NCERT In Text

What processes would you consider essential for maintaining life?

Life processes such as nutrition, respiration, transportation, excretion, etc. are essential for maintaining life.

Related Questions Life Processes

25. Which of the following is an incorrect statement?
(a) Organisms grow with time
(b) Organisms must repair and maintain their structure
(c) Movement of molecules does not take place among cells
(d) Energy is essential for life processes
Ans. (c) Movement of molecules does no take place among cells
Explanation: Movement of molecules is an important aspect of life process and it is necessary that such movements take place among cells.

26. The internal (cellular) energy reserve in autotrophs is
(a) glycogen
(b) protein
(c) starch
(d) fatty acid
Ans. (c) Starch
Explanation: Plants store food in the form of starch. 

27. Which of the following equations is the summary of photosynthesis? 
(a) 6CO2 + 12H2O → C6H12O6 + 6H2O
(b) 6CO2 + H2O + Sunlight → C6H12O6 + O2 + 6H2O
(c) 6CO2 + 12H2O + Chlorophyll + Sunlight → C6H12O6 + 6O2 + 6H2O
(d) 6CO2 + 12H2O + Chlorophyll + Sunlight → C6H12O6 + 6CO2 + 6H2O

Ans. (c) 
Explanation: Option ‘a’ shows correct reaction. But option ‘c’ shows correct reaction as well as other important factors of reaction. Option ‘b’ is not a balanced equation. Option ‘d’ shows carbon dioxide among the products; which is wrong. 

28. Choose the event that does not occur in photosynthesis
(a) Absorption of light energy by chlorophyll
(b) Reduction of carbon dioxide to carbohydrates
(c) Oxidation of carbon to carbon dioxide
(d) Conversion of light energy to chemical energy
Ans. (c) Oxidation of carbon to carbon dioxide

29. The opening and closing of the stomatal pore depends upon
(a) oxygen
(b) temperature
(c) water in guard cells
(d) concentration of CO2 in stomata
Ans. (c) Water in guard cells
Explanation: When water enters the guard cells. they become turgid and facilitate the opening of guard cells. When water comes out of guard cells, they become flaccid and facilitate the closing of guard cells.

30. Choose the forms in which most plants absorb nitrogen
(i) Proteins
(ii) Nitrates and Nitrites
(iii) Urea
(iv) Atmospheric nitrogen
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Ans. (b) (ii) and (iii)
Explanation: Plants cannot take up atmospheric nitrogen and hence option ‘iv’ is incorrect. Protein is synthesized by plants and hence option ‘i’ is incorrect

31. Which is the first enzyme to mix with food in the digestive tract?
(a) Pepsin
(b) Cellulase
(c) Amylase
(d) Trypsin
Ans. (c) Amylase
Explanation: Amylase is present in saliva; which is secreted in mouth. Hence, this is the first enzyme to mix with food.

32. Which of the following statement(s) is (are) correct?
(i) Pyruvate can be converted into ethanol and carbon dioxide by yeast 
(ii) Fermentation takes place in aerobic bacteria
(iii) Fermentation takes place in mitochondria
(iv) Fermentation is a form of anaerobic respiration
(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i) and (iv)
(d) (ii) and (iii)
Ans. (c) (i) and (iv)
Explanation: Fermentation takes place in anaerobes. Fermentation does not take place in mitochondria. Hence, Options (ii) and (iii) are incorrect. 

33. Lack of oxygen in muscles often leads to cramps among cricketers. This results due to
(a) conversion of pyruvate to ethanol
(b) conversion of pyruvate to glucose
(c) non-conversion of glucose to pyruvate
(d) conversion of pyruvate to lactic acid
Ans. (d) conversion of pyruvate to lactic acid
Explanation: In case of excess demand of energy in muscles, anaerobic respiration takes place in muscle cells. This results in accumulation of lactic acid in muscles which results in cramps.

34. Choose the correct path of urine in our body
(a) kidney →ureter →urethra →urinary bladder
(b) kidney →urinary bladder →urethra →ureter
(c) kidney →ureters →urinary bladder →urethra
(d) urinary bladder →kidney →ureter →urethra
Ans. (c) kidney →ureters →urinary bladder →urethra
Explanation: Refer to fig: 6.13 (NCERT Text book) for proper sequence of organs in excretory system.

35. During deficiency of oxygen in tissues of human beings, pyruvic acid is converted into lactic acid in the
(a) cytoplasm
(b) chloroplast
(c) mitochondria
(d) golgi body
Ans. (a) cytoplasm
Explanation: Anaerobic respiration takes place in cytoplasm. 
 

(a) Trypsin
 Ans. Protein
(b) Amylase
 Ans. Starch
(c) Pepsin
 Ans. Protein
(d) Lipase
 Ans. Fat 

The human alimentary canal has following parts:
Buccal Cavity: Buccal cavity contains tongue, teeth and salivary glands. Food enters the digestive system through buccal cavity.
Oesophagus: Buccal cavity is connected to a long tube-like structure; called oesophagus. Oesophagus has a valve to prevent the backflow of food into mouth.
Stomach: Stomach is a J-shaped organ. The buccal cavity opens into the stomach. Walls of stomach are composed of muscles. Gastric glands are present in the stomach. These glands secrete hydrochloric acid, pepsin and mucus.
Small Intestine: This is long and highly coiled structure. The lumen of the small intestine is smaller than that of large intestine. The stomach opens into small intestine. The hepatopancreatic duct opens into the small intestine. Villi are present in small intestine to facilitate absorption of food.

Large Intestine: This is shorter than small intestine. The lumen of large intestine is larger than that of small intestine.
Rectum: Large intestine opens into rectum. Waste materials and undigested food are stored in rectum. 
 

Column (A)

Column (B)
(a) Trypsin (i) Pancreas
(b) Amylase (ii) Liver
(c) Bile (iii) Gastric glands
(d) Pepsin (iv) Saliva

Ans. (a)- i (b)- iv (c)- ii (d)- iii

The functional unit of kidney is called nephron.
A nephron is composed of a tuft of blood capillaries and highly coiled ducts. The tuft of blood capillaries is surrounded by a cup-shaped structure; called Bowman’s capsule.
• Waste material from blood are filtered out of the capillaries and they go through the wall of Bowman’s capsule.
• After that, the waste material and water pass through the ducts. When the mixture of water and other materials move through the duct, some materials and water are reabsorbed. This depends on excess amount of water present in the body.
• After reabsorption of water and other material, urine becomes concentrated. This then goes to the collecting duct.
• Urine from collecting ducts moves through ureter into the urinary bladder. From the urinary bladder, urine is expelled from the body as and when required.