This root pressure pushes water up to the base of the stem.
Upward movement (ascent of sap): Capillary action, adhesion–cohesion of water molecules forming a continuous water column, and mainly the transpiration pull created by evaporation through stomata draw water up the xylem to the stem and leaves.
Plants absorb water from the soil through root hairs by diffusion and osmosis; it then passes to the cortex and xylem by apoplast and symplast pathways, and is pulled upward by root pressure, capillary action and transpiration pull.
Show steps (9)
Definition: Transpiration is the evaporation of water from the aerial parts of the plant, especially through the stomata in leaves.
Mechanism: Stomata open during the day and close at night. The opening and closing is due to change in the turgidity of guard cells – when water enters they become turgid and the stoma opens; when they lose water they become flaccid and the stoma closes.
Transpiration pull: Water evaporates from mesophyll cells through the open stomata, lowering the water concentration in these cells. More water is then drawn from the xylem of the veins by osmosis, creating a pull that extends up to the roots.
Importance 1: It creates the transpirational pull which is responsible for the transport of water to great heights, even in the tallest plants.
Importance 2: It supplies water for photosynthesis.
Importance 3: It transports minerals from the soil to all parts of the plant.
Importance 4: It cools the surface of the leaves by evaporation.
Importance 5: It keeps the cells turgid and hence maintains their shape.
Factors affecting it: External factors – temperature, light, humidity and wind speed; internal factors – number and distribution of stomata, percentage of open stomata, water status of the plant and canopy structure.
Transpiration is the loss of water as vapour from aerial parts (mainly stomata); it creates transpiration pull, supplies water for photosynthesis, transports minerals, cools the leaf surface and keeps cells turgid.
Why are leucocytes classified as granulocytes and agranulocytes? Name each cell and mention its functions.
Show steps (7)
Basis of classification: Leucocytes are classified on the basis of the presence or absence of granules in their cytoplasm and the shape of the nucleus – those with cytoplasmic granules and irregular or lobed nuclei are granulocytes, and those without granules are agranulocytes.
Granulocytes – Neutrophils: Large cells with a 2–7 lobed nucleus, forming 60–65% of the total leucocytes. Their number increases during infection and inflammation.
Granulocytes – Eosinophils: Have a bilobed nucleus and form 2–3% of the total leucocytes. Their number increases during allergy and parasitic infections; they bring about detoxification of toxins.
Granulocytes – Basophils: Have a lobed nucleus and form 0.5–1.0% of the total leucocytes. They release chemicals during the process of inflammation.
Agranulocytes – Lymphocytes: About 20–25% of the total leucocytes. They produce antibodies during bacterial and viral infections.
Agranulocytes – Monocytes: The largest leucocytes, amoeboid in shape, forming 5–6% of the total leucocytes. They are phagocytic and can engulf bacteria.
General features: All WBCs are colourless, nucleated, lack haemoglobin, are formed in bone marrow, spleen, thymus and lymph nodes, and are capable of amoeboid movement.
Leucocytes are classified as granulocytes (neutrophils – fight infection; eosinophils – allergy and detoxification; basophils – release chemicals in inflammation) and agranulocytes (lymphocytes – produce antibodies; monocytes – phagocytic), based on the presence or absence of cytoplasmic granules.
Show steps (9)
Systole: Systole is the contraction phase of the heart chambers. Atrial systole (contraction of auricles) lasts 0.1 second and ventricular systole (contraction of ventricles) lasts 0.3 second, during which blood is forced out of the chambers.
Diastole: Diastole is the relaxation phase. Ventricular diastole lasts 0.4 second, during which the chambers relax and get filled with blood.
Pressure difference: During ventricular systole the left ventricle forces blood into the aorta and the pressure rises to a peak – systolic pressure (120 mm Hg). During diastole the ventricles relax and pressure falls to the lowest value – diastolic pressure (80 mm Hg).
