Summary
Chapter 10 of the Class 7 Science NCERT textbook (Curiosity) covers Life Processes in Plants — how plants grow, make food through photosynthesis, transport water and nutrients via xylem and phloem, and release energy through respiration.
- Leaves as food factories — Plants make their own food in the leaves, whose broad green surfaces hold chlorophyll to capture sunlight — the process of photosynthesis that combines carbon dioxide and water into glucose and releases oxygen.
- Proving what photosynthesis needs — Through experiments students confirm the ingredients: the iodine test reveals starch only in green sunlit parts, caustic soda deprives a leaf of carbon dioxide to stop starch, and bubbles show oxygen being released.
- Transport through the plant — Plants move materials over distance — xylem carries water and dissolved minerals up from the roots, while phloem distributes the food made in the leaves to every part of the plant.
- Respiration in plants — Making food isn't the whole story: all parts of a plant, green or not, respire — breaking glucose down with oxygen to release energy, carbon dioxide, and water, just as animals do.
Key points & formulas
- 01Plants require both sunlight and water for growth — the plant in sunlight with water grows best, the one without water may die, and the one in the dark shows the least growth.
- 02Leaves are the 'food factories' of plants; they are broad, flat, and green due to the pigment chlorophyll, which captures sunlight efficiently.
- 03Photosynthesis is the process by which plants use carbon dioxide, water, sunlight, and chlorophyll to produce glucose (a simple carbohydrate) and oxygen: Carbon dioxide + Water → Glucose + Oxygen.
- 04Starch is detected in a leaf using an iodine test — a blue-black colour indicates the presence of starch; the leaf must first be decolourised in alcohol so the colour change is visible.
- 05Only the green (chlorophyll-containing) parts of a leaf in sunlight produce starch; leaves kept in the dark do not produce starch even if they have chlorophyll.
- 06Carbon dioxide from the air is essential for photosynthesis — the part of a leaf inside a bottle containing caustic soda (which absorbs CO₂) does not produce starch.
- 07Oxygen is released during photosynthesis — demonstrated by bubbles collecting in an inverted test tube placed in sunlight, and confirmed when a lit matchstick produces an intense flame in that gas.
- 08Stomata are tiny pores on the surface of leaves that allow the exchange of carbon dioxide and oxygen during photosynthesis and respiration.
- 09Water and dissolved minerals are transported from roots to all plant parts through tube-like structures called xylem; food prepared in the leaves is transported to all parts through phloem.
- 10Respiration in plants breaks down glucose using oxygen to release carbon dioxide, water, and energy: Glucose + Oxygen → Carbon dioxide + Water + Energy. All plant parts, green and non-green, carry out respiration.
Frequently asked questions
01What is Chapter 10 of Class 7 Science Curiosity about?
Chapter 10 is titled 'Life Processes in Plants.' It covers how plants grow, how they make food through photosynthesis, how they transport water and food through xylem and phloem, and how they release energy through respiration.
02What is photosynthesis and what are its raw materials?
Photosynthesis is the process by which plants prepare food in the presence of sunlight and chlorophyll. The raw materials are carbon dioxide (from air) and water. The products are glucose and oxygen. The word equation is: Carbon dioxide + Water → (Sunlight/Chlorophyll) → Glucose + Oxygen.
03Why are leaves called the 'food factories' of plants?
Leaves are called the 'food factories' of plants because they are the primary site for photosynthesis. Their broad, flat shape and green chlorophyll pigment help them capture sunlight efficiently to produce food (glucose) for the plant.
04What is chlorophyll and why is it important?
Chlorophyll is a green pigment present in leaves. It helps in capturing sunlight efficiently and is essential for the preparation of starch (food) in plants. Without chlorophyll, photosynthesis cannot take place.
05How do you test for the presence of starch in a leaf?
First, boil the leaf in water for five minutes, then dip it in alcohol placed in a beaker of boiling water until the leaf becomes colourless (decolourised). Then place a few drops of diluted iodine solution on the leaf. A blue-black colour change indicates the presence of starch.
06What is the role of carbon dioxide in photosynthesis?
Carbon dioxide from the air is essential for plants to prepare starch. When a leaf is placed inside a bottle containing caustic soda (sodium hydroxide), which absorbs carbon dioxide, that part of the leaf cannot produce starch even in the presence of sunlight, water, and chlorophyll.
07What gas is released during photosynthesis and how is it detected?
Oxygen is released during photosynthesis. It can be detected by collecting the gas produced by a water plant in an inverted test tube placed in sunlight — when a lit matchstick is inserted into the collected gas, it produces an intense flame, confirming the gas is rich in oxygen.
08What are stomata and what is their function?
Stomata are tiny pores present on the surface of leaves. They help in the exchange of oxygen and carbon dioxide during photosynthesis and respiration.
09What is the difference between xylem and phloem?
Xylem is a set of thin tube-like structures that transport water and dissolved minerals from the roots upward to all parts of the plant. Phloem is another set of thin tube-like structures that transport food (prepared in the leaves by photosynthesis) to all other parts of the plant, where it may be used or stored.
10Do plants respire? What is the word equation for plant respiration?
Yes, all parts of a plant — green and non-green — carry out respiration. During respiration, glucose is broken down in the presence of oxygen, releasing carbon dioxide, water, and energy. The word equation is: Glucose + Oxygen → Carbon dioxide + Water + Energy. The energy released is used for the plant's growth and development.
11What do plants need to grow — can they grow without sunlight or water?
Plants require both sunlight and water for growth. An experiment with three pots shows that the plant in direct sunlight with adequate water grows best; the plant in direct sunlight without water may die; and the plant in the dark with water shows the least growth.
12Why do some plant leaves appear red, violet, or brown instead of green?
Some plant leaves appear red, violet, or brown because they contain more of those coloured pigments than the green-coloured chlorophyll, which hides the green colour. Some of these pigments also help in photosynthesis, and an iodine test can confirm that starch is still produced in such leaves.
13Is the NCERT Class 7 Science Chapter 10 PDF free to download? Do I need to sign up?
Yes, the PDF is completely free to access on cbseprepmaster.com. No sign-up or account is required.
More chapters in Curiosity
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