NCERT Solutions for Class 12 Biology Chapter 13

Organisms and Populations Class 12

Chapter 13 Organisms and Populations Exercise Solutions

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Exercise : Solutions of Questions on Page Number : 239

Q1 :  

How is diapause different from hibernation?


Answer :

Diapause is a stage of suspended development to cope with unfavourable conditions. Many species of Zooplankton and insects exhibit diapause to tide over adverse climatic conditions during their development.

Hibernation or winter sleep is a resting stage where in animals escape winters (cold) by hiding themselves in their shelters. They escape the winter season by entering a state of inactivity by slowing their metabolism. The phenomenon of hibernation is exhibited by bats, squirrels, and other rodents.

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Q2 :  

If a marine fish is placed in a fresh water aquarium, will the fish be able to survive? Why or why not?


Answer :

If a marine fish is placed in a fresh water aquarium, then its chances of survival will diminish. This is because their bodies are adapted to high salt concentrations of the marine environment. In fresh water conditions, they are unable to regulate the water entering their body (through osmosis). Water enters their body due to the hypotonic environment outside. This results in the swelling up of the body, eventually leading to the death of the marine fish.

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Q3 :  

Define phenotypic adaptation. Give one example.


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Q4 :  

Most living organisms cannot survive at temperature above 45°C°. How are some microbes able to live in habitats with temperatures exceeding 100°C?


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Q5 :  

List the attributes that populations but not individuals possess.


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Q6 :  

If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase (r) of the population?


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Q7 :  

Name important defence mechanisms in plants against herbivory.


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Q8 :  

An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?


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Q9 :  

What is the ecological principle behind the biological control method of managing with pest insects?


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Q10 :  

Distinguish between the following:

(a) Hibernation and Aestivation

(b) Ectotherms and Endotherms


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Q11 :  

Write a short note on

(a) Adaptations of desert plants and animals

(b) Adaptations of plants to water scarcity

(c) Behavioural adaptations in animals

(d) Importance of light to plants

(e) Effect of temperature or water scarcity and the adaptations of animals.


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Q12 :  

List the various abiotic environmental factors.


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Q13 :  

Give an example for:

(a) An endothermic animal

(b) An ectothermic animal

(c) An organism of benthic zone


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Q14 :  

Define population and community.


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Q15 :  

Define the following terms and give one example for each:

(a) Commensalism

(b) Parasitism

(c) Camouflage

(d) Mutualism

(e) Interspecific competition


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Q16 :  

With the help of suitable diagram describe the logistic population growth curve.


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Q17 :  

Select the statement which explains best parasitism.

(a) One organism is benefited.

(b) Both the organisms are benefited.

(c) One organism is benefited, other is not affected.

(d) One organism is benefited, other is affected.


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Q18 :  

List any three important characteristics of a population and explain


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<< Previous Chapter 12 : Biotechnology and its Applications Next Chapter 14 : Ecosystem >>

Biology : CBSE NCERT Exercise Solutions for Class 12th for Organisms and Populations will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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