Chapter 5 · Life Processes
NCERT Class 10 Science Chapter 5 Intext Questions (Page 96)
All 5 questions of NCERT Class 10 Science Chapter 5 Intext Questions (Page 96) — Life Processes — in the book's order, each with its answer and a step-by-step solution.
- Q1What are the components of the transport system in human beings? What are the functions of these components?Step-by-step solution →
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The heart pumps blood, vessels carry it, blood transports materials and clots at injuries, and lymph carries absorbed fat and returns tissue fluid.
The transport system in human beings has four components. (1) The heart — a muscular organ with four chambers — is the pump: its atria receive blood and its thick-walled ventricles push it out, the right side sending carbon dioxide-rich blood to the lungs and the left side sending oxygen-rich blood to the body, with valves preventing any backward flow. (2) The blood vessels are the network of tubes: arteries carry blood away from the heart under high pressure and so have thick elastic walls; capillaries, one cell thick, are where materials are exchanged between the blood and the cells; veins collect the blood from the organs and bring it back to the heart, with valves to keep the flow one way. (3) The blood is the fluid that is carried: its plasma transports food, carbon dioxide, nitrogenous wastes and salts in dissolved form, its red blood corpuscles carry oxygen, and its platelets clot the blood at an injury to plug the leak and keep up the pressure. (4) Lymph, or tissue fluid, formed from plasma that escapes through the capillary pores, drains through lymphatic capillaries and lymph vessels into the larger veins; it carries the digested and absorbed fat from the intestine and returns excess fluid from the tissues to the blood. - Q2Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?Step-by-step solution →
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Warm-blooded mammals and birds need much energy, so unmixed oxygen-rich blood must reach the body for an efficient oxygen supply.
Mammals and birds are warm-blooded: they constantly use energy to maintain their body temperature, so their energy needs are high and continuous. That energy is released by oxidising food with oxygen, so their cells need a highly efficient, uninterrupted supply of oxygen. If oxygenated blood from the lungs mixed with deoxygenated blood from the body in the heart, the blood pumped to the body would carry less oxygen in every round and the supply of energy would fall. Keeping the two kinds of blood separate — the right side of the four-chambered heart handling only carbon dioxide-rich blood bound for the lungs and the left side only oxygen-rich blood bound for the body — ensures that the body always receives fully oxygenated blood, giving the highly efficient oxygen supply these animals need. Animals with lower energy needs, such as amphibians and reptiles, whose body temperature depends on the surroundings, can tolerate some mixing in a three-chambered heart. - Q3What are the components of the transport system in highly organised plants?Step-by-step solution →
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Xylem (vessels, tracheids) carries water and minerals upwards; phloem (sieve tubes, companion cells) carries food in both directions.
The transport system of a highly organised plant consists of two independently organised conducting tissues. (1) Xylem — made of vessels and tracheids, which in the roots, stems and leaves are interconnected into a continuous system of water-conducting channels reaching all parts of the plant; it transports water and the minerals dissolved in it, absorbed from the soil, from the roots upward. (2) Phloem — made of sieve tubes with adjacent companion cells; it transports the soluble products of photosynthesis (food) from the leaves, where they are made, to the storage organs of roots, fruits and seeds and to growing organs, along with amino acids and other substances, in both upward and downward directions. - Q4How are water and minerals transported in plants?Step-by-step solution →
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Water and dissolved minerals rise in the xylem, pushed by root pressure and pulled mainly by transpiration pull from the leaves.
Water and minerals are transported in the xylem, whose vessels and tracheids in the roots, stems and leaves form one continuous system of water-conducting channels. (1) At the roots, the cells in contact with the soil actively take up ions (minerals). This creates a difference in ion concentration between the root and the soil, so water moves from the soil into the root to eliminate the difference. The steady entry of water into the root xylem creates a column of water that is pushed upward — root pressure. (2) Root pressure alone cannot lift water to the heights seen in tall plants. Water evaporates from the cells of the leaves and is lost through the stomata as vapour (transpiration); the water lost is replaced from the xylem vessels in the leaf, and this evaporation creates a suction — the transpiration pull — that pulls water up from the xylem of the roots to the highest parts of the plant. (3) During the day, when the stomata are open, the transpiration pull is the major driving force; root pressure matters more at night. The minerals, taken up as ions at the root, travel dissolved in this rising water. Transpiration thus helps in the absorption and upward movement of water and minerals, and also in temperature regulation. - Q5How is food transported in plants?Step-by-step solution →
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Food is translocated in the phloem: sucrose loaded using ATP draws in water, and the pressure moves food to where it is needed.
Food — the soluble products of photosynthesis, chiefly sucrose, together with amino acids and other substances — is transported in the phloem; this transport is called translocation. It takes place in the sieve tubes with the help of the adjacent companion cells, and it delivers the food from the leaves to the storage organs of roots, fruits and seeds and to growing organs. Unlike transport in the xylem, which can be explained by simple physical forces, translocation uses energy: (1) sucrose is transferred into the phloem tissue using energy from ATP; (2) this increases the osmotic pressure of the phloem, so water moves into it; (3) the pressure so created moves the material in the phloem to tissues which have less pressure. Because the flow goes from the loaded tissue to any tissue of lower pressure, the phloem can move food according to the plant's needs, both upward and downward — for example, in spring the sugar stored in root or stem tissue is transported up to the buds, which need energy to grow.