Botany: Solved Previous Year’s Question Paper for NCERT/CBSE Class 12th Botany

Botany: Solved Previous Year’s Question Paper for NCERT/CBSE Class 12th Botany

Question: What is Semiconservative DNA Replication? Describe the mechanism on the same with suitable diagrams. (Important)

Ans: Already discussed 

Question: Who proposed the concept of Lac operon? 

Ans: François Jacob and Jacques Monod, two French biologists, first introduced the concept of the lac operon in 1961.

Question: (b) Draw the labelled schematic representation of a Lac operon.

Question: (c) Explain how this operon gets switched ‘on’ and ‘off. 

Ans: Transcriptional regulation is a process that turns the operon “on” and “off.” In this procedure, a certain molecule (referred to as a repressor) binds to the operon’s promoter region and inhibits transcription. The operon is “turned on” and transcription can start when the repressor is taken out.

On the other hand, the operon is “turned off” and transcription is stopped when the repressor binds once more. In some circumstances, the operon can also be controlled by a molecule known as an inducer; when the inducer binds to the repressor, it stops the repressor from binding to the promoter, enabling transcription to take place.

Question: What are Negative interactions? Describe various negative interactions among organisms. (Important)

Ans: Already discussed 

Question: (a) What are the hot spots of Diversity? 

Ans: There are several locations with high concentrations of individuals from various cultural origins, including cities, institutions, and other places. New York City, Los Angeles, San Francisco, Houston, and Miami are among the locations with a lot of diversity. College campuses, where students from different backgrounds congregate to learn and develop, as well as diverse communities and neighbourhoods like Little Ethopias, Little Italys, and Chinatowns, are other hotspots for diversity.

Question:  (b) List four main criteria for determining a particular place as a Hot spot

Ans: 1. Accessibility: The location needs to be simple to get to using public transit or other modes of transportation.

2. Facilities: Hotspots ought to be filled with amenities including dining establishments, shopping, parks, theatres, and other tourist attractions.

 3. Variety: A wide range of experiences and activities has to be offered nearby.

4. Safety: Popular areas should be secure and safe for both locals and tourists.

Question: (c) Among the hot spots of the world, list two which are located in India 

Ans: 1. Kashmir Valley 2. Northeastern India

 (Short Answer Type Questions) 

Question: What is Apomixis and what is its importance? 

Ans: The formation of seeds by asexual reproduction is known as apomixis in plants.

A population of plants needs to have reproductive stability because it lessens the requirement for inbreeding and enables the plants to maintain genetic homogeneity throughout generations. Apomixis has been used in plant breeding to produce hybrid varieties and can also be utilised to propagate desired features. Additionally, since plants may reproduce without the aid of pollinators, it enables more effective resource usage.

Question: In a Pisum sativum, the pods may be inflated (I. dominant) or constricted (i. recessive). What proportion of the offspring in the following crosses would be expected to be inflated? 

(a) II x ii 

(b) li x ii . 

(c) II x II 

Ans: (A) It would be assumed that all of the offspring would be inflated (100%).

(b) It would be assumed that 50% of the offspring would be inflated.

(c) It would be assumed that all of the offspring would be inflated (100%).

Question: Do you think microbes can also be used as a source of energy? If yes how? 

Ans: Yes, it is possible to obtain energy from bacteria. Biofuels like ethanol and biodiesel can be created using microorganisms like bacteria and algae. These biofuels can be used as a direct substitute for fossil fuels in a variety of situations, including the operation of vehicles and the heating of homes. Microbial fuel cells, which harness the metabolic activity of bacteria to create electricity, are another way that microbes can be utilised to power devices.

 (Very Short Answer Type Questions) 

Question: The following very short answer type questions of two marks, each may be answered in a few words or few sentences or as may be required: 

Question: (a) Write briefly about Xenogamy. 

Ans: When pollen from one species of plant is transferred to the stigma of another species of plant, this process is known as xenogamy. For plant hybridization to occur and to maintain the genetic diversity of different plant species, this kind of pollination is necessary. Crops can also benefit from it since plant hybridization can produce more resilient and tolerant kinds that are better adapted to the local climate.

Question: (b) Define: (a) Hybridization 

Ans: In botany, hybridization is the process of mating two genetically unrelated plant species—or subspecies within a species—to create a hybrid offspring that combines the best traits of the two parent plants. Through hybridization, new plant kinds can be produced with superior flavour, higher yields, and other desirable characteristics. For plant breeders, hybridization is a crucial method that has been employed in agriculture for thousands of years.

Question: (b) Hardening in botany

Ans: In botany, the term “hardening” refers to the process of enhancing a plant’s internal tissue structures so they are more resilient to external pressures. Pruning, applying fertiliser, and minimising water stress are just a few techniques that can be used to achieve this. Plants can become more drought, cold, and heat-resistant through the hardening process. Additionally, it can help plants develop stronger against diseases and pests. Both edible and ornamental plants can benefit from hardening.

Question: (c) What is Ecology? Who coined the term? 

Ans: The scientific study of how organisms and their surroundings interact is called ecology. In 1869, German zoologist Ernst Haeckel first used the term.

Question: (d) Differentiate between In-situ. and Ex-situ Conservation of Biodiversity. 

Ans: The preservation of ecosystems and natural habitats in their current environments is referred to as in-situ biodiversity conservation. Along with species, their habitats, and their interactions are also protected. Additionally, creating protected areas like national parks, wildlife preserves, and marine protected zones is necessary.

The preservation of species and genetic diversity away from their natural habitats is referred to as ex-situ conservation of biodiversity. It entails gathering and preserving wild specimens, their offspring, and other relevant materials like tissue cultures and seeds. Botanical gardens, zoos, aquariums, seed banks, and tissue culture collections are a few examples of ex-situ conservation.

(Objective Type Questions) 

Question: (i) Define Apomixis. 

Ans: Apomixis is a method of reproduction in which a new organism is produced from a single parent without the use of gametes or meiosis.

Question: (ii) Number of Meiotic divisions required to produce 200 seeds of Pea would be 

A 200 

B. 400 

C. 300 

D. 250 

Ans: B. 400

Question: (iii) Introns are essential parts of a gene. 


Ans: True

Question: (iv) An unorganised undifferentiated mass of actively dividing cells is called a. 

Ans: A cell proliferation.

Question: (v) Biogas rich in Methane is produced by 

Ans: Anaerobic digestion.

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