Take three test-tubes. Fill æth of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2?
Three test-tubes are taken and labelled A, B and C. Each test- tube is half filled with water.
(a) In test-tube A, a snail is kept,
(b) In test-tube B, a water plant is kept, and
(c) In test-tube C contains both a snail and a water plant.
(a) Test-tube A contains a snail in water. The snail will use up oxygen for respiration and produce carbon dioxide.
(b) Test-tube B contains a ‘water plant’ in water. The water plant will do photosynthesis by using carbon dioxide and water and produce oxygen. The water plant will use some of this oxygen for respiration and produce carbon dioxide will then be used by the plant in photosynthesis.
(c) Test-tube C contains both, a snail and a water plant. The carbon dioxide produced by the snail through the respiration is used by the plant for the synthesis of food and oxygen is released by the plant which is used by the snail for the respiration.
From the above, we conclude that the test-tube A containing only snail will have the highest concentration of carbon dioxide because there is no plant to use up the carbon dioxide produced during the respiration in snail.
Popular Questions of Class 7 Science
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Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food - Q:-
Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.
Down Across
(D) 1 : Thorough washing (A) 1 : Keeps warm
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3 : Long thread like structure 3 : Hatches from egg of moth
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Sketch the cross section of soil and label the various layers.
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Here is a crossword puzzle: Good luck!
Across
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from human bodyDown
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water - Q:-
Sketch the reproductive parts of a flower.
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Solve the following crossword puzzle with the clues given:
Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil. - Q:-
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- Q:-
Match the items in Column I with those in Column II:
Column I Column II
(i) A home for living organisms (a) Large particles
(ii) Upper layer of the soil (b) All kinds of soil
(iii) Sandy soil (c) Dark in colour
(iv) Middle layer of the soil (d) Small particles and packed tight (v) Clayey soil (e) Lesser amount of humus - Q:-
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
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Write one similarity and one difference between the nutrition in amoeba and human beings.
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Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.
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Given below is a sequence of steps in the processing of wool. Which are the missing steps? Add them.
Shearing, __________, sorting, __________, __________, _________. - Q:-
Fill in the blanks:
(i) The average weather taken over a long time is called ___________. (ii) A place receives very little rainfall and the temperature is high throughout the year, the climate of that place will be ___________ and ___________ .
(iii) The two regions of the earth with extreme climatic conditions are ___________ and __________. - Q:-
Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.
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Fill in the blanks:
(a) The main steps of nutrition in humans are __________, __________, __________, _________ and __________.
(b) The largest gland in the human body is __________.
(c) The stomach releases hydrochloric acid and ___________ juices which act on food.
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(b) Kerala: ____________________________________________
(c) Rajasthan: __________________________________________
(d) North-east India: _____________________________________ - Q:-
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Give one use each of a concave and a convex mirror.
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Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T/F)
(b) Water shortage is a problem faced only by people living in rural areas. (T/F)
(c) Water from rivers is the only source for irrigation in the fields. (T/F)
(d) Rain is the ultimate source of water. (T/F) - Q:-
How does the process of fertilisation take place in flowers?
- NCERT Chapter