Transport of Substances PDF - Grade 7 Science Notes

Grade 7 – Science Transport of Substances in Animals and Plants– Notes 1. Why is the transport of materials necessary in a plant or an animal? Explain. Ans: The transport of materials is necessary for plants and animals because it ensures that nutrients and oxygen are ma...

Grade 7 – Science Transport of Substances in Animals and Plants– Notes 1. Why is the transport of materials necessary in a plant or an animal? Explain. Ans: The transport of materials is necessary for plants and animals because it ensures that nutrients and oxygen are made available to all parts of the body. Without the transport of these essential nutrients and oxygen, the body would not be able to survive. 2. What are stomata? Give two functions of stomata. Ans: Stomata are small openings found on the lower surface of leaves. These pores are surrounded by guard cells. Functions of stomata: 1. They help in the transpiration of water, i.e., the loss of excess water from the plant. 2. The loss of water through stomata creates an upward pull (suction pull), which aids in the absorption of water by the roots. 3. What are the components of blood? Ans: There are four components of blood: 1. Plasma: Plasma is the liquid part of blood, yellowish in color, and contains 90% water. It carries food, enzymes, waste products, proteins, and other essential substances. 2. Red Blood Cells (RBCs): These are disc-shaped cells containing a red-colored pigment called hemoglobin, which helps in the transportation of oxygen. 3. White Blood Cells (WBCs): These are the body's defense cells, protecting us against bacteria and foreign materials that cause infections. 4. Platelets: Platelets play a crucial role in blood clotting, preventing excessive bleeding during injuries. 4. Draw a diagram of the human excretory system, explain and label the various parts. The Excretory System is responsible for removing waste products and excess substances from the body to maintain a healthy internal environment. The main excretory organ in humans is the kidney. Key Components of the Human Excretory System: 1. Kidneys: Filter blood to remove waste products, forming urine. 2. Ureters: Tubes that carry urine from the kidneys to the bladder. 3. Urinary Bladder: A sac-like structure that stores urine temporarily.  4. Urethra: A tube through which urine is expelled from the body. Functions of the Excretory System: Removes nitrogenous waste like urea and uric acid. Maintains the water and salt balance in the body (osmoregulation). Helps in regulating blood pressure. Proper functioning of the excretory system is essential to prevent the accumulation of harmful substances in the body. 5. Explain the structure and functions of the human heart. The Heart is a muscular organ that pumps blood throughout the body, ensuring the transportation of oxygen, nutrients, and waste materials. It is a vital part of the circulatory system. Structure of the Heart: The heart has four chambers: 1. Right Atrium: Receives deoxygenated blood from the body through the vena cava. 2. Right Ventricle: Pumps deoxygenated blood to the lungs for oxygenation through the pulmonary artery. 3. Left Atrium: Receives oxygenated blood from the lungs through the pulmonary veins. 4. Left Ventricle: Pumps oxygenated blood to the entire body through the aorta. Valves in the Heart: The heart contains four main valves that prevent the backward flow of blood: 1. Tricuspid Valve: Between the right atrium and right ventricle. 2. Pulmonary Valve: Between the right ventricle and pulmonary artery. 3. Bicuspid (Mitral) Valve: Between the left atrium and left ventricle. 4. Aortic Valve: Between the left ventricle and the aorta. Arteries and Veins: Arteries carry oxygenated blood away from the heart. The aorta is the largest artery that carries oxygenated blood to the body. Veins carry deoxygenated blood back to the heart. The vena cava is the largest vein that brings deoxygenated blood from the body to the right atrium. The pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs, while the pulmonary veins carry oxygenated blood from the lungs to the left atrium.  Functions of the Heart: 1. Circulates oxygenated blood to all parts of the body through the arteries. 2. Transports deoxygenated blood to the lungs through the veins for purification (oxygenation). 3. Maintains a steady flow of blood to supply nutrients and remove waste products. 4. Prevents backward blood flow with the help of the valves. The heart works continuously and is protected by the ribcage. Its rhythmic contraction and relaxation are called the heartbeat, which is controlled by electrical signals within the heart. 6. What are the different types of blood vessels found in our circulatory system? Ans: The different types of blood vessels in our circulatory system are Arteries, Veins, and Capillaries. Arteries carry oxygen-rich blood from the heart to all parts of the body. Arteries have thick, elastic walls and do not have valves. Veins carry carbon dioxide-rich blood from all parts of the body back to the heart. Veins have thin walls and contain valves to ensure the blood flows only towards the heart. Capillaries: When arteries reach the tissues, they divide into extremely thin tubes called capillaries. These capillaries then join together to form veins. 7. Explain pulse and pulse rate. Ans: The throbbing movement produced by the blood flowing through the arteries is called the pulse. We can feel the pulse at various places on the body, such as the wrist, neck, side of the head, behind the eye, elbow, behind the knee, inner side of the foot, and groin. The number of pulse beats per minute is called the pulse rate. A resting person usually has a pulse rate between 72 and 80 beats per minute. 8. Explain the mechanism of transportation in plants. Ans: Plants absorb water and minerals through their roots. The root hairs on the roots increase the rate of absorption. Plants have specialized vascular tissues (xylem and phloem) to transport water, nutrients, and food throughout the plant. Xylem transports water and dissolved minerals from the roots to the entire plant. Phloem conducts food, produced by the leaves, to all parts of the plant.