Ans. Blood is the fluid which flows in blood vessels. It transports substances like digested food from the small intestine to the other parts of the body. It carries oxygen from the lungs to the cells of the body. It also transports waste for removal from the body.
Ans. Arteries - Arteries carry blood from the heart to all parts of the body.
Veins - Veins carry blood from all parts of the body back to the heart.
Capillaries – Capillaries are the smallest of the body's blood vessels. They carry oxygen and other nutrients from the bloodstream to other tissues in the body; they also collect carbon dioxide waste materials fluids for return to the veins.
Q51. What are stomata? Give two functions of stomata.
Ans. There are small openings on the surface of the leaves. These openings are called stomata. These openings are surrounded with guard cells.
Function of stomata
i. The water evaporates through the stomata present on the surface of the leaves by the process of transpiration.
ii. The evaporation of water from leaves generates a suction pull which can pull water to great heights in the tall trees.
iii. It helps in exchange of gases.
Ans. Blood is a liquid, which has cells of various kinds suspended in it.
i. The fluid part of the blood is called plasma.
ii. One type of cells are the red blood cells (RBC) which contain a red pigment called haemoglobin. Haemoglobin binds with oxygen and transports it to all the parts of the body and ultimately to all the cells.
iii. The blood also has white blood cells (WBC) which fight against germs that may enter our body.
iv. Another type of cells in the blood are called platelets. It helps in the clotting of the blood.
Ans. Difference between arteries and veins
1. Arteries carry blood from the heart to all parts of the body.
1. Veins carry blood from all parts of the body back to the heart.
2. Arteries carry oxygen-rich blood.
2. Veins carry carbon dioxide-rich blood.
3. There are no valves present in arteries.
3. There are valves present in veins which allow blood to flow only towards the heart.
4. The arteries have thick walls.
4. The veins have thin walls.
Ans. The heart is a hollow muscle in the middle of the chest that pumps blood around the body, supplying cells with oxygen and nutrients. A muscular wall, called the septum, divides the heart lengthways into left and right sides. A valve divides each side into chambers: upper atrium and a lower ventricle. When the heart muscle contracts, it squeezes blood through the atria and then through the ventricles. Oxygenated blood from the lungs flows from the pulmonary veins into the left atrium, through the left ventricle, and then out via the aorta to all parts of the body. Deoxygenated blood returning from the body flows from the vena cava into the right atrium, through the right ventricle, and then out via the pulmonary artery to the lungs for reoxygenation.
Image from NCERT
Image from NCERT
Ans. A mechanism to filter the blood is required. This is done by the blood capillaries in the kidneys. When the blood reaches the two kidneys, it contains both useful and harmful substances. The useful substances are absorbed back into the blood. The wastes dissolved in water are removed as urine. From the kidneys, the urine goes into the urinary bladder through tube-like ureters. It is stored in the bladder and is passed out through the urinary opening at the end of a muscular tube called urethra. The kindeys, ureters, bladder and urethra form the excretory system.
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