Page 14 - Biology - XII

Q5. What is a quadrat?
Ans. A quadrat is a sampling area.

Q6. Why did you use squares of 1 m × 1 m to know the plant population?
Ans. The squares can be of any suitable size.

Q7. How many quadrats did you study for frequency % calculation?
Ans. Five
Q8. How do you calculate the frequency percentage of plant species studied?

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Ans. Frequency Percentage = Total numberof quadratsinwhich plantsspecies occured ×100
Total numberof quadratsstudied
Q9. How does the population of individuals increase in a given area?
Ans. By increase in birth rate (natality) and by immigration (addition of individuals from outside).

Q10. Defi ne the term frequency.
Ans. Frequency is defi ned as the number of times a plant species occurs at a given time.
Q11. How will the farmer decide the frequency of the weeds in his fi eld along the main crop grown?
Ans. If the weeds are frequently seen all over the fi eld then the frequency of its occurrence is more in
percentage.
Q12. How do plants avoid plant density near to them?
Ans. The plant uses seed dispersal as one of the mechanisms for its distribution and to avoid plant
density at a place.

Q13. What do you understand by monospecifi c population?
Ans. The population consisting of one type/one species is called monospecifi c population.
Q14. Can we have any other sampling unit other than quadrats?
Ans. Yes. It can be circular or transects, also.

Q15. How does the population density of certain plants rapidly increase in monsoon season and
decrease in summer?
Ans. Population density is directly related to the birth rate, growth of new plants in favourable season,
and death of plants in unfavourable season.

EXPERIMENT - 3
Objective
Isolation of DNA from available plant materials such as spinach, peas, papaya, etc.

Principle/Theory
Living beings are made up of macromolecules like proteins, nucleic acids, lipids, and carbohydrates.
Nucleic acids are the major molecules having code for genetic information of the organisms and are the
molecules that transfer genetic information to the off springs.

DNA is known as Deoxyribose Nucleic Acid. It is a double helical structure, intertwined as pleated ropes
or thread. Isolation of DNA is done in laboratories for various purposes. There are multiple sources for
DNA isolation and methods.

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