Samacheer Class 10 Science - Plant Anatomy and Plant Physiology

Pericardium.

Biconcave / disc shaped.

Presence of red blood cells containing haemoglobin.

White blood corpuscles.

Semilunar valves.

Coronary artery.

(i) Stomata are open in the day and closed at night. The opening and closing of the stomata is due to the change in turgidity of the guard cells.
(ii) When water enters into the guard cells, they become turgid and the stoma open. When the guard cells lose water, it becomes flaccid and the stoma closes.

The force of attraction between molecules of water is called cohesion.

There are millions of root hairs on the tip of the root which absorb water and minerals by diffusion. Root hairs are thin walled, slender extension of epidermal cell that increase the surface area of absorption.
Pathway of Water Absorbed by Roots:
Once the water enters the root hairs, the concentration of water molecules in the root hair cells become more than that of the cortex. Thus water from the root hair moves to the cortical cells by osmosis and then reaches the xylem. From there the water is transported to the stem and leaves.
Types of Movement of Water into the Root Cells:
Once water is absorbed by the root hairs, it can move deeper into root layers by two distinct pathways:
(i) Apoplast pathway
(ii) Symplast pathway
(i) Apoplast Pathway :

Refer to textbook.

(ii) Symplast Pathway :

Refer to textbook.

Transpiration :
(i) Transpiration is the evaporation of water in plants through stomata in the leaves.
(ii) Water evaporates from mesophyll cells of leaves through the open stomata, this lowers water concentration in mesophyll cells.
(iii) As a result, more water is drawn into these cells from the xylem present in the veins through the process of osmosis.
(iv) As water is lost from the leaves, pressure is created at the top to pull more water from the xylem to the mesophyll cells, this process is called transpiration pull.
(v) This extends up to the roots causing the roots to absorb more water from the soil to ensure continuous flow of water from the roots to the leaves.

If the leaves of a plant transpire more water than its absorption in the roots, it can lead to the following:
(i) Absorption of water will increase since the cells will require more water to compensate the loss by transpiration.
(ii) The plants may also start wilting. If they are unable to absorb more water from the soil. This can happen in deserts where temperature is high and rate of transpiration will be more but soil will not be rich in water.

Structure : Heart is a muscular pumping organ that pumps out the blood into the blood vessels. Contraction of the heart is called systole and relaxation is called diastole.
(i) When the auricles are filled with blood they are in diastole. The tricuspid and bicuspid valves remain closed. This is called atrial diastole.
(ii) When the auricles are full they contract. This leads to opening of tricuspid and bicuspid valves. Blood from right and left auricles is pushed into right and left ventricles respectively. This is called atrial systole.
(iii) Following this the valves are closed the ventricles contract. The deoxygenated blood from right ventricle enters the pulmonary artery and oxygenated blood from left ventricle enters the aorta. This is called ventricular systole.
During this time the auricles are in diastole the atrial systole (0.1 sec), ventricular systole (0.3 sec) and ventricular diastole (0.4 sec) constitute a cardiac cycle.

In our body blood circulates twice through the heart in one complete cycle and it is called double circulation. In double circulation the oxygenated blood do not mix with the deoxygenated blood.

(i) The rhythmic closure and opening of the valves cause the sound of the heart.
(ii) The first sound LUBB is of longer duration and is produced by the closure of the tricuspid and bicuspid valves after the beginning of ventricular systole.
(iii) The second sound DUPP is of a shorter duration and produced by the closure of semilunar valves "at the end of ventricular systole.

(i) Regulate the flow of blood in a single direction. (ii) Prevent back flow of blood.

(i) Rh factor was discovered by Landsteiner and Wiener in 1940.
(ii) It is named as 'Rh' because it was first discovered is Rhesus monkeys.

S.No : ARTERY : VEIN

Refer to textbook.

Refer to textbook.

Refer to textbook.

Refer to textbook.

Refer to textbook.

Refer to textbook.

Refer to textbook.

