CBSE Questions for Class 7 Biology Respiration In Organisms Quiz 1 - MCQExams.com

• Anaerobic respiration occurs when oxygen is either not available or is present in less quantity to carry out respiration. 
• In yeasts, the process of anaerobic respiration occurs in the absence of oxygen and leads to the formation of alcohol. 
• In muscle cells, anaerobic respiration occurring due to lack of oxygen leads to the production of lactic acid.

• In humans, anaerobic respiration occurs most frequently during vigorous exercise. 
• In order to process energy, muscle cells have to switch to anaerobic pathways when their oxygen supply is depleted. 
• The lack of oxygen leads to lactic acid formation due to the incomplete breakdown of glucose.

Gaseous exchange in insects occurs through a system of air-filled internal tubes, the tracheal system, the finer branches of which extend to all parts of the body and may become functionally intracellular in muscle fibres. Thus, oxygen is carried in the gas phase directly to its sites of utilization.

$$\textbf{Correct answer: B}$$ 

$$\textbf{Option (B):}$$ 

$$\bullet$$ The number of times a person breaths in a minute is called the breathing rate of the individual.

$$\bullet$$ It normally ranges between 15 to 19 breaths every minute.

$$\bullet$$ This is breathing rate under resting conditions and that means under normal conditions this occurs. 

$$\bullet$$ But the breathing rate increases while working out as the oxygen requirement increases in the body. It may reach 25 breaths per minute.

• Spiracles are openings on the surface of some animals, which usually lead to respiratory systems. 
•  In the respiratory system of insects, the tracheal tubes primarily deliver oxygen directly into the animals' tissues.  The respiratory organs in cockroach are spiracles.

• Aquatic respiration is the process whereby an aquatic animal obtains oxygen from water.
  
• Most fish exchange gases using gills on either side of the pharynx (throat).

$$\textbf{Correct Option A}$$

$$\textbf{Solution}$$

$$\bullet$$ Lenticels are the small raised pores which are found in the stem of plants of secondary thickened organs such as bark of Woody stems.