CBSE Questions for Class 11 Medical Biology Biological Classification Quiz 16 - MCQExams.com

$$\textbf{Correct option: }$$ B

$$\textbf{Solution: }$$  

$$\textbf{Option (b) }$$

$$\bullet$$ Viruses are the organism which arises from the genetic elements that gained the ability to show movement between cells. 

$$\bullet$$ The origin of the viruses are the  free-living organisms that adapted a parasitic replication strategy which existed previously. 

$$\bullet$$ These viruses also lead to the evolution of cellular life. 

Hence, the correct option is (b).

Solution:

Correct answer is option B

Explanation for correct option:

• An endospore is a dormant, tough, non-reproductive structure produced by a small number of bacteria from the Firmicute family. 
• The primary function of most endospores is to ensure the survival of a bacterium through periods of environmental stress. 
They are therefore resistant to ultraviolet and gamma radiation, desiccation, lysozyme, temperature, starvation and chemical disinfectants. 

• Endospores are commonly found in soil and water, where they may survive for long periods of time. 

Citrus crop canker is caused due to Xanthomonas axonopodis.

 Late blight of potato is caused due to Phytophthora infestans .

Root knot in brinjal is because of the pathogen Meloidogyne infestans . 

Pigeon pea seed gall is caused by Fusarium udum.

Thus, the correct answer is option b.

• The adhesive pad of fungi penetrates the host with the help of mechanical pressure and enzymes. 
• It pushes against the cell wall of the host and releases cellulase to digest the cellulose of the host cell wall so that the hypha is able to penetrate the host cell wall.

Lichen is the composite organisms arising from algae or cyanobacteria. They are sensitive to $$SO_2$$ due to their efficient absorption system, which results in a fast accumulation of Sulphur. It results in the destruction of chlorophyll and inhibition of photosynthesis.

The correct answer is C.

• A lichen is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.
  
• If air is very badly polluted with sulfur dioxide( $$SO_2$$ ) there may be no lichens present, just green algae may be found. If the air is clean, shrubby, hairy and leafy lichens become abundant
  
• Hence Lichens are important in the studies on atmospheric pollution because they are very sensitive to pollutants like sulfur dioxide. 
• So, the correct answer is ' Are very sensitive to pollutants like $$SO_2$$ .

• Rous sarcoma is a virus which belongs to the group of the retrovirus. 
• This is an oncovirus which can induce or stimulate the oncogene. 
• The virus infection results in the formation of tumours due to activation of the proto- oncogene. 
• This virus is responsible for the formation of tumours in the chickens. 
• Thus, the correct answer is option D.