In-text Questions — Excretion — Life Processes

1. 13 marksNCERT Cl-10 Science, In-text Qs after §5.5, Q1

   Describe the structure and functioning of nephrons.

   Hint. Structure first (what a nephron is made of), then function (the two-step process it carries out).

   Step 1 — Structure. Each nephron is the basic filtration unit of the kidney, made up of a cluster of very thin-walled blood capillaries (the glomerulus) held within the cup-shaped end of a coiled tube called Bowman's capsule, since it's this thin-walled cluster that collects the filtrate. Each kidney packs in large numbers of these nephrons.

   Step 2 — Filtration. Blood is filtered at the glomerulus/Bowman's capsule, separating out water, glucose, amino acids, salts and urea into the tube.

   Step 3 — Selective reabsorption. As this filtrate flows along the tube, useful substances such as glucose, amino acids, salts and most of the water are reabsorbed back into the blood — how much water is reabsorbed depends on the body's excess water and the amount of waste still to be excreted.

   Step 4 — Final step. The remaining fluid, now urine, passes into the ureter, on to the bladder for storage, and out through the urethra.

   ✦ Answer: A nephron is a cluster of capillaries (glomerulus) inside a cup-shaped Bowman's capsule, connected to a long tube. It filters the blood at the glomerulus, then selectively reabsorbs useful substances (glucose, amino acids, salts, water) back into the blood as the filtrate flows along the tube — what's left becomes urine.

   Where students slip. Describing filtration as the only step — the selective reabsorption that follows is equally essential; without it, useful substances like glucose would simply be lost in the urine.

2. 22 marksNCERT Cl-10 Science, In-text Qs after §5.5, Q2

   What are the methods used by plants to get rid of excretory products?

   Hint. Plants don't have dedicated excretory organs — they use whatever tissue or process is already available.

   Step 1 — Gaseous waste. Excess oxygen (from photosynthesis) and carbon dioxide are released by simple diffusion through stomata.

   Step 2 — Water. Excess water is removed by transpiration.

   Step 3 — Other waste. Other waste products are stored in cell vacuoles, stored in leaves that are eventually shed, stored as resins and gums (especially in old xylem), or excreted directly into the surrounding soil, since plants have no dedicated excretory organ and so rely on whatever tissue is available.

   ✦ Answer: Plants release gaseous waste by diffusion through stomata, remove excess water by transpiration, and store other wastes in vacuoles, in leaves that fall off, as resins/gums in old xylem, or excrete them into the soil.

   Where students slip. Assuming plants have no excretion at all just because they lack organs like kidneys — they still remove waste, just through several different passive, tissue-based strategies rather than one dedicated organ.

3. 32 marksNCERT Cl-10 Science, In-text Qs after §5.5, Q3

   How is the amount of urine produced regulated?

   Hint. Think about what happens to reabsorption when the body already has plenty of water versus when it needs to conserve water.

   Step 1 — Recall the reabsorption step. As filtrate flows through the nephron's tubule, water is selectively reabsorbed back into the blood.

   Step 2 — Explain what controls how much. The amount of water reabsorbed depends on how much excess water is already in the body and how much dissolved waste needs to be excreted, since these are exactly the two things urine volume is meant to balance.

   Step 3 — Draw out both directions. If the body has excess water, less is reabsorbed, producing a larger volume of more dilute urine; if the body needs to conserve water, more is reabsorbed, producing a smaller volume of more concentrated urine.

   ✦ Answer: By adjusting how much water is reabsorbed in the nephron's tubule — more reabsorption (concentrated, less urine) when the body needs to conserve water, less reabsorption (dilute, more urine) when there's excess water to lose.

   Where students slip. Saying the kidneys 'always reabsorb a fixed amount' of water — reabsorption is variable and adjusts specifically to the body's current water balance and waste load.

Solutions written by the tuition.in editorial team and checked against the NCERT Class 10 Science textbook, Reprint 2026-27 (jesc105.pdf) — five in-text question sets (21 questions total) plus one end-of-chapter Exercise (13 questions, not 20 as some older manifests claim). Unchanged by rationalisation; the chapter describes the breathing passage and the nephron's tubule in generic functional terms rather than naming every intermediate structure.. Questions are referenced from the NCERT textbook for identification.