Ans. Platelets are tiny blood cells that help our body form clots to stop bleeding. When we don't have enough platelets in our blood, our body cannot form clots and bleeding won't stop which can be fatal.
Ans. The heart is muscular organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it. Blood provides the body with oxygen and nutrients, as well as assists in the removal of metabolic wastes.
Ans. Sometimes a person’s kidneys may stop working due to infection or injury. As a result of kidney failure, waste products start accumulating in the blood. Such persons cannot survive unless their blood is filtered periodically through an artificial kidney. This process is called dialysis.
Ans. Arteries and veins experience differences in the pressure of blood flow. Arteries experience a pressure wave as blood is pumped from the heart. This can be felt as a "pulse." Because of this pressure the walls of arteries are much thicker than those of veins.
Ans. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart.
Ans. Plants absorb water and minerals by the roots. The roots have root hair. The root hair increase the surface area of the root for the absorption of water and mineral nutrients dissolved in water. The root hair is in contact with the water present between the soil particles.
Ans. All organisms need food, water and oxygen for survival. They need to transport all these to various parts of their body. Further, they need to transport wastes to parts from where they can be removed. Thus, transport of materials is necessary in a plant or in an animal.
Ans. Animals such as sponges and hydra do not possess any circulatory system. The water in which they live brings food and oxygen as it enters their bodies. The water carries away waste materials and carbon dioxide as it moves out. Thus, these animals do not need a circulatory fluid like the blood.
Ans. Plants absorb mineral nutrients and water from the soil. Not all the water absorbed is utilised by the plant. The water evaporates through the stomata present on the surface of the leaves by the process of transpiration. The evaporation of water from leaves generates a suction pull which can pull water to great heights in the tall trees. Transpiration also cools the plant.
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. Thus blood is needed by all the parts of a body.
Ans. The three types of cells present in blood are:
i. Red blood cells (RBC) which contain a red pigment called haemoglobin.
ii. The blood also has white blood cells (WBC) which fight against germs that may enter our body.
iii. Platelets cells which helps in the clotting of the blood.
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