Activity . Take some freshly prepared lime water in a test tube. Blow air through this lime water. Note how long it takes for the lime water to turn milky.
Use a syringe or pichkari to pass air through some fresh lime water taken in another test tube (Fig. . ). Note how long it takes for this lime water to turn milky.
What does this tell us about the amount of carbon dioxide in the air that we breathe out? . What are the differences between autotrophic nutrition and heterotrophic nutrition? .
Where do plants get each of the raw materials required for photosynthesis? . What is the role of the acid in our stomach? .
What is the function of digestive enzymes? . How is the small intestine designed to absorb digested food? Tube Test tube containing lime water Lime water Rubber tube (a) (b) Pichkari