CBSE Class 7 Science Photosynthesis and Respiration in Plants Worksheet Set 14

Answer: (b) Chloroplast. Chloroplasts hold the chlorophyll that traps sunlight.

Teacher's Note:
1. Chlorophyll is a pigment, not an organelle.
2. Mitochondria are the sites of respiration.

Answer: (c) 2. Two kidney-shaped guard cells enclose each stoma.

Teacher's Note:
1. Guard cells open and close the pore.
2. They change shape as they gain or lose water.

Answer: (c) Glucose. Glucose is the first sugar made, and it is later stored as starch.

Teacher's Note:
1. Lactose is milk sugar and is not made by plants.
2. Glucose is also the fuel broken down in respiration.

Answer: (c) Ethyl alcohol. Yeast breaks glucose down without oxygen into alcohol and carbon dioxide.

Teacher's Note:
1. This process is called fermentation.
2. Oxygen is used up, not made, in respiration.

Answer: (c) Glucose. Glucose is the main fuel oxidised in cells.

Teacher's Note:
1. The energy released is stored as ATP.
2. Other sugars are first changed to glucose.

Answer: (a) Woody stems and mature roots. Lenticels are tiny openings in the bark for gas exchange.

Teacher's Note:
1. Stomata, not lenticels, are on the leaf surface.
2. Woody parts have no stomata, so lenticels take over.

Answer: Chlorophyll

Teacher's Note:
1. Chlorophyll traps light energy.
2. It gives leaves their green colour.

Answer: dark

Teacher's Note:
1. Stomata open mainly in sunlight.
2. They close at night to save water.

Answer: photosynthesis

Teacher's Note:
1. Light is the energy source for photosynthesis.
2. Less light means less food is made.

Answer: 6O₂

Teacher's Note:
1. Aerobic respiration needs oxygen.
2. Glucose is completely oxidised to carbon dioxide and water.

Answer: About 38 and about 2.

Teacher's Note:
1. Complete oxidation of glucose releases much more energy.
2. Anaerobic respiration is incomplete, so little energy is released.

Answer: False. They are the raw materials; oxygen is the by-product.

Teacher's Note:
1. Photosynthesis uses carbon dioxide and water.
2. It releases oxygen.

Answer: False. Aerobic respiration needs oxygen.

Teacher's Note:
1. Aerobic means 'with air'.
2. Respiration without oxygen is anaerobic.

Answer: True. Glucose is only partly broken down.

Teacher's Note:
1. The products still contain energy, such as alcohol.
2. So much less energy is released.

Answer: True. Living cells need energy all the time.

Teacher's Note:
1. Photosynthesis needs light, but respiration does not.
2. Plants respire continuously.

Answer: Stomata

Teacher's Note:
1. They allow gas exchange and loss of water vapour.
2. Each pore is guarded by two cells.

Answer: Lenticels

Teacher's Note:
1. They allow gases to pass through bark.
2. They are found where there are no stomata.

Answer: Carbon dioxide

Teacher's Note:
1. Limewater is used as a test for this gas.
2. It is produced during respiration.

Answer: Photosynthesis is the process by which green plants make glucose from carbon dioxide and water using sunlight trapped by chlorophyll, releasing oxygen.

Teacher's Note:
1. It happens in green parts of plants.
2. It is the main source of food and oxygen on Earth.

Answer: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in the presence of sunlight and chlorophyll).

Teacher's Note:
1. Carbon dioxide and water are the reactants.
2. Glucose and oxygen are the products.

Answer: Light intensity, carbon dioxide concentration, temperature and availability of water.

Teacher's Note:
1. Increasing light and carbon dioxide raises the rate up to a limit.
2. Very high temperature slows it down.

Answer: It makes food for plants and all other organisms, releases oxygen into the air and removes carbon dioxide.

Teacher's Note:
1. All food chains begin with plants.
2. It also keeps the air balanced.

Answer: Chlorophyll absorbs sunlight and gives the energy needed to join carbon dioxide and water into glucose.

Teacher's Note:
1. Without chlorophyll the leaf cannot make food.
2. Chlorophyll is stored in chloroplasts.

Answer: A stoma is a tiny pore on a leaf surface surrounded by two guard cells. When guard cells take in water they swell and open the pore; when they lose water they become slack and close it.

Teacher's Note:
1. Stomata allow carbon dioxide in and oxygen and water vapour out.
2. They are usually open by day and shut at night.

Answer: Respiration is the process in which food (glucose) is broken down in cells to release energy. Its two types are aerobic and anaerobic respiration.

Teacher's Note:
1. It takes place in all living cells.
2. The energy released is used for life activities.

Answer:

1. Aerobic needs oxygen; anaerobic does not.
2. Aerobic oxidises glucose completely to CO₂ and water; anaerobic does it incompletely (for example to alcohol and CO₂).
3. Aerobic releases much more energy (about 38 ATP) than anaerobic (about 2 ATP).

Teacher's Note:
1. Mitochondria are the main site of aerobic respiration.
2. Anaerobic respiration happens in the cytoplasm.

Answer: Breathing is the physical process of taking in air and giving out air (inhalation and exhalation). Respiration is the chemical process inside cells that breaks down food to release energy.

Teacher's Note:
1. Breathing supplies the oxygen for respiration.
2. Respiration happens in cells, not in the lungs or leaves.

Answer: Photosynthesis happens in chlorophyll-containing cells in light, uses CO₂ and water, makes glucose and stores energy. Respiration happens in all living cells all the time, uses glucose and oxygen, produces CO₂ and water and releases energy.

Teacher's Note:
1. The two processes are almost opposite.
2. Together they keep the gases of the air in balance.

Answer: Xylem carries water and minerals from roots to leaves, and phloem carries prepared food from leaves to other parts.

Teacher's Note:
1. Xylem and phloem together form the vascular tissue.
2. Water moves up while food moves in both directions.

Answer: Boil the leaf in water, then in alcohol to remove chlorophyll, rinse it, and add a few drops of iodine solution. A blue-black colour shows starch.

Teacher's Note:
1. Starch is made from the glucose formed in photosynthesis.
2. Alcohol is heated in a water bath, never directly.