Class 12th Biology 2014 Set3 Delhi Board Paper Solution
Question 15
Why does Bt toxin not kill the bacterium that produces it, but kill the insect that ingests it?
Answer
Bt toxin is produced by a soil bacterium called Bacillus thuringiensis. This toxin does not kill the bacteria because when it is present in the bacteria, it is in an inactive and crystalline form. It becomes active and toxic when it is consumed by insects such as such as lepidopterans (armyworm), coleopterans (beetles) and dipterans (flies/ mosquitoes).
The activated toxin (delta endotoxins) binds to the epithelial cells in the midgut of an insect and creates pores that cause lyses and swelling, eventually killing the insect.
Popular Questions of Class 12th biology
- Q:- What is spermatogenesis? Briefly describe the process of spermatogenesis.
- Q:- Why is reproduction essential for organisms? Answer
- Q:- 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. - Q:- With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
- Q:- What is DNA fingerprinting? Mention its application.
- Q:- What is oogenesis? Give a brief account of oogenesis.
- Q:- Describe the structure of a seminiferous tubule.
- Q:- What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
- Q:- With a neat, labelled diagram, describe the parts of a typical angiosperm ovule.
- Q:- Explain the Law of Dominance using a monohybrid cross.
Recently Viewed Questions of Class 12th biology
- Q:- The species diversity of plants (22 per cent) is much less than that of animals (72 per cent). What could be the explanations to how animals achieved greater diversification?
- Q:- List the various abiotic environmental factors.
- Q:- Find out from internet what is golden rice.
- Q:- How many eggs are released by a human ovary in a month?
How many eggs do you think would have been released if the mother gave birth to identical twins?
Would your answer change if the twins born were fraternal? - Q:- How does the transmission of each of the following diseases take place?
(a) Amoebiasis
(b) Malaria
(c) Ascariasis
(d) Pneumonia - Q:- Why is reproduction essential for organisms? Answer
- Q:- List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
- Q:- Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?
- Q:- Can we call human evolution as adaptive radiation?
- Q:- Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?