Section B (3 Marks)

Question 7: The data collected based on the survey conducted for species richness of groups of mammals in three different climatic regions of the world is shown in the bar graph given below. Panama has nearly 560 species of mammals, Canada has nearly 301 species of mammals, and Denmark has 67 species of mammals.                                                                                                                                     

• (i) Based on the species richness, identify the location of these countries in the respective climatic regions given.
• (ii) Plants and animals do not have a uniform diversity in the world.  Write the term given to this pattern of diversity, and why?    

Answer:

(i) As the graph represents the Taxonomic richness is directly proportional to the different regions. Therefore, following are the locations corresponding with their regions. 

• Panama with 560 species of mammals- Tropic region 
• Canada with 301 species of mammals- Temperate region
• Denmark with 67 species of mammals- Polar region        

(ii)   

• Latitudinal gradient.  
• A decrease in species diversity can be seen as we move away from equator towards the pole. 
• This change in species diversity can be explained by different climatic conditions and different latitudes.

Question 8: Biodiversification of life started to occur almost 3 billion years ago. Since then, new species have been evolving and then disappearing en masse from the earth.    

• (a.) How many episodes of mass extinctions of species have already taken place, and which one is in progress in the current era? 
• (b.) How is a current episode in progress different from the previous episodes, and why? Explain. 

Answer:

(a.) There are five mass extinctions have been occurred and the sixth one is going to occur in this era that means it is in progress. 

(b.) The current episode of mass extinction is the sixth episode that is much more approximately 100- 1000 times faster than the previous ones. Reason behind this could the industrialization, the loss of habitat, over exploitation etc.  

Question 9: Name two naturally occurring sources, one that transfers pathogenic genes into plant cells and the other into an animal cell, respectively, for their benefit.  Write how have these naturally occurring sources been used for the benefit of the human race by the biotechnologies. 

Answer:

Following are the naturally occurring sources, that transfer pathogenic genes:

• Plant- Agrobacterium tumefaciens, it transfers the disarmed Ti Plasmid that is used as a vector to introduce the gene of interest in the variety of plants.
• Animal- Retrovirus, the disarmed retroviruses can be used for transferring the genes of interest into mammalian host cells

Question 10: Enumerate the main sources of bio-fertilizers, giving one example of each. 

Answer:

Following the natural resources of fertilizers:

• Bacteria—Rhizobium, Azospirillum, Azotobacter 
• Fungi—Mycorrhiza, Glomus 
• Cyanobacteria—Anabaena, Nostoc, Oscillatoria 

Question 11: Explain giving the reason for the action plan followed by organic farmers that support their key belief “biodiversity furthers health of crop lands”

Answer:

“Biodiversity furthers health of crop lands”- The reason behind this could be not to eradicate the pests and keep them at negotiable or at a manageable level by using the various check and different type balances between the crop and the pests. 

• The pest can be further used as food for example: lamb’s-quarter (Bathua) is a pest wheat crop.
• Furthermore, various types of pests act as a beneficiary predators and parasites who would suffer and not survive. 

Question 12:

1. State the role of a selectable marker in rDNA technology. 
2. Name one such selectable marker which is considered to be useful for E. coli.
3. Give one reason why is it considered to be a useful marker. 

Answer:

(i.) Selectable markers plays a huge role in the transformed and non-transformed colonies of bacteria or in other words in helps in identifying the recombinant and non-recombinant bacteria. 

(ii.) The antibiotic selectable markers can be used for screening. Example: Ampicillin resistance, tetracycline resistance etc. 

(iii.) These markers are useful in identifying or isolating a transformed colony

or                  

Q12. What are plasmids? How are they different from cloning vectors? Give one example each for a viral and a bacterial cloning vector.                                                                                                                                                                                                                                                                    (3 marks)

Answer:

A plasmid is an extra-chromosomal circular DNA present in the prokaryotes(bacteria). It has the ability of self-replication. The plasmid is an extra-chromosomal DNA which is present inside the bacteria naturally whereas a vector can be a natural or synthetic plasmid which we can use as a vehicle to insert our gene of interest. 

Example:

• Bacterial cloning vector: pBR322
• Viral cloning vector: Bacteriophage

CBSE Class 12 Previous Year Question Papers for Biology help you to understand the level of questions asked in the previous exams, along with the changes in pattern. Practicing the past year’s question papers of Class 12 enhances time-management skills while appearing in the examination. It makes you understand the importance of different topics that have been asked previously.

Previous year’s CBSE Class 12 Biology Question Papers will boost your confidence level to appear in the examination with proper knowledge of different topics that are going to be asked. It enhances the understanding of the topic and acts as a checkpoint to see the level of preparation that you have done.