Heart sound: Closure of the tricuspid and bicuspid valves at the beginning of ventricular systole produces the first sound LUBB; closure of the semilunar valves at the end of ventricular systole produces the second sound DUPP.
Myogenic nature: The human heart beat is myogenic – it is initiated by a specialised group of modified heart muscle fibres and not by a nerve.
SA node – the pacemaker: Contraction is initiated by the sino-atrial (SA) node, situated in the wall of the right atrium near the opening of the superior vena cava. It is broader at the top, tapering below and made of thin fibres. It is called the pacemaker as it can initiate the impulse that stimulates the heart muscle to contract.
Atrial contraction: The impulse from the SA node spreads as a wave of contraction over the right and left atrial walls, pushing blood through the atrioventricular valves into the ventricles.
AV node and conduction: The wave of contraction reaches the atrioventricular (AV) node, which is stimulated to emit an impulse of contraction.
Bundle of His and Purkinje fibres: From the AV node the impulse spreads to the ventricular muscle through the atrioventricular bundle (Bundle of His) and the Purkinje fibres, causing the ventricles to contract and pump blood out.
Systole is contraction (atrial 0.1 s, ventricular 0.3 s) and diastole is relaxation (0.4 s) of the heart chambers; the heart beat is myogenic, initiated by the SA node (pacemaker) and conducted through the AV node, Bundle of His and Purkinje fibres to the ventricles.
Show steps (8)
Transport of respiratory gases: Blood transports oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs, with the help of the pigment haemoglobin in RBCs.
Transport of digested food: It carries digested food materials to the different body cells.
Transport of hormones: Hormones secreted by the endocrine glands are carried by blood to their target organs.
Transport of excretory products: It transports nitrogenous excretory products like ammonia, urea and uric acid to the excretory organs.
Defence: Blood is involved in the protection of the body and defence against diseases – WBCs produce antibodies and engulf bacteria.
Clotting: Platelets form a clot at the site of injury and prevent blood loss.
Regulation: It acts as a buffer and helps in the regulation of pH and body temperature.
Water balance: It maintains proper water balance in the body.
Blood transports respiratory gases, digested food, hormones and excretory wastes, defends the body against disease, clots to prevent blood loss, and regulates pH, body temperature and water balance.
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.
Assertion: RBC plays an important role in the transport of respiratory gases. Reason: RBC do not have cell organelles and nucleus.
Assertion (A) is true: RBC contains the respiratory pigment haemoglobin, and it is involved in the transport of oxygen from the lungs to the tissues (and of CO2).
Reason (R) is also true: matured mammalian RBCs do not possess cell organelles and nucleus.
But the actual cause of the gas-transporting role of RBC is the presence of haemoglobin, not the absence of the nucleus and organelles. The loss of nucleus/organelles only gives a biconcave shape, more space and flexibility — it is a supporting feature, not the reason for gas transport.
Hence both A and R are true, but R is not the correct explanation of A.
b) If both A and R are true but R is not the correct explanation of A
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.
Assertion is true: AB group persons are called 'Universal Recipients' as they can receive blood from A, B, AB and O groups.
Reason is true: in AB group individuals both antigens A and B are present on the RBC surface, but no antibodies (anti-a and anti-b) are present in the plasma.
Since antibodies are absent, the donor's red cells are not agglutinated (clumped), so blood of any group can be safely received.
Hence R is the correct explanation of A.
a) If both A and R are true and R is correct explanation of A
X. Higher Order Thinking Skills (HOTS)
When any dry plant material is kept in water, they swell up. Name and define the phenomenon involved in this change.
The phenomenon is imbibition.
Imbibition is a type of diffusion in which a solid plant material absorbs water and gets swelled up.
Examples: absorption of water by dry seeds and grapes.
Importance: if it were not for imbibition, seedlings would not have been able to emerge out of the soil.
Imbibition – a type of diffusion in which a solid plant material absorbs water and swells up (e.g. dry seeds, grapes).
