Summary
Class 7 Science Chapter 7 explains how blood is pumped through the body by the four-chambered heart via arteries, veins, and capillaries, how kidneys remove waste as urine, and how plants transport water and minerals through xylem and food through phloem. It also covers transpiration, excretion in different animals, and the role of haemoglobin, platelets, and root hair.
Blood, composed of plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets, is pumped by the four-chambered human heart through arteries and veins. Haemoglobin in RBCs carries oxygen; WBCs fight infection; platelets help form clots. A resting adult's pulse rate is 72–80 beats per minute. The excretory system — two kidneys, two ureters, a urinary bladder, and urethra — removes urea in urine (1–1.8 L per day). Fish excrete ammonia; birds, lizards, and snakes excrete uric acid. In plants, xylem transports water and minerals from roots to leaves, while phloem carries food to all plant parts. Root hair increase surface area for water absorption, and transpiration through stomata generates a suction pull that draws water up tall trees and also cools the plant.
Key points & formulas
- 01Blood is made of plasma, RBCs (carry oxygen via haemoglobin), WBCs (fight germs), and platelets (help clot wounds); haemoglobin gives blood its red colour.
- 02Arteries carry oxygen-rich blood from the heart to body parts and have thick elastic walls; veins carry carbon dioxide-rich blood back to the heart and have valves; capillaries are extremely thin tubes connecting them.
- 03The human heart has four chambers — two atria (upper) and two ventricles (lower); a partition keeps oxygen-rich and carbon dioxide-rich blood from mixing.
- 04A resting person's pulse rate is 72–80 beats per minute; each heartbeat generates one pulse in the arteries; pulse can be felt at the inner wrist.
- 05The human excretory system consists of two kidneys, two ureters, a urinary bladder, and urethra; adult urine is about 1–1.8 L per day and contains 95% water, 2.5% urea, and 2.5% other wastes.
- 06Excretory products differ by animal: fish excrete ammonia (dissolves in water), birds/lizards/snakes excrete uric acid (semi-solid white compound), humans mainly excrete urea.
- 07Xylem transports water and mineral nutrients from roots to the entire plant through stems and branches; phloem transports food prepared in leaves to all plant parts.
- 08Transpiration — evaporation of water through stomata on leaves — creates a suction pull that draws water to great heights in tall trees and also helps cool the plant.
Frequently asked questions
01What is blood made of?
Blood is composed of a fluid called plasma in which different types of cells are suspended — red blood cells (RBCs), white blood cells (WBCs), and platelets.
02Why does blood appear red?
Blood appears red because RBCs contain a red pigment called haemoglobin.
03What is the function of haemoglobin?
Haemoglobin binds with oxygen and transports it to all parts of the body and ultimately to all the cells. Without haemoglobin it would be difficult to provide oxygen efficiently to all cells.
04What do white blood cells (WBCs) and platelets do?
WBCs fight against germs that may enter the body. Platelets help form a clot to stop bleeding when there is a cut on the body.
05What is the difference between arteries and veins?
Arteries carry oxygen-rich blood from the heart to all parts of the body and have thick elastic walls because blood flows at high pressure. Veins carry carbon dioxide-rich blood from all parts of the body back to the heart, have thin walls, and contain valves that allow blood to flow only towards the heart.
06How many chambers does the human heart have, and what are they called?
The human heart has four chambers — two upper chambers called atria (singular: atrium) and two lower chambers called ventricles. A partition between the two halves prevents oxygen-rich blood from mixing with carbon dioxide-rich blood.
07What is the normal pulse rate of a resting person?
A resting person usually has a pulse rate between 72 and 80 beats per minute. Each heartbeat generates one pulse in the arteries, so pulse rate indicates the rate of heartbeat.
08What is excretion, and what organs make up the human excretory system?
Excretion is the process of removal of wastes produced in the cells of living organisms. The human excretory system consists of two kidneys, two ureters, a urinary bladder, and urethra.
09How much urine does an adult pass per day and what does it contain?
An adult human normally passes about 1–1.8 L of urine in 24 hours. Urine consists of 95% water, 2.5% urea, and 2.5% other waste products.
10How do fish, birds, and humans differ in the type of waste they excrete?
Aquatic animals like fish excrete cell waste as ammonia, which directly dissolves in water. Birds, lizards, and snakes excrete uric acid, a semi-solid white compound. The major excretory product in humans is urea.
11What is the role of xylem and phloem in plants?
Xylem is the vascular tissue that transports water and mineral nutrients from roots to the entire plant through stems and branches. Phloem is the vascular tissue that transports food prepared by the leaves to all other parts of the plant.
12What is transpiration and why is it important for plants?
Transpiration is the evaporation of water from leaves through stomata. It generates a suction pull that draws water absorbed by roots upward to great heights in tall trees. Transpiration also helps cool the plant.
13What is dialysis?
When a person's kidneys stop working due to infection or injury, waste products accumulate in the blood. Dialysis is the process of filtering blood periodically through an artificial kidney to keep such a person alive.
14Is the NCERT PDF for Class 7 Science Chapter 7 free to access?
Yes — the NCERT PDF for Class 7 Science Chapter 7 (Transportation in Animals and Plants) is free to read and download on cbseprepmaster.com with no sign-up required.
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This is the complete Science Chapter 7 as published by NCERT — every diagram, solved example, and exercise included, free. Browse all NCERT Class 7 textbooks.
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