(a) List the three events that occur during the process of photosynthesis.
Explain the role of stomata in this process.
(b) Describe an experiment to show that "sunlight is essential for photosynthesis."
(a) The three events that occur during the process of photosynthesis are:
(i) Absorption of light energy by the green pigment chlorophyll.
(ii) Conversion of light energy into chemical energy and the splitting of water molecule into hydrogen and oxygen.
(iii) Reduction of carbon dioxide into carbohydrate.
Role of Stomata
Stomata are tiny pores present on the surface of leaves. They are also present on the surface of young stems. Stomata are mainly engaged in the exchange of gases (entry of CO2 and release of O2 ) associated with photosynthesis. Plant closes the stomata when it does not need CO2 for photosynthesis.
(b) Sunlight is essential for photosynthesis
Procedure:
(i) Place a healthy green potted plant in a dark room for 1-2 days. This is done to ensure
that the plant consumes all its reserve food and the leaves do not contain any starch.
(ii) Then, cover a portion of a leaf of this plant on both sides with two uniform pieces of black paper, fixed in position with two paper clips.
(iii) Now, expose this plant to bright light. After a few hours, remove the leaf and decolorize it with alcohol and test the presence of food (starch) with iodine solution.
Observation: It can be observed that the portion of the leaf covered with black paper does not (food),
Conclusion: This is because the food prepared by plants through the process of photosynthesis is stored as starch. Starch reacts with the iodine solution to give blue-black colour. Only those portions of the leaf that were exposed to sunlight could photosynthesise. Hence, gives blue- black colour when tested with iodine. The portion of the leaf covered with black paper did not receive sunlight. Hence, starch was not produced. Thus, it can be concluded that the sunlight is essential for photosynthesis.
What is the name of tiny projections on the inner surface of small intestine which help in absorbing the digested food ?
Name the process by which plant parts like roots, stems, and leaves get oxygen required for respiration.
(a) Define a nutrient. Name four important nutrients present in our food.
(b) What are the various types of heterotrophic nutrition ?
Write correct sequence of four steps of method for the preparation of temporary mount of a stained leaf peel.
(a) Draw a diagram to show open stomatal pore and label on it:
(i) guard cells
(ii) chloroplast
(b) State two functions of stomata.
(c) How do guard cells regulate the opening and closing of stomatal pore?
A Give one reason why multicellular organisms require special organs for exchange of gases between their body and their environment. :
(a) List the three events that occur during the process of photosynthesis.
Explain the role of stomata in this process.
(b) Describe an experiment to show that "sunlight is essential for photosynthesis."
(a) What is meant by breathing? What happens to the rate of breathing during vigorous exercise and why?
(b) Define translocation with respect to transport in plants. Why is it essential for plants? Where in plants are the following synthesised?
(i) Sugar (iii) Hormone
(a) What is common for Cuscuta, ticks and leeches ?
(b) Name the substances on which the following enzymes act in the human digestive system :
(i) Trypsin (ii) Amylase (iii) Pepsin (iv) Lipase
(c) Why does absorption of digested food occur mainly in the small intestine ?
(a) Define nutrition. Why is nutrition necessary for an organism ?
(b) What are the different modes of nutrition ? Explain with one example of each mode of nutrition.
(c) Name the mode of nutrition in (i) roundworm, and (ii) Plasmodium.
Name the final product/products obtained in the anaerobic respiration, if it takes place :
(a) in a plant (like yeast).
(b) in an animal tissue (like muscles).
State the three common features of all the respiratory organs like skin, gills and lungs.
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
(a) Name the pigment in leaves which absorbs sunlight energy.
(b) What is the colour of this pigment ?
(a) What is photosynthesis ?
(b) Write a chemical equation to show the process of photosynthesis in plants.
(c) Explain the mechanism of photosynthesis.
(a) Name the main organs of the human digestive system. Also name the associated glands.
(b) How do carbohydrates, fats and proteins get digested in human beings ?
State whether the following statements are true or false :
(a) During respiration, the plants take C02 and release 02.
(b) Energy can be produced in cells without oxygen.
(c) Fish and earthworm exchange gases during respiration in the same way.
Describe the process of respiration in the following parts of a plant :
(a) Root (b) Stem (c) Leaves
Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms ?
Name the correct substrates for the following enzymes
(a) Trypsin (b) Amylase (c) Pepsin (d) Lipase
In human alimentary canal, name the site of complete digestion of various components of food. Explain the process of digestion.