Q24 of 43 Page 1

Which one of the two ‘‘in-situ’’ or ‘‘ex-situ’’ biodiversity conservation measures help the larger number of species to survive? Explain.

In-situ conservation is the conservation of the biodiversity (plants and animals) in natural environment. It involves techniques which manage and monitor the biodiversity in the same area only.


Ex-situ conservation is the conservation of the biodiversity outside it’s natural habitat .It involves removing the endangered species from their natural habitat to another habitat.


Ex situ conservation helps to conserve large number of species as it conserves at all levels of biodiversity outside their natural habitat like zoo, botanical garden , gene bank and aquarium etc.


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22

Study the figure of vector pBR322 given below.


Identify A, B and C and explain their roles in cloning a vector.


OR


Many people are apprehensive of accepting GM crops. Give three reasons so as to convince them to use these crops.


 23

Draw a diagram of the sectional view of a human seminiferous tubule and label any six of its parts.

 25

(a) Draw the embryo sac of a flowering plant and label the following :

(i) Central cell


(ii) Chalazal end


(iii) Synergids


(b) Name the cell and explain the process it undergoes to develop into an embryo sac.


(c) Explain the development of endosperm in coconut.


OR


Write the duration and the events that occur in the ovary and the uterus during follicular and luteal phases of the menstrual cycle in humans. How do pituitary and ovarian hormones influence these two phases?


 26

(a) Describe aminoacylation of tRNA.

(b) Explain the process that takes place in the ribosomes when mRNA makes its entry into it in a prokaryote.


(c) Due to transcription error, ATG codon of DNA is transcribed into UAG in mRNA which translates a non-functional polypeptide chain in the ribosome. Justify the statement.


OR


Explain how does lac operon in E.coli operates:


(a) in the absence of an inducer.


(b) in the presence of an inducer.