Question

Which of the following respires only anaerobically?
A) Cockroach
B) Yeast
C) Fungi
D) All Bacteria

Answer 1

Aerobic respiration is the process of breakdown of food into simpler forms in the presence of oxygen. Anaerobic respiration is the process of the breakdown of food or glucose to liberate energy in the absence of oxygen. This process is also known as fermentation and is carried out exclusively by the organism and this process is widely harnessed for obtaining useful products like ethanol.

Complete answer:
There are several organisms/ cells which respires both aerobically and anaerobically. For example, muscle cells in our body. The respire aerobically and under strenuous condition respire anaerobically and produce lactic acid.
The organisms which cannot survive in the presence of oxygen are known as obligate or strict anaerobes. They cannot survive in the presence of oxygen as they cannot utilise it in metabolic activities. One such example of these animals is Yeast. Yeast or Saccharomyces cerevisiae is a fungus that is saprotrophic in nature. It converts the glucose present in the food to ethanol and carbon dioxide in the absence of oxygen. This process is known as fermentation.
Cockroach- Cockroach is an insect and cannot survive in the absence of oxygen. It requires oxygen to produce energy from the food it eats.
Fungi- Fungi can both be aerobic and anaerobic. Example of aerobic fungi is Fusarium, Penicillium etc.
Bacteria- The bacteria can both be aerobic and anaerobic. The bacteria present in the gut are anaerobic. The aerobic bacteria include Pseudomonas, Bacillus etc.

Therefore the correct answer is option ‘B’.

Note: Fermentation is an economically important process that is carried out by the yeast. The process of fermentation takes place in the absence of oxygen and yield economically important products like ethanol which is used in the beer-making industry. Also, through fermentation, yeast evolves carbon dioxide. This property is beneficial for using yeast in the bread and baking industry as it makes the dough soft.