(i) The human heart is myogenic in nature. The contraction of the heart is initiated by a specialised portion of the heart muscle called sinoatrial node.
(ii) This is situated in the wall of the right atrium near the opening of the superior venacava.
(iii) It is made up of thin fibres.
(iv) This is called the pacemaker of the heart because it is capable of initiating impulse which can stimulate the heart muscle to contract.

S.No. : Systemic circulation : Pulmonary circulation

Refer to textbook.

Refer to textbook.

Events of cardiac cycle - Total duration 0.8 sec.
a) Atrial systole (Contraction of auricles) - 0.1 sec
b) Ventricular systole (Contraction of ventricles) - 0.3 sec
c) Ventricular diastole (Relaxation of ventricles) - 0.4 sec
Total duration of cardiac cycle - 0.8 sec

(i) All minerals cannot be passively absorbed by the roots because minerals are present in the soil as charged particles (ions) that cannot move across cell membranes.
(ii) The concentration of minerals in the soil is usually lower than the concentration of minerals in the root. Hence most minerals enter the root by active absorption requiring energy. Hence minerals cannot be passively absorbed by the roots.

(i) Stomata are open in the day and closed at night. The opening and closing of the stomata is due to the change in turgidity of the guard cells.
(ii) When water enters into the guard cells, they become turgid and the stoma open. When the guard cells lose water, it becomes flaccid and the stoma closes.

(i) Phloem transports food (sucrose) from a source to a sink. The source is part of the plant that synthesize food, i.e., the leaf, and sink, is the part that needs or stores the food.
(ii) But, the source and sink may be reversed depending on the season, or the plants need.
(iii) The direction of movement in the phloem can be upwards or downwards, i.e., bidirectional.

(i) Minerals are remobilised from older dying leaves to younger leaves. eg. Elements like phosphorus, sulphur.
(ii) This phenomenon can be seen in deciduous plants.
(iii) Small amounts of material exchange takes place between xylem and phloem. Hence minerals are not lost when the leaf falls.

(i) The right ventricles have thicker walls to pump out blood with force away from the heart.
(ii) The right auricle is only receiving blood from the Pre caval and Post caval veins. Hence it is thin walled than the ventricle.

(i) Mammalian RBC lack nucleus and makes the cells biconcave which increase the surface area for oxygen binding.
(ii) Lack of mitochondria allows the RBC to transport all the oxygen to tissues, and loss of endoplasmic reticulum allows more flexibility for RBC to move through the narrow capillaries.

Root Hair-Water Absorbing Unit:
There are millions of root hairs on the tip of the root which absorb water and minerals by diffusion. Root hairs are thin walled, slender extension of epidermal cell that increase the surface area of absorption.
Root Tip with Root Hairs
Pathway of Water Absorbed by Roots :
(i) Once the water enters the root hairs, the concentration of water molecules in the root hair cells become more than that of the cortex.
(ii) Thus water from the root hair moves to the cortical cells by osmosis and then reaches the xylem.
(iii) From there the water is transported to the stem and leaves.
T. S. of the root showing movement of water from soil to xylem
Types of Movement of Water into the Root Cells : Once water is absorbed by the root hairs, it can move deeper into root layers by two distinct pathways:

Refer to textbook.

Apoplast Pathway :
(i) The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells.
(ii) Apoplastic movement does not involve crossing the cell membrane. This movement is dependent on the gradient.
Symplast Pathway :
(i) In symplastic movement, the water travels through the cells i.e. their cytoplasm; intercellular movement is through the plasmodesmata.
(ii) Water enter the cells through the cell membrane, hence the movement is relatively slower. Movement is again down a potential gradient.

Definition : Transpiration is the evaporation of water in plants through stomata in the leaves.
Importance of Transpiration :
(i) Creates transpirational pull for transport of water.
(ii) Supplies water for photosynthesis.
(iii) Transports minerals from soil to all parts of the plant.
(iv) Cools the surface of the leaves by evaporation.
(v) Keeps the cells turgid; hence, maintains their shape.

