NCERT Exemplar Problems
Short Answer Type
Question 61: Name the energy currency in the living organisms. When and where is it produced?
Answer: ATP (Adenosine triphosphate) is the energy currency in living organisms. It is produced at the end of respiration and is produced in the mitochondria.
Question 62: What is common for cuscuta, ticks and leeches?
Answer: All of them are parasites.
Question 63: Why do veins have thin walls as compared to arteries?
Answer: Veins carry the blood towards the heart. The blood; entering the vein; does not enter because of a pumping action; unlike the way it enters an artery. So, the walls of veins can afford to be thin.
Question 64: Explain the role of mouth in digestion of food.
Answer: Mouth plays following roles in digestion of food:
- Food is broken down into smaller pieces so that it becomes easier to swallow the food.
- Smaller particles also ensure that saliva is properly mixed with the food.
- Tongue plays the important role of mixing the food with saliva.
- Digestion of starch takes place in the mouth.
Question 65: What are the functions of gastric glands present in the wall of the stomach?
Answer: Gastric glands serve following purposes:
- They release mucus
- They produce gastric acid
- They release the gastric enzymes pepsin and rennin.
Question 66: Name the correct substrates for the following enzymes: (a) Trypsin (b) Amylase (c) Pepsin (d) Lipase
Answer: (a) Trypsin: peptide, (b) Amylase: starch, (c) Pepsin: protein, (d) Lipase: fat
Question 67: What will happen if platelets were absent in the blood?
Answer: Platelets play the important role of coagulation of blood. No blood coagulation would take place in the absence of platelets. This would be a dangerous situation; in case of an injury. No blood coagulation would result in excessive blood loss and can even prove lethal for the person.
Question 68: Plants have low energy needs as compared to animals. Explain.
Answer: Plants do not need to move from one place to another. Movements in a plant are usually at the cellular level and hence a far less amount of energy is required by plants. Animals, on the other hand, need to move from one place to another; in search of food. So, the energy need of animals is pretty higher than of plants.
Question 69: Why and how does water enter continuously into the root xylem?
Answer: Root pressure is responsible for transport of water up to root xylem.
Question 70: Why is transpiration important for plants?
Answer: Transpiration through stomata creates a transpiration pull in the underlying vascular tissue. This helps in pulling the water column and thus facilitates ascent of sap in plants. Moreover, transpiration is a way through which plants get rid of excess water. So, transpiration is important for plants.
Question 71: How do leaves of plants help in excretion?
Answer: Gaseous waste is removed through stomata in leaves. Some waste substances get accumulated in older leaves. These substances are removed along with the leaves, when a plant sheds its older leaves.
Question 72: Match the terms in Column (A) with those in Column (B)
|Column A||Column B|
|(a) Trypsin||(i) Pancreas|
|(b) Amylase||(ii) Liver|
|(c) Bile||(iii) Gastric glands|
|(d) Pepsin||(iv) Saliva|
Answer:(a) (i), (b) (iv), (c) (ii), (d) (iii)