Why are the walls of the left ventricle thicker than the other chambers of the heart?
The left ventricle gives rise to the aorta and has to pump oxygenated blood to all the organs of the body.
This needs a great force, so the blood must be pushed out at high pressure over a long distance.
The right ventricle pumps blood only up to the nearby lungs, so less force is needed.
Hence the wall of the left ventricle is about three times thicker than that of the right ventricle, and it is longer and narrower.
Because the left ventricle must pump blood with great force through the aorta to the whole body, its wall is about three times thicker than the right ventricle's.
A stethoscope is used to detect the sound produced by the internal organs of the human body.
The rhythmic closure and opening of the heart valves produce the heart sounds LUBB (closure of tricuspid and bicuspid valves) and DUPP (closure of semilunar valves).
By placing the stethoscope on the chest, the doctor hears these sounds and can judge whether the valves and heart beat are normal.
Thus it is a useful diagnostic tool to identify and localise health problems and diagnose disease.
To hear the heart sounds LUBB and DUPP produced by the closing of valves, which helps the doctor to diagnose and localise heart problems.
How does the pulmonary artery and pulmonary vein differ in their function when compared to a normal artery and vein?
Normally all arteries carry oxygenated blood away from the heart, and all veins carry deoxygenated blood to the heart.
Pulmonary artery: it arises from the right ventricle and carries deoxygenated blood to the lungs – the only artery carrying deoxygenated blood.
Pulmonary vein: it brings oxygenated blood from the lungs to the left atrium – the only vein carrying oxygenated blood.
So they are exceptions in the type of blood carried, though the direction of flow is the same as other arteries (away from heart) and veins (towards heart).
They are exceptions: the pulmonary artery carries deoxygenated blood to the lungs and the pulmonary vein carries oxygenated blood from the lungs to the heart.
Show steps (6)
Transpiration is the evaporation of water from the aerial parts of the plant, especially through the stomata of leaves.
It is an 'evil' because a large amount of absorbed water is lost as vapour; excess loss can cause wilting and even death of the plant in dry conditions.
But it is 'necessary' because it creates the transpiration pull that lifts water from the roots to the top of even the tallest plants.
It also supplies water for photosynthesis and transports minerals from the soil to all parts of the plant.
It cools the surface of the leaves by evaporation and keeps the cells turgid, thus maintaining their shape.
Since the plant cannot survive without these benefits, this unavoidable loss of water is called a necessary evil.
Transpiration wastes much water (evil), yet it is unavoidable and essential for transpiration pull, mineral transport, cooling and turgidity – hence a 'necessary evil'.
Quick check
Active transport involves
Question 1 of 5Show answer
Answer: (4) all of the above
Active transport uses energy (ATP) to pump molecules against the concentration gradient, from low to high concentration.
This 'uphill' transport is done by membrane bound proteins called pumps.
So all three statements given are true of active transport.
The wall of human heart is made of
Question 2 of 5Show answer
Answer: (4) All of the above
The heart wall is made of three layers — the outer epicardium, the middle cardiac muscle layer myocardium and the inner endocardium.
Since all three form the wall, the answer is all of the above.
During transpiration there is loss of
Question 3 of 5Show answer
Answer: (3) water
Transpiration is the evaporation of water from the aerial parts of the plant, especially through the stomata of leaves.
Hence the substance lost is water.
A patient with blood group O was injured in an accident and has blood loss. Which group of blood should be used by doctor for transfusion?
Question 4 of 5Show answer
Answer: (1) O group
'O' group plasma contains both antibodies anti-a and anti-b, so A, B or AB blood would be agglutinated.
An O group person can receive blood only from an O group donor.
Which of the following process requires energy?
Question 5 of 5Show answer
Answer: (1) active transport
Diffusion and osmosis are passive processes that need no energy.
Only active transport uses energy to pump molecules against the concentration gradient.