Q27 of 30 Page 1

How are Baculoviruses and Bacillus thuringiensis used as bio-control agents? Why are they preferred over readily available chemical pesticides?

Baculoviruses are pathogens that attack insects and other arthropods.

Baculovirus as bio-controls gents:


• These are excellent candidates for species-specific, which have to be mixed with water and sprayed onto vulnerable plants.


• they show no negative impact on plants, mammals, birds, fish or even non-target insects.


• These are especially desirable when beneficial insects are being conserved to aid in an overall IPM program( Integrated pest management)


Bacillus thuringiensis as bio-control agents:


• Through genetic engineering the gene coding for the toxic protein is introduced into crop plants, which make them resistant to insect pests.


• They re available in sachets and dried spores, which have to be mixed with water and sprayed onto the vulnerable plants.


• Who they are eaten by larva , the toxin becomes active in the gut of larvae and kills the larvae.


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25

Draw a schematic diagram of the E. coli cloning vector pBR322 and mark the following in it:

(a) ori


(b) rop


(c) ampicillin resistance gene


(d) tetracycline resistance gene


(e) restriction site BamHI


(f) restriction site EcoRI


OR


(a) Draw schematic diagrams of segments of a vector and a foreign DNA with the sequence of nucleotides recognised by EcoRI.


(b) Draw the vector DNA segment and foreign DNA segments after the action of EcoRI and label the sticky ends produced.


 26

Draw and explain expanding age pyramids of human population. Why is it so called?

 28

(a) Name the population growth pattern the equation represents. What does “r” represent in the equation? Write its importance in population growth.

(b) Explain the principle of carrying capacity by using population Verhulst-Perl logistic growth curve.


OR


(a) With suitable examples, explain the energy flow through different trophic levels. What does each bar in this pyramid represent?


(b) Write any two limitations of ecological pyramids.


 29

(a) Draw a longitudinal section of a pistil of an angiosperm showing the growth of the pollen tube up to the micropyle of the ovule. Label (i) stigma, (ii) embryo sac (iii) pollen tube (iv) micropyle.

(b) Explain the events that occur, upto fertilisation, when the compatible pollen grain lands on the stigma.


OR


(a) Draw a transverse section of a human ovary showing the sequential development of different follicles up to the corpus luteum.


(b) Comment on the corresponding ovarian and pituitary hormone levels during these events.