Higher plants possess xylem which is associated with the transport of water. (2) Water absorbed by the root from the soil is transported to stem, branches, leaves and flowers. (3) The main structural components of the xylem responsible for the transport of water are tracheids and vessels. (4) As the root cells are directly in contact with soil,they take up ions. ue to this, a difference is created between concentration of these ions between the root and the soil. (5) Water moves into the root from the soil to elimlnate this difference. This water movement creates a column of water that is steadily pushed upwards. (6) Plants use another strategy to move water in the xylem upwards to the highest points of the plant body. (7) If adequate water is available then the water which lost through the stomata is replaced by the water present in xylem vessel. 8) During day time the transpiration pull becomes the major driving force in the movement of water in the xylem.
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Explain transport of food and other substances in plants. A. 2 (1) Carbohydrates are synthesized in the green leaves by the process of photosynthesis. (2) These photosynthetic products are transported to the various parts of the plant body. (3) Transport of photosynthetic products is known as translocation and it is performed by sieve tubes and sieve cells of vascular tissue known as phloem. 4) Besides the carbohydrates, the phloem transports amino acids, several plant hormones which are synthesized at the shoot and root tips and other substance (5) The translocation takes place in both, upward and downward directions. (6) Translocation of substances requires energy which is obtained from ATP.
When the material like sucrose is transferred into phloem tissue,the osmotic pressure of tissue increases leading to entry of water into it. (8) This pressure moves the material in the phloem to tissue which have less pressure. 9) This allows the phloem to move material according to the need of plant. Q. 3 Explain the structure of human heart. A. 3 The human heart is conical in shape and is of the size of a closed fist. It is located in the small space between two lungs and slightly towards the left side. As both carbon dioxide and oxygen are transported by blood,the heart is four chambered in order to prevent the mixing of oxygen rich blood with the blood containing carbon dioxide. The upper two chambers are called atria. Of these one is left atrium and the other is right atrium.
The two lower chambers are known as ventricles,of these one is left ventricle and the other is right ventricle. The walls of atria are thin while the walls of ventricles are thick,All the four chambers are separated from each other by partitions called septa. For the flow of blood from the left atrium to the left ventricle,there is a bicuspid valve. Similarly there is a tricuspid valve between right atrium and right ventricle. These valves prevent backward flow of the blood from ventricles to atria. Q. 4 Explain functioning of heart. A. Deoxygenated blood from various organs of the body is received by the right atrium through the superior and inferior vena cava. At the same time left atrium receives oxygenated blood from the lung through the pulmonary veins. Now both the atria contract and the deoxygenated blood from right atrium is poured into right ventricle and oxygenated blood from left atrium is poured into left ventricle. Now both the ventricles contract. Due to contraction of right ventricle,the blood enters into lungs through arteries. In lungs CO2is released from blood and O2 diffuses into it.
While due to contraction of left ventricle,oxygenated blood is distributed to all the parts of body through the aorta. The separation of both types of the blood in the heart allows a highly efficient supply of oxygen to the body. This is useful in the animals which have high energy need,such as birds and mammals,which constantly use energy to maintain their body temperature. Q. 5 Write short note on Lymphatic system. A. 5 Lymphatic system consists of lymph,lymph vessels,lymphatic capillaries and lymphatic nodes. Lymph is another type of fluid which is also involved in transportation.
Some amount of plasma, proteins and blood cells,escape into the intercellular spaces through the pores present in the wall of capillaries,form lymph. Lymph is colorless and contains less proteins as compared to that in the blood. Lymph drains into lymphatic capillaries form intercellular spaces. Lymphatic capillaries join to form lymph vessels that finally open into large veins. Lymphatic system performsfollowing three important functions: 1) Collect intercellular fluid through the medium of lymph vessels and returns it to blood circulation. ) In the villi of small intestine, lymph vessels absorb lipids and conduct them to blood circulation. 3) Protects against diseases. Q. 6 Explain removal of waste products in plants. A. 6 In plants O2 may be considered as waste product generated during photosynthesis and released back to the atmosphere directly. They remove excess water by the process of transpiration. Sometimes they store excretory waste in the leaves that fall off. Many plant waste products are stored in cellular vacuoles. Other waste products are stored as resins and gums. Q. 7 Write short note on Excretory system of human being.
Excretory system of human being includes a pair of reddish brown bean shaped kidneys located in the abdomen on the dorsal side, a pair of ureters,one from each kidney,a urinary bladder and a muscular tube called urethra. (2) Urethra opens out by a small opening known as urinary opening. (3) Kidney is divided into cortex and medulla. (4) These regions consist of the excretory units called nephrons. Q. 8 Descibe structure of nephron. A. 8 Each kidney has very minute tubular and convoluted structures known as uriniferous tubules. Nephrons in each kidney has ten lacs such tubules.
Each nephron has a double walled cup shaped structure called Bowman’s capsule at its upper end. The Bowman’s capsule possesses a mass of capillaries called glomerulus. The short tubular region after the Bowman’s capsule is called neck. After this the tubule is narrow and coiled. It consists of a proximal convoluted tubule,a Henle’s loop and a distal convoluted tubule. The post end of nephron is called collecting tubule. Collecting tubule opens in the renal pelvis,which opens into the ureter. Q. 9 Explain the process of urine formation. A. 9 The waste material along with blood is brought to kidneys by the renal arteries.
As the blood is under pressure in the arteries,it is filtered out from the blood capillaries into Bowman’s capsule. This process is known as ultrafiltration. This filtrate passes through the lumen of tubular parts of nephron. During this useful substances like water, amino acids, minerals ions etc. are reabsorbed by blood capillaries surrounding the nephron. The remaining fluid contains excretory substances and is called urine. From the ureter urine passes into urinary bladder where it is stored. When the bladder is filled with the urine,it contracts and urine passes out of the body.