Granulocytes : They contain granules in their cytoplasm. Hence they are called as granulocytes. The granulocytes are of three types.
i. Neutrophils, ii. Eosinophils, iii. Basophils
(i) Neutrophils and its function : These corpuscles form 60% - 65% of the total leucocytes. Their number in increased during infection and inflammation.
(ii) Eosinophils and its function : Their number increases during conditions of allergy and parasitic infections. It brings about detoxification of toxins.
(iii) Basophils and its function : They form 0.5 - 1.0 % of the total leucocytes. They release chemicals during the process of inflammation.
Agranulocytes : Granules are not found in the cytoplasm of these cells.
They are of two types.
(i) Lymphocytes : They form 20 - 25% of the total leucocytes. They produce antibodies during bacterial and viral infections.
(ii) Monocytes : These cells form 5 - 6 % of the total leucocytes. They are phagocytic and can engulf bacteria.

Systole : Contraction phase of the heart
Diastole : Relaxation phase of the heart
Conduction of heart beat :
(i) Human heart is myogenic in nature. Contraction is initiated by a specialized muscle, the Sino-Atrial (SA) node which is situated in the wall of the right atrium near the opening of the superior vena cava.
(ii) The SA node is broader at the top and tapering below. It is made up of thin fibres.
(iii) SA node acts as the ‘pacemaker’ of the heart because it is capable of initiating impulse which can stimulate the heart muscles to contract.
(iv) Impulse from the SA node spreads as a wave of contraction over the right and left atrial wall pushing the blood through the atrioventricular valves into the ventricles.
(v) The wave of contraction from SA node reaches the AtrioVentricular (AV) node which is stimulated to emit an impulse of contraction spreading to the ventricular muscle via the atrioventricular bundle and the Purkinje fibres.

(i) Transport of respiratory gases.
(ii) Transport of digested food materials to the different body cells.
(iii) Transport of hormones.
(iv) Transport of nitrogenous excretory products like ammonia, urea and uric acid.
(v) It is involved in protection of the body and defense against diseases.
(vi) Blood acts as buffer and helps in regulation of pH and body temperature.
(vii) It maintains proper water balance in the body.

Reason: RBC do not have cell organelles and nucleus.
Answers: a. If both A and R are true and R is correct explanation of A

Reason: Antibodies are absent in persons with AB blood group.
Answers: a. If both A and R are true and R is correct explanation of A
X. Higher Order Thinking Skills (HOTS)

Imbibition (i) Imbibition is a type of diffusion in which a solid absorbs water and gets swelled up. E.g: absorption of water by seeds and dry grapes.

(i) The left ventricle has the major function of pumping out blood away from the heart with lot of force such that the oxygenated blood pumped by it should get distributed to all the body parts.
(ii) Aorta is the largest artery which leaves the left ventricle distributing oxygenated blood to the entire body.
(iii) Thus the left ventricular walls are thicker than other chambers of the heart.

(i) A stethoscope is used to detect the sound produced by the internal organs of human body.
(ii) The heart sound is heard by placing the stethoscope on the chest. It is a useful diagnostic tool to identify and localize health problems and diagnose disease.

(i) A normal artery carries (oxygenated) pure blood and a normal vein carries (deoxygenated) impure blood.
(ii) Pulmonary artery is the only artery in our body which carries deoxygenated blood.
(iii) It carries the blood to the lungs for purification from the heart.
(iv) Similarly pulmonary vein leaves the lungs with oxygenated blood and enters the left auricle of the heart, to be supplied to the whole body through left ventricle and aorta.
(v) Thus pulmonary vein is the only vein which carry pure blood.

(i) Transpiration is a necessary evil in plants, because transpiration is inevitable, but potentially harmful.
(ii) Loss of water from the surface of the leaves, is on a large scale, may result in wilting, desiccation and often lead to death of a plant in case of drought conditions.
(iii)The water stress may result in reduced growth rate and reduction in growth.
---